fix(plugins): call the runtime view's display_modes directly

Codacy flagged the getattr/callable indirection as 'lookup is not callable'.
The view is a PluginRuntimeView or None; anything else raises inside the
existing try and falls back to the manifest.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -19,6 +19,217 @@ accepts both, but the store flags the old spelling as deprecated
 
 ## Unreleased
 
+### Plugins ask for the screen in-process: `request_on_demand()` / `end_on_demand()`
+
+The in-process way in that stage 5 of the control socket needed
+(`docs/IPC_CONTROL_SOCKET.md`, "Plugins in the display process").
+
+- **`BasePlugin.request_on_demand(mode=None, duration=None, pinned=False)`**
+  shows the plugin now, and **`BasePlugin.end_on_demand()`** gives the
+  screen back. Both are safe from any thread (an MQTT callback, a timer
+  thread): `PluginManager.request_on_demand()` / `end_on_demand()` hand the
+  request to `DisplayController.submit_plugin_on_demand()`, which only
+  queues it (at most 32) and wakes the render thread through the control
+  socket's flag (`ControlServer.wake()`). The render thread applies it with
+  the socket's commands, through the same handler as a web on-demand
+  request, so it lands within a frame rather than on the mailbox's
+  once-a-second look. Both return the request id, or `None` when no display
+  runs in the process (the web interface, `scripts/check_plugin.py`) or the
+  queue is full.
+- **A plugin's stop ends only its own session.** A mailbox stop still ends
+  any session, whoever started it.
+- **Older cores.** Plugins detect the methods with `hasattr` and write the
+  `display_on_demand_request` mailbox when they are missing or answer
+  `None`; the pattern is in `docs/PLUGIN_API_REFERENCE.md` ("On-demand
+  display"). The display still reads the mailbox for plugins that write it.
+
+### Web UI: Schedule and General are ES-module pages (stage 3)
+
+- The Schedule and General tabs follow stage 2 (#727): their inline
+  `<script>` blocks are now `static/v3/js/pages/schedule.js` and
+  `pages/general.js`, started once per swap-in by the page registry and
+  stopped on swap-out. Neither partial has an inline script, `onclick`,
+  `onsubmit` or `oninput` any more.
+- Schedule: both pickers are drawn from the saved config the partial
+  carries as JSON in `data-schedule-config` / `data-dim-schedule-config`.
+  The forms' `hx-on` save handlers became one `htmx:afterRequest` listener
+  on the page; the forms are marked `data-reports-result`, which `app.js`
+  now honours like an `hx-on` after-request handler, so a save still shows
+  one notification.
+- General: the timezone picker reads the saved zone from `data-timezone`.
+  The Security section's forms and buttons carry `data-action` and use one
+  delegated submit and one delegated click listener, so a token row added
+  after a create needs no listener of its own. Requests go through
+  `core/api.js`: the optional login's "sign in again" answer no longer
+  flashes an error while the page navigates to the login form. A login
+  change made just before a swap is still reported.
+- Old globals keep working as deprecated aliases through `window.LEDMatrix`
+  (one console warning each): `handleScheduleResponse`,
+  `handleDimScheduleResponse`, and `webLogin` (its five methods).
+- New DOM suites `test/js/dom/test_{schedule,general}_page.js`;
+  `unit/test_general_web_login_token.js` imports the module instead of
+  slicing the template, and `unit/test_restart_banner.js` covers
+  `data-reports-result`.
+
+### The control socket carries every web command; the mailboxes are a fallback
+
+Stage 4 of the web → display control socket (`docs/IPC_CONTROL_SOCKET.md`).
+
+- **Mailbox only when the socket cannot carry it.** The on-demand routes
+  (`POST /api/v3/display/on-demand/start` and `/stop`) write the
+  `display_on_demand_request` mailbox only when the display never had the
+  request: no socket (a stopped display, one older than the socket), a
+  refused or timed-out connect, or a display too old to know the command.
+  A display that had it and refused or did not answer (a full queue, bad
+  arguments, silence after the send) is answered `503` (`400` for bad
+  arguments) with `socket_error`, and no mailbox copy is written: the
+  display may have applied it, or would refuse the copy too. A stop with
+  `stop_service` still stops the service. `src.ipc.client.should_fall_back()`
+  holds the rule; `ControlError.sent` says whether the display had the
+  request.
+- **`errors.clear`.** `POST /api/v3/errors/clear` goes over the socket: the
+  display clears its error records and republishes its error snapshot
+  before it answers, so the response says `applied: true` with the
+  display's own `cleared_count`. The `plugin_error_clear_request` mailbox
+  is written only on the same fallback rule (a display from before this
+  release answers `unknown_command`, and gets the mailbox). A display that
+  had it and failed answers `503`. The error snapshot gains
+  `applied_clear_cutoff`, so an older mailbox request is not shown as
+  pending once a wider clear has been applied.
+- **The display looks at the mailboxes less, and more cheaply.** While the
+  control socket is up, the on-demand mailbox is looked at once a second
+  instead of every 0.25 s (`MAILBOX_POLL_INTERVAL_WITH_SOCKET`), and both
+  mailboxes are read only when their file changed since the last look:
+  otherwise a look is one `stat()` (`CacheManager.file_signature`,
+  `MailboxWatch`). A socket command no longer reads or deletes the mailbox
+  file. A duplicate already processed is taken out of the mailbox, rather
+  than re-read for an hour. Without a socket (Windows,
+  `LEDMATRIX_CONTROL_SOCKET=off`) the mailbox is read every 0.25 s as before.
+- **Kept for one release.** The display still reads both mailboxes, so an
+  older web interface (or a web user not yet in the socket's group) keeps
+  working during an upgrade, and still writes `display_current_state`,
+  `display_on_demand_state` and `plugin_runtime_snapshot` for the readers'
+  fallback. A request that comes through the on-demand mailbox while the
+  socket is up is logged once per writer: plugins that write
+  `display_on_demand_request` themselves (birdnet-go, mqtt-notifications,
+  on-air, pomodoro-timer) now get the screen within a second rather than a
+  quarter second, and need an in-process way in before the mailbox goes.
+
+### Display loop stage 3: a ScreenRunner, and the Arbiter decides every screen
+
+Internal; no behaviour change. Stage 3 of `docs/RUN_LOOP_REDESIGN.md`.
+
+- Each screen runs in `ScreenRunner` (`src/screen_runner.py`): the first
+  frame, the 125 Hz or 1 Hz frame loop, the make-up dwell and the
+  dynamic-duration exit, moved out of `DisplayController.run()` with their
+  pacing unchanged. It paces with an injected clock and returns an
+  `Outcome` whose `ExitReason` is `DURATION`, `CYCLE_COMPLETE`, `EMPTY`,
+  `ERROR`, `DISPLAY_FALSE`, `RELOAD` or `PREEMPTED`. `PREEMPTED` replaces
+  the five "did the mode change under this screen?" re-checks.
+- `Arbiter.decide()` now answers for on-demand, live priority and the
+  rotation too (Sources `ON_DEMAND`, `LIVE`, `ROTATION`); `LEGACY` means
+  only Vegas, whose iteration moves to stage 4. The on-demand session, the
+  rotation's position and the live resume point are snapshotted into
+  `ArbiterState`, whose pure transitions (`next_on_demand`, `claim_live`,
+  `release_live`, `after`) replace the bookkeeping in `_resolve_active_mode`,
+  `_apply_live_priority` and `_advance_after_screen`.
+- Between frames, the runner's service points make one
+  `decide(..., running=plan)` call instead of `_check_live_takeover`,
+  `_screen_preempted` and `_wifi_notice_pending` one after another. The
+  WiFi notice file is still read exactly where it was (the read is
+  throttled and deletes an expired file).
+- A Vegas pass scans the live-priority plugins once instead of twice at the
+  same instant.
+- The golden traces are byte-identical, and a capture of all 67 harness
+  runs in the suite (every sleep, frame, read and scan) matches `main`
+  apart from the duplicate scan above and one moment: in the 125 Hz loop a
+  live takeover's state change is made after the frame's 8 ms sleep rather
+  than before it, ending the screen at the same frame as before.
+- New module: `src/screen_runner.py`. Core-internal: plugins have no reason
+  to import it, so it sets no `ledmatrix_min_version` floor.
+
+### A scrolling screen held by its plugin's update() is reported
+
+- While a plugin's `update()` runs it holds the plugin's lock, and that
+  plugin's frames are skipped: on a scroller, a frozen strip, with nothing
+  logged (and a freeze of 5 s or more is a gap, not a freeze, to the frame
+  stats). The high-FPS loop now times each run of skipped frames; one of
+  250 ms or more logs `Display of <plugin> held N ms by its update()`
+  (rate-limited per plugin) when it ends, and is recorded on the plugin's
+  health as a `display hold` busy skip, which never counts toward the
+  circuit breaker. The 1 Hz loop is left out: its frames are a second apart,
+  so one skipped frame there measures nothing and freezes nothing visible.
+
+### Fixed
+
+- Unloading a plugin now forgets the fonts its manifest registered, not only
+  the fonts it reported using. Its `plugin_id::family` entries kept resolving
+  and their cached font objects stayed alive until a restart, and a family a
+  reinstalled plugin's manifest dropped stayed registered. The new
+  `FontManager.forget_plugin_fonts(plugin_id)` does the cleanup;
+  `PluginManager.unload_plugin()` and a failed load call it alongside
+  `forget_manager_fonts()`, and a reload registers the manifest's fonts again.
+
+- The web preview and `/api/v3/display/current` no longer stay black for a
+  whole screen that draws its card once and then holds it. The snapshot is
+  written from `update_display()` at most once per write interval, so a frame
+  pushed inside that interval was skipped and left for the next
+  `update_display()` -- which such a screen never makes. Soccer's
+  recent/upcoming cards skip redundant redraws, and the first one after an
+  on-demand start lands a few milliseconds after the start's clear wrote a
+  black frame: on ledpi the preview showed 0 lit pixels for the whole 15 s
+  while the panel showed the card. `DisplayManager` now remembers a skipped
+  changed frame, and the render loop writes it (`write_owed_snapshot()`)
+  once the interval has passed. The cadence is unchanged, and nothing extra
+  runs when no frame is owed.
+- The installed-plugins list (`GET /api/v3/plugins/installed`) no longer
+  waits on GitHub. Its comment said the registry lookup made no network call,
+  but on a cold or expired cache `get_registry_info()` downloads plugins.json
+  (10 s timeout, three attempts), and with nothing cached to fall back on
+  every plugin's lookup repeated that: offline, 5 plugins took 11 s with DNS
+  failing and 2 plugins 65 s with the route black-holed, on every load. The
+  list now reads the registry copy already in memory, however old
+  (`get_cached_registry_info()`); with none yet it returns without update or
+  verified badges and starts one background refresh
+  (`refresh_registry_in_background()`, backing off for a minute after an
+  offline failure), so a later load has them. The store, install and update
+  paths still fetch as before.
+
+### ESPN date-range fetches: fewer requests, fewer at once
+
+A soccer board (8 leagues, ESPN rejecting `dates=` ranges) logged ~90
+`NameResolutionError` lines and an `update() timed out` at every start on a
+Pi: each league's fortnight-either-side window was 29 day requests, fetched
+by several managers at once, ~40 in flight. Measured against live ESPN with
+soccer-scoreboard 2.39.2, alternating runs: **~450 requests per start, peak
+~45 in flight, ~75 DNS lookups -> 46 requests, peak 13, ~30 lookups**.
+
+- `fetch_espn_date_chunks()` asks for a window's partial edge month whole
+  when the window covers `ESPN_MONTH_COVER_MIN_DAYS` (7) or more of its days,
+  and trims the answer to the window's days by each event's US Eastern start
+  date -- the day ESPN's `dates=YYYYMMDD` means (417 of 417 live soccer
+  events matched). A 29-day window spanning two months is 2 requests instead
+  of 29. Short windows (a live poll's 1-2 days) stay day by day. A trimmed
+  month that comes back at the 500-event cap re-asks only the window's days.
+  An event with no readable date is kept. New: `espn_request_chunks()`.
+- Chunk requests share one process-wide cap of `ESPN_CHUNK_WORKERS` (6) in
+  flight, across every window being fetched, instead of six per window.
+- A new process starts as if a range had just been rejected, so it no longer
+  spends one doomed 400 per window at every start (eleven at once from a
+  soccer board); the range is still retried `RANGE_RETRY_SECONDS` in.
+
+### Fetch stats: bytes on the wire, not just decoded
+
+`GET /api/v3/plugins/fetch-stats` reported only `bytes`, the decoded body
+size, and that read as the download volume. ESPN gzips every scoreboard, so
+it overstated what crossed the network about 14x: a college football
+Saturday's scoreboard is 865 KB decoded and 63 KB on the wire, and ledpi's
+"643 MB in 6 hours" of football was ~47 MB of actual traffic. Every counter
+set (totals, per plugin, per host) now has `wire_bytes` too, read from
+urllib3's count of the raw bytes it took off the socket. A response with no
+urllib3 response behind it is counted at its decoded size. `bytes` keeps its
+meaning.
+
 ### Cheap per-frame and per-fetch savings
 
 - `BaseOddsManager.get_odds()` no longer pretty-prints every odds response
@@ -488,6 +699,71 @@ policies are unchanged.
 
 ### Fixes
 
+- A cache key too long to be a filename is now cached. The calendar
+  plugin's key joins every calendar id the user picked; on a real install
+  it passed 300 bytes, ext4 refuses names over 255, and every write failed
+  with `File name too long` — logged as "(permission denied)", so it read
+  like a cache-directory ownership problem. `DiskCache.get_cache_path` now
+  keeps a key of up to 200 UTF-8 bytes as its filename, as before, and
+  turns a longer one into its first bytes plus a hash of the whole key. The
+  web UI's cache list and delete keep working, because the shortened name
+  maps back to the same file. A failed write now names the real error.
+- The cache's memory tier no longer serves data older than the reader asked
+  for. A record loaded from disk was timed in memory from the load, not
+  from when it was written, so `get(key, max_age=300)` could return data
+  close to 600 s old (after a restart, after the hourly memory sweep, or in
+  the other process, which only ever loads the record from disk), and a
+  stored `ttl` was stretched the same way. A memory hit is now also checked against
+  the record's own timestamp, and a stale one falls through to disk, which
+  returns a newer write if there is one.
+- An on-demand request that names a `*_live` mode now shows that mode. On
+  ledpi, `{"plugin_id": "football-scoreboard", "mode": "ncaa_fb_live"}` with
+  15 college games on answered 200 and showed `nfl_recent`. The session's
+  mode list kept a live mode only when the plugin's `has_live_content()`
+  said so. That method answers the live-priority question, and the sports
+  plugins answer it for favourite teams only. A mode the request names
+  (not one resolved from a bare plugin id) now leads the session, with the
+  plugin's other modes after it. If it has nothing to draw, the session
+  moves on to the next of those modes, like any empty on-demand mode. The
+  name is saved with the session (`named_mode` in
+  `display_on_demand_config`), so a restart resumes on it.
+- A restart during an on-demand session whose plugin then fails to load no
+  longer leaves a session with no modes. On ledpi, `clock-simple` failed
+  config validation after a crash. The display logged `No valid display
+  modes found for on-demand plugin 'clock-simple' after restoration` and
+  kept reporting the session as active until its first pass ended it as
+  `idle`. The cached request stayed behind for the next restart. The session
+  now ends at startup with status `error` and error `restore-failed`, which
+  `/display/on-demand/status` reports, and the cached request is dropped. The
+  same applies when the plugin system itself fails to start.
+- `POST /api/v3/config/schedule` and `/config/dim-schedule` accept a
+  disabled per-day schedule with every day off. That is the shape
+  `config.template.json` ships, so posting back what GET returned on a fresh
+  install answered 400 "At least one day must be enabled". An enabled per-day
+  schedule still needs a day on. A day that is off now keeps the times it
+  was posted with (the schedule picker sends them). Before, saving dropped
+  them, so turning the day back on showed the defaults.
+- `POST /api/v3/config/main` answers `restart_required: true` only when the
+  save changed a setting the running display does not apply by itself.
+  Brightness (`brightness.set` and the config watcher), the per-mode
+  durations and plugin sections are applied live. A brightness-only save,
+  such as the MQTT bridge's slider, or a save that changed nothing, no longer
+  shows the restart banner. Hardware, rotation order, timezone and every
+  other setting still ask for the restart.
+- `GET /api/v3/health` reports `degraded` when the display service is
+  stopped. Before, only the sub-checks changed, and the overall status stayed
+  `healthy` for as long as the last preview frame was under 60 s old.
+  `checks.display_loop.status` is now `stopped` when three things agree:
+  systemd says the service is not active, the control socket does not
+  answer, and there is no live heartbeat. Where the platform has no socket
+  (Windows) or it is switched off, nothing changes.
+- `GET /api/v3/display/current-status` no longer reports the stopped
+  display's last state (`is_display_active: true`) from the cache for up to
+  120 s. When the control socket does not answer and the render loop's
+  heartbeat is absent, stale, or from a process that is gone (#726's rules),
+  the answer is unknown, with every field `null`. A display that still beats
+  without a socket, Windows and a socket switched off read the cache as
+  before. New `web_interface.display_state.display_gone()`.
 - The garbage-collection timer (`GcMonitor`, above) no longer prints
   `Exception ignored while calling GC callback ... 'NoneType' object has no
   attribute 'perf_counter'` when the display service or a test run exits.
@@ -498,6 +774,16 @@ policies are unchanged.
   `DisplayManager.cleanup()` (reached from SIGTERM through `run()`'s
   `finally`) unregisters it with the frame recorder. New
   `frame_timing.uninstall_gc_monitor()`.
+- The web interface's state subscription (`StateSubscription`,
+  `src/ipc/client.py`) resubscribes about 1 s after a display restart, every
+  time. Its reconnect wait went back to the minimum only when the
+  subscription was stopped. A disconnect after a working connection kept
+  doubling the wait, so successive display restarts were followed by waits
+  of 1, 2, 4, 8, 16 and then 30 s for good.
+  During each wait the web answered from one-shot `state.get` connections
+  instead of its copy. The wait now resets once a connection has stored a
+  snapshot. A display that does not offer the stream is still retried
+  slowly.
 - A plugin reload after a store update (`plugin.reload`, #720) no longer
   freezes the panel during Vegas. On ledpi a football reload froze it for
   3.0 s (`Render stall over: no frame for 3043ms`). The reload ran on the
@@ -514,6 +800,25 @@ policies are unchanged.
   for the plugin is refused (`plugin-reloading`), and a config reconcile
   neither loads it twice nor unloads it mid-load. A Vegas fetch that waited
   out a reload for the lock skips the old instance.
+- A plugin display duration that is not a number no longer stops the
+  display. Several plugins (clock-simple, calendar, countdown) return their
+  `display_duration` setting as it is in config.json, so a value saved as
+  `"20"` or `null` (the raw config editor, a hand edit) reached the run loop
+  as a string or None. Comparing it with 0 raised a TypeError that no
+  handler in the loop caught: the display service exited when that plugin's
+  screen came up, and systemd restarted it into the same crash. The
+  controller now reads the plugin's answer as a number: a numeric string
+  counts, and anything else (or a `get_display_duration()` that raises)
+  shows the mode for 30 s, with one warning per plugin.
+- A scroll strip narrower than the panel scrolls instead of raising on every
+  frame. When a frame ran off the end of the strip, `ScrollHelper` copied
+  the strip's tail and then the rest of the frame from its head, which
+  assumed the head was that wide; for a narrower strip that raised
+  `ValueError: could not broadcast` at every position, so nothing was drawn
+  and each frame logged a traceback. Vegas builds such a strip, with no
+  lead-in, when its content is narrower than the chain. A frame that runs
+  off the strip now continues from its head column by column, so a narrow
+  strip repeats across the panel; a wide strip wraps exactly as before.
 - The schedule-off blank and the WiFi notice no longer start with a
   scroller's leftovers. Both are drawn by the display controller rather than
   dispatched to a plugin, so #716's handover never reached them: drawn while
@@ -523,6 +828,46 @@ policies are unchanged.
   scroller or Vegas) were counted as 0.5-1 s freezes and logged as a
   `Render stall ... mid-scroll`. The controller now ends the scroll state
   before drawing either.
+- A plugin that keeps helpers in a package (elections' `providers/`,
+  flights' `enrichment/`, olympics' `data/` and `renderers/`) now runs its
+  updated helpers after a reload. Unloading dropped the package itself but
+  left its modules (`providers.feed`) in `sys.modules`, so the reload after a
+  store update imported the new `manager.py` and got the old helpers back from
+  the cache until the display restarted. `PluginLoader` now drops a plugin's
+  package modules when it unloads, and when a load fails part-way.
+- Uninstalling a dev plugin that `scripts/dev/dev_plugin_setup.sh` linked
+  into the plugins directory now removes the link and leaves the checkout
+  alone. The store's removal passed the link to `shutil.rmtree`, which
+  refuses a symlink; its fallback then walked through the link and chmodded
+  every directory and file of the linked checkout to 0700, and the sudo stage
+  refused a path outside the plugins directory, so the uninstall failed with
+  the link still in place. The same removal discards the set-aside copy after
+  an install or update. A symlink, dangling or not, is now unlinked.
+- A dev plugin linked in under a name its checkout does not share now loads.
+  `dev_plugin_setup.sh link-github foo <url>` clones `ledmatrix-foo` (the
+  repository naming convention) and links it as `plugins/foo`. The loader's
+  containment check for dependency installs resolved the link and looked for
+  `ledmatrix-foo` among the plugins directory's entries, found none, and
+  refused the plugin, so the load failed with "Dependency installation
+  failed" even when it had no `requirements.txt`. The check now looks for the
+  entry the path itself names in the plugins directory, the link, and still
+  only ever answers with an entry it found there.
+- A plugin whose `update()` raises `asyncio.CancelledError` or `SystemExit`
+  no longer goes dark until a restart. Both derive from `BaseException`, not
+  `Exception`, and the update worker's bookkeeping caught only `Exception`:
+  the plugin kept its lock and stayed RUNNING, so it was never updated again
+  and every `display()` was skipped as busy. It is now recorded as that
+  update's failure, the same as any other raise. The plugin executor
+  reported such a call as a timeout; it now reports it as a failure.
+- Saving a config change no longer freezes the panel while a plugin is busy.
+  `ConfigService` told its subscribers about a change while holding its lock,
+  and the display's per-plugin subscriber waits up to 5 s for a plugin in the
+  middle of an update. A save that enables or disables a plugin also queues a
+  reconcile, which the render thread runs, and its `get_config()` and
+  `unsubscribe()` waited behind every one of those callbacks. Subscribers now
+  run after the lock is released. One reload's notifications still finish
+  before the next one's start, and a callback `unsubscribe()` removed is not
+  running, and will not run, once it returns.
 - A plugin whose `display()` raises now opens its circuit breaker. The first
   frame of each screen goes through the plugin executor, which caught the
   exception and returned False. The display read that as "no content" and
@@ -532,6 +877,57 @@ policies are unchanged.
   the plugin leaves rotation until the cooldown ends, the same as a raising
   `update()`. The display still moves straight on to the next mode. A hung
   `display()` is still recorded once, as a hang.
+- A plugin settings save that failed validation no longer leaks into the next
+  save. `ConfigManager.load_config()` returned its cached config itself (the
+  fast path from #410), so the form save's edits went into the cache before
+  validation ran, and a refused save left them there. The next save of any
+  other setting (another plugin's, a plugin toggle, the schedule) wrote them
+  to config.json: the refused value, and a nested secret typed into the same
+  form (`mqtt.password`, `league.espn_s2`, `flightaware.api_key`) in plain
+  text, because it had never reached config_secrets.json to be stripped.
+  The form also reloaded showing the refused values. `load_config()` now
+  returns a private copy, and the saves keep one, so nothing a caller edits
+  reaches the cache unless it is saved. The copy duplicates only the dicts
+  and lists (every other JSON value is immutable): 2.1 ms for a real 60 KiB
+  config on a Pi 4, against 6.8 ms for `copy.deepcopy`.
+- `GET /api/v3/plugins/config` no longer returns secrets. It sent back the
+  plugin's section with config_secrets.json merged in, API keys and tokens
+  in plain text: the masking #276 added was dropped in #330. It also took
+  any id, so `?plugin_id=web_auth` returned the login's cookie-signing key
+  and password hash and `?plugin_id=github` the Plugin Store token. Secret
+  fields now come back blank, as the settings page renders them, and a
+  plugin with no schema has its credential-named fields blanked, as
+  `GET /config/main` does. Blank rather than the `••••••••` of
+  `GET /config/secrets`, because the save reads a blank secret as
+  "unchanged", so a client can post the response back without erasing
+  one. Core sections and malformed ids get a 400, as they already did from
+  reset and uninstall.
+- Plugin settings with a table (a list of rows, such as geochron's cities
+  or the countdowns) save again when a text cell is blank or holds only
+  digits. A row posts its cells as `cities.0.timezone`, and the schema
+  lookup stopped at the list, so each cell was parsed with no schema: a
+  blank optional text cell became null, and a name like "2027" became a
+  number. Either failed validation, and every save of the page failed for
+  as long as the row existed. A plugin with a secret in its rows could not
+  be saved from the page at all, since the secret cell is drawn blank. The
+  lookup now steps from the index into the list's item schema.
+- A plugin whose API key is required and has no default (youtube-stats)
+  can be saved from its settings page without typing the key in again. The
+  page draws a stored secret blank and posts the blank back; for a required
+  secret the save read that blank as null, failed validation, and refused
+  every save of the page. A blank secret field now means "unchanged", as it
+  already did for an optional one.
+- `POST /api/v3/plugins/config` refuses a core section or a malformed
+  plugin id with a 400, as reset and uninstall already did.
+  `{"plugin_id": "display", ...}` merged unvalidated values into the core
+  display section (and added `"enabled": true` to it), and an id that was
+  not a string answered with a 500.
+- A plugin text setting saves what was typed when that looks like a
+  boolean or JSON. The form save tried `true`/`false` and `[...]`/`{...}`
+  before it looked at the schema, so a text field holding "true", "False",
+  "[1, 2]" or "{}" was stored as a boolean, list or object, and the save
+  failed validation. Text fields, nullable ones included, are now taken as
+  typed; other types convert as before.
 - A WiFi notice (such as "Connected to HomeNet" or "AP mode on") now shows
   within about a second of being posted. It was only checked between
   screens, so a 5 s notice posted during a 20 s screen expired before that
@@ -540,6 +936,42 @@ policies are unchanged.
   notice is what shows next, and Vegas resumes after it; before, a rotation
   screen showed instead and the notice expired behind it. An active
   on-demand session still holds the panel until it ends.
+- The Config Editor tab no longer shows API keys and tokens in plain
+  text. Its `config_secrets.json` editor (`/partials/raw-json`) was filled
+  with the file as it is on disk, so while the web login is off (the
+  default) anyone who could reach the port could read every credential,
+  although `GET /api/v3/config/secrets` masks them. The editor now shows the
+  same masked values. Saving it unchanged changes nothing, because the save
+  drops the masks and merges onto the stored file; to change a secret,
+  replace its mask. A list of secrets still needs every entry's real value
+  to be changed. The `config.json` editor is unchanged: its save writes the
+  file as given, so a mask there would be stored.
+- A disabled plugin keeps its place in the rotation order and its Vegas
+  exclusion when the Display or Rotation & Durations tab is saved. The order
+  lists show enabled plugins only and rewrite their hidden inputs from those
+  rows as soon as they are drawn, so any save of either tab stored the lists
+  without the disabled plugin. Once re-enabled, it came back at the end of
+  the rotation and scrolling in Vegas again. A disabled plugin's saved id
+  now stays in its saved place (`widgets/plugin-order-list.js`); the id of
+  a plugin that is no longer installed is still dropped.
+- Restoring a backup with "Reinstall missing plugins" installs only the
+  plugins that are missing. Every plugin the backup listed was sent to the
+  store's install, which replaces an installed copy with a fresh download,
+  so a restore onto the same device re-downloaded all of them in one
+  request. A plugin installed from its own URL is not in the registry, so
+  its "reinstall" failed and the restore answered "Restore failed" while
+  the plugin sat there installed. An installed plugin, found by the store's
+  own lookup (registry aliases included), is now listed under Skipped as
+  `plugin:<id> (installed)`.
+- `POST /api/v3/config/main` answers a JSON body that does not parse with
+  400 `Invalid JSON in request body`, as `/config/raw/main` does, and an
+  empty JSON body with 400 `No data provided`. Both were a 500
+  `CONFIG_SAVE_FAILED` suggesting file permissions and disk space, with a
+  traceback logged at ERROR: `get_json()` raised inside the handler's
+  catch-all.
+- Fonts restored from a backup show up in the Fonts tab and the font
+  pickers straight away. The font catalog is cached for five minutes, and
+  upload and delete cleared it but a restore did not.
 - A game that goes live now takes over the panel within about a second.
   Live priority was only checked between screens, so a game that went live
   during a 30 s screen waited for that screen to end. The frame loops and the
@@ -549,6 +981,45 @@ policies are unchanged.
   screen showed first and the game came after it. Each check also asks each
   plugin `has_live_content()` once, where a plugin registered under several
   modes used to be asked once per mode.
+- A plugin action whose params hold `true`, `false` or `null` runs again.
+  `/api/v3/plugins/action` wrote the params into the source of the wrapper
+  that runs the plugin's script, and those JSON words are not Python, so the
+  wrapper stopped with a NameError and the action answered "Action failed".
+  The plugin file manager's category toggle sends `"enabled": true`, so
+  turning a category on or off in of-the-day always failed. The params now
+  reach the wrapper on its stdin; the script still receives them as JSON on
+  its own stdin, as before.
+- An on-demand request that `/api/v3/display/on-demand/start` refuses no
+  longer runs later. With the display stopped the request goes to the
+  display's mailbox, and the display reads that mailbox for an hour without
+  looking at a request's age. So with "Start display service" unticked, the
+  answer was "Display service is not running", yet the next time the
+  display was started it ran that plugin, pinned if the request said so.
+  The same happened after "Failed to start display service". On either
+  refusal the route now takes its request back out of the mailbox, unless a
+  newer one has replaced it. A request the display acknowledges over the
+  control socket is now a success whatever systemd reports: a display run
+  by hand or in the emulator was told "not running" for a request it had
+  already taken, and with "Start display service" ticked the route tried to
+  start the service beside it.
+- `/api/v3/plugins/operation/<id>` reports a queued operation as `pending`
+  instead of answering 500. The queue keeps an operation's callback among
+  its parameters until it runs, and the status route tried to send that
+  function as JSON. An install queued behind another plugin's install
+  failed every status poll until the first one finished. Parameters whose
+  name starts with `_` are internal and are no longer in the answer.
+- A second click on Install while that plugin is still installing, or an
+  Uninstall during its install, now answers 409 "already has an install,
+  update or uninstall in progress" instead of 500 "An error occurred". The
+  first operation carried on either way. The uninstall route also stopped
+  recording a failed uninstall in the operation history for an uninstall
+  that never started.
+- `/api/v3/plugins/<plugin_id>/static/<path>` serves images and other
+  binary files. It opened every file as UTF-8 text, so a plugin's icon or
+  preview image answered 500 `UnicodeDecodeError`. Files are now sent as
+  they are on disk, an image with its own content type; HTML, JavaScript,
+  CSS, JSON and other text keep the types they had. The path checks are
+  unchanged.
 - The display schedule turns the panel off at exactly the end time. A window
   now runs from its start time up to, but not including, its end time: with
   07:00-23:00 the panel is on at 07:00 and off at 23:00. Before, the end
@@ -556,10 +1027,77 @@ policies are unchanged.
   the panel went off at 23:00 or at 23:01 depending on when in the minute
   that check ran. Windows that cross midnight and per-day schedules follow
   the same rule, and so does the dim schedule.
+- The MQTT bridge settings on the Tools tab can save a broker password with
+  TLS off. The server refuses that unless `allow_insecure_mqtt` is set, and
+  the form had no way to set it, so a password-protected broker on a home
+  network without TLS could not be saved from the web UI, and once such a
+  password was stored every later save failed too. While "Use TLS" is
+  unchecked the form now shows "Allow without TLS (trusted network)",
+  prefilled from the saved settings. It is off until ticked, so the server
+  still refuses a cleartext password by default.
+- The Overview's plugin-config warning check stops polling. It asked
+  `/api/v3/plugins/reconciliation-status` every 2 s until startup
+  reconciliation reported done, and the route reports not done whenever its
+  status file is missing: reconciliation raised before writing it, or /tmp
+  was cleaned under a long-running web service. The page then sent that
+  request every 2 s for as long as it stayed open, whichever tab was showing.
+  It now gives up after a minute and only polls while the Overview is on
+  screen.
+- Moving the Brightness slider on the Display tab no longer throws an error
+  in the browser console on every step. Its handler also updated a "LED
+  brightness" line that was removed from the page in #387; the lookup is
+  gone.
+- Creating an API token on the General tab no longer leaves the page asking
+  "Leave site?" on reload. The unsaved-changes guard marks a form when you
+  type in it and clears the mark only after an htmx save, and the token form
+  saves with a plain request, so it stayed marked after the token was
+  created. It is cleared once the token is saved.
 - An on-demand session that ends during scheduled-off hours, by expiring or
   being stopped, blanks the panel within about a second. It used to stay on
   until the next minute, because the once-a-minute schedule check had
   already run that minute and the session had overridden its answer.
+- Check & Update All updates what is installed now. A second run in the
+  same page sent the plugins the first run had seen, so a plugin uninstalled
+  since then failed with "plugin not found" and one installed since was
+  skipped. After a run the installed cards and the Updates badge show the
+  new versions; they kept offering "Update to vX" for what had just been
+  updated until the page was reloaded.
+- The Run On-Demand dialog lists a plugin's display modes, so a mode other
+  than the first can be started, and pinned. `/api/v3/plugins/installed`
+  never sent `display_modes`, which the dialog reads, so every plugin
+  offered only its own id under "This plugin exposes a single display
+  mode", and the display started its first mode. Each entry now carries
+  `display_modes`, the modes its manifest declares.
+- Installing Weather, Music, Stocks or Leaderboard from the Plugin Store
+  enables it, as installing any other plugin does. Each installs under the
+  id its manifest declares (`ledmatrix-weather` for the store's `weather`),
+  but the store enabled the store id, which `/api/v3/plugins/toggle`
+  answered with "Plugin not found": the plugin stayed disabled behind
+  "installed, but enabling it failed". `POST /api/v3/plugins/install` now
+  answers with the installed `plugin_id` (in the operation's result when it
+  is queued), and the store enables that.
+- Reinstalling a plugin from the Plugin Store leaves it enabled or disabled
+  as it was. Reinstall enabled it as a fresh install does, so a plugin the
+  user had switched off came back on.
+- A Plugin Store install that takes more than a minute is no longer
+  reported as failed. The store stopped waiting after 60 s and showed
+  "Install operation timed out" while the server, which allows the
+  plugin's dependency install 300 s on its own, carried on and usually
+  succeeded; the plugin was then neither enabled nor listed until the page
+  was reloaded. The store now waits up to 10 minutes, and if it still has
+  no answer it reloads the installed list and says the install may still
+  be running.
+- The Plugin Store's category filter lists every category its plugins
+  have. It offered a fixed seven while the registry uses about twenty, so
+  plugins filed under productivity, utility, transit and the rest could not
+  be filtered to, and "Financial" missed the plugin filed under "finance".
+  The choices are now built from the store's plugins, as the Starlark
+  section's are.
+- The Install button under Install Single Plugin (Plugin Manager > Install
+  from GitHub) runs one handler per click. It also had an inline `onclick`
+  whose handler threw a `ReferenceError` on every click; only the other
+  handler's request went out, and making the inline one work would have
+  sent every install twice. The inline handler is gone.
 - `/api/v3/plugins/installed` no longer reports the display's plugins as
   `live` while `/api/v3/health` says `display_loop: stalled`. The runtime
   snapshot is written from its own thread, which kept going while the render
@@ -571,11 +1109,41 @@ policies are unchanged.
   heartbeat when the service stops), is `stale` at once instead of `live`
   for up to 180 s. No new files or writes: both checks are on the reading
   side.
+- A scoreboard's scroll and Vegas cards with `scroll_card.date_format:
+  "weekday"` now show the printed date's own weekday. A Friday 8 PM ET game
+  read "Sat Oct 2". The card took the weekday in the plugin's own
+  `timezone` setting, which ships blank, so it fell back to UTC, while the
+  "Oct 2" beside it came from the zone the plugin actually resolves (its
+  setting, then the global one, then the system zone). Every zone is within a
+  day of UTC, so the card now finds which day near the start's UTC date has
+  the printed month and day and names that one. Games east of UTC (Auckland,
+  Kiritimati) were off by a day the other way and are fixed the same way.
+  The switch-mode scorebug, which already used the plugin's resolved zone,
+  shares the same formatter and draws what it drew before.
 - `/api/v3/display/current-status` reflects a wake from scheduled-off, a
   schedule-off blank, or an on-demand session starting or ending at once,
   even when the mode name stays the same. The display republished its
   current state only on a mode change or every 30 s, so `is_display_active`
   and `on_demand_active` could be up to 30 s out of date.
+- `/api/v3/display/current-status` no longer answers `mode: null` over the
+  control socket (#735) once the same mode has been on screen for more than
+  two minutes: a live game under live priority, Vegas, or a single plugin.
+  On ledpi it returned nulls in every sample for 90 minutes while the
+  display was live. The state stream's version leaves out the timestamps
+  that move on every publish, and a subscriber's keepalive tick carried only
+  the loop's heartbeat. So the web interface's copy kept the
+  `display.last_updated` of the last real change, and the reader's 120 s
+  rule called it unknown. The plugin runtime section had the same problem:
+  with no plugin changing state, `/plugins/state` and the `runtime` in
+  `/plugins/installed` read `stale` after 180 s. A tick (and a `state.get`
+  answer with `since`) now carries `volatile`: the current values of those
+  timestamps (`display.last_updated`, `on_demand.last_updated` and
+  `remaining`, `plugins.published_at`), and the subscription merges them
+  into its copy. The verdicts are unchanged. A render thread that stops
+  publishing still reads as `stalled` after 60 s and as unknown after 120 s,
+  a runtime publisher that stops still goes `stale`, and a subscription that
+  goes quiet still falls back to the cache. The cache path's 120 s rule is
+  unchanged.
 
 ### Scrolling
 

docs/ADVANCED_FEATURES.md

@@ -649,7 +649,9 @@ When nothing is running on demand, `data.state` is
 > on-demand machinery is internal — drive it through the REST endpoints
 > above (or the web UI buttons). The API handlers
 > (`start_on_demand_display()` / `stop_on_demand_display()` in
-> `web_interface/blueprints/api_v3/display.py`) write a request into the cache
+> `web_interface/blueprints/api_v3/display.py`) send the request over the
+> display's control socket ([IPC_CONTROL_SOCKET.md](IPC_CONTROL_SOCKET.md)).
+> Only when the socket cannot carry it do they write it into the cache
 > manager under the `display_on_demand_request` key, which
 > `DisplayController._poll_on_demand_requests()`
 > (`src/display_controller.py`) picks up. A separate
@@ -747,8 +749,14 @@ keys helps troubleshoot stuck states.
   "timestamp": 1234567890.123
 }
 ```
-**Purpose:** Communication from web interface to display controller
-**When Set:** API endpoint receives request
+**Purpose:** Communication from web interface to display controller, as the
+fallback when the control socket cannot carry the request (deprecated; it
+will be removed in a later release)
+**When Set:** API endpoint receives a request and the display's control
+socket is unavailable (display stopped, or older than the socket or the
+command); some plugins also write it directly
+**Read:** once a second while the display serves the control socket (0.25 s
+without it), and only when the file changed since the last look
 **Auto-Cleared:** After processing or 1 hour TTL
 
 **2. display_on_demand_config** (No TTL)

docs/ARCHITECTURE.md

@@ -42,11 +42,11 @@ each other. They share three things:
 | State | Where | Written by | Read by |
 |---|---|---|---|
 | On-demand command | control socket `/run/ledmatrix/control.sock` ([IPC_CONTROL_SOCKET.md](IPC_CONTROL_SOCKET.md)) | web: `start_on_demand_display()` / `stop_on_demand_display()` in [`api_v3/display.py`](../web_interface/blueprints/api_v3/display.py), via [`src/ipc/client.py`](../src/ipc/client.py) | display: [`src/ipc/server.py`](../src/ipc/server.py) acks; the render thread applies it in `_poll_on_demand_requests()` |
-| On-demand request (fallback) | cache `display_on_demand_request` | web, when the socket fails; four plugins write it directly | display: `_poll_on_demand_requests()` |
+| On-demand request (fallback) | cache `display_on_demand_request` | web, only when the socket could not carry the request (`should_fall_back`); four plugins write it directly | display: `_poll_on_demand_requests()`, a `stat()` every 1 s while the socket is up (0.25 s without), read only when the file changed |
 | On-demand state | cache `display_on_demand_state` | display: `_publish_on_demand_state()` | web: `/api/v3/display/on-demand/status` |
 | Current screen | cache `display_current_state` | display | web: `/api/v3/display/current-status` |
 | Plugin errors | cache `plugin_error_snapshot` | display: `ErrorSnapshotPublisher` ([`src/error_aggregator.py`](../src/error_aggregator.py)) | web: `read_error_report()` for `/api/v3/errors/*` |
-| Error clear | cache `plugin_error_clear_request` | web | display |
+| Error clear | control socket `errors.clear`; cache `plugin_error_clear_request` as the fallback | web: `POST /api/v3/errors/clear` | display: applied before the socket answers; the mailbox on the error publisher's 5 s tick, read only when the file changed |
 | Font usage | cache `font_usage_snapshot` | display: `FontUsagePublisher` ([`src/font_usage.py`](../src/font_usage.py)) | web: Fonts tab |
 | Fetch statistics (requests per plugin and host) | cache `fetch_stats_snapshot` | display: `FetchStatsPublisher` ([`src/common/fetch_service.py`](../src/common/fetch_service.py)), at most once a minute on change | web: `read_fetch_stats()` for `/api/v3/plugins/fetch-stats` |
 | Plugin health | cache `plugin_health:<id>` | display (web writes on reset) | web: `/api/v3/plugins/health` |
@@ -58,11 +58,16 @@ each other. They share three things:
 
 The on-demand start route starts `ledmatrix.service` when it is not running
 (`start_service`, on by default) but never restarts a running one. The routes
-send the command over the display's control socket and get an ack; when that
-fails (a stopped display, one older than the socket) they write the mailbox
-instead, which the display reads every `ON_DEMAND_POLL_INTERVAL` (0.25s), from
-its dwell sleep, its render loops and Vegas's interrupt check as well as the
-main loop. Both ways end in the same handler, `_handle_on_demand_request()`.
+send the command over the display's control socket and get an ack; only when
+the socket could not carry it (a stopped display, one older than the socket
+or the command) do they write the mailbox instead. A display that had the
+request and refused it is answered with the error, not posted a mailbox
+copy. The display looks at the mailbox every
+`MAILBOX_POLL_INTERVAL_WITH_SOCKET` (1 s) while it serves the socket, and
+every `ON_DEMAND_POLL_INTERVAL` (0.25 s) without one, from its dwell sleep,
+its render loops and Vegas's interrupt check as well as the main loop; a
+look is one `stat()` unless the file changed. Both ways end in the same
+handler, `_handle_on_demand_request()`.
 The socket's handlers only queue; see [IPC_CONTROL_SOCKET.md](IPC_CONTROL_SOCKET.md)
 for the protocol, the permission model and the plan to retire the mailboxes.
 
@@ -138,7 +143,9 @@ loaded and when. Nothing else keeps plugin state:
 `DisplayController` right after it creates the `PluginManager`, writes the
 cache key `plugin_runtime_snapshot`: per plugin `loaded`, `state`, `error`
 (type, a redacted message of at most 200 characters, when, recoverable),
-`version` and `loaded_at`, plus `published_at`, `stale_after` and `running`.
+`version`, `loaded_at` and `modes` (the display modes `DisplayController`
+registered -- `plugin.modes` when the plugin computes them, else the
+manifest's), plus `published_at`, `stale_after` and `running`.
 The cache is on disk, usually the SD card, so it writes when something a
 reader sees changes -- throttled to once per 10 s -- and otherwise once a
 minute as a heartbeat. RUNNING, which every `update()` passes through, is
@@ -154,6 +161,9 @@ truth cannot leak into a response. `/api/v3/plugins/installed` returns
 `loaded`, `state`, `error_info`, `loaded_version` and `loaded_at` per
 plugin and `data.runtime` (`status`, `published_at`, `age_seconds`);
 `/api/v3/plugins/state` returns the same beside the desired state.
+`PluginCatalog.get_plugin_display_modes` and `find_plugin_for_mode` prefer a
+live view's `modes` to the manifest's `display_modes`, so `/display/modes`
+and on-demand see modes a plugin generates from its config (#668).
 
 **Reconciliation**
 ([`state_reconciliation.py`](../src/plugin_system/state_reconciliation.py))

docs/FONT_MANAGER.md

@@ -203,6 +203,7 @@ Current methods:
 | `measure_text(text, font)` | `(width, height, baseline)` |
 | `get_font_height(font)` | Line height |
 | `register_plugin_fonts(plugin_id, font_manifest)` | Register a plugin's fonts (core calls it at load) |
+| `forget_plugin_fonts(plugin_id)` | Drop a plugin's manifest fonts and their cached objects (core calls it when a plugin unloads) |
 | `clear_cache()` | Drop cached fonts and metrics |
 | `font_catalog` (attribute) | Family name → file path |
 
@@ -218,5 +219,6 @@ Removed in 3.8.0, after logging a deprecation warning on first call since
 | `get_performance_stats()` | — |
 | `set_override()`, `remove_override()`, `get_overrides()` | a font field in your plugin's config schema |
 | `get_manager_fonts()`, `get_detected_fonts()` | — |
-| `get_plugin_fonts()`, `unregister_plugin_fonts()` | — |
+| `get_plugin_fonts()` | — |
+| `unregister_plugin_fonts()` | `forget_plugin_fonts()` (core calls it on unload) |
 | `add_font()`, `remove_font()`, `validate_font()` | the web UI's Fonts tab |

docs/IPC_CONTROL_SOCKET.md

@@ -7,14 +7,18 @@ status. Stage 2 makes those commands land within a frame on every kind of
 screen, and adds `brightness.set` and `plugin.reload`. Stage 3 adds a state
 stream (`state.get`, `state.subscribe`), so the web interface reads what the
 display is doing from the socket instead of from cache files the display
-wrote to the SD card. The file mailbox and the cache keys stay as a fallback
-for one release.
+wrote to the SD card. Stage 4 makes the socket the only way a command goes
+while it works: the web interface writes a mailbox only when the socket
+cannot carry the request, `errors.clear` replaces the last command that
+always went through a mailbox, and the display looks at the mailboxes once
+a second, with a `stat()`. The file mailboxes and the cache keys stay as a
+fallback for one release.
 
 | | |
 |---|---|
 | Socket | `/run/ledmatrix/control.sock` (tmpfs) |
 | Served by | the display process ([`src/ipc/server.py`](../src/ipc/server.py)), started by `DisplayController.run()` |
-| Used by | the web interface ([`src/ipc/client.py`](../src/ipc/client.py)): `POST /api/v3/display/on-demand/start` and `/stop`, `POST /api/v3/plugins/update` (reload), `POST /api/v3/config/main` (brightness); and through [`web_interface/display_state.py`](../web_interface/display_state.py) (the state stream), `GET /api/v3/display/current-status`, `/display/on-demand/status`, `/plugins/installed` (`runtime`), `/plugins/state` and the reconciliations, `/health` (`display_loop`) |
+| Used by | the web interface ([`src/ipc/client.py`](../src/ipc/client.py)): `POST /api/v3/display/on-demand/start` and `/stop`, `POST /api/v3/plugins/update` (reload), `POST /api/v3/config/main` (brightness), `POST /api/v3/errors/clear`; and through [`web_interface/display_state.py`](../web_interface/display_state.py) (the state stream), `GET /api/v3/display/current-status`, `/display/on-demand/status`, `/plugins/installed` (`runtime`), `/plugins/state` and the reconciliations, `/health` (`display_loop`) |
 | Contract | [`src/ipc/contract.py`](../src/ipc/contract.py): messages, versions, framing and the socket path; both sides import it |
 | Override | `LEDMATRIX_CONTROL_SOCKET=/some/path.sock` for both processes, or `=off` to disable it |
 
@@ -85,6 +89,17 @@ one. Clients branch on `error.code`, never on the message text.
 | `plugin.reload` | `{plugin_id}` | `{plugin_id, reloaded: true, version, modes}` | queued, awaited (10 s) |
 | `state.get` | `{since?, epoch?}` | a state snapshot (see "The state stream") | answered directly |
 | `state.subscribe` | — | a state snapshot, then pushed `state` / `tick` events | answered directly, then a stream |
+| `errors.clear` | `{cutoff: number}` (epoch seconds, finite, ≥ 0) | `{request_id, cutoff, cleared}` | answered directly, once applied |
+
+`errors.clear` (stage 4) forgets the plugin errors the display recorded at
+or before `cutoff` and rewrites its error snapshot (`plugin_error_snapshot`)
+before it answers, so the web interface's next read already has it. The
+request `id` is the clear's id, which the snapshot reports as
+`applied_clear_id`. It is answered on the connection thread by a handler the
+display registers (`ControlServer(handlers=...)`, the contract's
+`DIRECT_COMMANDS`): the error aggregator and its publisher have their own
+locks, and nothing the render thread owns is touched. A display that has no
+handler answers `unknown_command`, as an older display does.
 
 `duration` is a number of seconds, or a numeric string. `0`, `null` or `""`
 mean "until stopped". `pinned` must be a real boolean: the REST route has
@@ -146,7 +161,7 @@ connection until either side hangs up:
 
 ```json
 {"v": 1, "id": "<the subscribe id>", "event": "state", "result": {...a state snapshot...}}
-{"v": 1, "id": "<the subscribe id>", "event": "tick",  "result": {"version": 7, "epoch": "…", "pid": 812, "served_at": 1790000000.1, "changed": false, "loop": {...}}}
+{"v": 1, "id": "<the subscribe id>", "event": "tick",  "result": {"version": 7, "epoch": "…", "pid": 812, "served_at": 1790000000.1, "changed": false, "loop": {...}, "volatile": {"display": {"last_updated": 1790000000.0}, "...": "..."}}}
 ```
 
 An event has `event` where a response has `ok`, which is how a reader tells
@@ -216,8 +231,14 @@ socket.
   counts within an `epoch`, one run of the display process, so a reader that
   sees a new `epoch` has a restarted display.
 - `state.get` with `since` and `epoch` from an earlier answer gets just
-  `{changed: false, version, epoch, pid, served_at, loop}` while nothing has
-  changed.
+  `{changed: false, version, epoch, pid, served_at, loop, volatile}` while
+  nothing has changed. `volatile` is `{section: {key: value}}`: the current
+  values of those ignored timestamps, which the reader merges into the copy
+  it has. They don't make a new version, but they are still news:
+  `display.last_updated` is how a reader knows the render thread is still
+  publishing, and `plugins.published_at` the runtime publisher. Without
+  them a reader's copy kept the timestamps of the last real change, so a
+  mode on screen for over 120 s read as unknown.
 - A snapshot that would not fit in a message (hundreds of plugins) is sent
   without `plugins`, and `truncated: ["plugins"]` says so. Readers then use
   the cache for that section only.
@@ -226,8 +247,10 @@ socket.
 
 - a `state` event (a full snapshot) whenever the version changes, and
 - a `tick` at least every 5 s (`SUBSCRIBE_KEEPALIVE_SECONDS`) when nothing
-  changed. It carries `loop`, so a stalled render loop shows up within one
-  tick, and it tells the reader the connection is alive.
+  changed. It is the short `changed: false` answer, so it carries `loop`
+  (a stalled render loop shows up within one tick) and `volatile` (the
+  timestamps stay as fresh as the writers keep them), and it tells the
+  reader the connection is alive.
 
 A slow reader is never sent a backlog: each event is the latest version, so
 one that falls behind skips the versions in between. A reader that has heard
@@ -359,7 +382,9 @@ place it reads the mailbox:
   Vegas iteration is on the stack (`_apply_pending_plugin_reloads`). Until
   then the current screen ends early, as it does for a WiFi notice: the
   frame loops, the dwell and Vegas's interrupt check all treat a pending
-  reload as a reason to stop (`_screen_preempted`).
+  reload as a reason to stop (the frame loops through the Arbiter's
+  mid-screen check, `Source.RELOAD`; the dwell through
+  `_plugin_reload_pending`).
 - Only the quick half of the reload runs on the render thread
   (`_start_plugin_reload`): the plugin's modes leave the rotation, its
   config subscription is dropped, and `PluginManager.detach_plugin` takes
@@ -382,7 +407,7 @@ place it reads the mailbox:
   unloads it mid-load; a disable saved meanwhile is applied once the
   reload is done. A second reload of the same plugin runs after the first.
 
-The 0.25 s floor on the mailbox read does not apply to the queue, because
+The floor on the mailbox read (0.25 s, 1 s since stage 4) does not apply to the queue, because
 draining it costs no disk read. A queued command also lets
 `_service_pending_changes()` skip its own floor.
 
@@ -410,7 +435,7 @@ Now the queue wakes the render thread:
 
 So a command lands within a millisecond or so on a static screen and in a
 dwell, and within one frame in Vegas and on a scrolling screen. The mailbox
-keeps its old delays. Commands still run only on the render thread: the
+is slower on purpose (see "The mailboxes now"). Commands still run only on the render thread: the
 connection threads only queue them and set the event. The one exception is
 the slow half of `plugin.reload` (tearing down and loading the plugin),
 which runs on its own thread. Every change to the display's state still
@@ -428,11 +453,74 @@ bookkeeping. A client's send to the render thread waking took 0.72 ms median
 Without a socket (Windows, `LEDMATRIX_CONTROL_SOCKET=off`) the waits are the
 plain sleeps they were.
 
-**Exactly once.** A command and a mailbox write for the same request share
-one `request_id`. If the client times out after the display queued the
-command and then also writes the mailbox, the display processes the request
-once. The existing `on_demand_request_id` and processed-id checks drop the
-second copy.
+**Exactly once.** Since stage 4 the web interface writes the mailbox only
+when the display never had the request (see "When the web interface falls
+back"), so a request goes one way or the other, never both. A command and a
+mailbox write for the same request still share one `request_id`, and the
+`on_demand_request_id` and processed-id checks still drop a second copy: an
+older web interface (before stage 4) wrote the mailbox after a reply timed
+out, too. The display takes such a copy out of the mailbox when it drops it.
+
+## When the web interface falls back (stage 4)
+
+The client tells a request the display never had from one it had and then
+failed. `ControlError.sent` is True once the whole request was written to a
+connected display; a refusal the display sends before reading anything
+(`forbidden`, too many connections) carries no request id, and leaves it
+False. `src.ipc.client.should_fall_back()` is the one rule every route uses:
+
+| What happened | Example reasons | Mailbox? | The route answers |
+|---|---|---|---|
+| The display never had it | `no_socket`, `refused`, `disabled`, `unsupported`, a connect or send that timed out, `forbidden` / `busy` at the door, `invalid_request` (refused by the client itself) | yes | success, `transport: "mailbox"`, `socket_error` |
+| A display too old to know it (the upgrade case) | `unknown_command`, `unsupported_version` | yes | as above |
+| The display had it and failed | `busy` (queue full), `invalid_args`, `internal`, a timeout or hang-up after the send, `bad_response` | no | `503` (`400` for `invalid_args`), `socket_error` |
+
+A display that had the request may have applied it (a reply that timed out),
+or would refuse the mailbox copy as well (bad arguments), or is stuck and
+would not read the mailbox either (a full queue). Writing the copy anyway
+only turned that into a "success". An on-demand stop with `stop_service`
+still stops the service, which ends on-demand whatever happened.
+
+Brightness and plugin reload never had a mailbox: without the socket, the
+config watcher applies the saved brightness and a reload becomes the
+restart banner, as before.
+
+### The mailboxes now
+
+| Mailbox | Written by | Read by the display | While the socket is up |
+|---|---|---|---|
+| `display_on_demand_request` | the web interface, only on fallback; plugins that predate `BasePlugin.request_on_demand()`, or run on a core without it | the render thread, `_poll_on_demand_requests()` | looked at every 1 s (`MAILBOX_POLL_INTERVAL_WITH_SOCKET`), 0.25 s without a socket |
+| `plugin_error_clear_request` | the web interface, only on fallback | the error publisher's thread, every 5 s tick | unchanged rate |
+
+A look is one `stat()` of the mailbox file (`CacheManager.file_signature`):
+`(inode, mtime, size)`, and every write renames a new file into place, so a
+new write always looks different. `MailboxWatch` reads the file only when
+that changed since the last look, so a mailbox that holds nothing new, or
+nothing at all, costs no open and no parse. A socket command never reads or
+deletes the on-demand mailbox. A start already processed is taken out of
+the mailbox instead of being re-read until it expires.
+
+A request that comes through the on-demand mailbox while the socket is up
+is logged once per writer (`came through the file mailbox although the
+control socket is up`), which names the plugins that still write it.
+
+### Plugins in the display process
+
+A plugin asks for the screen with `BasePlugin.request_on_demand()` and gives
+it back with `end_on_demand()` (see "On-demand display" in
+[PLUGIN_API_REFERENCE.md](PLUGIN_API_REFERENCE.md)). Neither goes through
+the socket or a file: `PluginManager` hands the mailbox-shaped request,
+marked `source: 'plugin'`, to `DisplayController.submit_plugin_on_demand`,
+which queues it in memory (at most `PLUGIN_ON_DEMAND_QUEUE_SIZE`, 32) from
+whatever thread the plugin called on, and wakes the render thread through
+the socket's queue flag (`ControlServer.wake()`). The render thread applies
+it in `_drain_control_commands`, after the socket's commands, through the
+same `_handle_on_demand_request`, so it lands within a frame like a socket
+command. Without a socket it lands on the next pending-changes pass (typically
+within 0.25 s). A plugin's stop ends only a session that plugin owns. The four
+plugins that wrote the mailbox (birdnet-go, mqtt-notifications, on-air,
+pomodoro-timer) use it where the core has it and write the mailbox
+otherwise.
 
 ## Robustness
 
@@ -449,9 +537,10 @@ block the render loop or crash it:
   and the connection is closed, because the next message boundary cannot be
   found. A client that disconnects mid-message is dropped silently. No
   exception from a handler leaves the connection thread.
-- **Full queue.** When the queue is full, the client gets `busy` and falls
-  back to the mailbox. A full queue means the render thread is stuck, and the
-  systemd watchdog deals with that.
+- **Full queue.** When the queue is full, the client gets `busy`, and the web
+  interface answers `503` rather than write the mailbox, which the stuck
+  render thread would not read either. A full queue means the render thread
+  is stuck, and the systemd watchdog deals with that.
 - **Awaited commands.** The wait for an awaited command's outcome happens on
   its connection thread and is bounded (`AWAIT_SECONDS`), so a stuck render
   thread costs that client `pending` and one connection slot for at most
@@ -568,15 +657,32 @@ device never touches the live display.
      an uninstall that keeps its config, still answer `restart_required`.
      They can now use a load/unload command and report the result the same
      way the update route does.
-4. **Retire the mailboxes.** After a release in which every device has had the
-   socket, the web interface stops writing `display_on_demand_request`, and
-   the display stops polling it, logging the plugins that still write it so
-   they can move to an in-process `request_display()`. The other cache keys
-   used as messages (`plugin_error_clear_request` and the remaining
-   `display_*` keys) move to the socket or to tmpfs. The display also stops
-   writing `display_current_state`, `display_on_demand_state` and
-   `plugin_runtime_snapshot` once the web interface no longer falls back to
-   them.
+4. **The mailboxes become a fallback (done).**
+   - The web interface writes a mailbox only when the socket could not carry
+     the request (`should_fall_back`); a display that had it and failed is
+     answered as that (see "When the web interface falls back").
+   - `errors.clear` replaces `plugin_error_clear_request` as the way a clear
+     reaches the display.
+   - The display looks at the on-demand mailbox once a second while the
+     socket is up, reads either mailbox only when its file changed, and logs
+     who still writes the on-demand one (see "The mailboxes now").
+   - Not changed, deliberately: config saves (the schedule, the dim
+     schedule, plugin settings) still reach the display through
+     `config.json` and its watcher, which is the setting itself rather than
+     a message; see `config.reload` under stage 2. The preview viewer marker
+     (`/tmp/led_matrix_preview_viewer`) is a presence signal the display
+     already stats at most once a second. Plugin health and metrics resets
+     write the persisted record the display publishes and do not reach the
+     running display (their routes say so); they are not mailboxes.
+5. **Remove the mailboxes (next release).** Once every device has run a
+   display with stage 4, the web interface stops writing both mailboxes and
+   the display stops reading them. The four plugins that wrote
+   `display_on_demand_request` now have an in-process way to ask for the
+   screen (`BasePlugin.request_on_demand()` / `end_on_demand()`, see
+   "Plugins in the display process"); they keep the mailbox write only as
+   their fallback on older cores. The display also stops writing `display_current_state`,
+   `display_on_demand_state` and `plugin_runtime_snapshot` once the web
+   interface no longer falls back to them.
 
 ## Checking it on a device
 
@@ -591,7 +697,18 @@ curl -s -X POST localhost:5000/api/v3/display/on-demand/start \
 If the response says `"transport": "mailbox"`, `socket_error` gives the
 reason. `no_socket` means the display is stopped or predates the socket.
 `refused` usually means the web user is not in the socket's group, which
-takes effect when the web service restarts after the user is added.
+takes effect when the web service restarts after the user is added. A `503`
+with `"transport": "socket"` means the display had the request and did not
+take it (`busy`, `timeout`, ...): nothing was written to the mailbox.
+
+An error clear:
+
+```bash
+curl -s -X POST localhost:5000/api/v3/errors/clear \
+  -H 'Content-Type: application/json' -d '{"all":true}'
+# ... "applied": true, "transport": "socket"
+sudo journalctl -u ledmatrix | grep -E "Cleared .* plugin error|file mailbox"
+```
 
 Brightness and a plugin reload:
 

docs/PLUGIN_API_REFERENCE.md

@@ -488,6 +488,78 @@ working for the plugin itself. `get_vegas_segment_width()` read the
 `vegas_panel_count` config value, which has never affected Vegas — a card's
 width comes from `get_vegas_content()` and `vegas_width_pct`.
 
+### On-demand display
+
+A plugin that reacts to something outside the rotation (an MQTT message, a
+timer, a detection) can take the screen for it, and give it back. Both
+methods are safe from any thread, including an MQTT callback: they only
+queue the request, and the display applies it on its render thread within a
+frame or so, exactly like an on-demand start or stop from the web interface.
+
+#### `request_on_demand(mode=None, duration=None, pinned=False) -> Optional[str]`
+
+Show this plugin now.
+
+- `mode`: one of the plugin's display modes; `None` for its first.
+- `duration`: seconds before the rotation resumes; `None` (or `0`) for no
+  limit, until `end_on_demand()` or the user stops it.
+- `pinned`: stay on `mode` instead of cycling through the plugin's other
+  modes.
+
+Returns the request id once the display has queued it, or `None` when
+there is no display in this process to ask (the web interface's plugin
+manager, `scripts/check_plugin.py`) or its queue is full. A bad argument
+(a `mode` that is not a string, a `duration` that is not a number) raises
+`ValueError`.
+
+#### `end_on_demand() -> Optional[str]`
+
+Give the screen back. Ends only a session this plugin owns: a session the
+user started for another plugin, or one that already ended, is left alone.
+Returns the request id once queued, or `None` as above.
+
+#### Older cores: feature detection
+
+These methods are new after core 3.8.0 (see `CHANGELOG.md`). Before them,
+plugins wrote the `display_on_demand_request` cache key (the "mailbox")
+themselves. The display reads it only once a second while the control
+socket is up, and it will be removed in a future release (see
+[IPC_CONTROL_SOCKET.md](IPC_CONTROL_SOCKET.md), stage 5). A plugin that
+must keep working on older cores checks for the method, and writes the
+mailbox only when the method is missing or answers `None`:
+
+```python
+import time, uuid
+
+def _show_alert(self):
+    if hasattr(self, "request_on_demand") and self.request_on_demand(
+            mode="my_alert", duration=15):
+        return
+    # Older core, or no display in this process: the mailbox, as before.
+    self.cache_manager.set("display_on_demand_request", {
+        "request_id": str(uuid.uuid4()), "action": "start",
+        "plugin_id": self.plugin_id, "mode": "my_alert",
+        "duration": 15, "pinned": False, "timestamp": time.time(),
+    })
+
+def _release(self):
+    if hasattr(self, "end_on_demand") and self.end_on_demand():
+        return
+    self.cache_manager.set("display_on_demand_request", {
+        "request_id": str(uuid.uuid4()), "action": "stop",
+        "plugin_id": self.plugin_id, "timestamp": time.time(),
+    })
+```
+
+Keep `ledmatrix_min_version` where it is: the fallback is what keeps the
+plugin working on older cores. A mailbox stop ends any on-demand session,
+whoever started it; `end_on_demand()` ends only the plugin's own.
+
+Both methods answer a request id only when the plugin manager returned a
+string, so a test that gives the plugin a `MagicMock()` plugin manager gets
+`None` and exercises the mailbox path. To test the new path, set
+`plugin_manager.request_on_demand.return_value = "some-id"`.
+
 > The full source for `BasePlugin` lives in
 > `src/plugin_system/base_plugin.py`. If a method here disagrees with the
 > source, the source wins — please open an issue or PR to fix the doc.
@@ -966,6 +1038,14 @@ if info:
     self.logger.info(f"Plugin: {info['name']}, Version: {info.get('version')}")
 ```
 
+#### `request_on_demand(plugin_id, mode=None, duration=None, pinned=False)` / `end_on_demand(plugin_id)`
+
+What `BasePlugin.request_on_demand()` and `end_on_demand()` call, with the
+plugin's own id. Call those instead; see
+[On-demand display](#on-demand-display). The display controller routes them
+to itself with `set_on_demand_handler()`; a plugin manager without a
+display behind it answers `None`.
+
 #### `get_all_plugin_info() -> List[Dict[str, Any]]`
 
 Get information for all plugins.

docs/REST_API_REFERENCE.md

@@ -159,14 +159,16 @@ there an unchecked checkbox — which the browser omits — is saved as
 }
 ```
 
-`restart_required` is always true here: display hardware, rotation,
-durations and general settings take effect when the display restarts, and
-the web UI shows its restart banner on the flag. (Plugin sections saved
-through this route reach the running plugin live, like
-`POST /plugins/config`.)
+`restart_required` is true when the save changed a setting that takes
+effect when the display restarts: display hardware, rotation order,
+timezone, general settings and the rest. The web UI shows its restart banner
+on the flag. It is false when the save changed only what the running display
+applies by itself, or nothing: `brightness`, the per-mode durations
+(`duration__<mode>`, `display.display_durations`) and plugin sections, which
+reach the running plugin live, like `POST /plugins/config`.
 
-A saved `brightness` is the exception: it reaches the panel without a
-restart. The route also sends it to the running display over the control
+A saved `brightness` reaches the panel without a restart. The route also
+sends it to the running display over the control
 socket (`brightness.set`), which puts it on the panel at once, and the
 response adds `"brightness_transport": "socket"`. Otherwise it is
 `"config"`, with `brightness_socket_error` giving the reason, and the
@@ -246,7 +248,10 @@ Replace the schedule configuration.
 ```
 
 A day whose `<day>_enabled` key is absent counts as enabled, with default
-times `07:00`-`23:00`. At least one day must be enabled.
+times `07:00`-`23:00`. An enabled schedule needs at least one day enabled; a
+disabled one (`"enabled": false`) may have every day off, as
+`config.template.json` ships it. A day that is off keeps the times sent for
+it, when they are valid `HH:MM`.
 
 **Response**:
 ```json
@@ -343,7 +348,11 @@ control socket ([IPC_CONTROL_SOCKET.md](IPC_CONTROL_SOCKET.md)), and `cache`
 when it came from the `display_current_state` cache key (no socket: the
 display is stopped or older, or this is Windows). A display whose render
 loop has not refreshed its state for 120 seconds is reported with every
-field `null`, either way.
+field `null`, either way. So is a stopped display: when the socket does not
+answer and the render loop's heartbeat
+(`/run/ledmatrix/display-heartbeat.json`) is absent, stale or from a process
+that is gone, the cache's last entry is not used. A display still beating
+without a socket, Windows, or a socket switched off reads the cache.
 
 ### List Display Modes
 
@@ -354,9 +363,11 @@ it. This is the list the force-display dialog offers.
 
 Send the reported `plugin_id` alongside `mode` when starting an on-demand
 display: `/display/on-demand/start` falls back to `find_plugin_for_mode` when
-`plugin_id` is omitted, and that lookup only sees modes declared in a static
-manifest — a plugin whose modes are generated (each installed Starlark app is
-one) returns 404 there.
+`plugin_id` is omitted. While the display is running, this list and that
+lookup use the modes the display registered, including ones a plugin generates
+from its config (each installed Starlark app, each soccer `custom_leagues`
+entry). With the display stopped, or for a plugin it has not loaded, both see
+only the modes its manifest declares.
 
 Triggers plugin discovery, which is otherwise lazy — so a caller that never
 opens the dashboard still gets the full list.
@@ -455,7 +466,7 @@ Request a specific plugin to display on-demand.
 - `mode` (string, optional): Display mode name (plugin_id inferred if not provided)
 - `duration` (number, optional): Duration in seconds (0 = until stopped)
 - `pinned` (boolean, optional): Pin display (pause rotation)
-- `start_service` (boolean, optional): Start the display service if it is not running (default: true). A running service is never restarted: it picks the request up within about a quarter of a second. When false and the service is stopped, the route returns 400.
+- `start_service` (boolean, optional): Start the display service if it is not running (default: true). A running service is never restarted: it picks the request up within a frame over its control socket (within about a second through the mailbox fallback). When false and the service is stopped, the route returns 400.
 
 **Response**:
 ```json
@@ -480,10 +491,19 @@ display's control socket acknowledged it (it is queued for the render thread,
 which wakes for it and applies it within a frame; see
 [IPC_CONTROL_SOCKET.md](IPC_CONTROL_SOCKET.md)), `"mailbox"` means it was
 written to the cache mailbox the display polls, as before the socket existed.
-With `"mailbox"`, `socket_error` gives the reason the socket was not used
-(`no_socket` when the display is stopped or predates the socket, `timeout`,
-`refused`, `busy`, ...). Either way the request is applied the same way;
-`request_id` is the same id in both.
+The mailbox is used only when the socket could not carry the request. With
+`"mailbox"`, `socket_error` gives the reason (`no_socket` when the display is
+stopped or predates the socket, `refused`, a connect `timeout`,
+`unknown_command` from a display too old for the command, ...). Either way
+the request is applied the same way; `request_id` is the same id in both.
+
+When the display had the request and did not take it -- a full queue
+(`busy`), bad arguments (`invalid_args`), no answer after the request was
+sent (`timeout`, `closed`) -- the route answers `503` (`400` for
+`invalid_args`) with `status: "error"` and `data: {request_id, transport:
+"socket", socket_error}`, and writes nothing to the mailbox. The stop route
+does the same, except that with `stop_service: true` it still stops the
+service and answers success.
 
 ### Stop On-Demand Display
 
@@ -2239,13 +2259,11 @@ error with `"all": true` (`max_age_hours` is then ignored).
 }
 ```
 
-The clear is asynchronous. The web interface records a request
-(`plugin_error_clear_request` in the shared cache), and the display service
-applies it within about 5 seconds, rebuilding its counts from the errors it
-keeps and republishing. Reads hide the cleared errors from the moment the
-request is recorded. Until the display service applies an age-based clear,
-`recent_errors` and `active_patterns` are already filtered but the counts
-are the old ones, and `clear_pending` is `true`.
+The clear goes to the display service over its control socket
+(`errors.clear`, see [IPC_CONTROL_SOCKET.md](IPC_CONTROL_SOCKET.md)), which
+applies it, rebuilding its counts from the errors it keeps, and republishes
+before it answers: `applied` is `true`, `transport` is `"socket"`, and
+`cleared_count` is the display's own count.
 
 ```json
 {
@@ -2253,17 +2271,30 @@ are the old ones, and `clear_pending` is `true`.
   "data": {
     "cleared_count": 13,
     "clear_requested": true,
+    "applied": true,
+    "transport": "socket",
     "request_id": "5f0c1e...",
     "cutoff": "2026-09-23T09:59:02.310000"
   },
-  "message": "Clear of all errors requested; the display service applies it within about 5 seconds"
+  "message": "Cleared all errors"
 }
 ```
 
-`cleared_count` is how many of the reported errors the clear hides. It is
+When the socket cannot carry it (the display is stopped, or older than
+`errors.clear`) the clear is asynchronous, as before: the web interface
+records a request (`plugin_error_clear_request` in the shared cache),
+`applied` is `false` and `transport` is `"mailbox"`, and the display service
+applies it within about 5 seconds. Reads hide the cleared errors from the
+moment the request is recorded. Until the display service applies an
+age-based clear, `recent_errors` and `active_patterns` are already filtered
+but the counts are the old ones, and `clear_pending` is `true`. Then
+`cleared_count` is how many of the reported errors the clear hides, and
 `null` when that cannot be known before the display service applies it (an
-age-based clear over more errors than the report lists). A request that
-could not be written to the shared cache answers `500`.
+age-based clear over more errors than the report lists).
+
+A request that could not be written to the shared cache answers `500`. A
+display that had the request and failed it (`internal`, a timeout after the
+request was sent) answers `503`, with `context.socket_error`.
 
 ---
 
@@ -2281,7 +2312,11 @@ display snapshot. `data.status` is `healthy` or `degraded`, with
 (with `heartbeat_age_seconds`), `stalled` (no heartbeat for 60s: the panel is
 frozen even if the service is active; the status turns `degraded`), or
 `not_reported` when the display writes none (not started yet, the dev server,
-Windows), which does not affect the status. Its `source` is `socket` when the
+Windows), which does not affect the status, or `stopped` (with `source:
+"service"`) when the display service is not active, the control socket does
+not answer and there is no live heartbeat; the status then turns
+`degraded`. A platform with no control socket (Windows) or a socket switched
+off never reports `stopped`. Its `source` is `socket` when the
 age came from the display's state stream over the control socket (measured
 in memory by the display) and `heartbeat_file` when it came from
 `/run/ledmatrix/display-heartbeat.json`.
@@ -2344,8 +2379,9 @@ Replace the dim schedule. `dim_brightness` is 0-100 (default 30). In
 `per-day` mode the days can be sent either as the `days` object that GET
 returns, or as the web form's flat fields (`monday_enabled`,
 `monday_start`, `monday_end`, ...). A day that is not sent counts as
-enabled with default times `20:00`-`07:00`; at least one day must be
-enabled.
+enabled with default times `20:00`-`07:00`. As for the schedule above, an
+enabled dim schedule needs at least one day enabled and a disabled one may
+have every day off.
 
 ---
 

docs/RUN_LOOP_REDESIGN.md

@@ -36,122 +36,189 @@ Each pass, in order:
 1. `loop_pass()` (watchdog). Apply a pending plugin enable/disable, then
    any plugin reloads the control socket asked for
    (`_apply_pending_plugin_reloads`; a pending reload ends the screen
-   before it, like a WiFi notice, through `_screen_preempted`). The static
-   screen's frame sleep and the dwell wait on the socket's queue instead of
-   sleeping (`_wait_frame_interval`, `_sleep_with_plugin_updates`); without
-   a socket, as in the golden traces, they are the plain sleeps.
+   before it, like a WiFi notice, as `Source.RELOAD` at the runner's
+   service points). The static screen's frame sleep and the dwell wait on
+   the socket's queue instead of sleeping (`_wait_frame_interval`,
+   `_sleep_with_plugin_updates`); without a socket, as in the golden
+   traces, they are the plain sleeps.
 2. With no modes: dwell 1 s, next pass.
 3. Poll on-demand requests and expiry, release plugins loaded only for
    on-demand, tick plugin updates, drop an expired WiFi notice, evaluate
    the schedule (an on-demand session overrides scheduled-off), apply the
    brightness target. Then gather the Arbiter's inputs
-   (`_arbiter_inputs`) and call `Arbiter.decide()`, which picks one of
-   steps 4-6 or returns `LEGACY` for steps 7-9 (stage 2).
+   (`_arbiter_inputs`) and call `Arbiter.decide()`.
 4. **Scheduled off:** blank, dwell up to 60 s. `_blank_while_scheduled_off`
 5. **Follower:** render one frame from the leader. `_run_follower_frame`
 6. **WiFi notice** (unless on-demand): draw it, dwell 0.5 s. `_show_wifi_notice`.
-   It is also polled mid-screen (`_wifi_notice_pending`): the frame loops,
-   the dwell sleep and an interrupted Vegas iteration end within about a
-   second when one arrives, and a screen cut short resumes after it.
-7. **Live priority** (unless on-demand, or Vegas keeps live content in the
-   ticker): switch to the next live mode, or resume the rotation. A game
-   that goes live during a screen is caught sooner, by
-   `_check_live_takeover` in the frame loops and the dwell sleep (at most
-   once a second, and not while a live mode is showing).
-8. **Vegas** (unless on-demand, or live content preempts it): run one
-   iteration of up to `max_cycle_duration`. A completed iteration ends the
-   pass, and so does one that yielded for a WiFi notice or the schedule.
-   Any other interrupted one falls through to step 9 in the same pass.
-9. **One screen:** pick the mode (`_resolve_active_mode`), the plugin
-   (`_plugin_for_mode`), draw the first frame through the executor
-   (`_dispatch_first_frame`). On no content, rotate at once
-   (`_note_empty_pass`, `_skip_failed_plugin_modes`). Otherwise work out the
-   bounds (`_track_dynamic_cycle`, `_resolve_durations`,
-   `_clamp_to_on_demand`) and the frame rate (`_needs_high_fps`), run the
-   125 Hz or 1 Hz frame loop, make up the minimum duration, then pick the
-   next mode (`_advance_after_screen`).
+   It also ends a running screen within about a second (the runner's
+   service points), and a screen cut short resumes after it.
+7. **The Sources below the notice:** read whether Vegas is on and make the
+   live-priority scan (`_arbiter_inputs_below_wifi`, where run() always
+   read them), and call `decide()` again. It answers OnDemand (the
+   session's current mode), Live (the next live mode, round-robin; a game
+   that goes live during a screen takes over at the next service point, at
+   most once a second), Vegas (`LEGACY`) or Rotation. `_take_plan` applies
+   the answer: a live claim or the resume when live priority ends, the
+   on-demand index.
+8. **Vegas** (`_run_vegas_iteration`): one iteration of up to
+   `max_cycle_duration`. A completed iteration ends the pass, and so does
+   one that yielded for the schedule, a reload or a WiFi notice. Any other
+   interrupted one asks `decide()` once more (`vegas_yielded`): a game that
+   stopped the ticker, or an on-demand session that started, shows next.
+9. **One screen:** pick the plugin (`_plugin_for_mode`) and hand the plan
+   to the `ScreenRunner` (`src/screen_runner.py`). It draws the first frame
+   through the executor (`_dispatch_first_frame`), has the controller fill
+   in the plugin's durations, dynamic flag and frame policy
+   (`_complete_plan`), runs the 125 Hz or 1 Hz frame loop with a service
+   point after each frame, makes up the minimum duration, and returns an
+   `Outcome`. On `PREEMPTED` the pass ends without advancing. On no
+   content, rotate at once (`_note_empty_pass`, `_skip_failed_plugin_modes`).
+   Otherwise `ArbiterState.after()` picks the next mode
+   (`_advance_after_screen`).
 
-The helpers named above were extracted in stage 1 without changing
-behaviour. Since stage 2 the choice between steps 4, 5, 6 and the rest is
-made by `Arbiter.decide()` in `src/display_arbiter.py`. The frame loops, the
-Vegas branch and every early exit are still inline in `run()`.
-
-## Target design
+## Design
 
 ```python
 def run(self):
     while True:
-        inputs = self._drain_inputs()                 # requests, schedule, config, sync
-        plan = self.arbiter.decide(self.state, inputs, clock.now())
-        outcome = self.runner.run(plan)               # ExitReason + elapsed
-        self.state = self.state.after(plan, outcome)  # rotation, on-demand index, live resume
+        inputs = self._arbiter_inputs()                     # schedule, follower, notice
+        plan = Arbiter.decide(self._arbiter_state(), inputs, now)
+        ...                                                 # off / follower / notice
+        plan = self._take_plan(Arbiter.decide(state, self._arbiter_inputs_below_wifi(inputs), now))
+        if plan.source is Source.LEGACY:                    # Vegas, until stage 4
+            plan = self._run_vegas_iteration(...)
+        outcome = runner.run(plan, plugin)                  # ExitReason + elapsed
+        if outcome.exit_reason is not ExitReason.PREEMPTED:
+            self._advance_after_screen(plan, outcome)       # ArbiterState.after
 ```
 
+The controller's attributes (`current_display_mode`, `current_mode_index`,
+`on_demand_*`, `_live_resume_index`) stay the record that the web UI, the
+control socket and the on-demand cache read. `_arbiter_state()` snapshots
+them into a frozen `ArbiterState`; the transitions are pure methods on it,
+and the controller writes their result back (`_adopt_state`).
+
 ### Sources
 
 Each kind of content is a Source. A Source looks at the state and the
 inputs and either offers a screen or passes. The Arbiter asks them in this
 order:
 
-| Order | Source | Offers a screen when | Today |
+| Order | Source | Offers a screen when | Code |
 |---|---|---|---|
-| gate | ScheduledOff | the schedule is off and no on-demand session overrides it | step 4 |
-| 1 | Follower | a sync leader is driving this panel | step 5 |
-| 2 | OnDemand | a session is active (its mode list, index, expiry and pin) | `_resolve_active_mode` |
-| 3 | Wifi | a status message is pending and on-demand is not active | step 6 |
-| 4 | Live | a live-priority plugin has live content (round-robin across several) | step 7 |
-| 5 | Vegas | Vegas is enabled and nothing above wants the panel | step 8 |
-| 6 | Rotation | always: `available_modes[current_mode_index]` | step 9 |
+| gate | ScheduledOff | the schedule is off and no on-demand session overrides it | `decide` |
+| 1 | Follower | a sync leader is driving this panel | `decide` |
+| 2 | OnDemand | a session is active (its mode list, index, expiry and pin) | `_on_demand_plan` |
+| 3 | Wifi | a status message is pending and on-demand is not active | `decide` |
+| 4 | Live | a live-priority plugin has live content (round-robin across several) | `live_pick` |
+| 5 | Vegas | Vegas is enabled and nothing above wants the panel | `LEGACY`, run by `_run_vegas_iteration` |
+| 6 | Rotation | always: the rotation's current mode | `rotation_plan` |
 
 ScheduledOff is a gate in front of the Sources because that is how it works
 today: a scheduled-off panel stays blank even for a follower, and only an
 on-demand session overrides it.
 
+The Rotation answers `state.current_mode`, not
+`available_modes[current_mode_index]`: the two agree except where something
+moved the panel off the list and the rotation carries on from there (a live
+mode no rotation entry names, or None after a session ended with no enabled
+mode to resume to), and `run()` always showed `current_display_mode`.
+
 ### Arbiter
 
 ```python
-Arbiter.decide(state, inputs, now) -> ScreenPlan
+Arbiter.decide(state, inputs, now, running=None) -> ScreenPlan
 ```
 
 `decide` is a pure function: it does no I/O, takes no locks and does not
 sleep. It can be tested with plain tables of (state, inputs, now) mapped to
-an expected plan. It returns a `ScreenPlan`:
+an expected plan.
+
+- `ArbiterState`: the current mode; the rotation and its index; the
+  on-demand session's modes, index, expiry and pin; the live resume point;
+  whether a mid-screen takeover has not shown yet. Transitions:
+  `next_on_demand`, `showing`, `claim_live`, `release_live`, `after`.
+- `ArbiterInputs`: whether the schedule has the panel on, an on-demand
+  session, a follower, the WiFi notice, the live modes (None where no scan
+  was made), whether Vegas is on and keeps live content in its ticker,
+  whether this pass's Vegas iteration has yielded, and (mid-screen) whether
+  a plugin reload is waiting.
+- `ScreenPlan`:
 
 | Field | Meaning |
 |---|---|
 | `source` | which Source won |
-| `mode`, `plugin` | what to draw (None for a blank or follower plan) |
-| `min_duration`, `max_duration` | from `_resolve_durations` and `_clamp_to_on_demand` |
+| `mode`, `plugin` | what to draw (None for a blank or follower plan); the plugin id once resolved |
+| `min_duration`, `max_duration` | from `_resolve_durations` and the on-demand bound (`on_demand_bound`), filled in after the first frame; an on-demand plan's `max_duration` is what is left of the session at `now` |
 | `dynamic` | run until the plugin's cycle completes, between min and max |
-| `frame_policy` | today `_needs_high_fps` (125 Hz or 1 Hz); see stage 5 |
+| `frame_policy` | `HIGH_FPS` or `STATIC`, today `_needs_high_fps`; see stage 5 |
 | `preemptible_by` | the Sources allowed to interrupt this plan mid-screen |
+| `notice`, `deadline`, `ends_live` | the WiFi notice; the on-demand expiry for the bound; "live priority just ended, resume the rotation first" |
+
+`decide` cannot ask a plugin anything, so the fields a plugin answers are
+filled in by the controller after the first frame, where they were always
+read (`_complete_plan`).
+
+With `running`, `decide` answers the mid-screen question instead: `running`
+itself while the screen holds, else the plan that ends it
+(`_hold_or_preempt`), in the order the frame loops always checked:
+
+1. Live: a game went live while a non-live screen runs. It is the one
+   preemption that changes the state (the rotation moves to the live mode
+   and remembers where it was), and it is claimed even when a WiFi notice
+   is also pending; the next pass shows the notice, then the game.
+2. The panel's mode moved under the screen (on-demand started, ended or
+   changed mode; the rotation was rebuilt).
+3. The schedule turned the panel off.
+4. A WiFi notice (unless on-demand outranks it), compared with its expiry.
+5. A plugin reload is waiting (between frames only).
+
+Every screen is preemptible by the gate, OnDemand, Wifi, Live, Rotation and
+a reload (`SCREEN_PREEMPTERS`), except that a live screen leaves Live out
+(`LIVE_PREEMPTERS`): live games take turns between screens. A follower and
+Vegas are looked at only between screens.
 
 ### ScreenRunner
 
 ```python
-ScreenRunner(clock: FrameClock).run(plan) -> Outcome(exit_reason, elapsed)
+ScreenRunner(clock: FrameClock, host: ScreenHost).run(plan, plugin) -> Outcome
 ```
 
 The ScreenRunner draws the first frame (`_dispatch_first_frame`), runs the
 frame loop that the plan's frame policy selects, services pending changes
 between frames, and returns one `ExitReason`:
 
-| ExitReason | Today's equivalent (golden-trace exit) |
+| ExitReason | Golden-trace exit |
 |---|---|
 | `DURATION` | target duration reached (`duration`) |
 | `CYCLE_COMPLETE` | dynamic plugin finished after its minimum (`cycle-complete`) |
-| `EMPTY` | first frame returned False (`empty`; `raised` when display() raised inside the executor) |
+| `EMPTY` | first frame returned False, or no plugin (`empty`; `raised` when display() raised inside the executor; `no-plugin`, `breaker`) |
 | `ERROR` | the dispatch itself raised (`error`) |
 | `DISPLAY_FALSE` | a later frame returned False (`display-false`) |
-| `PREEMPTED` | another Source took the panel (`on-demand-*`, `schedule-off`, `vegas-interrupt`, ...) |
+| `PREEMPTED` | another Source took the panel (`on-demand-*`, `schedule-off`, `live`, `wifi`, ...) |
+| `RELOAD` | a plugin reload is waiting: the screen ends early but counts as shown, and the rotation advances |
 
 `PREEMPTED` replaces the five `current_display_mode != active_mode` checks.
-The runner asks the Arbiter, at the throttled service points it already has,
-whether a Source in `plan.preemptible_by` now wants the panel.
+The runner asks its host at named service points (`Checkpoint`): `FRAME`
+after each frame (and when a socket command wakes the 1 Hz wait),
+`AFTER_LOOP` / `AFTER_COMPLETED_LOOP` when the frame loop ends,
+`after_dwell` after the make-up dwell, and `FINAL` before the rotation
+advances. Each is one `decide(..., running=plan)` call
+(`DisplayController._screen_check`). The checkpoint says whether a pending
+reload counts there and when the WiFi notice file is read (`NoticeRead`):
+the read is throttled to once a second and deletes an expired file, so it
+happens exactly where the loop always read it.
 
-`FrameClock` provides `now()` and `sleep()`. In production it is
-`time.monotonic`/`time.sleep`. In the golden traces it is the fake clock
-that the harness patches in today.
+In the 125 Hz loop the live-priority scan is made before the frame's sleep
+(`_screen_service`), at the moments it always was, and weighed by the
+service point after the sleep, where the loop always decided to end the
+screen.
+
+`FrameClock` provides `time()`, `perf_counter()` and `sleep()`, the shape of
+the `time` module. In production it is `_ModuleClock`, which looks up
+`src.display_controller.time` on each call, so the golden traces' fake clock
+drives the runner as it drove the inline loops. The runner's log lines use
+the controller's logger, so they keep their source in the journal.
 
 ## Stages
 
@@ -181,13 +248,14 @@ that the harness patches in today.
   - dynamic duration (cycle complete, plugin cap, global cap)
   - live priority taking over and handing back; live round-robin
   - on-demand start/stop/expiry; pinned on-demand; a session resumed after
-    a restart
+    a restart, and one that cannot resume (its plugin did not load); a
+    request naming a live mode the plugin's live check would drop
   - schedule off and dim, with an on-demand override during downtime
   - WiFi notice; sync follower
   - Vegas, with and without `live_in_ticker`
 - Each trace row is `[start, mode, duration, exit_reason, frames,
   force_clear]`. The exit reason is the event that decided what came next.
-- All 16 tests run in under a second. The goldens were generated from
+- All 18 tests run in under a second. The goldens were generated from
   main's `run()` before any code moved.
 - Vegas uses `FakeVegas`, which implements only the contract the controller
   depends on: `run_iteration()` returns True after its duration and False
@@ -249,37 +317,84 @@ What shipped:
   Source, the dwells, the expiry comparison, the snapshot's reads, each
   dispatch in `run()`); every one failed a test.
 
-### Stage 3: ScreenRunner and `PREEMPTED`
+### Stage 3: ScreenRunner and `PREEMPTED` (done; awaiting the ledpi soak)
 
-Move the two frame loops, the make-up dwell and the dynamic-duration exit
-into `ScreenRunner.run(plan)` with an injected `FrameClock`. Replace the
-five re-checks with `PREEMPTED`. Add the OnDemand, Live and Rotation Sources
-so `LEGACY` is left meaning only Vegas.
-
-Concretely, from where stage 2 left off:
+The plan, from where stage 2 left off:
 
 1. `ArbiterState` gains the rotation index, the on-demand mode list, index,
-   expiry and pin, and the live resume point (today `current_mode_index`,
-   `on_demand_*` and the live-priority stash). `ArbiterInputs` gains the
-   live modes (`_collect_live_modes`) and whether Vegas is enabled and keeps
-   live content in the ticker.
-2. OnDemand returns its current mode with `_clamp_to_on_demand`'s bound,
-   reading `now` for the expiry. Live returns the next live mode
-   (round-robin). Rotation returns `available_modes[current_mode_index]`.
-   `ScreenPlan` gains `mode`, `plugin`, `min_duration`, `max_duration`,
-   `dynamic`, `frame_policy` and `preemptible_by`.
-3. `ScreenRunner.run(plan)` returns an `ExitReason`; `state.after(plan,
-   outcome)` replaces `_advance_after_screen` and the live-resume
-   bookkeeping. Each mid-screen check asks `decide()` whether a Source in
-   `plan.preemptible_by` now wins, so `_screen_preempted`,
-   `_check_live_takeover` and `_wifi_notice_pending` become one call.
+   expiry and pin, and the live resume point. `ArbiterInputs` gains the
+   live modes and whether Vegas is enabled and keeps live content in the
+   ticker.
+2. OnDemand returns its current mode with the session's bound, reading
+   `now` for the expiry. Live returns the next live mode (round-robin).
+   Rotation returns the rotation's mode. `ScreenPlan` gains `mode`,
+   `plugin`, `min_duration`, `max_duration`, `dynamic`, `frame_policy` and
+   `preemptible_by`.
+3. `ScreenRunner.run(plan)` returns an `ExitReason`; `state.after(outcome)`
+   replaces `_advance_after_screen`'s step and the live-resume bookkeeping.
+   Each mid-screen check asks `decide()` whether a Source in
+   `plan.preemptible_by` now wins.
 4. The control socket (`_drain_control_commands`, `_wait_for_control`) and
    state publishing stay where they are; the runner calls them at its
    service points.
 
+What shipped, one commit each: the runner; then the OnDemand, Live and
+Rotation Sources; then one `decide()` call at the service points.
+
+- `src/screen_runner.py` (on the mypy ratchet): `ScreenRunner`,
+  `FrameClock`, `ExitReason`, `Outcome`, `Checkpoint`, `NoticeRead`,
+  `Screen` and the `ScreenHost` protocol, which `DisplayController`
+  implements through `_ScreenHost` (one-line forwards to its own methods).
+  The two frame loops, the make-up dwell and the dynamic-duration exit
+  moved in unchanged, pacing included.
+- `src/display_arbiter.py`: `Source` gains `ON_DEMAND`, `LIVE`, `ROTATION`
+  and `RELOAD`; `LEGACY` means only Vegas. `FramePolicy`. `ArbiterState`
+  and `ArbiterInputs` as listed under "Arbiter". The pure helpers
+  `on_demand_bound` (`_clamp_to_on_demand`), `live_pick`
+  (`_check_live_priority`'s pick), `live_takeover` (the mid-screen claim)
+  and `rotation_plan`.
+- A pass asks `decide()` twice: once with the inputs every pass reads, and
+  once, only when nothing above the notice took the panel, with the Vegas
+  check and the live scan, read where run() always read them (the scan
+  asks every live-priority plugin, and the Vegas check applies queued
+  Vegas config, so reading them earlier, on a follower or notice pass,
+  would be a change). A Vegas iteration that yields asks a third time.
+- `_resolve_active_mode`, `_clamp_to_on_demand` and `_screen_preempted` are
+  gone. `_apply_live_priority`, `_check_live_priority`,
+  `_check_live_takeover` and `_wifi_notice_pending` remain (Vegas, the
+  dwell sleep and the tests call them), built on the same pure rules.
+- `_sleep_with_plugin_updates` keeps its own break rules. It also serves
+  the blank, the notice and the idle wait, which are not screens, and its
+  rules are edge-triggered (an on-demand session starting on the mode
+  already showing ends a dwell but not a frame loop); folding them into
+  `decide()` would change behaviour.
+
+Behaviour, checked three ways:
+
+- Golden traces: unchanged, no regeneration.
+- Every harness run in the suite (67: the goldens plus the live-takeover,
+  WiFi+live, socket-wake, plugin-reload, schedule and tick tests) was
+  captured with every sleep, `display()` call, WiFi read, live scan,
+  publish, dwell and scroll-state call logged, and diffed against
+  `origin/main`. Identical, except:
+  - a Vegas pass used to scan the live plugins twice at the same instant
+    (step 7, then step 8's "is anything live?"); it scans once;
+  - `_apply_live_priority(None)` calls that changed nothing are not made;
+  - throttled WiFi reads that returned the cached answer (no side effect)
+    after a notice had already ended the screen are not made;
+  - in the 125 Hz loop the live scan still runs before the frame's sleep,
+    but the claim is made by the service point after it, so the "live"
+    state change happens 8 ms later. The screen ends at the same frame as
+    before.
+- Tables: `test/test_display_arbiter.py` (OnDemand, Live, Vegas/Rotation,
+  `after`, the 24-row mid-screen table, `live_takeover`) and
+  `test/test_screen_runner.py` (the runner on a scripted host and fake
+  clock; the controller's service point and the reads it makes). A
+  mutation run broke each moved or new piece once; see the PR.
+
 This stage touches frame pacing (the 8 ms deadline sleep, the 1 ms yield),
-so it needs a frame soak on ledpi, A/B against main. Coordinate with
-whoever owns scroll performance (`docs/SCROLL_PERFORMANCE.md`).
+so it needs a frame soak on ledpi, A/B against main, before it merges.
+Coordinate with whoever owns scroll performance (`docs/SCROLL_PERFORMANCE.md`).
 
 ### Stage 4: Vegas as a Source
 
@@ -344,3 +459,13 @@ PR that updates the affected trace and explains why. All six are fixed:
 
 A new one found later goes the same way: record it here with the trace that
 shows it, then fix it in its own PR, not inside a restructure stage.
+
+Open:
+
+- Vegas stops for a sync follower (its interrupt check includes
+  `is_follower_active`), but the yield path never looks at a follower, so a
+  full rotation screen (20 s in the test) runs before the next pass hands
+  the panel to the leader. Found by stage 3's mutation run;
+  `test_screen_runner.py::TestThroughRun::test_vegas_yielding_to_a_follower_shows_a_rotation_screen_first`
+  pins it. Stage 4, which drops the interrupt callback, is the natural
+  place to fix it.

docs/WEB_FRONTEND_ARCHITECTURE.md

@@ -81,6 +81,14 @@ The conventions the converted pages share:
   to the module's export of the same name and warns once.
 - **Timers are cleared in `destroy()`**, the one thing `ctx.signal` cannot
   undo by itself.
+- **A page reports its own htmx saves.** A form whose result a page module
+  shows (an `htmx:afterRequest` listener on the page root, in place of an
+  `hx-on` attribute naming a global) carries `data-reports-result`. `app.js`
+  then leaves the server's message to the page, as it does for a form with
+  an `hx-on` after-request handler, so a save shows one notification.
+- **Server data for the module goes in `data-*` attributes**, as JSON where
+  it is structured (`data-schedule-config='{{ schedule_config | tojson }}'`),
+  not templated into a script.
 
 `core/registry.js` handles the rest:
 
@@ -239,8 +247,8 @@ are the inline script in each partial today.
 | 3 | Operation History | 293 lines, now 0 | **Done in stage 2.** Read-only list; rows drawn with `textContent`, the search debounce cleared on destroy. The "Showing x to y" counters now also reset when nothing matches |
 | 4 | Config Editor (`raw_json.html`) | 212 lines, now 0 | **Done in stage 2.** Plain textareas (no CodeMirror on this page). It defined 5 globals after all (`formatJson`, `manualValidateJson`, `validateJSON`, `saveMainConfig`, `saveSecretsConfig`); nothing else used them, and they are deprecated aliases now. The live "Invalid JSON" line no longer puts the parser's message into `innerHTML` |
 | 5 | Backup & Restore | 232 lines, now 0 | **Done in stage 2.** Its 5 globals (`exportBackup`, `loadBackupList`, `validateRestoreFile`, `clearRestore`, `runRestore`) are deprecated aliases; the buttons are delegated `data-action`s. Uploads go through `ctx.api.request(..., { body: formData })` (`api.js` gained a raw `body` option) |
-| 6 | Schedule | 193 | 2 globals used as `hx-on` response handlers. Moves `hx-on` handlers into page listeners |
-| 7 | General | 147 | `webLogin` global and the security section. The first page that touches login |
+| 6 | Schedule | 193 lines, now 0 | **Done in stage 3.** Its 2 `hx-on` response handlers (`handleScheduleResponse`, `handleDimScheduleResponse`) are one `htmx:afterRequest` listener on the page root, and deprecated aliases. The forms are marked `data-reports-result` so `app.js` does not repeat the server's message. The saved schedules reach the module as JSON in `data-schedule-config` / `data-dim-schedule-config` instead of being templated into the script |
+| 7 | General | 153 lines, now 0 | **Done in stage 3.** The Security section's three forms and two buttons are delegated `data-action`s (one submit and one click listener); `window.webLogin` is a deprecated alias of an object with its five methods. Login requests go through `ctx.api`, so the login redirect is quiet. The settings form keeps its `hx-on` call to the shared `showSaveResult`, as Rotation's does |
 | 8 | Display | 231 | First page with `LEDVisibility` timers: those move to a `ctx.visibility` service that stops on destroy |
 | 9 | Overview | 410 (4 scripts) | First-run surface: Getting Started, update banner, live preview. Five globals |
 | 10 | WiFi | 364 | `x-data="wifiSetup()"` is defined by its own script. Moves to `Alpine.data()` registered from the module. AP-mode first screen, so it needs the AP-mode test on a real device |
@@ -284,6 +292,8 @@ Unit suites need only node. They import the shipped modules directly:
 | `dom/test_durations_page.js` | DOM: real partial, real widget, real API shape | One plugin-list request per swap; Move down moves one place after five swaps; the swap cancels a request in flight; a late-loading widget is waited for, and a page swapped away while waiting starts nothing; hostile names stay text |
 | `dom/test_operation_history_page.js` | DOM: real partial, real API shape | One history request per swap and per Refresh; the plugin filter filled once (from `PluginAPI`'s cache when loaded); paging, filters, debounced search, Clear (one DELETE), error/network/login states, cancel on swap; hostile ids, users and errors stay text |
 | `dom/test_raw_json_page.js` | DOM: real partial, real config | One POST per Save after five swaps, to the right file; Format and Validate act once; invalid JSON never sent and its message stays text; a save survives a swap and is still reported; the old globals' entry points |
+| `dom/test_schedule_page.js` | DOM: real partial, real widget | Both pickers drawn once per swap from the saved config; after five swaps each form's answer is one notification (message, fallback, refused, non-JSON, `null`), a request from outside the forms none; the brightness label; a late widget waited for, a page swapped away while waiting draws nothing; the old globals' entry points |
+| `dom/test_general_page.js` | DOM: real partial, real widget, real API shape | The timezone picker drawn once per swap with the saved zone; the settings form left to htmx; after five swaps each Security action makes one request (create, copy, revoke and its cancel, password and its mismatch); hostile token names stay text; refused, network and login answers; a create made before a swap is still reported and draws nothing; `webLogin`'s entry points |
 | `dom/test_backup_restore_page.js` | DOM: real partial, real API shape | One request per Refresh, Delete, Export (busy button ignores a second click), Inspect and Restore after five swaps; the upload's fields and the six restore options; reads cancelled by a swap, writes not; hostile file and host names stay text; the old globals' entry points |
 | `test/web_interface/test_es_modules.py` | pytest | MIME type; `no-cache` without `?v` and immutable with it; `boot.js` loads last; every import resolves inside `core/` and `pages/`; the converted pages are exactly the registered ones, each with its module, `init`, and one root in the rendered partial; a converted partial has no `<script>` and no `onclick`; every moved global is aliased in `boot.js` and exported by its module, and no template defines it any more |
 | `test/test_field_model_parity.py` | pytest | The model against the macro for every available schema |

mypy-clean.txt

@@ -88,6 +88,7 @@ src/plugin_system/testing/vegas.py
 src/plugin_system/vegas_elements.py
 src/redaction.py
 src/scan_order.py
+src/screen_runner.py
 src/startup_validator.py
 src/vegas_mode/__init__.py
 src/vegas_mode/config.py

src/backup_manager.py

@@ -213,8 +213,9 @@ def list_installed_plugins(project_root: Path) -> List[Dict[str, Any]]:
     The plugins are the ``manifest.json`` files in the configured plugin
     directory (see :func:`_plugins_directory`), with the manifest's version;
     ``enabled`` is config.json's flag by the display's rule (a missing flag
-    is disabled). A restore reinstalls every listed plugin and takes enabled
-    state from the restored config.json, so ``enabled`` is informational.
+    is disabled). A restore installs each listed plugin that is missing and
+    takes enabled state from the restored config.json, so ``enabled`` is
+    informational.
 
     ``data/plugin_state.json`` is not read: it only ever repeated config's
     enabled flags and the manifests' versions, and is retired (nothing

src/cache/disk_cache.py

@@ -4,6 +4,7 @@ Disk Cache
 Handles persistent disk-based caching with atomic writes and error recovery.
 """
 
+import hashlib
 import json
 import math
 import os
@@ -31,6 +32,35 @@ except ImportError:  # pragma: no cover - exercised on hosts without the wheel
 # useful, and a half-written file was never useful.
 _ORPHAN_TEMP_MAX_AGE_SECONDS = 3600
 
+# Longest key, in UTF-8 bytes, used verbatim as a filename stem. ext4 caps a
+# name at 255 bytes and set()'s temp file is ".<stem>.json.<8 random>", 15
+# bytes longer than the stem, so anything near the cap could never be written:
+# the calendar plugin's key joins every calendar id and passed 300 bytes on a
+# real install, failing every write with ENAMETOOLONG. Longer keys keep this
+# many bytes as a readable prefix and end in a hash of the whole key.
+_MAX_KEY_FILENAME_BYTES = 200
+_KEY_HASH_CHARS = 16
+
+
+def _filename_stem(key: str) -> str:
+    """The filename stem for a key that is already a safe path component.
+
+    Short keys are used as they are, so every file already on disk keeps its
+    name. A long one becomes its first bytes plus a hash of the full key: the
+    prefix keeps the stem recognisable (and keeps the data-type words that
+    cleanup's retention lookup reads from it), the hash keeps two keys that
+    share a long prefix apart. The result is itself short, so a stem read back
+    from a filename -- which is how the web UI names a key it deletes -- maps to
+    the same file.
+    """
+    encoded = key.encode('utf-8')
+    if len(encoded) <= _MAX_KEY_FILENAME_BYTES:
+        return key
+    digest = hashlib.sha256(encoded).hexdigest()[:_KEY_HASH_CHARS]
+    keep = _MAX_KEY_FILENAME_BYTES - _KEY_HASH_CHARS - 1
+    prefix = encoded[:keep].decode('utf-8', errors='ignore')
+    return f"{prefix}-{digest}"
+
 
 
 class CacheStrategyProtocol(Protocol):
@@ -343,6 +373,8 @@ class DiskCache:
         derives them), so rejecting anything with a path component turns
         away only inputs that could never have been written here.
 
+        A key too long to be a filename is shortened by _filename_stem.
+
         Args:
             key: Cache key
 
@@ -356,7 +388,7 @@ class DiskCache:
         if safe_key is None:
             self.logger.warning("Rejected unsafe cache key %r", key)
             return None
-        return os.path.join(self.cache_dir, f"{safe_key}.json")
+        return os.path.join(self.cache_dir, f"{_filename_stem(safe_key)}.json")
     
     def get(self, key: str, max_age: Optional[int] = 300) -> Optional[Dict[str, Any]]:
         """
@@ -561,7 +593,7 @@ class DiskCache:
                             # If direct write also fails, try fallback location
                             self.logger.warning("Direct write failed for key '%s' to %s: %s", key, cache_path, write_error)
                             raise  # Re-raise to trigger fallback logic
-                except (IOError, OSError, PermissionError):
+                except (IOError, OSError, PermissionError) as primary_error:
                     # Attempt one-time fallback write to user's home cache directory
                     try:
                         # Try user's home cache directory as fallback
@@ -587,11 +619,14 @@ class DiskCache:
                         self.logger.debug("Fallback cache write also failed for key '%s': %s", key, e2)
                     
                     # If all write attempts failed, log warning but don't raise exception
-                    # Cache is a performance optimization, not critical for operation
+                    # Cache is a performance optimization, not critical for operation.
+                    # Name the real error: this used to say "permission denied"
+                    # whatever happened, which sent a too-long filename off to
+                    # be debugged as a directory-ownership problem.
                     self.logger.warning(
-                        "Could not write cache for key '%s' to %s (permission denied). "
+                        "Could not write cache for key '%s' to %s (%s). "
                         "Cache will be unavailable for this key, but application will continue.",
-                        key, cache_path
+                        key, cache_path, primary_error.strerror or primary_error
                     )
                     return  # Exit gracefully without raising exception
         

src/cache_manager.py

@@ -28,7 +28,7 @@ import os
 import time
 from datetime import datetime
 import pytz
-from typing import Any, Dict, List, Optional
+from typing import Any, Dict, List, Optional, Tuple
 import logging
 import threading
 import tempfile
@@ -46,6 +46,69 @@ from src.cache.disk_cache import DateTimeEncoder  # noqa: F401 - deliberate re-e
 # CacheManager.config_manager not built yet (None means "not available").
 _UNSET: Any = object()
 
+
+def _outlived(record: Any, max_age: Optional[float], now: float) -> bool:
+    """Whether a record's own timestamp puts it past max_age.
+
+    The memory tier times an entry from when it was put there, and a record
+    loaded from disk is put there when it is read, not when it was written: a
+    record 290 s old, read after a restart, could be served for another
+    max_age from memory. This is the age check DiskCache.get makes, with the
+    same rule that a stored ttl wins over the caller's max_age. A record that
+    carries no timestamp is left to the memory tier's own clock.
+    """
+    if not isinstance(record, dict):
+        return False
+    stored_ttl = record.get('ttl')
+    if isinstance(stored_ttl, (int, float)) and not isinstance(stored_ttl, bool) \
+            and stored_ttl >= 0:
+        max_age = stored_ttl
+    stamp = record.get('timestamp')
+    if max_age is None or stamp is None or isinstance(stamp, bool):
+        return False
+    try:
+        return now - float(stamp) > max_age
+    except (TypeError, ValueError):
+        return False
+
+
+_NOT_SEEN: Any = object()
+
+
+class MailboxWatch:
+    """Tells the poller of a mailbox key whether its file changed since the
+    last look, from one stat() (:meth:`CacheManager.file_signature`).
+
+    The display polls the mailboxes the web interface falls back to. Reading
+    one is an open and a JSON parse; with this a poll that finds the same file
+    (or none) costs a stat, and the file is read only after a new write. A
+    cache without ``file_signature`` (a test double) is read every time.
+    """
+
+    def __init__(self, key: str):
+        self.key = key
+        self._seen: Any = _NOT_SEEN
+
+    def changed(self, cache_manager: Any) -> bool:
+        """True when the poller should read the key now."""
+        signature = getattr(cache_manager, 'file_signature', None)
+        sig = signature(self.key) if callable(signature) else _NOT_SEEN
+        if sig is not None and not isinstance(sig, tuple):
+            return True   # cannot tell: read it
+        if sig is None:
+            self._seen = None
+            return False   # no file, nothing to read
+        if sig == self._seen:
+            return False
+        self._seen = sig
+        return True
+
+    def forget(self) -> None:
+        """Read the key on the next poll even if its file has not changed
+        (the last read failed)."""
+        self._seen = _NOT_SEEN
+
+
 class CacheManager:
     """Manages caching of API responses to reduce API calls."""
 
@@ -269,7 +332,25 @@ class CacheManager:
     def _get_cache_path(self, key: str) -> Optional[str]:
         """Get the path for a cache file."""
         return self._disk_cache_component.get_cache_path(key)
-        
+
+    def file_signature(self, key: str) -> Optional[Tuple[int, int, int]]:
+        """``(st_ino, st_mtime_ns, st_size)`` of ``key``'s file, or None when
+        there is no file (the key is absent, or this cache has no disk tier).
+
+        One stat(), no read: a poller of a mailbox another process writes
+        compares it with the last one it saw and reads the file only when it
+        changed. Every write replaces the file (a temp file renamed into
+        place), so a new write always has a new inode, however fast it came.
+        """
+        path = self._get_cache_path(key)
+        if not path:
+            return None
+        try:
+            st = os.stat(path)
+        except OSError:
+            return None
+        return (st.st_ino, st.st_mtime_ns, st.st_size)
+
     def get_cached_data(self, key: str, max_age: int = 300, memory_ttl: Optional[int] = None) -> Optional[Dict[str, Any]]:
         """Get data from cache (memory first, then disk) honoring TTLs.
 
@@ -284,7 +365,11 @@ class CacheManager:
         # 1) Memory cache
         cached = self._memory_cache_component.get(key, max_age=in_memory_ttl)
         if cached is not None:
-            return cached
+            if not _outlived(cached, max_age, time.time()):
+                return cached
+            # Too old for this reader. Disk may hold a newer write (from the
+            # other process), and if it does not, the miss is the right answer.
+            self._memory_cache_component.clear(key)
 
         # 2) Disk cache
         record = self._disk_cache_component.get(key, max_age=max_age)
@@ -318,7 +403,9 @@ class CacheManager:
         # Check memory cache first (1 minute TTL)
         cached = self._memory_cache_component.get(key, max_age=60)
         if cached is not None:
-            return cached
+            if not _outlived(cached, 3600, time.time()):
+                return cached
+            self._memory_cache_component.clear(key)
         
         # Check disk cache
         data = self._disk_cache_component.get(key, max_age=3600)  # 1 hour for load_cache

src/common/README.md

@@ -109,8 +109,11 @@ and the plugin test harness all use it. Most plugins get BDF text through
 [`espn_dates.py`](espn_dates.py). ESPN's site API rejects `dates=` ranges
 and truncates results when `limit` is above 500. `fetch_espn_scoreboard()`
 splits a range into month and day requests ESPN accepts and merges the
-results; `espn_date_chunks()`, `fetch_espn_date_chunks()`,
-`clamp_espn_limit()` and `merge_scoreboard_payloads()` are the pieces.
+results; `espn_date_chunks()`, `espn_request_chunks()`,
+`fetch_espn_date_chunks()`, `clamp_espn_limit()` and
+`merge_scoreboard_payloads()` are the pieces. A window's partial edge months
+are asked whole and trimmed to its days (US Eastern), and chunk requests share
+one process-wide cap of `ESPN_CHUNK_WORKERS` in flight.
 Every request goes through [`fetch_service`](#fetch_service), the chunks
 counted against the plugin that asked. Scoreboard plugins also bundle a copy
 for older cores.

src/common/espn_dates.py

@@ -26,10 +26,30 @@ A month can hold more than 500 events (college baseball's March does), and
 ESPN answers that with exactly ``limit`` events and no hint that more exist. A
 month chunk that comes back full is therefore re-asked day by day.
 
+A window's *partial* edge months are asked for whole, too, once the window
+covers ``ESPN_MONTH_COVER_MIN_DAYS`` or more of their days, and the answer is
+trimmed back to the window's days. A scoreboard's default fortnight either side
+of today (29 days, two partial months) was 29 day requests per league; it is
+now 2. Trimming needs ESPN's "game day", which is the event's start in US
+Eastern time -- checked against the live API on 2026-10-03: 417 of 417 soccer
+events across five leagues and three months (one of them spanning the end of
+daylight saving) came back from exactly the day query their Eastern date
+names. A short window (a live poll's one or two days) stays day by day, so it
+never downloads a whole month to read a day of it.
+
+Chunk requests share one process-wide budget of ``ESPN_CHUNK_WORKERS`` in
+flight, however many windows are being fetched at once. Each window used to get
+its own six, so a scoreboard starting eight leagues -- each with a recent and
+an upcoming manager -- had ~40 requests in flight, every one beyond a session's
+pool a new connection and a new DNS lookup. On a Pi whose resolver could not
+keep up, that was ~90 ``NameResolutionError`` lines within a minute of every
+start.
+
 Once a range has been rejected, later ranges skip straight to chunks for
 ``RANGE_RETRY_SECONDS`` instead of spending a doomed request first -- live
 scoreboards ask every 30 seconds. After that the range is tried again, so the
-workaround retires itself if ESPN reverts.
+workaround retires itself if ESPN reverts. A process starts inside that
+period, as if a range had just been rejected.
 
 ONE CACHE KEY PER SCOREBOARD
 ----------------------------
@@ -55,7 +75,7 @@ import re
 import threading
 import time
 from concurrent.futures import ThreadPoolExecutor
-from datetime import date, datetime, timedelta
+from datetime import date, datetime, timedelta, tzinfo
 from functools import partial
 from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple, cast
 
@@ -100,16 +120,57 @@ RANGE_RETRY_SECONDS = 6 * 60 * 60
 # pool_maxsize of 10 so the shared Session never has to discard connections.
 ESPN_CHUNK_WORKERS = 6
 
+#: An edge month the window covers at least this many days of is asked for
+#: whole and trimmed, instead of one request per day (see module docstring).
+#: Below it the days are cheaper than the month: a whole month is two to
+#: three times the bytes of the half of it a fortnight window holds.
+ESPN_MONTH_COVER_MIN_DAYS = 7
+
+# Every chunk request in the process holds one of these while it is in flight
+# -- the cap is per process, not per window (see module docstring).
+_chunk_slots = threading.BoundedSemaphore(ESPN_CHUNK_WORKERS)
+
+
+def _eastern_zone() -> Optional[tzinfo]:
+    """US Eastern, the zone ESPN's ``dates=YYYYMMDD`` means, or None when
+    this Python has no time zone data (no edge month is trimmed then)."""
+    zone: Optional[tzinfo] = None
+    try:
+        from zoneinfo import ZoneInfo
+        zone = ZoneInfo("America/New_York")
+    except Exception:  # noqa: BLE001 - no zoneinfo module or no tz database
+        zone = None
+    if zone is not None:
+        return zone
+    try:
+        import pytz
+        return cast(tzinfo, pytz.timezone("America/New_York"))
+    except Exception:  # noqa: BLE001
+        return None
+
+
+_EASTERN = _eastern_zone()
+
+# What _fetch_one_chunk returns for a month that came back at the cap.
+_CAPPED: Any = object()
+
 _range_lock = threading.Lock()
-_ranges_rejected_until = 0.0
+# A process starts out assuming ranges are still rejected, as they have been
+# since 2026-09-15, and tries one again RANGE_RETRY_SECONDS in. Starting
+# from "unknown" cost one doomed range request per window at every start --
+# eleven 400s at once from a soccer board, each fetching before any had
+# answered -- to learn what every start learns.
+_ranges_rejected_until = time.monotonic() + RANGE_RETRY_SECONDS
 
 __all__ = [
     "ESPN_MAX_LIMIT",
     "ESPN_CHUNK_WORKERS",
+    "ESPN_MONTH_COVER_MIN_DAYS",
     "RANGE_RETRY_SECONDS",
     "clamp_espn_limit",
     "parse_espn_date_range",
     "espn_date_chunks",
+    "espn_request_chunks",
     "merge_scoreboard_payloads",
     "fetch_espn_date_chunks",
     "fetch_espn_scoreboard",
@@ -220,6 +281,79 @@ def espn_date_chunks(start: date, end: date) -> List[str]:
     return chunks
 
 
+def espn_request_chunks(
+    start: date,
+    end: date,
+    month_cover_min_days: Optional[int] = None,
+) -> List[Tuple[str, Optional[Tuple[date, date]]]]:
+    """The requests that fetch ``[start, end]``, as ``(dates, trim)`` pairs.
+
+    :func:`espn_date_chunks`, except that a partial edge month with
+    ``month_cover_min_days`` (default ``ESPN_MONTH_COVER_MIN_DAYS``) or more
+    of its days in the window becomes one ``YYYYMM`` request whose ``trim``
+    is the first and last of those days: its events that start outside them
+    (US Eastern) are dropped. ``trim`` is None for every other request.
+    Without time zone data nothing can be trimmed, so the edge days stay day
+    requests.
+    """
+    if month_cover_min_days is None:
+        month_cover_min_days = ESPN_MONTH_COVER_MIN_DAYS
+    planned: List[Tuple[str, Optional[Tuple[date, date]]]] = []
+    run: List[str] = []
+
+    def flush() -> None:
+        if (_EASTERN is not None and month_cover_min_days > 0
+                and len(run) >= month_cover_min_days):
+            planned.append((run[0][:6], (_parse_day(run[0]), _parse_day(run[-1]))))
+        else:
+            planned.extend((day, None) for day in run)
+        run.clear()
+
+    for chunk in espn_date_chunks(start, end):
+        if run and (len(chunk) != 8 or chunk[:6] != run[0][:6]):
+            flush()
+        if len(chunk) == 8:
+            run.append(chunk)
+        else:
+            planned.append((chunk, None))
+    flush()
+    return planned
+
+
+def _parse_day(text: str) -> date:
+    return date(int(text[:4]), int(text[4:6]), int(text[6:8]))
+
+
+def _eastern_day(stamp: Any) -> Optional[date]:
+    """The US Eastern date of an ESPN event ``date`` ("2026-10-10T11:30Z"),
+    or None when it cannot be read."""
+    if not isinstance(stamp, str) or _EASTERN is None:
+        return None
+    try:
+        moment = datetime.fromisoformat(stamp.strip().replace("Z", "+00:00"))
+    except ValueError:
+        return None
+    if moment.tzinfo is None:
+        return None
+    return moment.astimezone(_EASTERN).date()
+
+
+def _trim_to_days(payload: Any, first: date, last: date) -> Any:
+    """Drop the events of a month payload that start outside ``[first, last]``
+    (US Eastern). An event whose date cannot be read is kept: its day query
+    might well have returned it, and a game is never dropped on a guess.
+    """
+    if not isinstance(payload, dict) or not isinstance(payload.get("events"), list):
+        return payload
+    kept = []
+    for event in payload["events"]:
+        day = _eastern_day(event.get("date")) if isinstance(event, dict) else None
+        if day is None or first <= day <= last:
+            kept.append(event)
+    payload["events"] = kept
+    return payload
+
+
 def merge_scoreboard_payloads(payloads: List[Any]) -> Dict[str, Any]:
     """Fold chunk responses into one scoreboard payload.
 
@@ -250,37 +384,54 @@ def merge_scoreboard_payloads(payloads: List[Any]) -> Dict[str, Any]:
 def _fetch_one_chunk(
     session, url: str, params: Dict[str, Any], headers, timeout, logger, chunk: str,
     cache_max_age: Optional[float] = None,
-) -> Optional[Dict[str, Any]]:
+    trims: Optional[Dict[str, Tuple[date, date]]] = None,
+) -> Any:
     """GET a single ``dates=`` chunk, or None when it failed.
 
     One bad chunk must not sink the rest of the season, so every error is
     logged and swallowed here rather than raised to the gather below.
+
+    A month that comes back at the cap is truncated: it returns ``_CAPPED``,
+    its payload dropped here before it is ever held beside the others. A
+    month in ``trims`` loses its events outside the days given there.
+
+    The request holds one of the process-wide ``_chunk_slots`` while it runs.
     """
     try:
-        response = fetch_get(
-            session,
-            url,
-            params=dict(params, dates=chunk, limit=ESPN_MAX_LIMIT),
-            headers=headers,
-            timeout=timeout,
-            **_memo_kwargs(cache_max_age),
-        )
-        response.raise_for_status()
-        return cast(Optional[Dict[str, Any]], response_json(response))
+        with _chunk_slots:
+            response = fetch_get(
+                session,
+                url,
+                params=dict(params, dates=chunk, limit=ESPN_MAX_LIMIT),
+                headers=headers,
+                timeout=timeout,
+                **_memo_kwargs(cache_max_age),
+            )
+            response.raise_for_status()
+            payload = response_json(response)
     except Exception as exc:  # noqa: BLE001 - see docstring
         if logger:
             logger.warning("ESPN chunk %s failed, skipping it: %s", chunk, exc)
         return None
+    if len(chunk) == 6 and isinstance(payload, dict):
+        if len(payload.get("events") or []) >= ESPN_MAX_LIMIT:
+            return _CAPPED
+        trim = (trims or {}).get(chunk)
+        if trim is not None:
+            payload = _trim_to_days(payload, *trim)
+    return payload
 
 
 def _fetch_chunks(
     session, url: str, params: Dict[str, Any], headers, timeout, logger,
     chunks: List[str], cache_max_age: Optional[float] = None,
-) -> List[Optional[Dict[str, Any]]]:
+    trims: Optional[Dict[str, Tuple[date, date]]] = None,
+) -> List[Any]:
     """Fetch every chunk, returning payloads positionally aligned with ``chunks``.
 
     Requests go out ``ESPN_CHUNK_WORKERS`` at a time because a cold season is
-    over a hundred of them. The order they come back in is not significant --
+    over a hundred of them -- and no more than that across every window the
+    process is fetching, which ``_fetch_one_chunk``'s slot enforces. The order they come back in is not significant --
     callers keep ``chunks`` order from the returned list -- but it does mean
     the session is shared across threads, which is why this only ever issues
     GETs and never touches session state.
@@ -293,7 +444,7 @@ def _fetch_chunks(
         return []
     fetch = partial(
         _fetch_one_chunk, session, url, params, headers, timeout, logger,
-        cache_max_age=cache_max_age,
+        cache_max_age=cache_max_age, trims=trims,
     )
     if len(chunks) == 1:
         return [fetch(chunks[0])]
@@ -340,7 +491,9 @@ def fetch_espn_date_chunks(
     if span is None:
         return None
 
-    chunks = espn_date_chunks(*span)
+    planned = espn_request_chunks(*span)
+    chunks = [chunk for chunk, _ in planned]
+    trims = {chunk: trim for chunk, trim in planned if trim is not None}
     if logger:
         logger.debug(
             "Fetching ESPN date range %s as %d month/day chunks",
@@ -349,32 +502,31 @@ def fetch_espn_date_chunks(
 
     results = _fetch_chunks(
         session, url, params, headers, timeout, logger, chunks, cache_max_age,
+        trims,
     )
     attempted = len(chunks)
 
-    # A month that came back at the cap is truncated; its days replace it in
-    # place, so merged events stay in chunk order however the requests raced.
+    # A month that came back at the cap is truncated; its days (only the
+    # window's, for a trimmed edge month) replace it in place, so merged
+    # events stay in chunk order however the requests raced. Its payload was
+    # already dropped in the worker: a capped college-baseball month is ~2MB
+    # of parsed JSON, and holding four of them through ~120 day requests added
+    # ~25MB to the peak -- more than the concurrency itself. Low-memory boards
+    # (docs/LOW_MEMORY_BOARDS.md) have under 200MB of headroom.
     slots: List[Any] = results
     capped: Dict[int, List[str]] = {}
     for index, chunk in enumerate(chunks):
-        payload = slots[index]
-        if payload is None or len(chunk) != 6:
+        if slots[index] is not _CAPPED:
             continue
-        events = payload.get("events") if isinstance(payload, dict) else None
-        if len(events or []) >= ESPN_MAX_LIMIT:
-            if logger:
-                logger.info(
-                    "ESPN month %s hit the %d-event cap; re-asking it day by day",
-                    chunk, ESPN_MAX_LIMIT,
-                )
-            capped[index] = _days_of_month(chunk)
-            # Drop the truncated month now rather than after its days arrive:
-            # a capped college-baseball month is ~2MB of parsed JSON, and
-            # holding four of them through ~120 day requests added ~25MB to
-            # the peak -- more than the concurrency itself. Low-memory boards
-            # (docs/LOW_MEMORY_BOARDS.md) have under 200MB of headroom.
-            slots[index] = None
-    payload = events = None
+        if logger:
+            logger.info(
+                "ESPN month %s hit the %d-event cap; re-asking it day by day",
+                chunk, ESPN_MAX_LIMIT,
+            )
+        trim = trims.get(chunk)
+        capped[index] = (_days_of_month(chunk) if trim is None
+                         else espn_date_chunks(*trim))
+        slots[index] = None
 
     if capped:
         days = [day for index in sorted(capped) for day in capped[index]]

src/common/fetch_service.py

@@ -59,7 +59,10 @@ says how old with ``cache_max_age`` (``fetch_get(..., cache_max_age=ttl)``;
 Identical means what the validator store keys on: URL, query, effective
 headers and, for a session with cookies or auth, the session.
 
-**Counters.** Requests, merged requests, bytes, 304s, errors, HTTP errors,
+**Counters.** Requests, merged requests, bytes (``bytes`` decoded, as the
+caller reads them; ``wire_bytes`` as they crossed the network, which is
+what a metered connection pays for -- ESPN gzips, so the two differ ~14x),
+304s, errors, HTTP errors,
 adapter retries, throttled requests and seconds waited, plus requests
 answered without the network: ``memo_hits`` (the response cache) and
 ``cache_hits`` / ``legacy_cache_hits`` (a shared ESPN scoreboard cache entry,
@@ -201,6 +204,7 @@ _COUNTER_FIELDS = (
     "throttled",     # requests that waited for a host budget
     "overruns",      # requests that went after max_wait_seconds anyway
     "bytes",         # decoded response body bytes received
+    "wire_bytes",    # body bytes as they came off the socket (still compressed)
     "wait_seconds",  # time spent waiting for host budgets
     "memo_hits",     # answered from the response cache (max-age); nothing sent
     "cache_hits",    # scoreboard fetches answered from a shared ESPN cache entry
@@ -616,6 +620,30 @@ def _body_of(response: Any) -> Optional[bytes]:
     return content if isinstance(content, bytes) else None
 
 
+def _wire_bytes_of(response: Any, body: Optional[bytes]) -> int:
+    """How many body bytes came off the socket for ``response``: the
+    compressed size when the server sent gzip, which ESPN does for every
+    scoreboard (63 KB on the wire for an 865 KB college football Saturday).
+
+    urllib3's ``HTTPResponse.tell()`` counts the raw bytes read before
+    decoding. A response without one (a test double, an adapter that is not
+    urllib3) or one whose body was not read is counted at its decoded size,
+    or as 0, so the counter never claims less than it can prove.
+    """
+    if body is None:
+        return 0
+    raw = getattr(response, "raw", None)
+    tell = getattr(raw, "tell", None)
+    if callable(tell):
+        try:
+            read = tell()
+        except Exception:
+            read = None
+        if isinstance(read, int) and not isinstance(read, bool) and read > 0:
+            return read
+    return len(body)
+
+
 def _retries_of(response: Any) -> int:
     raw = getattr(response, "raw", None)
     retries = getattr(raw, "retries", None)
@@ -1117,6 +1145,7 @@ class FetchService:
                         http_errors=int(status is not None and status >= 400),
                         retries=_retries_of(response),
                         bytes=len(body) if body is not None else 0,
+                        wire_bytes=_wire_bytes_of(response, body),
                         throttled=int(waited > 0), overruns=int(overrun),
                         wait_seconds=waited)
         except Exception:

src/common/scroll_helper.py

@@ -561,7 +561,7 @@ class ScrollHelper:
         width = self.display_width
         strip_width = self.cached_array.shape[1]
 
-        if start_x + width + 1 <= strip_width:
+        if 0 <= start_x and start_x + width + 1 <= strip_width:
             # Slice the backing array directly. Going via
             # _get_visible_portion_integer would build two PIL images only for
             # them to be converted straight back to arrays, which measured 15x
@@ -569,9 +569,10 @@ class ScrollHelper:
             near = self.cached_array[:, start_x:start_x + width]
             far = self.cached_array[:, start_x + 1:start_x + 1 + width]
         else:
-            # Close enough to the end that one of the slices wraps; let the
-            # integer path handle that and pay the conversion. Continuous mode
-            # extends the strip before reaching here, so this is the rare case.
+            # One of the slices wraps (close to the end, or a strip narrower
+            # than the panel); let the integer path handle that and pay the
+            # conversion. Continuous mode extends the strip before reaching
+            # here, so this is the rare case.
             near = np.asarray(
                 self._get_visible_portion_integer(start_x, start_x + width))
             far = np.asarray(
@@ -601,34 +602,33 @@ class ScrollHelper:
         _size = (self.display_width, self.display_height)
         img_w = self.cached_array.shape[1]
 
-        if end_x <= img_w:
+        if 0 <= start_x and end_x <= img_w:
             # Normal case: single contiguous slice (fastest path). tobytes()
             # on the column-slice view already returns C-order bytes, so
             # ascontiguousarray() first only added a second full-frame copy.
             return Image.frombytes(
                 'RGB', _size,
                 self.cached_array[:, start_x:end_x].tobytes())
+
+        # Ensure frame buffer is allocated for all non-simple paths
+        if self._frame_buffer is None or self._frame_buffer.shape != (self.display_height, self.display_width, 3):
+            self._frame_buffer = np.zeros((self.display_height, self.display_width, 3), dtype=np.uint8)
+
+        if img_w == 0:
+            self._frame_buffer[:] = 0
         else:
-            # Ensure frame buffer is allocated for all non-simple paths
-            if self._frame_buffer is None or self._frame_buffer.shape != (self.display_height, self.display_width, 3):
-                self._frame_buffer = np.zeros((self.display_height, self.display_width, 3), dtype=np.uint8)
+            # The frame runs off the strip, so it carries on from the head:
+            # frame column j is strip column (start_x + j) modulo the strip's
+            # width -- the tail and then the head, and a strip narrower than
+            # the panel repeated across it. Copying the tail and then the rest
+            # of the frame from the head assumed the head was that wide, and
+            # raised at every position for a strip narrower than the panel
+            # (Vegas composes one, with no lead-in, when its content is
+            # narrower than the chain).
+            np.take(self.cached_array, np.arange(start_x, end_x), axis=1,
+                    mode='wrap', out=self._frame_buffer)
 
-            width1 = img_w - start_x
-            if width1 > 0:
-                # Wrap-around: tail of image + head of image
-                self._frame_buffer[:, :width1] = self.cached_array[:, start_x:]
-                remaining_width = self.display_width - width1
-                self._frame_buffer[:, width1:] = self.cached_array[:, :remaining_width]
-            else:
-                # Edge case: start_x at or past image end — show from beginning,
-                # clamped to available width (scroll_position should wrap before
-                # reaching this state in normal operation).
-                available = min(self.display_width, img_w)
-                self._frame_buffer[:, :available] = self.cached_array[:, :available]
-                if available < self.display_width:
-                    self._frame_buffer[:, available:] = 0
-
-            return Image.frombytes('RGB', _size, self._frame_buffer.tobytes())
+        return Image.frombytes('RGB', _size, self._frame_buffer.tobytes())
     
     def calculate_dynamic_duration(self) -> int:
         """

src/common/sports_card.py

@@ -18,7 +18,7 @@ the extra guard only stops a None size raising TypeError.
 """
 
 import logging
-from datetime import datetime, timezone
+from datetime import datetime, timedelta, timezone
 from typing import Any, Dict, Optional, Tuple
 from zoneinfo import ZoneInfo
 
@@ -338,10 +338,46 @@ def format_game_date(config: Optional[Dict[str, Any]], logger, date_text: str,
     if not raw:
         return ""
     fmt = str(scroll_card_option(config, "date_format", "abbrev") or "abbrev")
-    return _format_date_as(fmt, raw, lambda: weekday_for(config, logger, game))
+    return _format_date_as(fmt, raw, lambda: weekday_for(config, logger, game),
+                           game=game)
 
 
-def _format_date_as(fmt: str, raw: str, weekday, months=MONTH_ABBR) -> str:
+def _printed_weekday(game: Optional[Dict], month: int, day: int) -> str:
+    """The weekday of the date a card prints as month/day, or '' if unknown.
+
+    The extractor prints "M/D" in the plugin's resolved zone (its own setting,
+    else the global one, else the system zone). The card cannot see that zone:
+    it is handed the plugin's config, whose ``timezone`` ships as "", so
+    card_tzinfo answers UTC and an evening kickoff in the Americas got the
+    next day's weekday ("Sat Oct 2" for a Friday game). Every zone is within
+    a day of UTC, so the printed date is the start's UTC date or a neighbour
+    of it; the one with that month and day is the date on the card.
+    """
+    if not isinstance(game, dict):
+        return ""
+    raw = game.get("start_time_utc") or game.get("start_time")
+    if not raw:
+        return ""
+    try:
+        start = raw if isinstance(raw, datetime) else datetime.fromisoformat(
+            str(raw).replace("Z", "+00:00"))
+        if start.utcoffset() is None:
+            return ""  # naive: no instant to place the date against
+        utc_day = start.astimezone(timezone.utc).date()
+    except (ValueError, TypeError, OverflowError):
+        return ""
+    for offset in (0, -1, 1):
+        try:
+            candidate = utc_day + timedelta(days=offset)
+        except OverflowError:
+            continue
+        if (candidate.month, candidate.day) == (month, day):
+            return WEEKDAY_ABBR[candidate.weekday()]
+    return ""
+
+
+def _format_date_as(fmt: str, raw: str, weekday, months=MONTH_ABBR,
+                    game: Optional[Dict] = None) -> str:
     """Render a stripped, non-empty "M/D" *raw* in style *fmt*.
 
     The body both date formatters share. They differ in which setting names the
@@ -349,6 +385,9 @@ def _format_date_as(fmt: str, raw: str, weekday, months=MONTH_ABBR) -> str:
     ``SportsCoreSharedMixin._format_game_date``), so those arrive as arguments:
     *weekday* is a zero-argument callable, only called for the "weekday" style.
     *months* lets the mixin keep reading its (overridable) ``_MONTH_ABBR``.
+    With *game*, the "weekday" style names the printed date's own weekday
+    (:func:`_printed_weekday`), and *weekday* is only the fallback for a
+    date its start time cannot place.
     """
     if fmt == "numeric":
         return raw
@@ -364,7 +403,7 @@ def _format_date_as(fmt: str, raw: str, weekday, months=MONTH_ABBR) -> str:
     if fmt == "day_first":
         return f"{day} {name}"
     if fmt == "weekday":
-        day_name = weekday()
+        day_name = _printed_weekday(game, month, day) or weekday()
         return f"{day_name} {name} {day}" if day_name else f"{name} {day}"
     return f"{name} {day}"
 

src/common/sports_shared.py

@@ -360,14 +360,16 @@ class SportsCoreSharedMixin:
         The formatting is sports_card's. What differs from the card's
         ``format_game_date`` is passed in: the setting (``switch_date_format``,
         see :meth:`_switch_date_format`) and the weekday, which comes from
-        :meth:`_weekday_for` and so from this plugin's resolved timezone.
+        :meth:`_weekday_for` and so from this plugin's resolved timezone
+        when the game's start cannot place the printed date. The game goes
+        in too, so both formatters name the printed date's own weekday.
         """
         raw = str(date_text or "").strip()
         if not raw:
             return raw
         return _card._format_date_as(self._switch_date_format(), raw,
                                      lambda: self._weekday_for(game),
-                                     self._MONTH_ABBR)
+                                     self._MONTH_ABBR, game=game)
 
     def _weekday_for(self, game: Optional[Dict]) -> str:
         """Weekday abbreviation from the game's start time, or ''."""

src/config_manager.py

@@ -46,6 +46,35 @@ from src.common.permission_utils import (
     get_config_dir_mode
 )
 
+
+def _private_copy(config: Dict[str, Any]) -> Dict[str, Any]:
+    """A deep copy of ``config`` that shares nothing with it.
+
+    load_config() hands one out per call, and the saves keep one, so the
+    cached config is never an object a caller holds. A web handler edits what
+    it loaded, validates, and may refuse the save; when the cache was that
+    same object, the refused edit stayed in it, and the next save of any
+    other setting wrote it to config.json -- a nested secret included, in
+    plain text, since it had never reached config_secrets.json to be
+    stripped.
+
+    The config is JSON data, so only its dicts and lists need copying; every
+    other value in it is immutable. On a Pi 4 with a real 60 KiB config this
+    takes 2.1 ms against copy.deepcopy's 6.8 ms, on a path ~30 handlers call
+    (a pickle round trip is no faster, 1.9 ms, and brings pickle into the
+    config path for nothing).
+    """
+    return _copy_containers(config)
+
+
+def _copy_containers(value: Any) -> Any:
+    if isinstance(value, dict):
+        return {key: _copy_containers(item) for key, item in value.items()}
+    if isinstance(value, list):
+        return [_copy_containers(item) for item in value]
+    return value
+
+
 class ConfigManager:
     """
     Reads and writes the main application configuration files.
@@ -126,9 +155,10 @@ class ConfigManager:
             validate_after_write=validate_after_write
         )
         
-        # Update in-memory config if save was successful
+        # Update in-memory config if save was successful. A copy: the caller
+        # still holds new_config_data (see _private_copy).
         if result.status == SaveResultStatus.SUCCESS:
-            self.config = new_config_data
+            self.config = _private_copy(new_config_data)
             # In-memory config now matches what was just written, so the
             # load_config fast path may return it. It still carries the
             # merged secrets that were stripped on disk; that matches a full
@@ -208,14 +238,16 @@ class ConfigManager:
 
         Fast path: when config.json, config_secrets.json and the template
         are all unchanged since the last successful load (mtime_ns + size),
-        the already-parsed self.config is returned without touching the
-        files — same aliasing semantics as the full path, which also
-        returns self.config.
+        a copy of the already-parsed self.config is returned without
+        touching the files.
+
+        Either way the caller gets its own copy (see _private_copy): editing
+        it changes nothing here until it is saved.
         """
         try:
             current_sig = self._files_signature()
             if self.config and self._loaded_sig == current_sig:
-                return self.config
+                return _private_copy(self.config)
 
             # Check if config file exists, if not create from template
             if not os.path.exists(self.config_path):
@@ -249,8 +281,8 @@ class ConfigManager:
             # Signature taken AFTER load + migration (migration may write the
             # config back), so it reflects exactly what was read/written.
             self._loaded_sig = self._files_signature()
-            return self.config
-            
+            return _private_copy(self.config)
+
         except FileNotFoundError as e:
             # Only config.json can get here: a missing or unreadable secrets
             # file is handled where it is read.
@@ -355,8 +387,9 @@ class ConfigManager:
         try:
             atomic_write_json(self.config_path, config_to_write)
 
-            # Update the in-memory config to the new state (which includes secrets for runtime)
-            self.config = new_config_data
+            # Update the in-memory config to the new state (which includes
+            # secrets for runtime), as a copy -- see _private_copy
+            self.config = _private_copy(new_config_data)
             self._loaded_sig = self._files_signature()
             self.logger.info(f"Configuration successfully saved to {os.path.abspath(self.config_path)}")
             if secrets_content:

src/config_service.py

@@ -14,7 +14,7 @@ import json
 import time
 import threading
 from pathlib import Path
-from typing import Dict, Any, Optional, List, Callable
+from typing import Dict, Any, Optional, List, Callable, Tuple
 from collections import defaultdict
 import logging
 import hashlib
@@ -52,7 +52,18 @@ class ConfigService:
         
         # Thread safety
         self._lock: threading.RLock = threading.RLock()
-        
+        # Held across a whole reload -- read, swap, notify -- so one reload's
+        # notifications finish before the next one's start. Subscribers run
+        # under this lock and never under _lock: the display's per-plugin
+        # subscriber can wait seconds for a busy plugin, and get_config(),
+        # subscribe() and unsubscribe() -- called from the render thread --
+        # must not wait behind it.
+        self._notify_lock: threading.RLock = threading.RLock()
+        # (key, callback, thread id) of the callback a notification is running,
+        # so unsubscribe() can wait for that one call; signalled on its return.
+        self._running_callback: Optional[Tuple[str, Callable[..., None], int]] = None
+        self._callback_done = threading.Condition(self._lock)
+
         # Current configuration
         self._current_config: Dict[str, Any] = {}
         self._current_checksum: Optional[str] = None
@@ -87,32 +98,33 @@ class ConfigService:
             True if config changed, False otherwise
         """
         try:
-            new_config = self.config_manager.load_config()
-            new_checksum = self._calculate_checksum(new_config)
-            
-            with self._lock:
-                # Check if config actually changed
-                if new_checksum == self._current_checksum:
-                    self.logger.debug("Configuration unchanged, skipping reload")
-                    return False
-                
-                # Store old config for change detection
-                old_config = self._current_config.copy()
-                
-                # Update current config
-                self._current_config = new_config
-                self._current_checksum = new_checksum
-                
-                # Notify subscribers
+            with self._notify_lock:
+                new_config = self.config_manager.load_config()
+                new_checksum = self._calculate_checksum(new_config)
+
+                with self._lock:
+                    # Check if config actually changed
+                    if new_checksum == self._current_checksum:
+                        self.logger.debug("Configuration unchanged, skipping reload")
+                        return False
+
+                    # Store old config for change detection
+                    old_config = self._current_config.copy()
+
+                    # Update current config
+                    self._current_config = new_config
+                    self._current_checksum = new_checksum
+
+                # Notify subscribers, outside _lock (see _notify_lock)
                 self._notify_subscribers(old_config, new_config)
-                
+
                 self.logger.info(
                     "Configuration reloaded (checksum: %s)",
                     new_checksum[:8]
                 )
-                
+
                 return True
-                
+
         except ConfigError as e:
             self.logger.error("Error loading configuration: %s", e, exc_info=True)
             return False
@@ -127,35 +139,64 @@ class ConfigService:
         Args:
             old_config: Previous configuration
             new_config: New configuration
+
+        Called without _lock held. The subscriber lists are copied under it,
+        and each callback is checked against them again just before it runs.
         """
+        with self._lock:
+            subscribers = {key: list(callbacks) for key, callbacks in self._subscribers.items()}
+
         # Notify global subscribers (key: '*')
-        for callback in self._subscribers.get('*', []):
-            try:
-                callback(old_config, new_config)
-            except Exception as e:
-                self.logger.error("Error in global config change callback: %s", e, exc_info=True)
-        
+        for callback in subscribers.get('*', []):
+            self._call_subscriber('*', callback, old_config, new_config)
+
         # Notify plugin-specific subscribers
-        for plugin_id in self._subscribers.keys():
+        for plugin_id, callbacks in subscribers.items():
             if plugin_id == '*':
                 continue
-            
+
             old_plugin_config = old_config.get(plugin_id, {})
             new_plugin_config = new_config.get(plugin_id, {})
-            
+
             # Only notify if plugin config actually changed
             if old_plugin_config != new_plugin_config:
-                for callback in self._subscribers[plugin_id]:
-                    try:
-                        callback(old_plugin_config, new_plugin_config)
-                    except Exception as e:
-                        self.logger.error(
-                            "Error in config change callback for %s: %s",
-                            plugin_id,
-                            e,
-                            exc_info=True
-                        )
-    
+                for callback in callbacks:
+                    self._call_subscriber(plugin_id, callback,
+                                          old_plugin_config, new_plugin_config)
+
+    def _call_subscriber(
+        self,
+        key: str,
+        callback: Callable[[Dict[str, Any], Dict[str, Any]], None],
+        old_config: Dict[str, Any],
+        new_config: Dict[str, Any],
+    ) -> None:
+        """Run one callback, unless it was unsubscribed since the snapshot.
+
+        unsubscribe() promises that once it returns the callback is neither
+        running nor will run: the display unloads the plugin straight after.
+        """
+        with self._lock:
+            if callback not in self._subscribers.get(key, ()):
+                return
+            self._running_callback = (key, callback, threading.get_ident())
+        try:
+            callback(old_config, new_config)
+        except Exception as e:
+            if key == '*':
+                self.logger.error("Error in global config change callback: %s", e, exc_info=True)
+            else:
+                self.logger.error(
+                    "Error in config change callback for %s: %s",
+                    key,
+                    e,
+                    exc_info=True
+                )
+        finally:
+            with self._lock:
+                self._running_callback = None
+                self._callback_done.notify_all()
+
     def _check_file_changes(self) -> bool:
         """
         Check if configuration files have been modified.
@@ -276,6 +317,11 @@ class ConfigService:
         """
         Unsubscribe from configuration changes.
         
+        Once this returns the callback is not running and will not be called
+        again. A notification that is running this very callback is waited
+        for (unless the callback is the caller); one running any other
+        callback is not.
+
         Args:
             callback: Callback function to remove
             plugin_id: Optional plugin ID (must match subscription)
@@ -285,6 +331,10 @@ class ConfigService:
             if callback in self._subscribers[key]:
                 self._subscribers[key].remove(callback)
                 self.logger.debug("Unsubscribed from config changes for %s", key)
+            while (self._running_callback is not None
+                   and self._running_callback[:2] == (key, callback)
+                   and self._running_callback[2] != threading.get_ident()):
+                self._callback_done.wait()
     
     def shutdown(self) -> None:
         """Shutdown the configuration service."""

src/display_arbiter.py

@@ -1,41 +1,56 @@
 """What the panel shows next: the Arbiter of docs/RUN_LOOP_REDESIGN.md.
 
 ``Arbiter.decide(state, inputs, now)`` takes a snapshot that
-``DisplayController.run()`` gathers once per pass and returns a
-:class:`ScreenPlan` naming the Source that gets the panel. It is a pure
-function: no I/O, no clock reads (``now`` is passed in), no locks, and it
-changes nothing it is given. That is what lets a plain table of cases test
-the priority order, which used to exist only as the order of ``if`` blocks
-in ``run()``.
+``DisplayController.run()`` gathers and returns a :class:`ScreenPlan` naming
+the Source that gets the panel. It is a pure function: no I/O, no clock
+reads (``now`` is passed in), no locks, and it changes nothing it is given.
+That is what lets a plain table of cases test the priority order, which
+used to exist only as the order of ``if`` blocks in ``run()``.
 
-The full order is
+The order is
 
     ScheduledOff (a gate), Follower, OnDemand, Wifi, Live, Vegas, Rotation
 
-Stage 2 decides the gate, Follower and Wifi. Every other case returns a
-``LEGACY`` plan, meaning "carry on with run()'s existing code" (live
-priority, Vegas, then one rotation screen). OnDemand is in the order already
-because it outranks the WiFi notice: an active session is a ``LEGACY`` plan
-even when a notice is pending.
+Every Source but Vegas is decided here (stage 3). Vegas is the ``LEGACY``
+plan: the Arbiter picks it, but its iteration is still run()'s own code
+until stage 4.
 
-The Wifi Source's mid-screen rule, :func:`wifi_notice_preempts`, lives here
-too, so both of its answers -- at the top of a pass and between frames --
-come from one module.
+A pass asks twice: once with the inputs every pass reads (the gate,
+Follower, OnDemand, Wifi), and once more, only when nothing above the
+notice took the panel, with the inputs the Sources below it need (whether
+Vegas is on, the live-priority scan), read where run() always read them.
+
+``decide(..., running=plan)`` is the other question, asked by the
+ScreenRunner (src/screen_runner.py) at its service points: does a Source
+in ``plan.preemptible_by`` now take the panel from the screen that is
+running? The mid-screen rules are :func:`_hold_or_preempt`.
+
+The state transitions (the next on-demand mode, a live claim and its
+release, the rotation's step after a screen) are pure methods of
+:class:`ArbiterState`; the controller applies what they return.
 """
 
-from dataclasses import dataclass
+from dataclasses import dataclass, replace
 from enum import Enum
-from typing import Optional
+from typing import FrozenSet, Optional, Protocol, Tuple
 
 __all__ = [
     "Arbiter",
     "ArbiterInputs",
     "ArbiterState",
+    "FramePolicy",
+    "LIVE_PREEMPTERS",
     "SCHEDULED_OFF_DWELL",
+    "SCREEN_PREEMPTERS",
+    "ScreenEnd",
     "ScreenPlan",
     "Source",
     "WIFI_NOTICE_DWELL",
     "WifiNotice",
+    "live_pick",
+    "live_takeover",
+    "on_demand_bound",
+    "rotation_plan",
     "wifi_notice_preempts",
 ]
 
@@ -53,11 +68,41 @@ class Source(Enum):
 
     SCHEDULED_OFF = "scheduled-off"
     FOLLOWER = "follower"
+    ON_DEMAND = "on-demand"
     WIFI = "wifi"
-    # Not decided by the Arbiter yet: on-demand, live priority, Vegas and the
-    # rotation are still chosen by run()'s own code. Stage 3 adds the
-    # OnDemand, Live and Rotation Sources; stage 4 adds Vegas.
+    LIVE = "live"
+    # Vegas: the Arbiter picks it, but its iteration is still run()'s own
+    # code (and its interrupt callback a second copy of this order) until
+    # stage 4 makes it a Source driven frame by frame.
     LEGACY = "legacy"
+    ROTATION = "rotation"
+    # Not a screen: a plugin reload waits at the top of the loop. It ends a
+    # screen between frames (the screen counts as shown and the rotation
+    # moves on), and the next pass reloads before it draws.
+    RELOAD = "reload"
+
+
+class FramePolicy(Enum):
+    """How often a screen draws: today's two frame loops (see
+    DisplayController._needs_high_fps). Stage 5 lets plugins declare it."""
+
+    #: The 125 Hz loop, paced to an 8 ms deadline: scrolling plugins.
+    HIGH_FPS = "high-fps"
+    #: The 1 Hz loop.
+    STATIC = "static"
+
+
+class ScreenEnd(Protocol):
+    """What ArbiterState.after needs to know about how a screen ended
+    (screen_runner.Outcome, filled in by the controller)."""
+
+    @property
+    def on_demand_active(self) -> bool:
+        """An on-demand session was running when the screen ended."""
+
+    @property
+    def still_live(self) -> bool:
+        """The mode's plugin still had live content: hold the rotation."""
 
 
 @dataclass(frozen=True)
@@ -76,11 +121,122 @@ class WifiNotice:
 class ArbiterState:
     """What the Arbiter remembers between passes.
 
-    Nothing yet: the stage-2 Sources decide from the inputs alone. The
-    on-demand index, the rotation index and the live resume point move here
-    with their Sources in stage 3.
+    A snapshot of the controller's own fields, taken when decide() is
+    called (DisplayController._arbiter_state); the transitions below return
+    the next state, and the controller writes it back.
+
+    Attributes:
+        current_mode: The mode on the panel or about to be
+            (``current_display_mode``).
+        on_demand_modes: The on-demand session's modes, in the order it
+            shows them (a pinned mode already moved to the front when the
+            session started, by _apply_on_demand_pin).
+        on_demand_index: Which of them is showing.
+        on_demand_expires_at: When the session ends (wall clock), or None
+            for a session with no duration.
+        on_demand_pinned: The session was started pinned. Carried for the
+            snapshot; the pin itself is already in ``on_demand_modes``.
+        rotation: The rotation's modes (``available_modes``).
+        rotation_index: Where the rotation is (``current_mode_index``).
+        live_resume_index: Where the rotation was when live priority took
+            the panel, so it resumes there once nothing is live; None while
+            live priority holds nothing.
+        live_takeover_unshown: A mid-screen takeover chose current_mode and
+            it has not been shown yet, so the next pass must not advance the
+            live round-robin past it.
     """
 
+    current_mode: Optional[str] = None
+    on_demand_modes: Tuple[str, ...] = ()
+    on_demand_index: int = 0
+    on_demand_expires_at: Optional[float] = None
+    on_demand_pinned: bool = False
+    rotation: Tuple[str, ...] = ()
+    rotation_index: int = 0
+    live_resume_index: Optional[int] = None
+    live_takeover_unshown: bool = False
+
+    def next_on_demand(self) -> "ArbiterState":
+        """The session's next mode, wrapping round. Needs a mode list."""
+        index = (self.on_demand_index + 1) % len(self.on_demand_modes)
+        return replace(self, on_demand_index=index,
+                       current_mode=self.on_demand_modes[index])
+
+    def claim_live(self, mode: str) -> "ArbiterState":
+        """Live priority takes the panel for ``mode``.
+
+        The rotation's position is saved only on the first claim, not on
+        each re-check while the hold continues, so it resumes where live
+        priority interrupted it instead of after the live mode (which would
+        skip every mode between the two).
+        """
+        if self.current_mode == mode:
+            return self
+        resume = self.rotation_index if self.live_resume_index is None else self.live_resume_index
+        index = self.rotation.index(mode) if mode in self.rotation else self.rotation_index
+        return replace(self, current_mode=mode, rotation_index=index,
+                       live_resume_index=resume)
+
+    def after(self, outcome: "ScreenEnd") -> "ArbiterState":
+        """The state once a screen has run its course: the next mode.
+
+        An on-demand session moves to its next mode. Otherwise the rotation
+        advances -- unless the mode just shown is a live-priority mode that
+        is still live, which holds the panel. A session with no modes left
+        is ended by the controller before it asks (that is not pure: it
+        resumes the rotation and clears the cache).
+        """
+        if outcome.on_demand_active:
+            return self.next_on_demand() if self.on_demand_modes else self
+        if outcome.still_live or not self.rotation:
+            return self
+        index = (self.rotation_index + 1) % len(self.rotation)
+        return replace(self, rotation_index=index, current_mode=self.rotation[index])
+
+    def release_live(self) -> "ArbiterState":
+        """Nothing is live any more: the rotation resumes where it was."""
+        if self.live_resume_index is None or not self.rotation:
+            return self
+        index = self.live_resume_index % len(self.rotation)
+        return replace(self, current_mode=self.rotation[index], rotation_index=index,
+                       live_resume_index=None)
+
+    def showing(self, plan: "ScreenPlan") -> "ArbiterState":
+        """The state once ``plan`` is on the panel.
+
+        An on-demand plan puts the session's index on the mode it shows (an
+        index past the end of a shortened list starts it again at 0).
+        """
+        state = replace(self, current_mode=plan.mode)
+        if plan.source is Source.ON_DEMAND and self.on_demand_modes:
+            state = replace(state, on_demand_index=_on_demand_index(self))
+        return state
+
+
+def _on_demand_index(state: ArbiterState) -> int:
+    """The session's index, or 0 once it is past the end of its list."""
+    index = state.on_demand_index
+    return index if index < len(state.on_demand_modes) else 0
+
+
+def on_demand_bound(min_duration: float, max_duration: float,
+                    deadline: Optional[float],
+                    now: float) -> Optional[Tuple[float, float]]:
+    """Shorten a screen's (min, max) seconds to what is left of a timed
+    on-demand session ending at ``deadline``. None when nothing is left.
+
+    The OnDemand Source's bound, applied after the screen's first frame,
+    where it always was (``now`` is read then).
+    """
+    if deadline is None:
+        return min_duration, max_duration
+    remaining = max(0.0, deadline - now)
+    min_duration = min(min_duration, remaining)
+    max_duration = min(max_duration, remaining)
+    if max_duration <= 0:
+        return None
+    return min_duration, max_duration
+
 
 @dataclass(frozen=True)
 class ArbiterInputs:
@@ -95,57 +251,122 @@ class ArbiterInputs:
             when it could win (the panel is on, and neither a follower nor
             on-demand outranks it), because reading it has side effects: a
             1 Hz throttle and deleting an expired file.
+        live_modes: The modes with live content, from a live-priority scan,
+            in registration order; None when no scan was made (on-demand,
+            Vegas keeping live content in its ticker, a throttled
+            mid-screen check). A scan asks every live-priority plugin, so it
+            is made only where run() always made it.
+        vegas_enabled: Vegas mode is on (and no on-demand session holds it
+            off).
+        vegas_live_in_ticker: Vegas keeps live content in its ticker
+            instead of yielding the panel to it.
+        vegas_yielded: This pass's Vegas iteration has run and yielded, so
+            the Vegas Source passes and the screen it fell through to is
+            decided.
+        reload_pending: Mid-screen only: a plugin reload is waiting for the
+            top of the loop, at a service point where that ends the screen.
     """
 
     schedule_on: bool
     on_demand_active: bool
     follower_active: bool
     wifi_notice: Optional[WifiNotice] = None
+    live_modes: Optional[Tuple[str, ...]] = None
+    vegas_enabled: bool = False
+    vegas_live_in_ticker: bool = False
+    vegas_yielded: bool = False
+    reload_pending: bool = False
 
 
 @dataclass(frozen=True)
 class ScreenPlan:
     """The Arbiter's answer for one pass.
 
+    decide() is pure, so it cannot ask a plugin anything: the fields a
+    plugin answers (its durations, whether it runs a dynamic cycle, how
+    often it draws) are filled in by the controller after the screen's first
+    frame, when they have always been read (DisplayController.complete_plan).
+
     Attributes:
         source: The Source that gets the panel.
+        mode: The display mode to draw (None for a blank, follower or notice).
+        plugin: The id of the plugin drawing ``mode``, once resolved.
+        min_duration: Seconds the screen runs at least (dynamic duration).
         max_duration: How long the plan holds the panel, in seconds, at most
             (its dwell ends early when what the panel should show changes).
-            None when the Source paces itself: a follower frame, or LEGACY.
+            None when the Source paces itself (a follower frame, Vegas), and
+            for a rotation or live plan until its first frame.
+        dynamic: Run until the plugin's cycle completes, between min and max.
+        frame_policy: Which frame loop the screen runs.
+        preemptible_by: The Sources that may end the screen mid-way.
         notice: The WiFi notice to draw, for a WIFI plan.
+        deadline: For an on-demand plan, when the session ends (wall
+            clock): after the first frame the screen's durations are cut to
+            what is left (:func:`on_demand_bound`).
+        ends_live: Nothing is live any more and live priority had
+            interrupted the rotation: taking this plan resumes the rotation
+            where it was (ArbiterState.release_live) before it shows.
     """
 
     source: Source
+    mode: Optional[str] = None
+    plugin: Optional[str] = None
+    min_duration: Optional[float] = None
     max_duration: Optional[float] = None
+    dynamic: bool = False
+    frame_policy: Optional[FramePolicy] = None
+    preemptible_by: FrozenSet[Source] = frozenset()
     notice: Optional[WifiNotice] = None
+    deadline: Optional[float] = None
+    ends_live: bool = False
 
 
 SCHEDULED_OFF_PLAN = ScreenPlan(Source.SCHEDULED_OFF, max_duration=SCHEDULED_OFF_DWELL)
 FOLLOWER_PLAN = ScreenPlan(Source.FOLLOWER)
-LEGACY_PLAN = ScreenPlan(Source.LEGACY)
+RELOAD_PLAN = ScreenPlan(Source.RELOAD)
+
+#: What may end a screen mid-way: the schedule, an on-demand session
+#: starting or ending, a WiFi notice, a live game, the rotation moving
+#: under the screen, and a plugin reload. Not a follower or Vegas: those
+#: are only looked at between screens.
+SCREEN_PREEMPTERS: FrozenSet[Source] = frozenset(
+    {Source.SCHEDULED_OFF, Source.ON_DEMAND, Source.WIFI, Source.LIVE, Source.ROTATION,
+     Source.RELOAD})
+
+#: A live screen is not preempted by Live: live games take turns between
+#: screens, never mid-screen.
+LIVE_PREEMPTERS: FrozenSet[Source] = SCREEN_PREEMPTERS - {Source.LIVE}
 
 
 class Arbiter:
     """Decides which Source gets the panel. Stateless; see the module docstring."""
 
     @staticmethod
-    def decide(state: ArbiterState, inputs: ArbiterInputs, now: float) -> ScreenPlan:
+    def decide(state: ArbiterState, inputs: ArbiterInputs, now: float,
+               running: Optional[ScreenPlan] = None) -> ScreenPlan:
         """The plan for this pass, from the Sources in priority order.
 
+        With ``running``, the question is the ScreenRunner's at one of its
+        service points instead: does a Source in ``running.preemptible_by``
+        now take the panel from that screen? The answer is ``running``
+        itself (the same object) while it holds, else the plan that ends it.
+        See :func:`_hold_or_preempt` for the rules.
+
         Args:
-            state: What the Arbiter remembers between passes (nothing yet).
+            state: What the Arbiter remembers between passes.
             inputs: This pass's snapshot.
-            now: Wall-clock time of the snapshot. No stage-2 Source reads it:
-                the top-of-pass WiFi check takes the notice as read, and only
-                the mid-screen check (:func:`wifi_notice_preempts`) compares
-                it with the expiry. It is in the signature for the Sources
-                stage 3 adds (on-demand expiry, durations).
+            now: Wall-clock time of the snapshot. The OnDemand Source reads
+                it for what is left of a timed session, and the mid-screen
+                WiFi rule (:func:`wifi_notice_preempts`) to compare with the
+                notice's expiry. The top-of-pass WiFi check does not: it
+                takes the notice as read.
+            running: The screen on the panel, for a mid-screen check.
 
         Returns:
-            The winning Source's plan, or LEGACY_PLAN when the winner is one
-            run() still decides itself.
+            The winning Source's plan (LEGACY for Vegas), or ``running``.
         """
-        del state, now  # not read by the stage-2 Sources; see the docstring
+        if running is not None:
+            return _hold_or_preempt(state, inputs, now, running)
 
         # ScheduledOff is a gate, not a Source: a scheduled-off panel stays
         # blank even for a follower, and only an on-demand session overrides
@@ -157,17 +378,161 @@ class Arbiter:
         if inputs.follower_active:
             return FOLLOWER_PLAN
 
-        # 2. OnDemand: decided by run() until stage 3. It outranks the notice.
+        # 2. OnDemand: the session's current mode. It outranks the notice.
         if inputs.on_demand_active:
-            return LEGACY_PLAN
+            return _on_demand_plan(state, now)
 
         # 3. Wifi: a pending notice, held for one short dwell per pass.
         if inputs.wifi_notice is not None:
             return ScreenPlan(Source.WIFI, max_duration=WIFI_NOTICE_DWELL,
                               notice=inputs.wifi_notice)
 
-        # 4-6. Live, Vegas, Rotation: still run()'s own code.
-        return LEGACY_PLAN
+        # 4. Live: the next live game, round-robin across several. With
+        # nothing live, a rotation that live priority interrupted resumes.
+        ends_live = False
+        if _live_applies(inputs):
+            pick = live_pick(inputs.live_modes, state.current_mode,
+                             advance=not state.live_takeover_unshown)
+            if pick is not None:
+                return ScreenPlan(Source.LIVE, mode=pick, preemptible_by=LIVE_PREEMPTERS)
+            ends_live = state.live_resume_index is not None and bool(state.rotation)
+
+        # 5. Vegas: one iteration of the ticker, run by run()'s own code
+        # until stage 4. Passes once this pass's iteration has yielded.
+        if inputs.vegas_enabled and not inputs.vegas_yielded:
+            return ScreenPlan(Source.LEGACY, ends_live=ends_live)
+
+        # 6. Rotation: the rotation's current mode (after the resume, when
+        # live priority just ended).
+        return rotation_plan(state.release_live() if ends_live else state,
+                             ends_live=ends_live)
+
+
+def _hold_or_preempt(state: ArbiterState, inputs: ArbiterInputs, now: float,
+                     running: ScreenPlan) -> ScreenPlan:
+    """The mid-screen rules: ``running``, or the plan that ends it.
+
+    What the frame loops used to check one by one (_check_live_takeover,
+    then _screen_preempted with _wifi_notice_pending in it, before stage 3),
+    in their order:
+
+    1. Live: a game went live while a non-live screen runs (the inputs
+       carry a scan only when one was due, at most once a second). Checked
+       first because it is the one preemption that changes the state -- the
+       rotation moves to the live mode and remembers where it was -- and it
+       still happens when a WiFi notice is also pending: the next pass then
+       shows the notice, and the game after it.
+    2. The panel's mode moved under the screen: an on-demand session
+       started, ended or changed mode, or the rotation was rebuilt (a
+       plugin enabled, disabled or reloaded).
+    3. The schedule turned the panel off.
+    4. A WiFi notice arrived (unless on-demand outranks it), compared with
+       its expiry because the read throttle can hand back a stale one.
+    5. A plugin reload is waiting at the top of the loop.
+
+    A follower and Vegas are never mid-screen preemptions; they are looked
+    at between screens.
+    """
+    by = running.preemptible_by
+    if Source.LIVE in by:
+        takeover = live_takeover(state, inputs)
+        if takeover is not None:
+            return ScreenPlan(Source.LIVE, mode=takeover, preemptible_by=LIVE_PREEMPTERS)
+    if state.current_mode != running.mode:
+        source = Source.ON_DEMAND if inputs.on_demand_active else Source.ROTATION
+        if source in by:
+            return ScreenPlan(source, mode=state.current_mode, preemptible_by=SCREEN_PREEMPTERS)
+    if (Source.SCHEDULED_OFF in by and not inputs.schedule_on
+            and not inputs.on_demand_active):
+        return SCHEDULED_OFF_PLAN
+    notice = inputs.wifi_notice
+    if (Source.WIFI in by and notice is not None
+            and wifi_notice_preempts(notice, inputs.on_demand_active, now)):
+        return ScreenPlan(Source.WIFI, max_duration=WIFI_NOTICE_DWELL, notice=notice)
+    if Source.RELOAD in by and inputs.reload_pending:
+        return RELOAD_PLAN
+    return running
+
+
+def live_takeover(state: ArbiterState, inputs: ArbiterInputs) -> Optional[str]:
+    """The live mode that takes the panel mid-screen, or None.
+
+    The first live mode, when a scan found one and the panel is not on a
+    live mode already. Never while on-demand holds the panel, while it is
+    scheduled off, or while Vegas keeps live content in its ticker.
+    """
+    if not _live_applies(inputs) or inputs.on_demand_active or not inputs.schedule_on:
+        return None
+    live = inputs.live_modes
+    if not live or state.current_mode in live:
+        return None
+    return live[0]
+
+
+def _on_demand_plan(state: ArbiterState, now: float) -> ScreenPlan:
+    """The OnDemand Source: the session's current mode.
+
+    ``max_duration`` is what is left of a timed session at ``now`` (None
+    without a duration); ``deadline`` carries the expiry so the bound can be
+    applied again after the first frame. A session with no modes left (its
+    plugin was unloaded under it) gets a plan with no mode: the controller
+    ends the session and shows the rotation's mode instead.
+    """
+    modes = state.on_demand_modes
+    if not modes:
+        return ScreenPlan(Source.ON_DEMAND)
+    expires_at = state.on_demand_expires_at
+    remaining = None if expires_at is None else max(0.0, expires_at - now)
+    return ScreenPlan(Source.ON_DEMAND, mode=modes[_on_demand_index(state)],
+                      max_duration=remaining, deadline=expires_at,
+                      preemptible_by=SCREEN_PREEMPTERS)
+
+
+def rotation_plan(state: ArbiterState, ends_live: bool = False) -> ScreenPlan:
+    """The Rotation Source: the mode the rotation is on.
+
+    That is ``state.current_mode``, which is ``rotation[rotation_index]``
+    except where something moved the panel off the list and the rotation
+    carries on from there: a live mode no rotation entry names, or None
+    when a session ended with no enabled mode to resume to.
+    """
+    return ScreenPlan(Source.ROTATION, mode=state.current_mode, ends_live=ends_live,
+                      preemptible_by=SCREEN_PREEMPTERS)
+
+
+def _live_applies(inputs: ArbiterInputs) -> bool:
+    """Whether the Live Source has a say: a scan was made, and Vegas is not
+    keeping live content in its ticker (where the live plugin takes extra
+    turns in the marquee instead of the panel)."""
+    if inputs.live_modes is None:
+        return False
+    return not (inputs.vegas_enabled and inputs.vegas_live_in_ticker)
+
+
+def live_pick(live_modes: Optional[Tuple[str, ...]], current_mode: Optional[str],
+              advance: bool) -> Optional[str]:
+    """The live mode to show, or None when nothing is live.
+
+    When several plugins are live at once this round-robins between them, so
+    the panel alternates each dwell instead of pinning to the first one
+    registered. The mode on the panel is the cursor, so this stays right as
+    games start and end.
+
+    Args:
+        live_modes: The live modes, in registration order.
+        current_mode: The mode on the panel.
+        advance: True for the rotation's pick (the live mode after the one
+            showing). False for a peek (the one showing if it is still live,
+            else the first), which Vegas uses to ask whether anything is.
+    """
+    if not live_modes:
+        return None
+    if current_mode in live_modes:
+        if advance:
+            index = live_modes.index(current_mode)
+            return live_modes[(index + 1) % len(live_modes)]
+        return current_mode
+    return live_modes[0]
 
 
 def wifi_notice_preempts(notice: Optional[WifiNotice], on_demand_active: bool,

src/display_manager.py

@@ -317,6 +317,11 @@ class DisplayManager:
         # is handed to the writer; this only once it has been saved, so an
         # mtime touch never vouches for a frame still waiting to be written.
         self._saved_snapshot_digest: Optional[int] = None
+        # A changed frame reached _write_snapshot_if_due() inside the write
+        # interval and was skipped. Nothing writes it unless update_display()
+        # runs again, and a screen that draws once and holds never calls it
+        # again -- see write_owed_snapshot().
+        self._snapshot_owed = False
         self._snapshot_dir_prepared = False
         # Background writer used mid-scroll; see _write_snapshot_if_due.
         self._snapshot_cond = threading.Condition()
@@ -1788,9 +1793,10 @@ class DisplayManager:
 
             if frame_checksum is not None:
                 digest = frame_checksum
+                frame_changed = digest != self._last_snapshot_digest
                 action = snapshot_policy.decide(
                     now, self._last_snapshot_ts, self._last_snapshot_touch_ts,
-                    viewer_fresh, digest != self._last_snapshot_digest)
+                    viewer_fresh, frame_changed)
             else:
                 # Ask as if the frame had changed before paying to find out.
                 # decide() is monotone in frame_changed -- a SKIP for a
@@ -1802,22 +1808,36 @@ class DisplayManager:
                     now, self._last_snapshot_ts, self._last_snapshot_touch_ts,
                     viewer_fresh, True)
                 if action is snapshot_policy.SnapshotAction.SKIP:
+                    # Not hashed, so not known to be unchanged: owed until a
+                    # later look finds it written or unchanged.
+                    self._snapshot_owed = True
                     return
                 digest = zlib.adler32(self.image.tobytes())
-                if digest == self._last_snapshot_digest:
+                frame_changed = digest != self._last_snapshot_digest
+                if not frame_changed:
                     # Unchanged after all: the decision an unchanged frame gets.
                     action = snapshot_policy.decide(
                         now, self._last_snapshot_ts,
                         self._last_snapshot_touch_ts, viewer_fresh, False)
             if action is snapshot_policy.SnapshotAction.SKIP:
+                # A changed frame inside the write interval stays owed: the
+                # next update_display() would write it, but a static screen
+                # may not make one -- write_owed_snapshot() covers that.
+                self._snapshot_owed = frame_changed
                 return
             if (action is snapshot_policy.SnapshotAction.TOUCH
                     and self._saved_snapshot_digest == digest):
                 # mtime bump only: keeps the health check (snapshot age)
                 # green without paying for a PNG encode of an unchanged frame
+                # (this frame is already on disk, so nothing is owed).
+                self._snapshot_owed = False
                 os.utime(self._snapshot_path, None)
                 self._last_snapshot_touch_ts = now
                 return
+            # Owed until the write below succeeds: if it raises, the frame
+            # stays owed and write_owed_snapshot() retries it, rather than a
+            # held screen leaving the preview stale after one failed write.
+            self._snapshot_owed = True
             # (A TOUCH for a frame that isn't on disk yet -- still queued, or
             # its write failed -- is written instead: touching would make the
             # older file on disk look current.)
@@ -1842,9 +1862,39 @@ class DisplayManager:
             self._last_snapshot_ts = now
             self._last_snapshot_touch_ts = now
             self._last_snapshot_digest = digest
+            self._snapshot_owed = False
         except Exception as e:
             self._log_snapshot_failure(e)
 
+    def write_owed_snapshot(self) -> None:
+        """Write a frame the snapshot throttle skipped, once it is due.
+
+        The preview snapshot is only ever written from update_display(), and
+        at most once per write interval (snapshot_policy). A frame pushed
+        inside that interval is skipped, and is written by the next
+        update_display() that comes after it -- but a screen that draws its
+        card once and then holds it makes no further call. Its frame was on
+        the panel and never in the preview: soccer's recent/upcoming cards
+        skip redundant redraws, and the first one after an on-demand start
+        (pushed a few milliseconds after the controller's clear) left
+        /api/v3/display/current and the web preview black for the whole
+        screen while the panel showed the card.
+
+        The render loop calls this after each frame. Cheap when nothing is
+        owed (one attribute read); otherwise the usual policy decides, so
+        the write still waits out the interval and an unchanged frame is
+        never re-encoded.
+        """
+        if not self._snapshot_owed:
+            return
+        try:
+            if self._writes_suppressed():
+                return
+            with self._update_lock:
+                self._write_snapshot_if_due()
+        except Exception as e:  # pylint: disable=broad-except
+            self._log_snapshot_failure(e)
+
     def _log_snapshot_failure(self, error: Exception) -> None:
         # Snapshot failures must never break display — but they must not
         # be silent either: the snapshot's mtime is the web UI's display

src/error_aggregator.py

@@ -490,10 +490,13 @@ def record_error(
 # user reads, and the other way round for the clear request.
 #
 #   ERROR_SNAPSHOT_KEY       written by the display service only
-#   ERROR_CLEAR_REQUEST_KEY  written by the web interface only
+#   ERROR_CLEAR_REQUEST_KEY  written by the web interface only, as a fallback
 #
-# A clear is asynchronous: the web interface records a request, and the
-# display service applies it (clear_before) on its next tick and republishes.
+# A clear goes over the control socket (``errors.clear``): the display applies
+# it (clear_before) and republishes the snapshot before it answers. Only when
+# the socket cannot carry it (no socket, or a display older than the command)
+# does the web interface record a request in the mailbox, which the display
+# applies on its next tick; its tick reads that file only when it changed.
 # Until it has, the web interface hides whatever the snapshot shows from
 # before the cutoff, so a clear takes effect for readers immediately and a
 # snapshot published just before the request cannot bring old errors back.
@@ -598,13 +601,43 @@ class ErrorSnapshotPublisher:
         self._published_version: Optional[int] = None
         self._last_attempt: Optional[float] = None
         self._applied_clear_id: Optional[str] = None
+        # The widest cutoff applied in this process: a clear request at or
+        # before it has nothing left to clear (see _pending_cutoff).
+        self._applied_clear_cutoff: Optional[float] = None
+        from src.cache_manager import MailboxWatch  # the display's cache, loaded already
+        self._mailbox = MailboxWatch(ERROR_CLEAR_REQUEST_KEY)
         self._tick_lock = threading.Lock()
         self._stop = threading.Event()
         self._thread: Optional[threading.Thread] = None
 
+    def _clear(self, request_id: str, cutoff: float) -> int:
+        """Apply one clear and remember it. Caller holds _tick_lock."""
+        cleared = 0
+        if math.isfinite(cutoff):
+            cleared = self.aggregator.clear_before(datetime.fromtimestamp(cutoff))
+            _snapshot_logger.info("Cleared %d plugin error record(s) as requested (%s)",
+                                  cleared, request_id)
+            if self._applied_clear_cutoff is None or cutoff > self._applied_clear_cutoff:
+                self._applied_clear_cutoff = cutoff
+        # A malformed request is acknowledged too, so it is not retried forever.
+        self._applied_clear_id = request_id
+        return cleared
+
     def _apply_clear_request(self) -> bool:
-        """Honour a clear request we have not applied yet. True if one was."""
-        request = self.cache_manager.get(ERROR_CLEAR_REQUEST_KEY, max_age=None, memory_ttl=0)
+        """Honour a mailbox clear request we have not applied yet. True if one was.
+
+        The mailbox is the fallback for a web interface that could not use
+        the control socket (``errors.clear``, :meth:`clear_now`). It is read
+        only when its file changed since the last tick; otherwise a tick
+        costs one stat().
+        """
+        if not self._mailbox.changed(self.cache_manager):
+            return False
+        try:
+            request = self.cache_manager.get(ERROR_CLEAR_REQUEST_KEY, max_age=None, memory_ttl=0)
+        except Exception:
+            self._mailbox.forget()
+            raise
         if not isinstance(request, dict):
             return False
         request_id = request.get("request_id")
@@ -614,14 +647,30 @@ class ErrorSnapshotPublisher:
             cutoff = float(request.get("cutoff"))
         except (TypeError, ValueError):
             cutoff = float("nan")
-        if math.isfinite(cutoff):
-            cleared = self.aggregator.clear_before(datetime.fromtimestamp(cutoff))
-            _snapshot_logger.info("Cleared %d plugin error record(s) as requested (%s)",
-                                  cleared, request_id)
-        # A malformed request is acknowledged too, so it is not retried forever.
-        self._applied_clear_id = request_id
+        self._clear(request_id, cutoff)
         return True
 
+    def clear_now(self, request_id: str, cutoff: float) -> int:
+        """``errors.clear`` over the control socket: apply a clear at once and
+        republish the snapshot, so the web interface's next read has it.
+        Returns how many records were cleared. Raises when the snapshot
+        could not be written, so the caller is not told it worked."""
+        with self._tick_lock:
+            cleared = self._clear(request_id, float(cutoff))
+            self._publish(self.aggregator.version, self._clock())
+            return cleared
+
+    def _publish(self, version: int, now: float) -> None:
+        """Write the snapshot. Caller holds _tick_lock."""
+        # Stamp the attempt before writing: a cache that keeps failing
+        # is retried at the throttled rate, not on every tick.
+        self._last_attempt = now
+        snapshot = self.aggregator.build_snapshot()
+        snapshot["applied_clear_id"] = self._applied_clear_id
+        snapshot["applied_clear_cutoff"] = self._applied_clear_cutoff
+        self.cache_manager.set(ERROR_SNAPSHOT_KEY, snapshot)
+        self._published_version = version
+
     def tick(self) -> bool:
         """Apply a pending clear and publish if due. True if a snapshot was written."""
         with self._tick_lock:
@@ -635,13 +684,7 @@ class ErrorSnapshotPublisher:
                     if (self._last_attempt is not None
                             and now - self._last_attempt < self.min_interval):
                         return False
-                # Stamp the attempt before writing: a cache that keeps failing
-                # is retried at the throttled rate, not on every tick.
-                self._last_attempt = now
-                snapshot = self.aggregator.build_snapshot()
-                snapshot["applied_clear_id"] = self._applied_clear_id
-                self.cache_manager.set(ERROR_SNAPSHOT_KEY, snapshot)
-                self._published_version = version
+                self._publish(version, now)
                 return True
             except Exception as err:  # never let reporting break the display
                 _snapshot_logger.debug("Could not publish the plugin error snapshot: %s",
@@ -693,6 +736,22 @@ def start_error_snapshot_publisher(cache_manager: Any) -> Optional[ErrorSnapshot
         return None
 
 
+def apply_error_clear(request_id: str, args: Any) -> Dict[str, Any]:
+    """The display's handler for ``errors.clear`` on the control socket.
+
+    ``args`` is the contract's ErrorsClearArgs (``cutoff``, epoch seconds).
+    Runs on the socket's connection thread: the aggregator and the publisher
+    have their own locks, and nothing here touches rendering. Returns
+    ErrorsClearResult once the clear is applied and the snapshot rewritten.
+    """
+    publisher = _snapshot_publisher
+    if publisher is None:
+        raise RuntimeError("the error snapshot publisher is not running")
+    cutoff = float(args.cutoff)
+    cleared = publisher.clear_now(request_id, cutoff)
+    return {"request_id": request_id, "cutoff": cutoff, "cleared": cleared}
+
+
 # --- Reading side (web interface) -------------------------------------------
 
 def read_error_report(cache_manager: Any) -> Tuple[Optional[Dict[str, Any]], Optional[Dict[str, Any]]]:
@@ -731,7 +790,15 @@ def _pending_cutoff(snapshot: Optional[Dict[str, Any]],
         cutoff = float(clear_request.get("cutoff"))
     except (TypeError, ValueError):
         return None
-    return cutoff if math.isfinite(cutoff) else None
+    if not math.isfinite(cutoff):
+        return None
+    # A wider clear has been applied since (over the control socket): this
+    # older request has nothing left to hide.
+    applied = snapshot.get("applied_clear_cutoff") if snapshot is not None else None
+    if (isinstance(applied, (int, float)) and not isinstance(applied, bool)
+            and applied >= cutoff):
+        return None
+    return cutoff
 
 
 def _is_after(item: Any, field_name: str, cutoff: float) -> bool:
@@ -831,13 +898,31 @@ def _count_cleared(summary: Dict[str, Any], cutoff: float) -> Optional[int]:
     return None
 
 
-def request_error_clear(cache_manager: Any, cutoff: float) -> Dict[str, Any]:
+#: ``send(request_id, cutoff)`` hands a clear to the display over the control
+#: socket and returns its ErrorsClearResult, or None when the socket could
+#: not carry it and the mailbox should be written instead. Any exception it
+#: raises reaches the caller: the display had the request and failed it.
+ClearSender = Callable[[str, float], Optional[Dict[str, Any]]]
+
+
+def request_error_clear(cache_manager: Any, cutoff: float,
+                        send: Optional[ClearSender] = None) -> Dict[str, Any]:
     """Ask the display service to forget errors recorded at or before ``cutoff``.
 
-    Returns ``request_id``, ``cutoff`` (ISO, local time), ``cleared_count``
-    (see _count_cleared) and ``clear_requested``. Raises OSError when the
-    request did not reach the shared cache, since a cache without a usable
-    directory accepts set() and keeps nothing.
+    Over the control socket when ``send`` is given and carries it: the
+    display applies the clear and republishes its snapshot before it
+    answers, so nothing is written here. Otherwise (no socket, or a display
+    older than ``errors.clear``) a request is written to the
+    ``plugin_error_clear_request`` mailbox, which the display applies on
+    its next tick, and readers hide the cleared errors until then.
+
+    Returns ``request_id``, ``cutoff`` (ISO, local time), ``cleared_count``,
+    ``clear_requested``, ``applied`` (the display has already cleared them)
+    and ``transport`` (``socket`` or ``mailbox``). ``cleared_count`` is the
+    display's own count over the socket, else an estimate from the snapshot
+    (see _count_cleared). Raises OSError when a mailbox request did not reach
+    the shared cache, since a cache without a usable directory accepts set()
+    and keeps nothing.
 
     A request the display has not applied yet is only ever widened: a later,
     narrower one ("older than 24 hours" after "everything") overwriting it
@@ -848,8 +933,21 @@ def request_error_clear(cache_manager: Any, cutoff: float) -> Dict[str, Any]:
     if pending is not None:
         cutoff = max(cutoff, pending)
     before = error_summary_from_report(snapshot, clear_request)
+    request_id = uuid.uuid4().hex
+    answer = {
+        "clear_requested": True,
+        "request_id": request_id,
+        "cutoff": datetime.fromtimestamp(cutoff).isoformat(),
+    }
+    if send is not None:
+        result = send(request_id, cutoff)
+        if result is not None:
+            count = result.get("cleared")
+            return dict(answer, applied=True, transport="socket",
+                        cleared_count=count if isinstance(count, int) and not isinstance(count, bool)
+                        else _count_cleared(before, cutoff))
     request = {
-        "request_id": uuid.uuid4().hex,
+        "request_id": request_id,
         "cutoff": cutoff,
         "requested_at": time.time(),
     }
@@ -857,9 +955,5 @@ def request_error_clear(cache_manager: Any, cutoff: float) -> Dict[str, Any]:
     stored = cache_manager.get(ERROR_CLEAR_REQUEST_KEY, max_age=None, memory_ttl=0)
     if not isinstance(stored, dict) or stored.get("request_id") != request["request_id"]:
         raise OSError("the clear request was not stored in the shared cache")
-    return {
-        "cleared_count": _count_cleared(before, cutoff),
-        "clear_requested": True,
-        "request_id": request["request_id"],
-        "cutoff": datetime.fromtimestamp(cutoff).isoformat(),
-    }
+    return dict(answer, applied=False, transport="mailbox",
+                cleared_count=_count_cleared(before, cutoff))

src/font_manager.py

@@ -222,6 +222,39 @@ class FontManager:
             logger.error(f"Error registering fonts for plugin {plugin_id}: {e}", exc_info=True)
             return False
 
+    def forget_plugin_fonts(self, plugin_id: str) -> bool:
+        """Drop the fonts ``plugin_id``'s manifest registered: its manifest
+        and catalog, its ``plugin_id::family`` entries in font_catalog, and
+        cached font objects for those families. Called by core when a plugin
+        is unloaded, so a reload registers from its current manifest and a
+        removed plugin's fonts stop resolving.
+
+        FontManager takes no locks; like forget_manager_fonts this relies on
+        single dict operations being atomic and iterates snapshots, so a
+        render thread calling get_font() meanwhile cannot break it. Returns
+        True if the plugin had registered fonts.
+        """
+        prefix = f"{plugin_id}::"
+        manifest = self.plugin_fonts.pop(plugin_id, None)
+        catalog = self.plugin_font_catalogs.pop(plugin_id, None)
+        # Every namespaced entry, not just the families in the catalog: one
+        # whose file failed to load never made it into the catalog, and a
+        # caller may have added one directly.
+        for family in list(self.font_catalog):
+            if family.startswith(prefix):
+                self.font_catalog.pop(family, None)
+        # get_font() keys the cache f"{family}_{size_px}".
+        dropped = [key for key in list(self.font_cache) if key.startswith(prefix)]
+        for key in dropped:
+            self.font_cache.pop(key, None)
+        if dropped:
+            # Font objects someone may hold were dropped; see cache_generation.
+            self.cache_generation += 1
+        if manifest is None and catalog is None:
+            return False
+        logger.info("Forgot fonts of plugin %s", plugin_id)
+        return True
+
     def _validate_font_manifest(self, font_manifest: Dict[str, Any]) -> bool:
         """Validate the structure of a plugin's font manifest."""
         required_fields = ["fonts"]

src/ipc/client.py

@@ -3,8 +3,13 @@
 Every failure -- no socket (the display is stopped, or predates the socket),
 a refused or timed-out connection, a reply that breaks the contract, or an
 error the display returned -- raises :class:`ControlError` with a short
-``reason``, and the caller falls back to the file mailbox. Nothing here
-blocks for longer than ``timeout`` in total.
+``reason``. Nothing here blocks for longer than ``timeout`` in total.
+
+Whether the caller may then write the file mailbox instead is
+:func:`should_fall_back`: only when the display never took the request (it
+could not be reached, or it is too old to know the command). A display that
+took the request and then failed, refused or went quiet is answered as
+that, not posted a second time through the mailbox.
 """
 
 from __future__ import annotations
@@ -22,6 +27,7 @@ from src.ipc.contract import (
     SUBSCRIBE_KEEPALIVE_SECONDS,
     SUPPORTED_VERSIONS,
     Command,
+    ErrorCode,
     FrameReader,
     ProtocolError,
     Request,
@@ -49,17 +55,49 @@ class ControlError(Exception):
     ``refused``, ``timeout``, ``closed``, ``bad_response``, ``invalid_request``.
     When the display answered with an error, ``reason`` is that error's
     :class:`~src.ipc.contract.ErrorCode` (``busy``, ``unknown_command``, ...).
+
+    ``sent`` is True once the whole request was written to a connected
+    display, which may then have acted on it. A refusal the display sends
+    before it reads anything (``forbidden``, too many connections) carries
+    no request id and leaves ``sent`` False.
     """
 
-    def __init__(self, reason: str, message: str = ''):
+    def __init__(self, reason: str, message: str = '', *, sent: bool = False):
         super().__init__(reason, message)
         self.reason = reason
         self.message = message
+        self.sent = sent
 
     def __str__(self) -> str:
         return f'{self.reason}: {self.message}' if self.message else self.reason
 
 
+#: Answers from a display that read the request but does not speak it: one
+#: older than the command (an upgrade in progress) or the protocol version.
+#: It did nothing, so the mailbox is the way to reach it.
+UPGRADE_REASONS = frozenset({ErrorCode.UNKNOWN_COMMAND, ErrorCode.UNSUPPORTED_VERSION})
+
+
+def should_fall_back(error: BaseException) -> bool:
+    """May the caller write the file mailbox after ``error``?
+
+    Yes when the display never took the request: there is no socket (the
+    display is stopped, predates the socket, or it is switched off), the
+    connection was refused or timed out, the display turned the connection
+    away before reading it, or it is too old to know the command
+    (:data:`UPGRADE_REASONS`). Also for an error that is not a
+    :class:`ControlError` (a bug in the client), as before.
+
+    No once the display had the request: a ``busy`` queue, ``invalid_args``,
+    an ``internal`` error, or a timeout or hang-up after the request was
+    sent. The display may have applied it, or would refuse it from the
+    mailbox too, so a second copy there only hides the failure.
+    """
+    if not isinstance(error, ControlError):
+        return True
+    return not error.sent or error.reason in UPGRADE_REASONS
+
+
 def request(cmd: str, args: Optional[Mapping[str, Any]] = None, *,
             request_id: Optional[str] = None,
             timeout: float = DEFAULT_TIMEOUT_SECONDS,
@@ -93,11 +131,14 @@ def request(cmd: str, args: Optional[Mapping[str, Any]] = None, *,
     # A refusal before the request was read (forbidden, too many
     # connections) carries no id.
     if response.id != request_id and not (response.id is None and not response.ok):
-        raise ControlError('bad_response', 'the reply is for a different request')
+        raise ControlError('bad_response', 'the reply is for a different request', sent=True)
     if not response.ok:
         error = response.error
+        # No id: refused at the door (forbidden, too many connections),
+        # before the display read the request.
         raise ControlError(error.code if error else 'bad_response',
-                           error.message if error else '')
+                           error.message if error else '',
+                           sent=response.id is not None)
     return dict(response.result or {})
 
 
@@ -142,26 +183,31 @@ def _connect(paths: Sequence[str], deadline: float) -> socket.socket:
 
 
 def _exchange(sock: socket.socket, payload: bytes, deadline: float) -> Response:
+    """Send ``payload`` and read the reply. A failure once the whole request
+    is written raises with ``sent=True``: the display may have it."""
+    sent = False
     try:
         sock.settimeout(_remaining(deadline))
         sock.sendall(payload)
+        sent = True
         reader = FrameReader(MAX_MESSAGE_BYTES)
         while True:
             sock.settimeout(_remaining(deadline))
             data = sock.recv(4096)
             if not data:
-                raise ControlError('closed', 'the display closed the connection')
+                raise ControlError('closed', 'the display closed the connection', sent=sent)
             lines = reader.feed(data)
             if lines:
                 return Response.from_dict(decode_message(lines[0]))
     except socket.timeout:
-        raise ControlError('timeout', 'no reply in time') from None
+        raise ControlError('timeout', 'no reply in time', sent=sent) from None
     except ProtocolError as e:
-        raise ControlError('bad_response', e.message) from None
-    except ControlError:
+        raise ControlError('bad_response', e.message, sent=sent) from None
+    except ControlError as e:
+        e.sent = e.sent or sent
         raise
     except OSError as e:
-        raise ControlError('closed', str(e)) from None
+        raise ControlError('closed', str(e), sent=sent) from None
 
 
 # -- commands ---------------------------------------------------------------------------
@@ -227,6 +273,21 @@ def plugin_reload(plugin_id: str, *, timeout: Optional[float] = None,
                    else timeout, paths=paths)
 
 
+def errors_clear(request_id: str, cutoff: float, *,
+                 timeout: float = DEFAULT_TIMEOUT_SECONDS,
+                 paths: Optional[Sequence[str]] = None) -> Dict[str, Any]:
+    """Have the display forget the plugin errors recorded at or before
+    ``cutoff`` (epoch seconds) and publish its error snapshot again.
+
+    Returns :class:`~src.ipc.contract.ErrorsClearResult` once it is done.
+    Raises :class:`ControlError`: ``unknown_command`` from a display older
+    than the command, which still reads the ``plugin_error_clear_request``
+    mailbox.
+    """
+    return request(Command.ERRORS_CLEAR, {'cutoff': cutoff}, request_id=request_id,
+                   timeout=timeout, paths=paths)
+
+
 def ping(*, timeout: float = DEFAULT_TIMEOUT_SECONDS,
          paths: Optional[Sequence[str]] = None) -> Dict[str, Any]:
     return request(Command.PING, {}, timeout=timeout, paths=paths)
@@ -283,6 +344,29 @@ def snapshot_loop_age(snapshot: Mapping[str, Any],
     return max(float(age), 0.0) + snapshot_age(snapshot, now_mono)
 
 
+def _merge_volatile(state: Dict[str, Any], volatile: Any) -> None:
+    """Fold a tick's ``volatile`` values (``{section: {key: value}}``) into
+    ``state``, copying each section it touches.
+
+    These are the timestamps the hub leaves out of its version --
+    ``display.last_updated``, ``on_demand.last_updated``/``remaining``,
+    ``plugins.published_at`` -- and the readers judge freshness by them, so
+    a copy that only full ``state`` events updated would go stale while the
+    same mode stayed on screen. Only keys the section already has are taken:
+    a tick never adds a section or a key the last snapshot did not carry
+    (a section left out of a truncated snapshot stays out).
+    """
+    if not isinstance(volatile, dict):
+        return  # a display from before ticks carried them
+    for name, values in volatile.items():
+        section = state.get(name)
+        if not isinstance(section, dict) or not isinstance(values, dict):
+            continue
+        fresh = {k: v for k, v in values.items() if k in section}
+        if fresh:
+            state[name] = dict(section, **fresh)
+
+
 #: A subscription that has heard nothing for this long is not trusted: the
 #: display sends a tick at least every SUBSCRIBE_KEEPALIVE_SECONDS.
 SUBSCRIPTION_SILENCE_SECONDS = 3 * SUBSCRIBE_KEEPALIVE_SECONDS
@@ -373,9 +457,9 @@ class StateSubscription:
     def _run(self) -> None:
         backoff = _RECONNECT_MIN_SECONDS
         while not self._stop.is_set():
+            snapshots = self.snapshots
             try:
                 self._follow()
-                backoff = _RECONNECT_MIN_SECONDS
             except ControlError as e:
                 self.last_error = e.reason
                 if e.reason in _SLOW_RETRY_REASONS:
@@ -391,6 +475,11 @@ class StateSubscription:
                         sock.close()
                     except OSError:
                         pass
+            if self.snapshots != snapshots:
+                # This connection got as far as the display's state: whatever
+                # ended it (a restart, most often), it was working, so the
+                # next try starts from the shortest wait again.
+                backoff = _RECONNECT_MIN_SECONDS
             if self._stop.wait(backoff):
                 return
             backoff = min(backoff * 2, _RECONNECT_MAX_SECONDS)
@@ -449,12 +538,17 @@ class StateSubscription:
                 self.snapshots += 1
             elif (self._snapshot is not None
                   and result.get('epoch') == self._snapshot.get('epoch')):
-                # A tick: nothing changed but the render loop's liveness.
+                # A tick: nothing changed but the render loop's liveness and
+                # the volatile keys (timestamps) the writers keep refreshing.
                 snap = dict(self._snapshot)
+                state = dict(snap.get('state') or {})
+                if result.get('version') == snap.get('version'):
+                    _merge_volatile(state, result.get('volatile'))
                 loop = result.get('loop')
                 if isinstance(loop, dict):
-                    snap['state'] = dict(snap.get('state') or {}, loop=loop)
+                    state['loop'] = loop
                     snap['loop'] = loop
+                snap['state'] = state
                 snap['served_at'] = result.get('served_at', snap.get('served_at'))
                 self._snapshot = snap
             else:

src/ipc/contract.py

@@ -149,12 +149,13 @@ class Command:
     PLUGIN_RELOAD = 'plugin.reload'
     STATE_GET = 'state.get'
     STATE_SUBSCRIBE = 'state.subscribe'
+    ERRORS_CLEAR = 'errors.clear'
 
 
 #: Every command version 1 defines, in the order ``hello`` reports them.
-#: ``brightness.set`` and ``plugin.reload`` came in stage 2, and ``state.get``
-#: and ``state.subscribe`` in stage 3, all within version 1 (see the module
-#: docstring on adding commands).
+#: ``brightness.set`` and ``plugin.reload`` came in stage 2, ``state.get``
+#: and ``state.subscribe`` in stage 3, and ``errors.clear`` in stage 4, all
+#: within version 1 (see the module docstring on adding commands).
 COMMANDS: Tuple[str, ...] = (
     Command.HELLO,
     Command.PING,
@@ -165,8 +166,15 @@ COMMANDS: Tuple[str, ...] = (
     Command.PLUGIN_RELOAD,
     Command.STATE_GET,
     Command.STATE_SUBSCRIBE,
+    Command.ERRORS_CLEAR,
 )
 
+#: Commands the connection thread answers itself, through a handler the
+#: display registers (``ControlServer(handlers=...)``), because they touch
+#: nothing the render thread owns. A display that registered none answers
+#: ``unknown_command``, and the client falls back as from an older display.
+DIRECT_COMMANDS = frozenset({Command.ERRORS_CLEAR})
+
 #: Commands that are queued for the render thread.
 QUEUED_COMMANDS = frozenset({Command.ON_DEMAND_START, Command.ON_DEMAND_STOP,
                              Command.BRIGHTNESS_SET, Command.PLUGIN_RELOAD})
@@ -191,7 +199,7 @@ MAX_SUBSCRIBERS = 4
 
 #: A subscriber hears from the display at least this often: a ``state``
 #: event when something changed, else a ``tick`` carrying the render loop's
-#: liveness. A client that has heard nothing for a few of these treats its
+#: liveness and the latest volatile timestamps. A client that has heard nothing for a few of these treats its
 #: copy as unknown.
 SUBSCRIBE_KEEPALIVE_SECONDS = 5.0
 
@@ -530,8 +538,10 @@ class StateGetArgs:
     """``state.get``: the display's state, as a versioned snapshot.
 
     With ``since`` and the ``epoch`` it came from, the answer is only
-    ``{changed: false, version, epoch, served_at, loop}`` while the state is
-    still at that version, so a poller that already has it is sent no state.
+    ``{changed: false, version, epoch, served_at, loop, volatile}`` while the
+    state is still at that version, so a poller that already has it is sent
+    no state -- only the latest values of the keys that do not count as a
+    change (``volatile``, see :class:`StateSnapshot`).
     """
     since: Optional[int] = None
     epoch: Optional[str] = None
@@ -563,8 +573,32 @@ class StateSubscribeArgs:
         return cls()
 
 
+@dataclass(frozen=True)
+class ErrorsClearArgs:
+    """``errors.clear``: forget the plugin errors recorded at or before
+    ``cutoff`` (seconds since the epoch), as ``POST /api/v3/errors/clear``
+    asks. The request id is the clear's id, which the display's error
+    snapshot then reports as ``applied_clear_id``.
+    """
+    cutoff: float
+
+    def to_dict(self) -> Dict[str, Any]:
+        return {'cutoff': self.cutoff}
+
+    @classmethod
+    def from_dict(cls, args: Mapping[str, Any]) -> 'ErrorsClearArgs':
+        value = args.get('cutoff')
+        if isinstance(value, bool) or not isinstance(value, (int, float)):
+            raise ProtocolError(ErrorCode.INVALID_ARGS, 'cutoff must be a number of seconds')
+        if not math.isfinite(value) or value < 0:
+            raise ProtocolError(ErrorCode.INVALID_ARGS,
+                                'cutoff must be a finite, non-negative number of seconds')
+        return cls(cutoff=float(value))
+
+
 CommandArgs = Union[HelloArgs, OnDemandStartArgs, OnDemandStopArgs, NoArgs,
-                    BrightnessSetArgs, PluginReloadArgs, StateGetArgs, StateSubscribeArgs]
+                    BrightnessSetArgs, PluginReloadArgs, StateGetArgs, StateSubscribeArgs,
+                    ErrorsClearArgs]
 
 #: The arguments of a command that goes on the render thread's queue.
 QueuedArgs = Union[OnDemandStartArgs, OnDemandStopArgs, BrightnessSetArgs, PluginReloadArgs]
@@ -579,6 +613,7 @@ _ARG_TYPES: Dict[str, Any] = {
     Command.PLUGIN_RELOAD: PluginReloadArgs,
     Command.STATE_GET: StateGetArgs,
     Command.STATE_SUBSCRIBE: StateSubscribeArgs,
+    Command.ERRORS_CLEAR: ErrorsClearArgs,
 }
 
 
@@ -651,6 +686,13 @@ class PluginReloadResult(TypedDict):
     modes: List[str]
 
 
+class ErrorsClearResult(TypedDict):
+    """``errors.clear``, once applied and the error snapshot republished."""
+    request_id: str
+    cutoff: float
+    cleared: int
+
+
 class LoopState(TypedDict):
     """``loop``: is the render loop still going round?
 
@@ -672,9 +714,13 @@ class StateSnapshot(TypedDict, total=False):
     ``version`` counts changes to the state within one ``epoch`` (one run of
     the display process): a reader that sees a new epoch starts over.
     ``changed`` is False only for a ``state.get`` whose ``since`` is still
-    current, and then ``state`` is absent. ``served_at`` is the display's
-    wall clock when it answered. ``loop`` is measured at that moment, so it
-    is also inside ``state``.
+    current, and then ``state`` is absent and ``volatile`` is there instead:
+    ``{section: {key: value}}``, the current values of the keys the version
+    ignores (``display.last_updated``, ``on_demand.last_updated`` and
+    ``remaining``, ``plugins.published_at``). A reader merges them into the
+    copy it has; they are how it can tell the writers are still publishing.
+    ``served_at`` is the display's wall clock when it answered. ``loop`` is
+    measured at that moment, so it is also inside ``state``.
 
     ``state`` holds the sections in :data:`STATE_SECTIONS`:
 
@@ -696,12 +742,13 @@ class StateSnapshot(TypedDict, total=False):
     served_at: float
     changed: bool
     state: Dict[str, Any]
+    volatile: Dict[str, Dict[str, Any]]
     loop: LoopState
 
 
 class StateEventKind:
     STATE = 'state'   # result: a full StateSnapshot, the latest version
-    TICK = 'tick'     # result: {version, epoch, pid, served_at, loop}; nothing changed
+    TICK = 'tick'     # result: {version, epoch, pid, served_at, loop, volatile}; nothing changed
 
 
 @dataclass(frozen=True)

src/ipc/server.py

@@ -6,7 +6,9 @@ rendering: a command that changes the panel is validated, put on a bounded
 queue and acknowledged, and the render thread drains that queue at the point
 where it reads the file mailbox (``DisplayController._poll_on_demand_requests``),
 handing each command to the same code. Queries (``on_demand.status``) are
-answered from a snapshot callable the display provides.
+answered from a snapshot callable the display provides, and the few commands
+that touch nothing the render thread owns (``errors.clear``) by a handler the
+display registers, on the connection thread.
 
 The queue also wakes the render thread: :meth:`ControlServer.wait_for_command`
 is what it waits on in place of a sleep, so a command lands within a frame on
@@ -62,6 +64,7 @@ from src.ipc.contract import (
     AWAITED_COMMANDS,
     COMMANDS,
     DEFAULT_SOCKET_DIR,
+    DIRECT_COMMANDS,
     DEFAULT_SOCKET_PATH,
     MAX_MESSAGE_BYTES,
     MAX_SUBSCRIBERS,
@@ -107,7 +110,8 @@ MAX_CLIENTS = 8
 
 #: Commands waiting for the render thread. It drains them at least every
 #: 0.25 s, so a full queue means the render thread is stuck, and the client
-#: is told ``busy`` (and falls back to the mailbox) instead of piling up work.
+#: is told ``busy`` instead of piling up work. The mailbox would not be read
+#: either, so the web interface reports the failure rather than fall back.
 QUEUE_SIZE = 16
 
 #: Timeout for one recv()/send() on a connection.
@@ -222,6 +226,22 @@ def _fingerprint(value: Optional[Mapping[str, Any]], volatile: Iterable[str]) ->
     return {k: v for k, v in value.items() if k not in skip} if skip else dict(value)
 
 
+def _volatile_values(sections: Mapping[str, Optional[Dict[str, Any]]],
+                     volatile: Mapping[str, FrozenSet[str]]) -> Dict[str, Dict[str, Any]]:
+    """``{section: {key: value}}``: the volatile keys each published section
+    has now. The sections are never mutated after publish (a publish swaps
+    in a new dict), so reading them outside the lock is safe."""
+    values: Dict[str, Dict[str, Any]] = {}
+    for name, keys in volatile.items():
+        value = sections.get(name)
+        if not keys or not isinstance(value, dict):
+            continue
+        present = {k: value[k] for k in keys if k in value}
+        if present:
+            values[name] = present
+    return values
+
+
 def _unknown_loop() -> Dict[str, Any]:
     return {'heartbeat_age_seconds': None, 'armed': False, 'stale_after': None}
 
@@ -259,7 +279,11 @@ class StateHub:
     (``loop_probe``), so it keeps ageing while the render thread is stuck.
 
     The version goes up when a section's value changes, ignoring the keys
-    the publisher names as volatile (timestamps). Publishing never blocks on
+    the publisher names as volatile (timestamps). Those keys still carry
+    news -- ``display.last_updated`` is the render thread's proof of life --
+    so the short ``changed: false`` answer, which is what a subscriber's
+    tick carries, has their current values in ``volatile``; a reader merges
+    them into its copy. Publishing never blocks on
     a reader: the lock is held only to swap a dict reference and compare it,
     and every socket write happens on the reader's own thread, outside it.
     A reader that is slow gets the latest version when it next asks, not
@@ -274,6 +298,7 @@ class StateHub:
         self._cond = threading.Condition(threading.Lock())
         self._sections: Dict[str, Optional[Dict[str, Any]]] = {}
         self._fingerprints: Dict[str, Any] = {}
+        self._volatile: Dict[str, FrozenSet[str]] = {}
         self._version = 0
         self.epoch = epoch or uuid.uuid4().hex[:16]
         self.pid = os.getpid() if pid is None else pid
@@ -301,9 +326,11 @@ class StateHub:
         The value is copied (one level), so the caller may reuse its dict.
         """
         stored = None if value is None else dict(value)
-        fingerprint = _fingerprint(stored, volatile)
+        skip = frozenset(volatile)
+        fingerprint = _fingerprint(stored, skip)
         with self._cond:
             self._sections[section] = stored
+            self._volatile[section] = skip
             if self._fingerprints.get(section, _MISSING) == fingerprint:
                 return False
             self._fingerprints[section] = fingerprint
@@ -333,11 +360,14 @@ class StateHub:
         """The :class:`~src.ipc.contract.StateSnapshot` now.
 
         ``since`` with this hub's ``epoch``, still the current version, gives
-        the short ``changed: false`` form.
+        the short ``changed: false`` form, with ``volatile``: each section's
+        volatile keys at their latest values (the rest of the section is
+        what the reader already has).
         """
         with self._cond:
             version = self._version
             sections = dict(self._sections)
+            volatile = dict(self._volatile)
         loop = self.loop()
         result: Dict[str, Any] = {
             'schema': STATE_SCHEMA,
@@ -349,6 +379,7 @@ class StateHub:
         }
         if since is not None and epoch == self.epoch and since == version:
             result['changed'] = False
+            result['volatile'] = _volatile_values(sections, volatile)
             return result
         state: Dict[str, Any] = {name: sections.get(name) for name in STATE_SECTIONS
                                  if name != 'loop'}
@@ -525,6 +556,12 @@ def server_socket_path(environ: Optional[Mapping[str, str]] = None) -> Optional[
 
 StatusProvider = Callable[[], Dict[str, Any]]
 
+#: A handler for one of DIRECT_COMMANDS, ``(request_id, args) -> result``. It
+#: runs on the connection thread, so it must not touch what the render thread
+#: owns. It may raise ProtocolError to answer with that error's code; any
+#: other exception is answered ``internal``.
+DirectHandler = Callable[[str, Any], Mapping[str, Any]]
+
 
 class ControlServer:
     """Serves the control socket on background threads.
@@ -542,9 +579,12 @@ class ControlServer:
                  await_seconds: Optional[Mapping[str, float]] = None,
                  state_hub: Optional[StateHub] = None,
                  max_subscribers: int = MAX_SUBSCRIBERS,
-                 keepalive: float = SUBSCRIBE_KEEPALIVE_SECONDS):
+                 keepalive: float = SUBSCRIBE_KEEPALIVE_SECONDS,
+                 handlers: Optional[Mapping[str, DirectHandler]] = None):
         self.path = path
         self.state_hub = state_hub
+        self._handlers: Dict[str, DirectHandler] = {
+            cmd: fn for cmd, fn in (handlers or {}).items() if cmd in DIRECT_COMMANDS}
         self._subscriber_slots = threading.BoundedSemaphore(max_subscribers)
         self._keepalive = keepalive
         self._await_seconds: Dict[str, float] = dict(AWAIT_SECONDS)
@@ -732,8 +772,22 @@ class ControlServer:
         """
         return self._pending.wait(timeout)
 
+    def wake(self) -> None:
+        """Wake the render thread as a queued command would, with nothing queued.
+
+        For work that reaches the display another way in the same process (a
+        plugin's on-demand request, ``DisplayController.submit_plugin_on_demand``):
+        the render thread returns from :meth:`wait_for_command` and drains,
+        and reads the caller's own queue there. Safe from any thread.
+        """
+        self._pending.set()
+
     def drain(self) -> List[QueuedCommand]:
-        """Every queued command, oldest first. Called from the render thread."""
+        """Every queued command, oldest first. Called from the render thread.
+
+        Clears the wake flag first, so anything queued (or woken for) while
+        this runs wakes the next wait again.
+        """
         commands: List[QueuedCommand] = []
         self._pending.clear()
         while True:
@@ -1001,6 +1055,9 @@ class ControlServer:
                 snap = hub.snapshot()
             return Response.success(request.id, fit_snapshot(snap), v=request.v)
 
+        if request.cmd in DIRECT_COMMANDS:
+            return self._direct(request, args)
+
         if request.cmd in QUEUED_COMMANDS and isinstance(args, (
                 OnDemandStartArgs, OnDemandStopArgs, BrightnessSetArgs, PluginReloadArgs)):
             awaited = request.cmd in AWAITED_COMMANDS
@@ -1028,6 +1085,25 @@ class ControlServer:
         return Response.failure(request.id, ErrorCode.INTERNAL,
                                 f'{request.cmd} is not implemented', v=request.v)
 
+    def _direct(self, request: Request, args: Any) -> Response:
+        """A command the display answers on this thread (DIRECT_COMMANDS)."""
+        handler = self._handlers.get(request.cmd)
+        if handler is None:
+            # Answered as an older display would, so the client falls back.
+            return Response.failure(request.id, ErrorCode.UNKNOWN_COMMAND,
+                                    f'{request.cmd} is not served by this display',
+                                    v=request.v)
+        try:
+            result = handler(request.id, args)
+        except ProtocolError as e:
+            return Response.failure(request.id, e.code, e.message, v=request.v)
+        except Exception:  # pylint: disable=broad-except
+            logger.exception("Control socket: %s %s failed", request.cmd, request.id)
+            return Response.failure(request.id, ErrorCode.INTERNAL,
+                                    'the display failed to apply it', v=request.v)
+        logger.info("Control socket applied %s %s", request.cmd, request.id)
+        return Response.success(request.id, dict(result), v=request.v)
+
     def _await_outcome(self, request: Request, outcome: CommandOutcome) -> Response:
         """Answer an awaited command once the render thread has applied it.
 
@@ -1052,7 +1128,9 @@ class ControlServer:
 def start_control_server(status_provider: Optional[StatusProvider] = None,
                          cache_dir: Optional[str] = None,
                          environ: Optional[Mapping[str, str]] = None,
-                         state_hub: Optional[StateHub] = None) -> Optional[ControlServer]:
+                         state_hub: Optional[StateHub] = None,
+                         handlers: Optional[Mapping[str, DirectHandler]] = None,
+                         ) -> Optional[ControlServer]:
     """Start the display's control socket, or return None when it can't run.
 
     None covers Windows, ``LEDMATRIX_CONTROL_SOCKET=off`` and any failure to
@@ -1064,7 +1142,7 @@ def start_control_server(status_provider: Optional[StatusProvider] = None,
         logger.debug("Control socket disabled or unsupported here; using the file mailbox only")
         return None
     server = ControlServer(path, status_provider, resolve_socket_group(cache_dir),
-                           state_hub=state_hub)
+                           state_hub=state_hub, handlers=handlers)
     return server if server.start() else None
 
 

src/plugin_system/base_plugin.py

@@ -1070,6 +1070,65 @@ class BasePlugin(ABC):
         if callable(notify):
             notify(self.plugin_id)
 
+    def request_on_demand(self, mode: Optional[str] = None,
+                          duration: Optional[float] = None,
+                          pinned: bool = False) -> Optional[str]:
+        """
+        Take the screen now: show this plugin on demand. Safe from any thread.
+
+        For a plugin that reacts to something outside the rotation -- an MQTT
+        message, a timer, a detection -- and wants the panel for it. The
+        request goes straight to the display in this process and is applied
+        on its render thread within a frame or so, exactly like an on-demand
+        start from the web interface.
+
+        Args:
+            mode: One of this plugin's display modes; None for its first.
+            duration: Seconds to show it before the rotation resumes; None
+                (or zero) for no limit, until end_on_demand() or the user
+                stops it.
+            pinned: Stay on ``mode`` instead of cycling through the
+                plugin's other modes.
+
+        Returns:
+            The request id once the display has queued it, or None when
+            there is no display in this process to ask (the web interface,
+            scripts/check_plugin.py) or its queue is full. A plugin that
+            also runs on cores without this method writes the
+            ``display_on_demand_request`` mailbox on None, as before; see
+            "On-demand display" in docs/PLUGIN_API_REFERENCE.md.
+
+        Example::
+
+            if not (hasattr(self, 'request_on_demand')
+                    and self.request_on_demand(mode='my_alert', duration=15)):
+                self._write_on_demand_mailbox(...)   # older cores
+        """
+        request = getattr(getattr(self, 'plugin_manager', None), 'request_on_demand', None)
+        if not callable(request):
+            return None
+        request_id = request(self.plugin_id, mode=mode, duration=duration, pinned=pinned)
+        # Only a real id counts: a test's MagicMock manager answers a mock,
+        # which must read as "not taken" so the plugin's fallback runs.
+        return request_id if isinstance(request_id, str) else None
+
+    def end_on_demand(self) -> Optional[str]:
+        """
+        Give the screen back: end this plugin's on-demand session. Any thread.
+
+        Ends only a session this plugin owns. One the user started for
+        another plugin, or a session that already ended, is left alone. The
+        rotation resumes where it left off.
+
+        Returns:
+            The request id once queued, or None as request_on_demand() does.
+        """
+        end = getattr(getattr(self, 'plugin_manager', None), 'end_on_demand', None)
+        if not callable(end):
+            return None
+        request_id = end(self.plugin_id)
+        return request_id if isinstance(request_id, str) else None
+
     def get_vegas_participation(self) -> str:
         """
         How this plugin takes part in Vegas mode: ``'scroll'``, ``'pause'`` or

src/plugin_system/operation_types.py

@@ -48,12 +48,19 @@ class PluginOperation:
     completed_at: Optional[datetime] = None
     
     def to_dict(self) -> Dict[str, Any]:
-        """Convert operation to dictionary for serialization."""
+        """Convert operation to dictionary for serialization.
+
+        Parameters whose name starts with ``_`` are internal and left out:
+        PluginOperationQueue keeps the operation's callback there as
+        ``_callback`` until its worker runs it, and a pending operation's
+        status answered 500 because that function cannot be serialized.
+        """
         return {
             'operation_id': self.operation_id,
             'operation_type': self.operation_type.value,
             'plugin_id': self.plugin_id,
-            'parameters': self.parameters,
+            'parameters': {key: value for key, value in self.parameters.items()
+                           if not str(key).startswith('_')},
             'status': self.status.value,
             'progress': self.progress,
             'message': self.message,

src/plugin_system/plugin_catalog.py

@@ -15,7 +15,8 @@ reads through a catalog unchanged. It has nothing that runs a plugin: no
 ``load_plugin``, ``get_plugin`` or ``plugins``.
 
 Runtime state -- whether the display has a plugin loaded, its health, its
-errors -- is not here either. The display process publishes what it knows to
+errors -- is not here either, with one exception: given a ``runtime_source``,
+the mode lookups prefer the modes the running display registered. The display process publishes what it knows to
 the shared cache (health and resource metrics, the current mode, the error
 aggregator snapshot), and the web routes read those publications. What the
 display does not publish (which plugins it has loaded, its plugin state
@@ -26,8 +27,9 @@ See docs/ARCHITECTURE.md ("Web and display processes").
 
 import json
 import threading
+import time
 from pathlib import Path
-from typing import Any, Dict, List, Optional, Union, cast
+from typing import Any, Callable, Dict, List, Optional, Union, cast
 
 from src.common.permission_utils import (
     ensure_directory_permissions, get_plugin_dir_mode,
@@ -39,6 +41,10 @@ from src.plugin_system.plugin_dirs import (
 
 PathLike = Union[str, Path]
 
+#: How long one read of the display's runtime view answers mode lookups. A
+#: listing asks once per plugin; the cache copy is a file read each time.
+_RUNTIME_VIEW_TTL_SECONDS = 1.0
+
 
 class PluginCatalog:
     """Manifests, schemas, config and versions of the installed plugins.
@@ -49,10 +55,17 @@ class PluginCatalog:
     """
 
     def __init__(self, plugins_dir: PathLike, config_manager: Optional[Any] = None,
-                 schema_manager: Optional[Any] = None) -> None:
+                 schema_manager: Optional[Any] = None,
+                 runtime_source: Optional[Callable[[], Any]] = None) -> None:
         self.plugins_dir: Path = Path(plugins_dir)
         self.config_manager = config_manager
         self.schema_manager = schema_manager
+        # Returns the display's PluginRuntimeView
+        # (src/plugin_system/plugin_runtime.py). Its live view carries the
+        # modes the display registered, which the mode lookups below prefer
+        # to the manifest's. None: manifests only.
+        self.runtime_source = runtime_source
+        self._runtime_view_memo: Optional[tuple] = None
         self.logger = get_logger(__name__)
 
         # Guards plugin_manifests/plugin_directories: request threads read
@@ -172,22 +185,64 @@ class PluginCatalog:
             by_manifest=False)
         return str(plugin_dir) if plugin_dir is not None else None
 
-    def get_plugin_display_modes(self, plugin_id: str) -> List[str]:
-        """The manifest's ``display_modes``, or [].
+    def _runtime_view(self) -> Any:
+        """The display's runtime view, read at most once a second; None
+        without a source or when reading it fails."""
+        if self.runtime_source is None:
+            return None
+        now = time.monotonic()
+        memo = self._runtime_view_memo
+        if memo is not None and now - memo[0] < _RUNTIME_VIEW_TTL_SECONDS:
+            return memo[1]
+        try:
+            view = self.runtime_source()
+        except Exception as exc:  # a lookup must still answer from manifests
+            self.logger.debug("Could not read the display's runtime view: %s", exc)
+            view = None
+        self._runtime_view_memo = (now, view)
+        return view
 
-        What the display actually rotates can differ: a plugin may compute
-        its modes at run time (``plugin.modes``). This is the declared list.
+    def _live_display_modes(self, plugin_id: str) -> Optional[List[str]]:
+        """The modes the running display registered for ``plugin_id``, or None."""
+        view = self._runtime_view()
+        if view is None:
+            return None
+        try:
+            modes = view.display_modes(plugin_id)
+        except Exception as exc:  # includes a source returning something else
+            self.logger.debug("Could not read display modes for %s: %s", plugin_id, exc)
+            return None
+        return list(modes) if isinstance(modes, list) and modes else None
+
+    def get_plugin_display_modes(self, plugin_id: str) -> List[str]:
+        """The modes the display registered for the plugin, else the
+        manifest's ``display_modes``, else [].
+
+        A plugin may compute its modes at run time (``plugin.modes``): each
+        league soccer-scoreboard's ``custom_leagues`` adds is a mode no
+        manifest can list ahead of time (#668). The running display
+        publishes what it registered, and that wins while the display is
+        live and has the plugin loaded. Otherwise -- display stopped, plugin
+        disabled -- the declared list is the best answer there is.
         """
+        live = self._live_display_modes(plugin_id)
+        if live is not None:
+            return live
         with self._lock:
             manifest = self.plugin_manifests.get(plugin_id)
         modes = (manifest or {}).get('display_modes', [])
         return list(modes) if isinstance(modes, list) else []
 
     def find_plugin_for_mode(self, mode: str) -> Optional[str]:
-        """The plugin whose manifest declares ``mode`` (case-insensitive)."""
+        """The plugin that registered ``mode`` on the running display, else
+        the one whose manifest declares it (case-insensitive both ways)."""
         wanted = mode.strip().lower()
         with self._lock:
             manifests = dict(self.plugin_manifests)
+        for plugin_id in manifests:
+            live = self._live_display_modes(plugin_id)
+            if live and any(m.lower() == wanted for m in live):
+                return plugin_id
         for plugin_id, manifest in manifests.items():
             modes = manifest.get('display_modes')
             if isinstance(modes, list) and any(

src/plugin_system/plugin_executor.py

@@ -92,7 +92,10 @@ class PluginExecutor:
                 with plugin_scope(plugin_id):
                     result_container['value'] = operation()
                 result_container['completed'] = True
-            except Exception as e:
+            except BaseException as e:  # pylint: disable=broad-except
+                # asyncio.CancelledError and SystemExit too: uncaught, one
+                # ended this thread with 'completed' unset, and an operation
+                # that failed at once was reported as timing out.
                 result_container['exception'] = e
                 result_container['completed'] = True
         

src/plugin_system/plugin_loader.py

@@ -199,9 +199,22 @@ def contained_plugin_dir(plugin_dir: Path, plugins_dir: Path) -> Optional[str]:
     name that came out of ``os.scandir()`` on the trusted root carries no
     taint, which is a real containment guarantee (and one CodeQL's
     path-injection query can follow), not a string sanitiser.
+
+    The entry looked for is the one ``plugin_dir`` itself names when it sits
+    directly in ``plugins_dir``: for a dev plugin symlinked in under its id,
+    the link's name. Resolving the link first and looking for the target's
+    folder name refused ``plugins/foo -> ~/.ledmatrix-dev-plugins/ledmatrix-foo``
+    (what ``dev_plugin_setup.sh link-github foo <url>`` makes), so the plugin
+    never loaded. Any other path is resolved and matched by its final name,
+    as before.
     """
-    plugin_dir_real = os.path.realpath(str(plugin_dir))
     plugins_dir_real = os.path.realpath(str(plugins_dir))
+    plugin_dir_abs = os.path.abspath(str(plugin_dir))
+    if os.path.realpath(os.path.dirname(plugin_dir_abs)) == plugins_dir_real:
+        matched_name = find_trusted_subdir(plugins_dir_real, os.path.basename(plugin_dir_abs))
+        if matched_name is not None:
+            return os.path.join(plugins_dir_real, matched_name)
+    plugin_dir_real = os.path.realpath(str(plugin_dir))
     matched_name = find_trusted_subdir(plugins_dir_real, os.path.basename(plugin_dir_real))
     if matched_name is None:
         return None
@@ -243,6 +256,10 @@ class PluginLoader:
         self.logger = logger or get_logger(__name__)
         self._loaded_modules: Dict[str, Any] = {}
         self._plugin_module_registry: Dict[str, set] = {}  # Maps plugin_id to set of module names
+        # plugin_id -> {dotted name: module} for the modules of the plugin's
+        # own packages (``providers.feed``). They keep their names while the
+        # plugin runs and are dropped with it; see _iter_plugin_submodules.
+        self._plugin_submodules: Dict[str, Dict[str, Any]] = {}
         # Lock to serialize module loading when plugins share module names
         # (e.g., scroll_display.py, game_renderer.py across sport plugins).
         # During exec_module, bare-name sub-modules temporarily appear in
@@ -449,6 +466,45 @@ class PluginLoader:
                 continue
         return result
 
+    @staticmethod
+    def _iter_plugin_submodules(
+        plugin_dir: Path, before_keys: set
+    ) -> list:
+        """Return dotted-name modules from plugin_dir added after before_keys.
+
+        The modules of a package the plugin ships (``providers.feed`` from
+        ``providers/feed.py``). _iter_plugin_bare_modules skips them, so the
+        bare ``providers`` was namespaced and dropped on unload while
+        ``providers.feed`` stayed in sys.modules: a reload after a store update
+        imported a fresh ``providers`` and then got the old ``feed`` back from
+        the cache, running the new manager.py against the old helpers until the
+        display restarted.
+
+        A module counts when its ``__file__`` -- or, for a namespace package,
+        which has none, every ``__path__`` entry -- is inside plugin_dir, so a
+        library the plugin imports (``requests.adapters``) never does.
+
+        Returns a list of (mod_name, module) tuples.
+        """
+        resolved_dir = plugin_dir.resolve()
+        result = []
+        for key in set(sys.modules.keys()) - before_keys:
+            if "." not in key:
+                continue
+            mod = sys.modules.get(key)
+            if mod is None:
+                continue
+            mod_file = getattr(mod, "__file__", None)
+            locations = [mod_file] if mod_file else list(getattr(mod, "__path__", None) or [])
+            if not locations:
+                continue
+            try:
+                if all(Path(loc).resolve().is_relative_to(resolved_dir) for loc in locations):
+                    result.append((key, mod))
+            except (ValueError, TypeError, OSError):
+                continue
+        return result
+
     def _evict_stale_bare_modules(self, plugin_dir: Path) -> dict:
         """Temporarily remove bare-name sys.modules entries from other plugins.
 
@@ -527,6 +583,13 @@ class PluginLoader:
         # Track for cleanup during unload
         self._plugin_module_registry[plugin_id] = namespaced_names
 
+        # The modules of the plugin's own packages keep their dotted names
+        # while it runs -- as they always have, so the package and its
+        # children stay a matching set in sys.modules -- and are dropped
+        # with the plugin by unregister_plugin_modules().
+        self._plugin_submodules[plugin_id] = dict(
+            self._iter_plugin_submodules(plugin_dir, before_keys))
+
         if namespaced_names:
             self.logger.info(
                 "Namespace-isolated %d module(s) for plugin %s",
@@ -537,10 +600,16 @@ class PluginLoader:
         """Remove namespaced sub-modules and cached module for a plugin from sys.modules.
 
         Called by PluginManager during unload to clean up all module entries
-        that were created when the plugin was loaded.
+        that were created when the plugin was loaded, including the dotted
+        modules of its packages. A dotted name is dropped only while it still
+        holds this plugin's module: the name is not namespaced, so another
+        plugin may have put its own there since.
         """
         for ns_name in self._plugin_module_registry.pop(plugin_id, set()):
             sys.modules.pop(ns_name, None)
+        for name, mod in self._plugin_submodules.pop(plugin_id, {}).items():
+            if sys.modules.get(name) is mod:
+                sys.modules.pop(name, None)
         self._loaded_modules.pop(plugin_id, None)
 
     def load_module(
@@ -646,11 +715,13 @@ class PluginLoader:
                     if evicted_name not in sys.modules:
                         sys.modules[evicted_name] = evicted_mod
                 # Clean up the partially-initialized main module and any
-                # bare-name sub-modules that were added during exec_module
-                # so they don't leak into subsequent plugin loads.
+                # bare-name or package sub-modules that were added during
+                # exec_module so they don't leak into subsequent plugin loads.
                 sys.modules.pop(module_name, None)
                 for key, _ in self._iter_plugin_bare_modules(plugin_dir, before_keys):
                     sys.modules.pop(key, None)
+                for key, _ in self._iter_plugin_submodules(plugin_dir, before_keys):
+                    sys.modules.pop(key, None)
                 raise
 
             self._loaded_modules[plugin_id] = module

src/plugin_system/plugin_manager.py

@@ -15,6 +15,7 @@ import sys
 import time
 import threading
 import types
+import uuid
 from pathlib import Path
 from typing import Callable, Dict, List, NamedTuple, Optional, Any, Tuple, Union
 import logging
@@ -214,6 +215,9 @@ class PluginManager:
         # add_update_listener(). A tuple, replaced rather than mutated, so the
         # worker can iterate it without a lock.
         self._update_listeners: Tuple[Callable[[str], None], ...] = ()
+        # Where plugins' on-demand requests go: the display controller's
+        # submit_plugin_on_demand. See set_on_demand_handler().
+        self._on_demand_handler: Optional[Callable[[Dict[str, Any]], bool]] = None
         # Config changes that found the plugin's lock busy, latest per plugin,
         # with the instance they were meant for. See apply_config_change().
         self._deferred_config_changes: Dict[str, Tuple[Any, Dict[str, Any]]] = {}
@@ -597,11 +601,21 @@ class PluginManager:
             self.plugin_loader.unregister_plugin_modules(plugin_id)
         except Exception as e:  # pragma: no cover - defensive
             self.logger.debug("Could not drop modules of %s: %s", plugin_id, e)
-        try:
-            if self.font_manager is not None and hasattr(self.font_manager, 'forget_manager_fonts'):
-                self.font_manager.forget_manager_fonts(plugin_id)
-        except Exception as e:
-            self.logger.debug("Could not forget fonts of %s: %s", plugin_id, e)
+        self._forget_plugin_fonts(plugin_id)
+
+    def _forget_plugin_fonts(self, plugin_id: str) -> None:
+        """Drop what the FontManager holds for a plugin: the fonts its
+        instance reported using (the Fonts tab's "Used by") and the fonts its
+        manifest registered. Never raises."""
+        if self.font_manager is None:
+            return
+        for name in ('forget_manager_fonts', 'forget_plugin_fonts'):
+            if not hasattr(self.font_manager, name):
+                continue
+            try:
+                getattr(self.font_manager, name)(plugin_id)
+            except Exception as e:
+                self.logger.debug("Could not forget fonts of %s (%s): %s", plugin_id, name, e)
     
     #: Config keys the **core** reads out of a plugin's own config block. The
     #: plugin never declares them, so a schema with
@@ -846,12 +860,9 @@ class PluginManager:
             # Delegate sub-module and cached-module cleanup to the loader
             self.plugin_loader.unregister_plugin_modules(plugin_id)
 
-            # Its font registrations go with it (the Fonts tab's "Used by").
-            try:
-                if self.font_manager is not None and hasattr(self.font_manager, 'forget_manager_fonts'):
-                    self.font_manager.forget_manager_fonts(plugin_id)
-            except Exception as e:
-                self.logger.debug("Could not forget fonts of %s: %s", plugin_id, e)
+            # Its font registrations go with it: the fonts it reported using
+            # and the ones its manifest registered.
+            self._forget_plugin_fonts(plugin_id)
 
             # Update state
             self.state_manager.set_state(plugin_id, PluginState.UNLOADED)
@@ -1163,7 +1174,7 @@ class PluginManager:
     def _record_update_failure(
         self,
         plugin_id: str,
-        exc: Optional[Exception] = None,
+        exc: Optional[BaseException] = None,
         log: bool = True,
         count_failure: bool = True,
     ) -> None:
@@ -1187,7 +1198,7 @@ class PluginManager:
         """
         failure_time = time.time()
         if exc is not None:
-            err: Exception = exc
+            err: BaseException = exc
             error_type = type(exc).__name__
         else:
             err = Exception(f"Plugin {plugin_id} execution failed (timeout or executor error)")
@@ -1653,7 +1664,7 @@ class PluginManager:
         finish_guard = threading.Lock()
         finished = {'done': False}
 
-        def _finish(success: bool, exc: Optional[Exception] = None) -> None:
+        def _finish(success: bool, exc: Optional[BaseException] = None) -> None:
             with finish_guard:
                 if finished['done']:
                     return
@@ -1727,7 +1738,13 @@ class PluginManager:
                     self.resource_monitor.monitor_call(plugin_id, plugin_instance.update)
                 else:
                     plugin_instance.update()
-            except Exception as exc:
+            except BaseException as exc:  # pylint: disable=broad-except
+                # BaseException, not just Exception: asyncio.CancelledError
+                # and SystemExit derive from it. Either one skipped _finish,
+                # so the plugin kept its lock and stayed RUNNING for good --
+                # never rescheduled, and every display() skipped as busy.
+                # Re-raised for the executor, which reports it as this
+                # update's failure.
                 _finish(False, exc=exc)
                 raise
             else:
@@ -1838,3 +1855,73 @@ class PluginManager:
             done = sorted(self._completed_updates)
             self._completed_updates.clear()
             return done
+
+    # -- on-demand requests from plugins -------------------------------------
+
+    def set_on_demand_handler(
+            self, handler: Optional[Callable[[Dict[str, Any]], bool]]) -> None:
+        """Route plugins' on-demand requests to ``handler`` (None: nowhere).
+
+        The display controller sets its ``submit_plugin_on_demand`` here
+        before any plugin loads. The handler takes a mailbox-shaped request
+        from any thread, queues it for the render thread and returns True,
+        or False when it could not. A plugin manager with no handler (the
+        web interface's, a test's, scripts/check_plugin.py's) has no screen
+        to give, so request_on_demand() there answers None.
+        """
+        self._on_demand_handler = handler
+
+    def request_on_demand(self, plugin_id: str, mode: Optional[str] = None,
+                          duration: Optional[float] = None,
+                          pinned: bool = False) -> Optional[str]:
+        """Ask the display to show ``plugin_id`` now. Safe from any thread.
+
+        BasePlugin.request_on_demand() lands here; see it for the arguments.
+        Returns the request id once the display has queued the request (it
+        is applied on the render thread within a frame or so), or None when
+        this process has no display to ask or its queue is full.
+        """
+        if not isinstance(plugin_id, str) or not plugin_id:
+            raise ValueError('plugin_id is required')
+        if mode is not None and (not isinstance(mode, str) or not mode):
+            raise ValueError('mode must be a non-empty string or None')
+        if duration is not None:
+            if isinstance(duration, bool) or not isinstance(duration, (int, float)):
+                raise ValueError('duration must be a number of seconds or None')
+            if not math.isfinite(duration) or duration <= 0:
+                duration = None   # the display reads these as "no limit" too
+            else:
+                duration = float(duration)
+        return self._submit_on_demand({
+            'action': 'start', 'plugin_id': plugin_id, 'mode': mode,
+            'duration': duration, 'pinned': bool(pinned)})
+
+    def end_on_demand(self, plugin_id: str) -> Optional[str]:
+        """Give the screen back, if ``plugin_id``'s on-demand session has it.
+
+        BasePlugin.end_on_demand() lands here. A session the plugin does not
+        own (the user started another plugin from the web interface, say) is
+        left alone. Returns the request id once queued, or None as
+        request_on_demand() does.
+        """
+        if not isinstance(plugin_id, str) or not plugin_id:
+            raise ValueError('plugin_id is required')
+        return self._submit_on_demand({'action': 'stop', 'plugin_id': plugin_id})
+
+    def _submit_on_demand(self, request: Dict[str, Any]) -> Optional[str]:
+        # __dict__.get: tests build bare managers with PluginManager.__new__.
+        handler = self.__dict__.get('_on_demand_handler')
+        if handler is None:
+            return None
+        request_id = str(uuid.uuid4())
+        request.update({'request_id': request_id, 'timestamp': time.time(),
+                        'source': 'plugin'})
+        try:
+            accepted = handler(request)
+        except Exception as exc:  # pylint: disable=broad-except
+            self._warn_rate_limited(
+                "on-demand-handler",
+                "The on-demand request from plugin %s failed: %r",
+                request.get('plugin_id'), exc)
+            return None
+        return request_id if accepted else None

src/plugin_system/plugin_runtime.py

@@ -56,7 +56,7 @@ import os
 import threading
 import time
 from dataclasses import dataclass, field, replace
-from typing import Any, Callable, Dict, Optional
+from typing import Any, Callable, Dict, List, Optional
 
 from src import display_watchdog
 from src.logging_config import get_logger
@@ -100,6 +100,9 @@ _ERROR_MESSAGE_CHARS = 200
 _ERROR_TYPE_CHARS = 80
 _ID_CHARS = 100
 _VERSION_CHARS = 40
+#: Bounds on a plugin's published ``modes``: a plugin computes them, so a
+#: runaway list must not bloat a file written to the SD card.
+_MAX_MODES = 200
 
 #: Reader statuses. Only LIVE carries runtime facts.
 LIVE = "live"
@@ -154,6 +157,13 @@ def summarize_error(error_info: Optional[Dict[str, Any]]) -> Optional[Dict[str,
     }
 
 
+def _published_modes(modes: Any) -> Optional[List[str]]:
+    """The registered display modes as a snapshot carries them, or None."""
+    if not isinstance(modes, list):
+        return None
+    return [_clip(m, _ID_CHARS) for m in modes[:_MAX_MODES] if isinstance(m, str)]
+
+
 def build_runtime_snapshot(state_manager: Any, *, started_at: float,
                            now: Optional[float] = None,
                            running: bool = True,
@@ -173,6 +183,7 @@ def build_runtime_snapshot(state_manager: Any, *, started_at: float,
                 "error": summarize_error(record.get("error_info")),
                 "version": _clip(version, _VERSION_CHARS) if version else None,
                 "loaded_at": _epoch(record.get("loaded_at")),
+                "modes": _published_modes(record.get("modes")),
             }
     return {
         "schema": SNAPSHOT_SCHEMA,
@@ -416,6 +427,21 @@ class PluginRuntimeView:
             "loaded_at": record.get("loaded_at"),
         }
 
+    def display_modes(self, plugin_id: str) -> Optional[List[str]]:
+        """The display modes the display registered for ``plugin_id``: what
+        it rotates and accepts on-demand, including modes a plugin computes
+        from its config. None unless the view is live and the plugin is
+        loaded with its modes registered -- the caller then falls back to
+        the manifest's ``display_modes``."""
+        if not self.live:
+            return None
+        record = self.plugins.get(plugin_id)
+        modes = record.get("modes") if isinstance(record, dict) else None
+        if not isinstance(modes, list):
+            return None
+        modes = [m for m in modes if isinstance(m, str)]
+        return modes or None
+
     def describe(self) -> Dict[str, Any]:
         """The view's own status, for a response to carry beside the facts."""
         return {

src/plugin_system/plugin_state.py

@@ -10,7 +10,7 @@ snapshot ``plugin_runtime.PluginRuntimePublisher`` publishes from it.
 import threading
 import time
 from enum import Enum
-from typing import Optional, Dict, Any
+from typing import Any, Dict, List, Optional
 from datetime import datetime
 import logging
 
@@ -231,6 +231,26 @@ class PluginStateManager:
             }
             self._note_change()
 
+    def record_modes(self, plugin_id: str, modes: List[str]) -> None:
+        """Record the display modes the display registered for ``plugin_id``.
+
+        Called by the DisplayController each time it registers the plugin.
+        These are the modes it actually rotates and accepts on-demand --
+        ``plugin.modes`` when the plugin computes them (a soccer league the
+        user added under ``custom_leagues``), else the manifest's list -- and
+        the web interface has no other way to learn them (#668). Kept on the
+        loaded record, so an unload or a reload's fresh record_loaded()
+        forgets them until the plugin is registered again.
+        """
+        with self._lock:
+            loaded = self._loaded.get(plugin_id)
+            if loaded is None:
+                return
+            modes = [str(m) for m in modes]
+            if loaded.get('modes') != modes:
+                loaded['modes'] = modes
+                self._note_change()
+
     def record_unloaded(self, plugin_id: str) -> None:
         """Forget the loaded record alone, keeping state and error info: for
         an unload that failed after the instance was already dropped."""
@@ -243,7 +263,8 @@ class PluginStateManager:
         section so a concurrent load or unload is seen whole or not at all.
 
         Per plugin: ``state`` (published_state()'s value), ``loaded``,
-        ``version`` and ``loaded_at`` (None unless loaded) and ``error_info``
+        ``version``, ``loaded_at`` and ``modes`` (None unless loaded; ``modes``
+        also None until the display registers it) and ``error_info``
         (a copy, or None).
         """
         with self._lock:
@@ -257,6 +278,7 @@ class PluginStateManager:
                     'loaded': loaded is not None,
                     'version': loaded['version'] if loaded else None,
                     'loaded_at': loaded['loaded_at'] if loaded else None,
+                    'modes': list(loaded['modes']) if loaded and 'modes' in loaded else None,
                     'error_info': dict(info) if info is not None else None,
                 }
             return records

src/plugin_system/store_manager.py

@@ -138,6 +138,11 @@ class PluginStoreManager(_RegistryMixin, _InstallMixin, _UpdateMixin):
         # the registry cache expires. Only one thread fetches; others wait and
         # then get the result from the warm cache (double-checked locking).
         self._registry_fetch_lock = threading.Lock()
+        # refresh_registry_in_background: the one refresh thread, and when
+        # an offline one may be retried (see that method).
+        self._registry_refresh_lock = threading.Lock()
+        self._registry_refresh_thread: Optional[threading.Thread] = None
+        self._registry_refresh_retry_after = 0.0
 
         # Per-plugin locks for _reinstall_with_rollback: the web UI runs
         # Flask with threaded=True, so two overlapping requests for the
@@ -344,12 +349,26 @@ class PluginStoreManager(_RegistryMixin, _InstallMixin, _UpdateMixin):
         2. Fix permissions via os.chmod() then retry (works for same-owner files)
         3. Use sudo rm -rf as last resort (works for root-owned __pycache__, etc.)
 
+        A symlink -- a dev plugin linked in by scripts/dev/dev_plugin_setup.sh
+        -- is removed as a link, before any of that: rmtree refuses one, and
+        stage 2 would walk through it and chmod the developer's checkout.
+
         Args:
             path: Path to directory to remove
 
         Returns:
             True if directory was removed successfully, False otherwise
         """
+        if path.is_symlink():
+            # Checked before exists(), which follows the link: a dangling one
+            # would read as already removed and be left behind.
+            try:
+                path.unlink()
+                return True
+            except OSError as e:
+                self.logger.error(f"Could not remove the symlink {path}: {e}")
+                return False
+
         if not path.exists():
             return True  # Already removed
 

src/plugin_system/store_registry.py

@@ -7,6 +7,7 @@ methods reach shared state and helpers through ``self``.
 
 import json
 import requests
+import threading
 import time
 from concurrent.futures import ThreadPoolExecutor
 from datetime import datetime
@@ -985,10 +986,14 @@ class _RegistryMixin:
 
     def get_registry_info(self, plugin_id: str) -> Optional[Dict]:
         """
-        Get plugin information from the registry cache only (no GitHub API calls).
+        Get plugin information from the registry (plugins.json).
 
-        Use this for lightweight lookups where only registry fields are needed
-        (e.g., verified status, latest_version).
+        Makes no GitHub API calls, but it does go through `fetch_registry`:
+        when the in-memory copy is missing or older than
+        ``registry_cache_timeout`` it downloads plugins.json, and with no
+        network that waits out the timeout and retries. A caller that must
+        not block on the network (the installed-plugins list) uses
+        `get_cached_registry_info` instead.
 
         Args:
             plugin_id: Plugin identifier
@@ -999,3 +1004,52 @@ class _RegistryMixin:
         registry = self.fetch_registry()
         plugins = registry.get('plugins', []) or []
         return self._match_registry_entry(plugins, plugin_id)
+
+    def get_cached_registry_info(self, plugin_id: str) -> Optional[Dict]:
+        """The registry entry for ``plugin_id`` from the copy already in
+        memory, however old; never touches the network.
+
+        None when no registry has been loaded yet, or the plugin isn't in it.
+        When the copy is missing or past ``registry_cache_timeout`` this
+        starts `refresh_registry_in_background`, so a later call has it.
+        """
+        cache = getattr(self, 'registry_cache', None)
+        cache_time = getattr(self, 'registry_cache_time', None)
+        if (not cache or not cache_time
+                or (time.time() - cache_time) >= self.registry_cache_timeout):
+            self.refresh_registry_in_background()
+        plugins = cache.get('plugins') if isinstance(cache, dict) else None
+        if not isinstance(plugins, list):
+            return None
+        return self._match_registry_entry(
+            [p for p in plugins if isinstance(p, dict)], plugin_id)
+
+    def refresh_registry_in_background(self) -> bool:
+        """Fetch the registry on a daemon thread; True when one was started.
+
+        At most one runs at a time. After a fetch that left no registry in
+        memory (offline), no new one starts for ``_failure_backoff_seconds``,
+        so an offline Pi doesn't retry on every page load.
+        """
+        with self._registry_refresh_lock:
+            running = self._registry_refresh_thread
+            if running is not None and running.is_alive():
+                return False
+            if time.time() < self._registry_refresh_retry_after:
+                return False
+            thread = threading.Thread(
+                target=self._background_registry_refresh,
+                name='registry-refresh', daemon=True)
+            self._registry_refresh_thread = thread
+            thread.start()
+            return True
+
+    def _background_registry_refresh(self) -> None:
+        try:
+            self.fetch_registry()
+        except Exception as e:  # noqa: BLE001 - a background warm-up must not crash
+            self.logger.warning("Background registry refresh failed: %s", e)
+        if not getattr(self, 'registry_cache', None):
+            with self._registry_refresh_lock:
+                self._registry_refresh_retry_after = (
+                    time.time() + self._failure_backoff_seconds)

src/screen_runner.py

@@ -0,0 +1,484 @@
+"""Runs one screen: the ScreenRunner of docs/RUN_LOOP_REDESIGN.md.
+
+``ScreenRunner.run(plan, plugin)`` draws a screen's first frame, runs the
+frame loop its plan's ``frame_policy`` picks (125 Hz or 1 Hz), makes up the
+minimum duration when the loop ended early, and returns one
+:class:`Outcome` saying why the screen ended. Everything that touches the
+plugin, the panel or the controller's state goes through a
+:class:`ScreenHost` (the DisplayController); everything that reads or waits
+on the clock goes through an injected :class:`FrameClock`. The runner itself
+holds no state between screens.
+
+What can end a screen early is decided at the runner's service points: after
+each frame, after the frame loop, and after the make-up dwell. At each one
+the host gathers a snapshot and asks the Arbiter, once, whether a Source in
+``plan.preemptible_by`` now wants the panel (:meth:`ScreenHost.check`). A yes
+is ``ExitReason.PREEMPTED``: the next pass of the loop decides what shows,
+and the rotation does not advance past the screen that was cut short.
+
+The frame pacing is the loop that used to be inline in
+``DisplayController.run()``, unchanged: the 125 Hz loop paces to an 8 ms
+deadline from the start of each frame (sleeping at least 1 ms, so a frame
+that overran still yields the GIL), and the 1 Hz loop sleeps a flat second
+between frames, woken early by a control socket command.
+"""
+
+import logging
+from dataclasses import dataclass
+from enum import Enum
+from typing import Any, NamedTuple, Optional, Protocol, Tuple
+
+from src.display_arbiter import FramePolicy, ScreenPlan, Source
+
+__all__ = [
+    "AFTER_COMPLETED_LOOP",
+    "AFTER_LOOP",
+    "Checkpoint",
+    "DYNAMIC_GRACE",
+    "ExitReason",
+    "FINAL",
+    "FRAME",
+    "FirstFrame",
+    "FrameClock",
+    "HIGH_FPS_INTERVAL",
+    "NoticeRead",
+    "Outcome",
+    "STATIC_INTERVAL",
+    "Screen",
+    "ScreenHost",
+    "ScreenRunner",
+    "after_dwell",
+]
+
+#: Seconds between frames in the high-FPS loop (125 Hz), for scrolling plugins.
+HIGH_FPS_INTERVAL = 0.008
+
+#: Seconds between frames in the static loop (1 Hz).
+STATIC_INTERVAL = 1.0
+
+#: A dynamic-duration screen ends on cycle completion only this long after its
+#: minimum, so timing jitter around the minimum can't end it early.
+DYNAMIC_GRACE = 0.5
+
+
+class ExitReason(Enum):
+    """Why a screen ended. The value is the golden traces' exit column where
+    one exists (test/test_run_loop_golden.py)."""
+
+    #: The screen ran its target duration.
+    DURATION = "duration"
+    #: A dynamic-duration plugin finished its cycle after its minimum.
+    CYCLE_COMPLETE = "cycle-complete"
+    #: The first frame had nothing to show (display() returned False or
+    #: raised inside the executor), or no plugin draws the mode.
+    EMPTY = "empty"
+    #: The first frame's dispatch itself raised.
+    ERROR = "error"
+    #: A later frame returned False (a dynamic-duration screen on the 1 Hz
+    #: loop keeps going instead).
+    DISPLAY_FALSE = "display-false"
+    #: Another Source took the panel, or an on-demand session ran out before
+    #: the screen began. The rotation does not advance.
+    PREEMPTED = "preempted"
+    #: A plugin reload is waiting for the top of the loop. The screen is cut
+    #: short but counts as shown: the rotation advances, and the next pass
+    #: reloads before it draws.
+    RELOAD = "reload"
+
+
+@dataclass(frozen=True)
+class Outcome:
+    """How a screen ended.
+
+    Attributes:
+        exit_reason: Why it ended.
+        elapsed: Seconds from the end of the first frame to the end.
+        preempted_by: For PREEMPTED, the plan that took the panel when the
+            Arbiter named one (None when the session simply ran out).
+        on_demand_active: Filled in by the controller when the screen is
+            over: an on-demand session was running at that moment.
+        still_live: Filled in by the controller: the mode's plugin still had
+            live content at that moment, which holds the rotation on it.
+    """
+
+    exit_reason: ExitReason
+    elapsed: float = 0.0
+    preempted_by: Optional[ScreenPlan] = None
+    on_demand_active: bool = False
+    still_live: bool = False
+
+
+class FrameClock(Protocol):
+    """The clocks the runner reads and the sleep it paces with.
+
+    The shape of the ``time`` module, so production passes it (through an
+    indirection that lets tests patch the module) and the golden traces pass
+    their fake clock.
+    """
+
+    def time(self) -> float:
+        """Wall-clock seconds: what screen durations are measured in."""
+
+    def perf_counter(self) -> float:
+        """A monotonic high-resolution clock: what the 8 ms pacing reads."""
+
+    def sleep(self, seconds: float) -> None:
+        """Block for ``seconds``."""
+
+
+class NoticeRead(Enum):
+    """When a service point reads the WiFi notice file.
+
+    The read is throttled to once a second and deletes an expired file, so
+    *when* it happens is behaviour: each service point reads it exactly
+    when the loop always did.
+    """
+
+    #: Not at all.
+    NEVER = "never"
+    #: Only if nothing cheaper has already ended the screen: no on-demand
+    #: session, the panel on, the mode unchanged and no live takeover.
+    IF_UNDECIDED = "if-undecided"
+    #: Whenever no on-demand session is running.
+    ALWAYS = "always"
+
+
+@dataclass(frozen=True)
+class Checkpoint:
+    """What one kind of service point considers.
+
+    Attributes:
+        name: For logs and tests.
+        notice: When the WiFi notice is read (see NoticeRead).
+        notice_counts: Whether a pending notice ends the screen here. After
+            the make-up dwell it does only while the screen had time left.
+        reload: Whether a pending plugin reload ends the screen here. Only
+            between frames: once the frame loop is over the screen is too.
+    """
+
+    name: str
+    notice: NoticeRead
+    reload: bool
+    notice_counts: bool = True
+
+
+#: Between frames: the frame loops' check, and the socket wake in the 1 Hz wait.
+FRAME = Checkpoint("frame", NoticeRead.IF_UNDECIDED, reload=True)
+#: After a frame loop that ended early (display() returned False, a reload).
+AFTER_LOOP = Checkpoint("after-loop", NoticeRead.IF_UNDECIDED, reload=False)
+#: After a frame loop that ran its course: only a mode change or the schedule.
+AFTER_COMPLETED_LOOP = Checkpoint("after-completed-loop", NoticeRead.NEVER, reload=False)
+#: The last look before the rotation advances.
+FINAL = Checkpoint("final", NoticeRead.NEVER, reload=False)
+
+
+def after_dwell(time_left: bool) -> Checkpoint:
+    """After the make-up dwell: a notice that cut it short ends the screen,
+    so the mode resumes after the notice instead of rotating past it."""
+    return Checkpoint("after-dwell", NoticeRead.ALWAYS, reload=False,
+                      notice_counts=time_left)
+
+
+class FirstFrame(NamedTuple):
+    """What the first frame's dispatch returned (see _dispatch_first_frame)."""
+
+    shown: bool
+    raised: bool
+    accepts_display_mode: bool
+
+
+@dataclass
+class Screen:
+    """One running screen: its completed plan, the plugin drawing it and
+    when it started. Mutable only in that the runner owns it."""
+
+    plan: ScreenPlan
+    plugin: Any
+    accepts_display_mode: bool
+    start: float
+
+    @property
+    def mode(self) -> Optional[str]:
+        return self.plan.mode
+
+
+class ScreenHost(Protocol):
+    """The controller's side of a screen. See DisplayController."""
+
+    def first_frame(self, plan: ScreenPlan, plugin: Any) -> FirstFrame:
+        """Draw the first frame through the plugin executor."""
+
+    def complete_plan(self, plan: ScreenPlan, plugin: Any) -> Optional[ScreenPlan]:
+        """The plan with the plugin's durations, dynamic flag and frame
+        policy, read after the first frame. None when an on-demand session
+        has no time left for it."""
+
+    def draw(self, screen: Screen) -> Any:
+        """One later frame: what display() returned."""
+
+    def after_frame(self, screen: Screen) -> None:
+        """After a frame that did not end the screen (the follower frame)."""
+
+    def tick(self) -> None:
+        """Plugin updates that have come due (throttled)."""
+
+    def service(self, screen: Screen) -> Optional[Tuple[str, ...]]:
+        """Apply pending changes (on-demand requests, schedule, brightness,
+        finished reloads). Returns the live modes when a live-priority scan
+        was due, else None."""
+
+    def wait_frame(self, interval: float, screen: Screen) -> Optional[ScreenPlan]:
+        """The 1 Hz loop's sleep between frames. The plan that takes the
+        panel when a control socket command ended the screen, else None."""
+
+    def check(self, screen: Screen, checkpoint: Checkpoint,
+              live_scan: Optional[Tuple[str, ...]] = None) -> Optional[ScreenPlan]:
+        """The service point: the plan that now takes the panel from this
+        screen, or None while it holds. One Arbiter.decide() call."""
+
+    def dwell(self, seconds: float) -> None:
+        """Sleep up to ``seconds``, servicing changes; returns early on one."""
+
+    def cycle_complete(self, screen: Screen) -> bool:
+        """The plugin's dynamic-duration cycle is complete."""
+
+
+class ScreenRunner:
+    """Runs one screen at a time for a ScreenHost. See the module docstring."""
+
+    def __init__(self, clock: FrameClock, host: ScreenHost,
+                 log: Optional[logging.Logger] = None):
+        self.clock = clock
+        self.host = host
+        # The controller passes its own logger, so these lines keep the
+        # source they always had in the journal.
+        self.log = log or logging.getLogger(__name__)
+
+    # -- the screen ------------------------------------------------------
+
+    def run(self, plan: ScreenPlan, plugin: Any) -> Outcome:
+        """Run ``plan``'s screen, drawn by ``plugin`` (None: nothing draws it)."""
+        if plugin is None:
+            return Outcome(ExitReason.EMPTY)
+        first = self.host.first_frame(plan, plugin)
+        if not first.shown:
+            return Outcome(ExitReason.ERROR if first.raised else ExitReason.EMPTY)
+        completed = self.host.complete_plan(plan, plugin)
+        if completed is None:
+            return Outcome(ExitReason.PREEMPTED)
+        screen = Screen(completed, plugin, first.accepts_display_mode,
+                        start=self.clock.time())
+
+        if completed.frame_policy is FramePolicy.HIGH_FPS:
+            reason, by = self._high_fps_loop(screen)
+        else:
+            reason, by = self._static_loop(screen)
+        if reason is ExitReason.PREEMPTED:
+            # The service point that ended the loop has decided; looking
+            # again now, at the same instant, gives the same answer.
+            return self._outcome(screen, reason, by)
+
+        loop_completed = reason in (ExitReason.DURATION, ExitReason.CYCLE_COMPLETE)
+        # LOAD-BEARING: a change the frame loop did not end on (a dwell
+        # inside it, a later frame returning False) must not fall into the
+        # make-up dwell below. It can run for the rest of the screen's
+        # duration, and a freshly requested on-demand mode would sit
+        # invisible for that long -- or be clobbered by a queued stop.
+        by = self.host.check(screen, AFTER_COMPLETED_LOOP if loop_completed else AFTER_LOOP)
+        if by is not None:
+            return self._outcome(screen, ExitReason.PREEMPTED, by)
+
+        # Honour the minimum duration when a static, non-dynamic screen's
+        # loop ended early. A screen cut short for a plugin reload is over:
+        # the dwell returns at once and the rotation advances.
+        if (not completed.dynamic and not loop_completed
+                and completed.frame_policy is not FramePolicy.HIGH_FPS):
+            elapsed = self.clock.time() - screen.start
+            remaining = max(0.0, self._max(screen) - elapsed)
+            if remaining > 0:
+                self.host.dwell(remaining)
+                time_left = self.clock.time() - screen.start < self._max(screen)
+                by = self.host.check(screen, after_dwell(time_left))
+                if by is not None:
+                    return self._outcome(screen, ExitReason.PREEMPTED, by)
+
+        if completed.dynamic:
+            self._log_dynamic_end(screen)
+
+        # The dwells above return early when a pending change (on-demand
+        # started or stopped, the panel scheduled off) has already decided
+        # what comes next; rotating now would skip it.
+        by = self.host.check(screen, FINAL)
+        if by is not None:
+            return self._outcome(screen, ExitReason.PREEMPTED, by)
+        return self._outcome(screen, reason, None)
+
+    def _outcome(self, screen: Screen, reason: ExitReason,
+                 by: Optional[ScreenPlan]) -> Outcome:
+        return Outcome(reason, self.clock.time() - screen.start, preempted_by=by)
+
+    @staticmethod
+    def _max(screen: Screen) -> float:
+        return float(screen.plan.max_duration or 0.0)
+
+    @staticmethod
+    def _min(screen: Screen) -> float:
+        return float(screen.plan.min_duration or 0.0)
+
+    @staticmethod
+    def _ended_by(by: ScreenPlan) -> ExitReason:
+        return ExitReason.RELOAD if by.source is Source.RELOAD else ExitReason.PREEMPTED
+
+    # -- the frame loops ---------------------------------------------------
+
+    def _high_fps_loop(self, screen: Screen) -> Tuple[ExitReason, Optional[ScreenPlan]]:
+        """Ultra-smooth frames for scrolling plugins (8 ms = 125 FPS)."""
+        clock, host, log = self.clock, self.host, self.log
+        interval = HIGH_FPS_INTERVAL
+        log.debug("Entering high-FPS loop for %s with display_interval=%.3fs (%.1f FPS)",
+                  screen.mode, interval, 1.0 / interval)
+        target = self._max(screen)
+        while True:
+            frame_start = clock.perf_counter()
+            try:
+                result = host.draw(screen)
+                if isinstance(result, bool) and not result:
+                    log.debug("Display returned False, breaking early")
+                    return ExitReason.DISPLAY_FALSE, None
+            except Exception:  # pylint: disable=broad-except
+                log.exception("Error during display update")
+
+            # Multi-display sync: send follower frame after each render
+            host.after_frame(screen)
+            host.tick()
+            # Throttled: one clock compare between passes. A live-priority
+            # scan, when one is due, happens here, before the sleep, as it
+            # always has; the Arbiter weighs it after the sleep.
+            live_scan = host.service(screen)
+
+            # Pace to the frame deadline rather than sleeping a flat
+            # interval on top of the work. display() has already blocked on
+            # the panel's vsync by this point, so an unconditional sleep is
+            # added to a wait that already happened. Measured on a 2x128x64
+            # chain at limit_refresh_rate_hz=100: ~4ms of render plus a flat
+            # 8ms put each iteration at ~12ms against a 10ms refresh grid, so
+            # every swap missed a refresh and the loop settled at 50fps where
+            # display_interval asks for 125 -- and with zero headroom, ~14% of
+            # frames slipped a further refresh, which is what reads as scroll
+            # stutter.
+            remaining = interval - (clock.perf_counter() - frame_start)
+            # Yield even when the frame overran its budget, so plugin update
+            # threads and the web UI are not starved of the GIL.
+            clock.sleep(remaining if remaining > 0 else 0.001)
+
+            by = host.check(screen, FRAME, live_scan)
+            if by is not None:
+                log.debug("Mode changed during high-FPS loop, breaking early")
+                return self._ended_by(by), by
+
+            elapsed = clock.time() - screen.start
+            if elapsed >= target:
+                log.debug("Reached high-FPS target duration %.2fs for mode %s",
+                          target, screen.mode)
+                return ExitReason.DURATION, None
+            if self._should_exit_dynamic(screen, elapsed):
+                log.debug("Dynamic duration cycle complete for %s after %.2fs",
+                          screen.mode, elapsed)
+                return ExitReason.CYCLE_COMPLETE, None
+
+    def _static_loop(self, screen: Screen) -> Tuple[ExitReason, Optional[ScreenPlan]]:
+        """One frame a second for everything else."""
+        clock, host, log = self.clock, self.host, self.log
+        interval = STATIC_INTERVAL
+        log.debug("Entering normal FPS loop for %s with display_interval=%.3fs",
+                  screen.mode, interval)
+        target = self._max(screen)
+        dynamic = screen.plan.dynamic
+        while True:
+            # Wakes for a control socket command and applies it at once,
+            # instead of up to a second later.
+            by = host.wait_frame(interval, screen)
+            if by is not None:
+                log.info("Mode changed during display loop from %s to %s (%s), "
+                         "breaking early", screen.mode, by.mode, by.source.value)
+                return self._ended_by(by), by
+            host.tick()
+
+            elapsed = clock.time() - screen.start
+            if elapsed >= target:
+                log.debug("Reached standard target duration %.2fs for mode %s",
+                          target, screen.mode)
+                return ExitReason.DURATION, None
+
+            try:
+                result = host.draw(screen)
+                if isinstance(result, bool) and not result:
+                    # A dynamic-duration screen doesn't end on False: it
+                    # keeps looping until its cycle completes or its maximum.
+                    if not dynamic:
+                        log.info("Display returned False for %s (no dynamic duration), "
+                                 "breaking early", screen.mode)
+                        return ExitReason.DISPLAY_FALSE, None
+                    log.debug("Display returned False for %s (dynamic duration enabled), "
+                              "continuing loop", screen.mode)
+            except Exception:  # pylint: disable=broad-except
+                log.exception("Error during display update")
+
+            # Multi-display sync: send follower frame after each render
+            host.after_frame(screen)
+
+            live_scan = host.service(screen)
+            by = host.check(screen, FRAME, live_scan)
+            if by is not None:
+                log.info("Mode changed during display loop from %s to %s (%s), "
+                         "breaking early", screen.mode, by.mode, by.source.value)
+                return self._ended_by(by), by
+
+            if self._should_exit_dynamic(screen, elapsed):
+                log.info("Dynamic duration cycle complete for %s after %.2fs",
+                         screen.mode, elapsed)
+                return ExitReason.CYCLE_COMPLETE, None
+
+    # -- dynamic duration --------------------------------------------------
+
+    def _should_exit_dynamic(self, screen: Screen, elapsed: float) -> bool:
+        if not screen.plan.dynamic:
+            return False
+        minimum = self._min(screen)
+        # A small grace period after min_duration prevents premature exits
+        # due to timing issues.
+        if elapsed < minimum + DYNAMIC_GRACE:
+            self.log.debug(
+                "_should_exit_dynamic: elapsed %.2fs < min_duration %.2fs + grace %.2fs, "
+                "returning False", elapsed, minimum, DYNAMIC_GRACE)
+            return False
+        cycle_complete = self.host.cycle_complete(screen)
+        self.log.debug(
+            "_should_exit_dynamic: elapsed %.2fs >= min %.2fs, cycle_complete=%s, returning %s",
+            elapsed, minimum + DYNAMIC_GRACE, cycle_complete, cycle_complete)
+        if cycle_complete:
+            self.log.debug("Cycle complete detected for %s after %.2fs (min: %.2fs, grace: %.2fs)",
+                           screen.mode, elapsed, minimum, DYNAMIC_GRACE)
+        return cycle_complete
+
+    def _log_dynamic_end(self, screen: Screen) -> None:
+        """How a dynamic-duration screen ended, for the log. Asks the plugin
+        once more whether its cycle is complete, as the loop always did."""
+        elapsed_total = self.clock.time() - screen.start
+        cycle_done = self.host.cycle_complete(screen)
+        minimum, maximum = self._min(screen), self._max(screen)
+        if cycle_done:
+            self.log.info(
+                "Dynamic duration cycle completed for %s after %.2fs "
+                "(target: %.2fs, min: %.2fs, max: %.2fs)",
+                screen.mode, elapsed_total, maximum, minimum, maximum)
+        elif elapsed_total >= maximum:
+            self.log.info(
+                "Dynamic duration cap reached before cycle completion for %s "
+                "(%.2fs/%ds, min: %.2fs)",
+                screen.mode, elapsed_total, int(maximum), minimum)
+        else:
+            self.log.debug(
+                "Dynamic duration cycle in progress for %s: %.2fs elapsed "
+                "(target: %.2fs, min: %.2fs, max: %.2fs)",
+                screen.mode, elapsed_total, maximum, minimum, maximum)

test/_run_loop_harness.py

@@ -143,12 +143,24 @@ class FakeCache:
     def __init__(self):
         self.data: Dict[str, Any] = {}
         self.cache_dir = "/nonexistent/run-loop-harness"
+        self._writes = 0
+        self._written: Dict[str, int] = {}
 
     def get(self, key, max_age=None, memory_ttl=None):
         return self.data.get(key)
 
     def set(self, key, data, ttl=None):
         self.data[key] = data
+        # Every write is a new file, as DiskCache's rename makes it.
+        self._writes += 1
+        self._written[key] = self._writes
+
+    def file_signature(self, key):
+        """CacheManager.file_signature: None without a file, else a value
+        that changes with every write."""
+        if key not in self.data:
+            return None
+        return (self._written.get(key, 0), 0, 0)
 
     def delete(self, key):
         self.data.pop(key, None)
@@ -724,11 +736,14 @@ class RunLoopHarness:
         self.clock.at(t, post)
 
     def restore_on_demand(self, plugin_id: str, mode: Optional[str] = None,
-                          duration: Optional[float] = None, pinned: bool = False):
+                          duration: Optional[float] = None, pinned: bool = False,
+                          named_mode: Optional[str] = None):
         """Start with an on-demand session resumed from the cache, as after
         a restart: the state _select_startup_plugins restores, then
-        _populate_on_demand_modes_from_plugin, as __init__ calls it."""
+        _populate_on_demand_modes_from_plugin, as __init__ calls it. A
+        session that cannot resume is logged as ``on-demand-error``."""
         dc = self.controller
+        dc._on_demand_named_mode = named_mode
         dc.on_demand_active = True
         dc.on_demand_plugin_id = plugin_id
         dc.on_demand_mode = mode
@@ -739,6 +754,8 @@ class RunLoopHarness:
         dc.on_demand_status = 'active'
         dc.on_demand_schedule_override = True
         dc._populate_on_demand_modes_from_plugin()
+        if dc.on_demand_status == 'error':
+            self.log("on-demand-error", dc.on_demand_last_error)
 
     def wifi_message(self, t: float, message: str, duration: float = 5):
         def write():

test/fixtures/run_loop_golden/on_demand_named_live.json

@@ -0,0 +1,29 @@
+{
+  "screens": [
+    [0.0, "clock", 5.0, "on-demand-start", 6, false],
+    [5.0, "sports_live", 15.0, "duration", 15, true],
+    [20.0, "sports_recent", 15.0, "duration", 15, true],
+    [35.0, "sports_upcoming", 5.0, "on-demand-requested-stop", 6, true],
+    [40.0, "clock", 20.0, "duration", 20, true],
+    [60.0, "sports_live", 15.0, "display-false", 11, true],
+    [75.0, "sports_recent", 15.0, "duration", 15, true],
+    [90.0, "sports_upcoming", 10.0, "on-demand-start", 11, true],
+    [100.0, "sports_live", 0.0, "empty", 1, true],
+    [100.0, "sports_recent", 15.0, "duration", 15, true],
+    [115.0, "sports_upcoming", 15.0, "duration", 15, true],
+    [130.0, "sports_live", 0.0, "empty", 1, true],
+    [130.0, "sports_recent", 10.0, "on-demand-requested-stop", 11, true],
+    [140.0, "sports_upcoming", 15.0, "duration", 15, true],
+    [155.0, "clock", 5.0, "horizon", 5, true]
+  ],
+  "events": [
+    [5.0, "request", "start:n1"],
+    [5.0, "on-demand-start", "sports"],
+    [40.0, "request", "stop:n2"],
+    [40.0, "on-demand-requested-stop"],
+    [100.0, "request", "start:n3"],
+    [100.0, "on-demand-start", "sports"],
+    [140.0, "request", "stop:n4"],
+    [140.0, "on-demand-requested-stop"]
+  ]
+}

test/fixtures/run_loop_golden/on_demand_restore_failed.json

@@ -0,0 +1,10 @@
+{
+  "screens": [
+    [0.0, "clock", 20.0, "duration", 20, false],
+    [20.0, "weather", 20.0, "duration", 20, true],
+    [40.0, "clock", 20.0, "horizon", 20, true]
+  ],
+  "events": [
+    [0.0, "on-demand-error", "restore-failed"]
+  ]
+}

test/js/README.md

@@ -45,7 +45,12 @@ server has none.
 |---|---|---|
 | `unit/test_list_filter.js` | no | `ListFilter` search/filter/sort/count/sticky, and the installed-plugins config **extracted verbatim** from `plugins_manager.js` so the test can't drift from it |
 | `unit/test_update_all.js` | no | `PluginInstallManager.updateAll` from `plugins/install_manager.js`: Check & Update All sends only plugin ids (never `starlark:` app entries), re-sends a request that got no HTTP answer (web service restarting) instead of skipping that plugin, never re-sends one that got any HTTP answer (the real `api_client.js` classifies a proxy 502 or a JSON error without `error_code` as `API_ERROR`), and counts a no-op update as already up to date in the summary. Also run by `test/web_interface/test_update_all_plugins.py` so CI covers it |
+| `unit/test_store_install.js` | no | The store's Install button, with the whole of `plugins_manager.js` run by `plugins_manager_sandbox.js` (a vm context, fake DOM and API): a fresh install reloads the list, then enables the id the plugin was installed as -- the answer's `plugin_id`, else the installed entry the store entry matches (Weather installs as `ledmatrix-weather`); a Reinstall leaves the enabled state alone |
+| `unit/test_install_polling.js` | no | How long Install waits for a queued install (sandbox): at least the server's 300 s dependency-install timeout; when it stops waiting it reloads the installed list and warns, rather than reporting a failure or enabling anything |
+| `unit/test_store_categories.js` | no | The store's category filter (sandbox): the template ships only All Categories, the rest come from the store's plugins (one per category whatever its case), choosing one filters to it, and a swapped-in select is refilled from the cache keeping the choice |
+| `unit/test_github_url_install.js` | no | Install Single Plugin (sandbox, the button as `plugins.html` ships it): no inline `onclick`, so a click or Enter sends exactly one `install-from-url` request and raises no error |
 | `unit/test_render_cards.js` | no | `renderInstalledCards` markup, both empty states, and HTML-escaping of hostile plugin metadata |
+| `unit/test_plugin_order_list.js` | no | `widgets/plugin-order-list.js` (the Vegas and rotation order lists): a disabled plugin, which gets no row, keeps its slot in the saved order and its Vegas exclusion when the list rewrites its hidden inputs, around reordering and include/exclude; an uninstalled plugin's id is dropped, a failed plugin list leaves the inputs as saved, and only string ids are carried over, once each |
 | `unit/test_style_editor_element_keys.js` | no | `elementKeys()`/`styleRows()`/`positionRows()` from `widgets/style-editor.js`: every `customization.layout` entry gets exactly one row -- paired with its style element through core's `x-layout-key` (so `score` belongs to `score_text`, not a second row), or a position row of its own, leaves included -- since the widget claims the whole `layout` block from the generic fallback renderer |
 | `unit/test_style_editor_layout_leaf_columns.js` | no | `columnsFor()` from `widgets/style-editor.js`: a layout-only key whose own value is a leaf (no x/y sub-object, e.g. a `show_logo` toggle) gets a self-keyed column instead of a blank, uneditable row |
 | `unit/test_style_editor_layout_leaf_collision.js` | no | `columnsFor()` from `widgets/style-editor.js`: a layout-only leaf key still gets its own column even when its name collides with an unrelated element's style sub-field or another layout axis's sub-field |
@@ -53,6 +58,9 @@ server has none.
 | `unit/test_store_registry_fields.js` | no | The store card's registry fields from `plugins_manager.js`: the commit that introduced the listed version (a hex SHA only, linked to that tree), the "Needs LEDMatrix X+" warning, a card from an older registry without either, and `isStorePluginInstalled` answering to `aliases` |
 | `unit/test_page_registry.js` | no | The page lifecycle in `js/core/registry.js` (a minimal DOM shim): one `init` per `data-page` root, `destroy` and an aborted `ctx.signal` when htmx swaps it away, a vetoed swap keeps it, lazy page modules, a root removed without htmx swept on the next swap |
 | `unit/test_core_modules.js` | no | `js/core/api.js` (JSON envelope, HTTP/`status: error`/network errors, abort passthrough, the #683 login redirect, same-server paths only) and `js/core/facade.js` (`window.LEDMatrix`, deprecated aliases) |
+| `unit/test_overview_reconciliation_poll.js` | no | The Overview's reconciliation-banner poll from `partials/overview.html`, run in a vm: it gives up after a bounded number of requests when the status never says done, runs only while the Overview is on screen (`LEDVisibility`, its own key), and stops once the banner is shown |
+| `unit/test_display_partial_ids.js` | no | `partials/display.html`: every literal `getElementById()` in its inline scripts names an id the partial renders, and moving the brightness slider (the shipped script, in a vm with a fake DOM) updates its label without throwing |
+| `unit/test_general_web_login_token.js` | no | `createToken` from `js/pages/general.js`, imported with a fake DOM and fetch: a created API token clears the form's `data-dirty` mark (so a reload does not ask "Leave site?"), a refused one keeps it |
 | `unit/test_plugin_action_delegation.js` | no | The document-level card-action delegation and `handlePluginAction` from `plugins_manager.js`, run with the handler inside an IIFE as in the real file: each action is handled once, a Starlark app uninstall goes to `DELETE /starlark/apps/<id>`, and an uninstall is confirmed once |
 | `dom/test_installed_dom.js` | yes | The toolbar in a real DOM: pill/search/sort interaction, the HTMX partial re-swap, and a `getComputedStyle` check that `.filter-pill[data-active]` really matches the emitted markup |
 | `dom/test_store_dom.js` | yes | Store pagination, per-page, category, tri-state Installed button, and persistence across a re-boot, against the live registry |
@@ -61,6 +69,8 @@ server has none.
 | `dom/test_durations_page.js` | yes | The Rotation tab (`js/pages/durations.js`) with the real `plugin-order-list.js` widget: one plugin-list request per swap, one move per click after repeated swaps, a swap cancels the request in flight, a late widget is waited for |
 | `dom/test_operation_history_page.js` | yes | The Operation History tab (`js/pages/operation-history.js`): one request per swap and per Refresh, the plugin filter filled once, paging, filters, search, Clear, error/login states, hostile values stay text |
 | `dom/test_raw_json_page.js` | yes | The Config Editor tab (`js/pages/raw-json.js`): one POST per Save after repeated swaps, Format/Validate, invalid JSON never sent, a save survives a swap, the old global entry points |
+| `dom/test_schedule_page.js` | yes | The Schedule tab (`js/pages/schedule.js`) with the real `schedule-picker` widget: both pickers drawn once per swap from the saved config, one notification per save answer after repeated swaps, the brightness label, a late widget waited for, the old global entry points |
+| `dom/test_general_page.js` | yes | The General tab (`js/pages/general.js`) with the real `timezone-selector` widget: the picker drawn once per swap, one request per Security action after repeated swaps, hostile token names stay text, refused/network/login answers, a write survives a swap, `webLogin`'s entry points |
 | `dom/test_backup_restore_page.js` | yes | The Backup & Restore tab (`js/pages/backup-restore.js`): one request per action after repeated swaps, the upload and restore options, reads cancelled and writes not on a swap, hostile names stay text, the old global entry points |
 | `dom/test_tools_sections.js` | yes | The Tools tab's MQTT bridge and Pixlet editor sections: form prefill, the write-only password (blank means unchanged), the running-session banner and countdown, and that the editor link points at the host you loaded the page from |
 

test/js/dom/test_durations_page.js

@@ -98,7 +98,11 @@ const ok = (l, c, x) => c ? (pass++, console.log('  ok   ' + l))
 
   const lists = () => requests.filter(r => r.url === '/api/v3/plugins/installed').length;
   const $ = id => doc.getElementById(id);
-  const order = () => JSON.parse($('rotation_plugin_order_value').value || '[]');
+  // The rows' ids, in order. The input also keeps saved ids that have no row
+  // (a disabled plugin's place, see test/js/unit/test_plugin_order_list.js),
+  // and the saved order comes from whatever config the server has.
+  const SHOWN = plugins.filter(p => p.enabled).map(p => p.id);
+  const order = () => JSON.parse($('rotation_plugin_order_value').value || '[]').filter(id => SHOWN.includes(id));
   async function swap() {
     panel.dispatchEvent(new window.CustomEvent('htmx:beforeSwap', { bubbles: true, detail: { target: panel, shouldSwap: true } }));
     panel.innerHTML = partial;

test/js/dom/test_general_page.js

@@ -0,0 +1,272 @@
+// The General tab as a page module (static/v3/js/pages/general.js), in a real
+// DOM (jsdom) with the real server-rendered partial, the real timezone
+// widget and the real web-login endpoints' answer shapes. Built like
+// test_cache_page.js:
+//
+//   * the partial ships no <script> and no inline handlers; its root is
+//     data-page="general" and the Security section's forms and buttons name
+//     an action
+//   * the timezone picker is drawn once per swap-in, with the saved zone
+//   * after five swaps, each Security action makes exactly one request
+//   * a login change is a write: a swap does not cancel it, its result is
+//     still reported, and nothing is drawn into the page that has gone
+//   * token names reach the page as text
+//   * the settings form itself is left to htmx
+//   * window.webLogin's entry points still work
+const http = require('http');
+const fs = require('fs');
+const path = require('path');
+const { pathToFileURL } = require('url');
+const { JSDOM, VirtualConsole } = require('jsdom');
+
+const BASE = process.env.BASE || 'http://localhost:5000';
+const JS = path.resolve(__dirname, '../../../web_interface/static/v3/js');
+const get = p => new Promise((res, rej) =>
+  http.get(BASE + p, r => { let d = ''; r.on('data', c => d += c); r.on('end', () => res(d)); }).on('error', rej));
+const load = f => import(pathToFileURL(path.join(JS, f)).href);
+const tick = ms => new Promise(r => setTimeout(r, ms || 0));
+
+let pass = 0, fail = 0;
+const ok = (l, c, x) => c ? (pass++, console.log('  ok   ' + l))
+  : (fail++, console.log('  FAIL ' + l + (x !== undefined ? '  -> ' + JSON.stringify(x).slice(0, 300) : '')));
+
+(async () => {
+  const partial = await get('/partials/general');
+  const realTokens = JSON.parse(await get('/api/v3/auth/tokens'));
+  const { createRegistry } = await load('core/registry.js');
+  const { createApi } = await load('core/api.js');
+  const generalPage = await load('pages/general.js');
+
+  console.log('\n── General tab: page module (real DOM) ──');
+  ok('the partial ships no inline script', !/<script/i.test(partial));
+  ok('the partial has no inline click or submit handlers', !/\son(click|submit|input)=/i.test(partial));
+  ok('the partial root is data-page="general"', /data-page="general"/.test(partial));
+  const security = /id="web-login-settings"/.test(partial);
+  ok('the server renders the Security section (it has a login store)', security);
+  ok('the real token list answers in the shape the section shows',
+     realTokens.status === 'success' && realTokens.data && Array.isArray(realTokens.data.tokens), realTokens);
+  ok('the Security forms name their action',
+     /<form[^>]*data-action="set-password"/.test(partial) && /<form[^>]*data-action="create-token"/.test(partial));
+  ok('the Copy button names its action', /data-action="copy-token"/.test(partial));
+
+  const errs = [];
+  const logged = [];
+  const vc = new VirtualConsole();
+  vc.on('jsdomError', e => errs.push(String(e.message || e).split('\n')[0]));
+  vc.on('error', (...a) => logged.push(a.join(' ')));
+  const dom = new JSDOM(`<!doctype html><html><body><div id="general-content">${partial}</div></body></html>`,
+    { url: BASE + '/', virtualConsole: vc, runScripts: 'outside-only' });
+  const { window } = dom;
+  const doc = window.document;
+  const panel = doc.getElementById('general-content');
+  require('../led_escape').install(window);
+  window.eval(fs.readFileSync(path.join(JS, 'widgets/registry.js'), 'utf8'));
+  window.eval(fs.readFileSync(path.join(JS, 'widgets/timezone-selector.js'), 'utf8'));
+  const widgets = window.LEDMatrixWidgets;
+  ok('the widget scripts register timezone-selector', !!(widgets && widgets.get('timezone-selector')));
+
+  let confirmAnswer = true;
+  const confirms = [];
+  window.confirm = m => { confirms.push(m); return confirmAnswer; };
+  const reloads = [];
+  window.htmx = { ajax: (method, url, opts) => reloads.push([method, url, opts.target]) };
+
+  const HOSTILE = '<img src=x onerror="window.pwned=1">';
+  let mode = 'ok';
+  let nextId = 1;
+  const requests = [];
+  const pending = [];
+  function fakeFetch(url, init) {
+    requests.push({ url, method: init.method, body: init.body ? JSON.parse(init.body) : undefined });
+    const respond = (status, body, headers) => Promise.resolve({
+      status, ok: status >= 200 && status < 300,
+      headers: { get: h => (headers || {})[h] || null },
+      text: () => Promise.resolve(JSON.stringify(body)),
+    });
+    if (mode === 'network') return Promise.reject(new TypeError('Failed to fetch'));
+    if (mode === 'login') return respond(401, { status: 'error' }, { 'X-LEDMatrix-Login': '/login' });
+    if (mode === 'refuse') return respond(400, { status: 'error', message: 'Give the token a name.' });
+    if (url === '/api/v3/auth/tokens' && init.method === 'POST') {
+      const id = 'tok' + (nextId++);
+      const name = JSON.parse(init.body).name;
+      const answer = () => respond(201, {
+        status: 'success', message: 'Token created. Copy it now: it is not shown again.',
+        data: { token: 'lmx_' + id, record: { id, name, prefix: 'lmx_' + id.slice(0, 3), created_at: '2026-10-04T00:00:00' } },
+      });
+      if (mode === 'hang') return new Promise(resolve => pending.push(() => resolve(answer())));
+      return answer();
+    }
+    if (url.startsWith('/api/v3/auth/tokens/') && init.method === 'DELETE') {
+      return respond(200, { status: 'success', message: 'Token revoked.', data: { tokens: [] } });
+    }
+    if (url === '/api/v3/auth/password') {
+      return respond(200, { status: 'success', message: 'Login is on. Other browsers now need the password.' });
+    }
+    return respond(404, { status: 'error', message: 'unexpected ' + url });
+  }
+  const notes = [];
+  const registry = createRegistry({
+    document: doc,
+    context: { api: createApi({ fetch: fakeFetch }), notify: (m, t) => notes.push([m, t]) },
+  });
+  registry.register('general', generalPage);
+
+  const $ = id => doc.getElementById(id);
+  const root = () => doc.querySelector('[data-page="general"]');
+  const timezoneWidgets = () => $('timezone_container').querySelectorAll('.timezone-selector-widget').length;
+  const rows = () => doc.querySelectorAll('#web-login-tokens [data-token-id]');
+  const calls = (method, prefix) => requests.filter(r => r.method === method && r.url.startsWith(prefix));
+  const lastNote = () => notes[notes.length - 1] || [];
+  function submit(form) {
+    const event = new window.Event('submit', { bubbles: true, cancelable: true });
+    form.dispatchEvent(event);
+    return event;
+  }
+  const form = action => root().querySelector(`form[data-action="${action}"]`);
+  async function swap(html) {
+    panel.dispatchEvent(new window.CustomEvent('htmx:beforeSwap', { bubbles: true, detail: { target: panel, shouldSwap: true } }));
+    panel.innerHTML = html === undefined ? partial : html;
+    panel.dispatchEvent(new window.CustomEvent('htmx:afterSwap', { bubbles: true, detail: { target: panel } }));
+    await tick(20);
+  }
+
+  await registry.start();
+  await tick(20);
+
+  // ── the timezone picker ─────────────────────────────────────────────────
+  const savedZone = $('timezone_container').dataset.timezone;
+  ok('the partial carries the saved timezone', !!savedZone, savedZone);
+  ok('the timezone picker is drawn once', timezoneWidgets() === 1, timezoneWidgets());
+  ok('...holding the saved zone', $('timezone_data') && $('timezone_data').value === savedZone,
+     $('timezone_data') && $('timezone_data').value);
+  ok('...posted as "timezone"', $('timezone_data') && $('timezone_data').name === 'timezone');
+
+  for (let i = 0; i < 5; i++) await swap();
+  ok('one mounted page after five swaps', registry.list().length === 1, registry.list().length);
+  ok('the timezone picker is drawn once, not stacked', timezoneWidgets() === 1, timezoneWidgets());
+
+  // ── the settings form is htmx's ─────────────────────────────────────────
+  const settings = root().querySelector('form[hx-post="/api/v3/config/main"]');
+  ok('submitting the settings form is not prevented', settings && !submit(settings).defaultPrevented);
+  ok('...and makes no request of the page\'s own', requests.length === 0, requests.length);
+
+  if (security) {
+    // ── create a token ────────────────────────────────────────────────────
+    const before = rows().length;
+    const create = form('create-token');
+    create.querySelector('[name="name"]').value = HOSTILE;
+    create.setAttribute('data-dirty', '');
+    ok('Create token is handled by the page', submit(create).defaultPrevented);
+    await tick(20);
+    ok('one POST to /api/v3/auth/tokens', calls('POST', '/api/v3/auth/tokens').length === 1, requests);
+    ok('...with the name typed', calls('POST', '/api/v3/auth/tokens')[0].body.name === HOSTILE);
+    ok('a row is added', rows().length === before + 1, rows().length);
+    ok('the hostile token name is shown as text', root().querySelector('#web-login-tokens').textContent.includes(HOSTILE));
+    ok('...and created no element', !root().querySelector('#web-login-tokens img') && !window.pwned);
+    ok('the "No tokens yet" line is gone', !root().querySelector('#web-login-tokens [data-empty]'));
+    ok('the token is shown once', $('web-login-new-token-value').textContent === 'lmx_tok1'
+       && !$('web-login-new-token').classList.contains('hidden'));
+    ok('the form is clean again (no "Leave site?")', !create.hasAttribute('data-dirty'));
+    ok('one success notification', lastNote()[1] === 'success' && /Token created/.test(lastNote()[0]), notes);
+
+    // ── copy it (plain http: not a secure context, so it is selected) ────
+    root().querySelector('button[data-action="copy-token"]').click();
+    ok('Copy selects the token where the clipboard API is unavailable',
+       window.getSelection().toString() === 'lmx_tok1' && /Selected/.test(lastNote()[0]), lastNote());
+
+    // ── revoke it (the row drawn by the page, so delegation covers it) ───
+    confirmAnswer = false;
+    const added = rows()[rows().length - 1];
+    added.querySelector('button[data-action="revoke-token"]').click();
+    await tick(20);
+    ok('a cancelled Revoke sends nothing', calls('DELETE', '/api/v3/auth/tokens/').length === 0);
+    ok('...after asking with the token name as written', confirms.length === 1 && confirms[0].includes(HOSTILE), confirms);
+    confirmAnswer = true;
+    added.querySelector('button[data-action="revoke-token"]').click();
+    await tick(20);
+    ok('Revoke sends one DELETE for that token',
+       calls('DELETE', '/api/v3/auth/tokens/').length === 1 && calls('DELETE', '/api/v3/auth/tokens/')[0].url === '/api/v3/auth/tokens/tok1',
+       calls('DELETE', '/api/v3/auth/tokens/'));
+    ok('...and removes its row', rows().length === before, rows().length);
+
+    // ── the password ──────────────────────────────────────────────────────
+    const pw = form('set-password');
+    pw.querySelector('[name="new_password"]').value = 'correct horse battery';
+    pw.querySelector('[name="confirm_password"]').value = 'correct horse batterY';
+    submit(pw);
+    await tick(20);
+    ok('mismatched passwords are never sent', calls('POST', '/api/v3/auth/password').length === 0);
+    ok('...and say so', lastNote()[1] === 'error' && /do not match/.test(lastNote()[0]), lastNote());
+    pw.querySelector('[name="confirm_password"]').value = 'correct horse battery';
+    submit(pw);
+    await tick(20);
+    const sent = calls('POST', '/api/v3/auth/password');
+    ok('a matching password is sent once', sent.length === 1, sent.length);
+    ok('...with the current password only when the form has one',
+       sent[0] && sent[0].body.new_password === 'correct horse battery'
+         && (('current_password' in sent[0].body) === !!pw.querySelector('[name="current_password"]')), sent[0]);
+    ok('...and the section is reloaded once', reloads.length === 1 && reloads[0][1] === '/v3/partials/general'
+       && reloads[0][2] === '#general-content', reloads);
+
+    // ── refused, network failure, login redirect ──────────────────────────
+    mode = 'refuse';
+    submit(form('create-token'));
+    await tick(20);
+    ok('a refused request shows the server message', lastNote()[1] === 'error' && lastNote()[0] === 'Give the token a name.', lastNote());
+    mode = 'network';
+    submit(form('create-token'));
+    await tick(20);
+    ok('a network failure says the request failed', lastNote()[1] === 'error' && /^Request failed: /.test(lastNote()[0]), lastNote());
+    mode = 'login';
+    const quiet = notes.length;
+    submit(form('create-token'));
+    await tick(20);
+    ok('the login redirect shows nothing (the page is leaving)', notes.length === quiet, notes.slice(quiet));
+
+    // ── a write survives a swap ───────────────────────────────────────────
+    mode = 'hang';
+    await swap();
+    const rowsBefore = rows().length;
+    form('create-token').querySelector('[name="name"]').value = 'Late';
+    submit(form('create-token'));
+    await tick(5);
+    await swap();
+    pending.shift()();
+    await tick(20);
+    ok('a token created before a swap is still reported', lastNote()[1] === 'success', lastNote());
+    ok('...and draws nothing into the new page', rows().length === rowsBefore
+       && $('web-login-new-token').classList.contains('hidden'), rows().length);
+    mode = 'ok';
+
+    // ── window.webLogin ────────────────────────────────────────────────────
+    const viaAlias = calls('POST', '/api/v3/auth/tokens').length;
+    form('create-token').querySelector('[name="name"]').value = 'Alias';
+    await generalPage.webLogin.createToken(form('create-token'));
+    ok('webLogin.createToken(form) creates one token', calls('POST', '/api/v3/auth/tokens').length === viaAlias + 1);
+    ok('webLogin has the five old methods',
+       ['setPassword', 'disable', 'createToken', 'copyToken', 'revoke'].every(m => typeof generalPage.webLogin[m] === 'function'));
+  }
+
+  // ── the widget loads late ───────────────────────────────────────────────
+  delete window.LEDMatrixWidgets;
+  await swap();
+  ok('nothing drawn while the widget is missing', timezoneWidgets() === 0, timezoneWidgets());
+  window.LEDMatrixWidgets = widgets;
+  await tick(150);
+  ok('drawn once the widget arrives', timezoneWidgets() === 1, timezoneWidgets());
+
+  delete window.LEDMatrixWidgets;
+  await swap();
+  const kept = root();
+  await swap('<p>another tab</p>');
+  window.LEDMatrixWidgets = widgets;
+  await tick(250);
+  ok('a page swapped away while waiting draws nothing', kept.querySelectorAll('.timezone-selector-widget').length === 0);
+  ok('nothing left mounted', registry.list().length === 0, registry.list().length);
+
+  ok('no console errors', logged.length === 0, logged);
+  ok('no DOM errors', errs.length === 0, errs);
+
+  console.log(`\n${pass} passed, ${fail} failed`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.error(e); process.exit(1); });

test/js/dom/test_schedule_page.js

@@ -0,0 +1,167 @@
+// The Schedule tab as a page module (static/v3/js/pages/schedule.js), in a
+// real DOM (jsdom) with the real server-rendered partial and the real
+// widget registry and schedule-picker widget. Built like test_cache_page.js:
+//
+//   * the partial ships no <script> and no inline handlers; its root is
+//     data-page="schedule" and carries both saved schedules as JSON
+//   * both pickers are drawn once per swap-in, from the saved config, however
+//     many swaps came first
+//   * each form's save is reported in exactly one notification (the forms
+//     are marked data-reports-result so app.js stays quiet)
+//   * the dim brightness label follows the slider
+//   * a widget that loads late is waited for, and a page swapped away while
+//     waiting draws nothing
+//   * the old globals' entry points still work
+const http = require('http');
+const fs = require('fs');
+const path = require('path');
+const { pathToFileURL } = require('url');
+const { JSDOM, VirtualConsole } = require('jsdom');
+
+const BASE = process.env.BASE || 'http://localhost:5000';
+const JS = path.resolve(__dirname, '../../../web_interface/static/v3/js');
+const get = p => new Promise((res, rej) =>
+  http.get(BASE + p, r => { let d = ''; r.on('data', c => d += c); r.on('end', () => res(d)); }).on('error', rej));
+const load = f => import(pathToFileURL(path.join(JS, f)).href);
+const tick = ms => new Promise(r => setTimeout(r, ms || 0));
+
+let pass = 0, fail = 0;
+const ok = (l, c, x) => c ? (pass++, console.log('  ok   ' + l))
+  : (fail++, console.log('  FAIL ' + l + (x !== undefined ? '  -> ' + JSON.stringify(x).slice(0, 300) : '')));
+
+(async () => {
+  const partial = await get('/partials/schedule');
+  const { createRegistry } = await load('core/registry.js');
+  const schedulePage = await load('pages/schedule.js');
+
+  console.log('\n── Schedule tab: page module (real DOM) ──');
+  ok('the partial ships no inline script', !/<script/i.test(partial));
+  ok('the partial has no inline handlers', !/\son(click|input|change|submit)=/i.test(partial));
+  ok('the forms carry no hx-on handler', !/hx-on/i.test(partial));
+  ok('the partial root is data-page="schedule"', /data-page="schedule"/.test(partial));
+  ok('both forms are marked data-reports-result',
+     (partial.match(/<form[^>]*data-reports-result/g) || []).length === 2);
+
+  const errs = [];
+  const logged = [];
+  const vc = new VirtualConsole();
+  vc.on('jsdomError', e => errs.push(String(e.message || e).split('\n')[0]));
+  vc.on('error', (...a) => logged.push(a.join(' ')));
+  const dom = new JSDOM(`<!doctype html><html><body><div id="schedule-content">${partial}</div></body></html>`,
+    { url: BASE + '/', virtualConsole: vc, runScripts: 'outside-only' });
+  const { window } = dom;
+  const doc = window.document;
+  const panel = doc.getElementById('schedule-content');
+  // base.html defines LEDEscape (app-early.js) before any tab loads; the
+  // widget escapes with it.
+  require('../led_escape').install(window);
+  window.eval(fs.readFileSync(path.join(JS, 'widgets/registry.js'), 'utf8'));
+  window.eval(fs.readFileSync(path.join(JS, 'widgets/schedule-picker.js'), 'utf8'));
+  const widgets = window.LEDMatrixWidgets;
+  ok('the widget scripts register schedule-picker', !!(widgets && widgets.get('schedule-picker')));
+
+  const notes = [];
+  const registry = createRegistry({
+    document: doc,
+    context: { api: null, notify: (m, t) => notes.push([m, t]) },
+  });
+  registry.register('schedule', schedulePage);
+
+  const $ = id => doc.getElementById(id);
+  const root = () => doc.querySelector('[data-page="schedule"]');
+  const saved = key => JSON.parse(root().dataset[key]);
+  const drawn = () => ['schedule_picker_container', 'dim_schedule_picker_container']
+    .map(id => $(id).querySelectorAll('.schedule-picker-widget').length);
+  async function swap(html) {
+    panel.dispatchEvent(new window.CustomEvent('htmx:beforeSwap', { bubbles: true, detail: { target: panel, shouldSwap: true } }));
+    panel.innerHTML = html === undefined ? partial : html;
+    panel.dispatchEvent(new window.CustomEvent('htmx:afterSwap', { bubbles: true, detail: { target: panel } }));
+    await tick(20);
+  }
+  function answer(formId, xhr) {
+    $(formId).dispatchEvent(new window.CustomEvent('htmx:afterRequest', {
+      bubbles: true, detail: { xhr, elt: $(formId), successful: xhr.status < 300 } }));
+  }
+
+  await registry.start();
+  await tick(20);
+
+  // ── first load ──────────────────────────────────────────────────────────
+  ok('both pickers drawn once', drawn().join() === '1,1', drawn());
+  const schedule = saved('scheduleConfig');
+  const dim = saved('dimScheduleConfig');
+  ok('the saved config reaches the page as JSON', schedule && typeof schedule === 'object' && dim && typeof dim === 'object');
+  const mode = cfg => cfg.mode ? cfg.mode.replace('-', '_') : (cfg.days ? 'per_day' : 'global');
+  ok('the display picker shows the saved mode', $('schedule_mode_value').value === mode(schedule),
+     [$('schedule_mode_value').value, schedule.mode]);
+  ok('the dim picker shows the saved mode', $('dim_schedule_mode_value').value === mode(dim),
+     [$('dim_schedule_mode_value').value, dim.mode]);
+  ok('the dim picker shows the saved start time',
+     $('dim_schedule_start_time_hidden').value === (dim.start_time || '20:00'), $('dim_schedule_start_time_hidden').value);
+
+  // ── repeated swaps ──────────────────────────────────────────────────────
+  for (let i = 0; i < 5; i++) await swap();
+  ok('one mounted page after five swaps', registry.list().length === 1, registry.list().length);
+  ok('each picker drawn once, not stacked', drawn().join() === '1,1', drawn());
+
+  const okXhr = body => ({ status: 200, responseText: JSON.stringify(body) });
+  answer('schedule_form', okXhr({ status: 'success', message: 'Schedule configuration saved successfully' }));
+  ok('a schedule save is reported once', notes.length === 1, notes);
+  ok('...with the server message and status',
+     notes[0] && notes[0][0] === 'Schedule configuration saved successfully' && notes[0][1] === 'success', notes[0]);
+  answer('dim_schedule_form', okXhr({ status: 'success' }));
+  ok('a dim schedule save without a message says so',
+     notes.length === 2 && notes[1][0] === 'Dim schedule settings saved' && notes[1][1] === 'success', notes[1]);
+  answer('schedule_form', { status: 400, responseText: JSON.stringify({ status: 'error' }) });
+  ok('a refused save without a message says so',
+     notes.length === 3 && notes[2][0] === 'Error saving schedule' && notes[2][1] === 'error', notes[2]);
+  answer('dim_schedule_form', { status: 502, responseText: '<html>Bad gateway</html>' });
+  ok('a non-JSON answer is an error',
+     notes.length === 4 && notes[3][0] === 'Invalid response from server' && notes[3][1] === 'error', notes[3]);
+  answer('schedule_form', { status: 200, responseText: 'null' });
+  ok('a JSON null answer is an error, not a crash',
+     notes.length === 5 && notes[4][1] === 'error', notes[4]);
+  // An htmx request from elsewhere on the page (outside both forms) is not a save.
+  root().querySelector('.settings-filter').dispatchEvent(new window.CustomEvent('htmx:afterRequest', {
+    bubbles: true, detail: { xhr: okXhr({ status: 'success', message: 'x' }) } }));
+  ok('a request from outside the two forms reports nothing', notes.length === 5, notes.length);
+
+  // ── the brightness label ────────────────────────────────────────────────
+  $('dim_brightness').value = '42';
+  $('dim_brightness').dispatchEvent(new window.Event('input', { bubbles: true }));
+  ok('the dim brightness label follows the slider', $('dim_brightness_display').textContent === '42%',
+     $('dim_brightness_display').textContent);
+
+  // ── the widget loads late ───────────────────────────────────────────────
+  delete window.LEDMatrixWidgets;
+  await swap();
+  ok('nothing drawn while the widget is missing', drawn().join() === '0,0', drawn());
+  window.LEDMatrixWidgets = widgets;
+  await tick(150);
+  ok('drawn once the widget arrives', drawn().join() === '1,1', drawn());
+
+  delete window.LEDMatrixWidgets;
+  await swap();
+  const kept = root();
+  await swap('<p>another tab</p>');
+  window.LEDMatrixWidgets = widgets;
+  await tick(250);
+  ok('a page swapped away while waiting draws nothing',
+     kept.querySelectorAll('.schedule-picker-widget').length === 0);
+  ok('nothing left mounted', registry.list().length === 0, registry.list().length);
+
+  // ── the old globals ─────────────────────────────────────────────────────
+  await swap();
+  const before = notes.length;
+  schedulePage.handleScheduleResponse({ target: $('schedule_form'), detail: { xhr: okXhr({ status: 'success' }) } });
+  schedulePage.handleDimScheduleResponse({ target: $('dim_schedule_form'), detail: { xhr: okXhr({ status: 'success' }) } });
+  ok('handleScheduleResponse(event) and handleDimScheduleResponse(event) report once each',
+     notes.length === before + 2 && notes[before][0] === 'Schedule settings saved'
+       && notes[before + 1][0] === 'Dim schedule settings saved', notes.slice(before));
+
+  ok('no console errors', logged.length === 0, logged);
+  ok('no DOM errors', errs.length === 0, errs);
+
+  console.log(`\n${pass} passed, ${fail} failed`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.error(e); process.exit(1); });

test/js/dom/test_tools_sections.js

@@ -98,8 +98,50 @@ const get = p => new Promise((res, rej) =>
   window.saveMqttBridge();
   await tick(150);
   ok('save includes password once typed', sent && sent.mqtt_password === 'typed-secret');
+
+  // A password with TLS off is refused unless allow_insecure_mqtt is set
+  // (CWE-319, api_v3/misc.py). The form has to be able to send it, or a
+  // plain-LAN broker with a password can never be saved from here.
+  const allowRow = () => $('mqtt-allow-insecure-row');
+  const shown = el => !!el && !el.classList.contains('hidden');
+  ok('allow-without-TLS control rendered', !!$('mqtt-allow-insecure'));
+  ok('allow-without-TLS starts as saved',
+     !!$('mqtt-allow-insecure') && $('mqtt-allow-insecure').checked === !!bridge.data.config.allow_insecure_mqtt);
+  ok('allow-without-TLS shown only while TLS is off',
+     shown(allowRow()) === !$('mqtt-tls').checked);
+  $('mqtt-tls').checked = true;
+  $('mqtt-tls').dispatchEvent(new window.Event('change', { bubbles: true }));
+  ok('ticking TLS hides it', !shown(allowRow()));
+  $('mqtt-tls').checked = false;
+  $('mqtt-tls').dispatchEvent(new window.Event('change', { bubbles: true }));
+  ok('unticking TLS shows it again', shown(allowRow()));
+
+  const setAllow = v => { if ($('mqtt-allow-insecure')) $('mqtt-allow-insecure').checked = v; };
+  setAllow(false);
+  window.saveMqttBridge();
+  await tick(150);
+  ok('save sends allow_insecure_mqtt false when unticked', !!sent && sent.allow_insecure_mqtt === false, sent);
+  setAllow(true);
+  window.saveMqttBridge();
+  await tick(150);
+  ok('save sends allow_insecure_mqtt true when ticked', !!sent && sent.allow_insecure_mqtt === true, sent);
   onPut = null;
 
+  // Prefilled from the saved settings, and hidden while TLS is saved on.
+  bridgePayload = JSON.parse(JSON.stringify(bridge));
+  bridgePayload.data.config.allow_insecure_mqtt = true;
+  bridgePayload.data.config.mqtt_tls = false;
+  window.loadMqttBridge();
+  await tick(150);
+  ok('a saved opt-in is prefilled', !!$('mqtt-allow-insecure') && $('mqtt-allow-insecure').checked === true);
+  bridgePayload.data.config.mqtt_tls = true;
+  window.loadMqttBridge();
+  await tick(150);
+  ok('hidden on load when TLS is saved on', !shown(allowRow()));
+  bridgePayload = bridge;
+  window.loadMqttBridge();
+  await tick(150);
+
   // ── Pixlet editor, idle ────────────────────────────────────────────────
   const appIds = (apps.data.apps || []).map(a => a.id);
   ok('editor lists the apps on disk',

test/js/plugins_manager_sandbox.js

@@ -0,0 +1,212 @@
+// The whole of plugins_manager.js (and list_filter.js before it, as the page
+// loads them), evaluated in a node vm context against a small fake DOM.
+//
+// For suites that drive the plugin manager's real flows -- install, polling,
+// store filters, the GitHub-URL button -- rather than one function sliced
+// out of the file. Nothing is mocked inside the script: only what the page
+// gives it (document, fetch, timers, showNotification, LEDEscape).
+//
+//   const sb = create({ route: (method, url, body) => ({ status, json }) });
+//   sb.el('plugin-store-grid');          // make an element exist by id
+//   sb.window.installPlugin('weather');
+//   await sb.until(() => sb.requests.some(r => r.url.includes('/toggle')));
+//
+// Timers ignore their delays and run on the next turn, so a poll loop that
+// would take minutes in a browser finishes in milliseconds. The page is in
+// readyState "loading" with no #installed-plugins-grid, so the script's own
+// start-up does nothing until a suite asks for it (window.initPluginsPage()).
+const fs = require('fs');
+const path = require('path');
+const vm = require('vm');
+const ledEscape = require('./led_escape');
+
+const V3 = path.resolve(__dirname, '../../web_interface/static/v3');
+const PLUGINS_HTML = path.resolve(__dirname, '../../web_interface/templates/v3/partials/plugins.html');
+
+class FakeClassList {
+  constructor() { this.set = new Set(); }
+  add(...c) { c.forEach(x => this.set.add(x)); }
+  remove(...c) { c.forEach(x => this.set.delete(x)); }
+  contains(c) { return this.set.has(c); }
+  toggle(c, force) {
+    const on = force === undefined ? !this.set.has(c) : !!force;
+    if (on) this.set.add(c); else this.set.delete(c);
+    return on;
+  }
+}
+
+function create({ route } = {}) {
+  const elements = new Map();
+  const requests = [];
+  const toasts = [];
+  const errors = [];
+  const restartNotes = [];
+
+  class FakeElement {
+    constructor(id, tag = 'div', attributes = {}) {
+      this.id = id;
+      this.tagName = tag.toUpperCase();
+      this.attributes = { ...attributes };
+      this.listeners = {};
+      this.children = [];
+      this.classList = new FakeClassList();
+      this.style = { removeProperty() {} };
+      this.dataset = {};
+      this.value = '';
+      this.textContent = '';
+      this.disabled = false;
+      this.parentNode = null;
+      this._html = '';
+    }
+    get innerHTML() { return this._html; }
+    set innerHTML(v) { this._html = String(v); this.children = []; }
+    getAttribute(n) { return n in this.attributes ? this.attributes[n] : null; }
+    setAttribute(n, v) { this.attributes[n] = String(v); }
+    hasAttribute(n) { return n in this.attributes; }
+    removeAttribute(n) { delete this.attributes[n]; }
+    addEventListener(type, fn) { (this.listeners[type] = this.listeners[type] || []).push(fn); }
+    removeEventListener(type, fn) {
+      this.listeners[type] = (this.listeners[type] || []).filter(f => f !== fn);
+    }
+    appendChild(child) { this.children.push(child); child.parentNode = this; return child; }
+    querySelector() { return null; }
+    querySelectorAll() { return []; }
+    closest() { return null; }
+    cloneNode() {
+      const copy = new FakeElement(this.id, this.tagName, this.attributes);
+      copy._html = this._html;
+      copy.value = this.value;
+      return copy;
+    }
+    replaceChild(next, prev) {
+      next.parentNode = this;
+      prev.parentNode = null;
+      if (next.id) elements.set(next.id, next);
+      return prev;
+    }
+    replaceWith(next) { if (this.parentNode) this.parentNode.replaceChild(next, this); }
+    // A browser runs an inline on<type> attribute first (it was set before
+    // any listener was added), then the listeners, and an exception in one
+    // does not stop the next: it is reported, which is what `errors` holds.
+    dispatch(type, init = {}) {
+      const event = {
+        type, target: this, currentTarget: this, key: init.key,
+        defaultPrevented: false,
+        preventDefault() { this.defaultPrevented = true; },
+        stopPropagation() {}, stopImmediatePropagation() {},
+      };
+      const inline = this.getAttribute('on' + type);
+      const handlers = [];
+      if (inline !== null) {
+        handlers.push(vm.runInContext(`(function(event) {\n${inline}\n})`, ctx));
+      }
+      handlers.push(...(this.listeners[type] || []));
+      for (const h of handlers) {
+        try { h.call(this, event); } catch (e) { errors.push(e); }
+      }
+      return event;
+    }
+    click() { return this.dispatch('click'); }
+  }
+
+  function el(id, tag, attributes) {
+    if (!elements.has(id)) {
+      const parent = new FakeElement(null);
+      parent.appendChild(new FakeElement(id, tag, attributes));
+      elements.set(id, parent.children[0]);
+    }
+    return elements.get(id);
+  }
+
+  const timers = [];
+  const ctx = {
+    // Warnings are the script noting elements this fake page doesn't have.
+    console: { log: console.log.bind(console), error: console.error.bind(console),
+               warn: () => {}, info: () => {}, debug: () => {} },
+    debugLog: () => {},
+    addEventListener() {},
+    URL,
+    document: {
+      readyState: 'loading',
+      body: { addEventListener() {} },
+      getElementById: id => elements.get(id) || null,
+      querySelector: () => null,
+      querySelectorAll: () => [],
+      addEventListener() {},
+      dispatchEvent() { return true; },
+      createElement: tag => new FakeElement(null, tag),
+    },
+    CustomEvent: class { constructor(type, init) { this.type = type; this.detail = init && init.detail; } },
+    setTimeout: (fn, _ms, ...args) => { timers.push(setImmediate(() => fn(...args))); return timers.length; },
+    clearTimeout: () => {},
+    setInterval: () => 0,
+    clearInterval: () => {},
+    requestAnimationFrame: fn => setImmediate(fn),
+    getComputedStyle: () => ({ display: 'block' }),
+    scrollTo() {},
+    sessionStorage: { getItem: () => null, setItem() {}, removeItem() {} },
+    localStorage: { getItem: () => null, setItem() {}, removeItem() {} },
+    confirm: () => true,
+    alert: () => {},
+    showNotification: (message, type) => {
+      toasts.push({ message: String(message),
+                    type: type && typeof type === 'object' ? type.type : type });
+    },
+    noteRestartRequired: (body) => { restartNotes.push(body); },
+    fetch: async (url, opts = {}) => {
+      const method = (opts.method || 'GET').toUpperCase();
+      let body = null;
+      try { body = opts.body ? JSON.parse(opts.body) : null; } catch (e) { body = opts.body; }
+      requests.push({ method, url: String(url), body });
+      const answer = (route && route(method, String(url), body)) || { status: 200, json: { status: 'success' } };
+      const status = answer.status || 200;
+      return { ok: status < 400, status, json: async () => answer.json };
+    },
+  };
+  ctx.window = ctx;
+  vm.createContext(ctx);
+  ledEscape.install(ctx);
+  for (const file of ['js/plugins/list_filter.js', 'plugins_manager.js']) {
+    vm.runInContext(fs.readFileSync(path.join(V3, file), 'utf8'), ctx, { filename: file });
+  }
+
+  // Resolves once cond() is true, letting timers and promises run between
+  // checks; rejects if it never is.
+  async function until(cond, label = 'condition', turns = 20000) {
+    for (let i = 0; i < turns; i++) {
+      if (cond()) return;
+      await new Promise(r => setImmediate(r));
+    }
+    throw new Error('timed out waiting for ' + label);
+  }
+
+  // Lets every pending timer and promise run.
+  async function settle(turns = 50) {
+    for (let i = 0; i < turns; i++) await new Promise(r => setImmediate(r));
+  }
+
+  return { window: ctx, el, FakeElement, requests, toasts, errors, restartNotes, until, settle };
+}
+
+// The attributes of the element with this id in partials/plugins.html, as
+// the template ships them (no Jinja on the tags these suites read).
+function templateAttributes(id) {
+  const html = fs.readFileSync(PLUGINS_HTML, 'utf8');
+  const at = html.indexOf(`id="${id}"`);
+  if (at < 0) throw new Error(`no element with id ${id} in plugins.html`);
+  const start = html.lastIndexOf('<', at);
+  let end = start, quote = null;
+  for (; end < html.length; end++) {
+    const ch = html[end];
+    if (quote) { if (ch === quote) quote = null; } else if (ch === '"' || ch === "'") quote = ch;
+    else if (ch === '>') break;
+  }
+  const tag = html.slice(start, end + 1);
+  const attrs = {};
+  const re = /([\w:-]+)\s*=\s*("([^"]*)"|'([^']*)')/g;
+  let m;
+  while ((m = re.exec(tag))) attrs[m[1]] = m[3] !== undefined ? m[3] : m[4];
+  return { tag: tag.match(/^<(\w+)/)[1], attrs, source: tag };
+}
+
+module.exports = { create, templateAttributes };

test/js/run_all.js

@@ -17,17 +17,27 @@ const fs = require('fs');
 
 const BASE = process.env.BASE || 'http://localhost:5000';
 const UNIT = ['unit/test_list_filter.js', 'unit/test_render_cards.js',
+              'unit/test_plugin_order_list.js',
               'unit/test_html_escaping.js', 'unit/test_style_editor_element_keys.js',
               'unit/test_style_editor_layout_leaf_columns.js',
               'unit/test_style_editor_layout_leaf_collision.js',
-              'unit/test_update_all.js', 'unit/test_inline_handler_escaping.js',
+              'unit/test_update_all.js',
+              'unit/test_store_install.js',
+              'unit/test_install_polling.js',
+              'unit/test_store_categories.js',
+              'unit/test_github_url_install.js',
+              'unit/test_inline_handler_escaping.js',
               'unit/test_plugin_action_delegation.js', 'unit/test_file_upload_widget.js',
               'unit/test_store_registry_fields.js', 'unit/test_restart_banner.js',
-              'unit/test_page_registry.js', 'unit/test_core_modules.js'];
+              'unit/test_page_registry.js', 'unit/test_core_modules.js',
+              'unit/test_overview_reconciliation_poll.js',
+              'unit/test_display_partial_ids.js',
+              'unit/test_general_web_login_token.js'];
 const DOM = ['dom/test_installed_dom.js', 'dom/test_store_dom.js', 'dom/test_no_double_fetch.js',
              'dom/test_tools_sections.js', 'dom/test_cache_page.js',
              'dom/test_durations_page.js', 'dom/test_operation_history_page.js',
-             'dom/test_raw_json_page.js', 'dom/test_backup_restore_page.js'];
+             'dom/test_raw_json_page.js', 'dom/test_backup_restore_page.js',
+             'dom/test_schedule_page.js', 'dom/test_general_page.js'];
 
 function reachable(url) {
   return new Promise(res => {

test/js/unit/test_display_partial_ids.js

@@ -0,0 +1,108 @@
+// The Display tab's inline script must only look up elements the partial
+// renders.
+//
+// Its brightness slider handler also wrote to #brightness-display, a "LED
+// brightness: N%" line that #387 removed from partials/display.html. The
+// lookup returned null, so every movement of the slider threw a TypeError.
+// This checks every literal getElementById() in the partial's inline scripts
+// against the ids its markup renders, and runs the shipped script in a vm
+// with a fake DOM (null for an id the markup lacks, as in a browser) to move
+// the slider.
+//
+// No jsdom and no server needed.
+
+const fs = require('fs');
+const path = require('path');
+const vm = require('vm');
+
+const PARTIAL = path.resolve(__dirname, '../../../web_interface/templates/v3/partials/display.html');
+
+let pass = 0, fail = 0;
+const ok = (label, cond, extra) => cond
+  ? (pass++, console.log('  ok   ' + label))
+  : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  ' + JSON.stringify(extra) : '')));
+
+const html = fs.readFileSync(PARTIAL, 'utf8');
+const blocks = [...html.matchAll(/<script\b[^>]*>([\s\S]*?)<\/script[^>]*>/gi)];
+const scripts = blocks.map(m => m[1]);
+// The markup is what lies between the script blocks (sliced around them, not
+// a replace(), which CodeQL reads as an incomplete HTML sanitizer).
+let markup = '';
+let from = 0;
+for (const m of blocks) {
+  markup += html.slice(from, m.index);
+  from = m.index + m[0].length;
+}
+markup += html.slice(from);
+const rendered = new Set([...markup.matchAll(/\bid="([^"{}]+)"/g)].map(m => m[1]));
+
+console.log('\n── Display partial: element lookups ──');
+
+// 1. Static: every literal lookup names an id the partial renders.
+const lookups = scripts.flatMap(s => [...s.matchAll(/getElementById\('([^']+)'\)/g)].map(m => m[1]));
+const missing = [...new Set(lookups.filter(id => !rendered.has(id)))];
+ok('the inline scripts look elements up', lookups.length > 0, lookups.length);
+ok('every looked-up id is rendered by the partial', missing.length === 0, missing);
+
+// 2. Behaviour: moving the brightness slider updates its label and throws nothing.
+function fakeElement(id) {
+  const listeners = {};
+  const classes = new Set();
+  return {
+    id, value: '', textContent: '', min: '', max: '', checked: false,
+    style: {}, dataset: {}, className: '',
+    classList: {
+      add: c => classes.add(c), remove: c => classes.delete(c),
+      toggle: (c, on) => (on === undefined ? (classes.has(c) ? classes.delete(c) : classes.add(c)) : (on ? classes.add(c) : classes.delete(c))),
+      contains: c => classes.has(c),
+    },
+    addEventListener: (type, fn) => { (listeners[type] ||= []).push(fn); },
+    dispatchEvent() { return true; },
+    appendChild() {},
+    listeners,
+  };
+}
+
+const main = scripts.find(s => s.includes("getElementById('brightness')"));
+ok('found the script that wires the brightness slider', !!main);
+if (main) {
+  const elements = new Map();
+  const document = {
+    readyState: 'complete',
+    hidden: false,
+    getElementById: id => {
+      if (!rendered.has(id)) return null;
+      if (!elements.has(id)) elements.set(id, fakeElement(id));
+      return elements.get(id);
+    },
+    createElement: () => fakeElement(''),
+    createTextNode: () => ({}),
+    addEventListener() {},
+  };
+  const window = {
+    LEDEscape: { html: v => String(v), attr: v => String(v) },
+    LEDVisibility: { onActive() {} },
+  };
+  const context = {
+    window, document, console, URLSearchParams,
+    fetch: () => new Promise(() => {}),
+    setTimeout: () => 0, clearTimeout() {}, setInterval: () => 0, clearInterval() {},
+  };
+  vm.createContext(context);
+  let loadError = null;
+  try { vm.runInContext(main, context); } catch (e) { loadError = e; }
+  ok('the script loads', !loadError, loadError && String(loadError));
+
+  const slider = elements.get('brightness');
+  const handlers = (slider && slider.listeners.input) || [];
+  ok('the slider has an input handler', handlers.length > 0);
+  let thrown = null;
+  slider.value = '42';
+  try { handlers.forEach(fn => fn.call(slider, { target: slider })); } catch (e) { thrown = e; }
+  ok('moving the slider throws nothing', !thrown, thrown && String(thrown));
+  ok('...and shows the new value', elements.get('brightness-value').textContent === '42',
+     elements.get('brightness-value').textContent);
+}
+
+console.log(`\n${pass} passed, ${fail} failed\n`);
+process.exit(fail ? 1 : 0);

test/js/unit/test_general_web_login_token.js

@@ -0,0 +1,94 @@
+// Creating an API token on the General tab must leave its form clean.
+//
+// app.js marks a form data-dirty on any input in it and clears the mark only
+// after a successful htmx request; its beforeunload handler then asks "Leave
+// site?" while any visible form is still dirty. The token form posts with
+// fetch (createToken in static/v3/js/pages/general.js), so after a token was
+// created the form stayed dirty and reloading the page while the General tab
+// was open prompted about changes that had been saved.
+//
+// Imports the shipped page module and runs createToken with a fake fetch and
+// DOM -- no jsdom and no server needed.
+
+const path = require('path');
+const { pathToFileURL } = require('url');
+
+const JS = path.resolve(__dirname, '../../../web_interface/static/v3/js');
+const load = f => import(pathToFileURL(path.join(JS, f)).href);
+
+let pass = 0, fail = 0;
+const ok = (label, cond, extra) => cond
+  ? (pass++, console.log('  ok   ' + label))
+  : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  ' + JSON.stringify(extra) : '')));
+
+function el() {
+  const classes = new Set(['hidden']);
+  return {
+    textContent: '', dataset: {}, style: {}, className: '',
+    classList: { add: c => classes.add(c), remove: c => classes.delete(c), contains: c => classes.has(c) },
+    appendChild() {}, addEventListener() {}, querySelector: () => null,
+  };
+}
+
+async function setup(answer) {
+  const { createApi } = await load('core/api.js');
+  const general = await load('pages/general.js');
+  const elements = {
+    '#web-login-tokens': el(),
+    '#web-login-new-token-value': el(),
+    '#web-login-new-token': el(),
+  };
+  const notes = [];
+  const doc = { createElement: () => el(), defaultView: { confirm: () => true } };
+  const root = { ownerDocument: doc, querySelector: sel => elements[sel] || null, querySelectorAll: () => [] };
+  const fetch = () => Promise.resolve({
+    ok: answer.ok, status: answer.ok ? 200 : 400,
+    headers: { get: () => null },
+    text: () => Promise.resolve(JSON.stringify(answer.body)),
+  });
+  const ctx = {
+    root, state: {}, signal: { aborted: false },
+    api: createApi({ fetch }),
+    notify: (m, t) => notes.push([m, t]),
+  };
+  return { general, ctx, elements, notes };
+}
+
+function dirtyForm() {
+  const attrs = new Map([['data-dirty', '']]);
+  return {
+    querySelector: sel => (sel === '[name="name"]' ? { value: 'Home Assistant' } : null),
+    reset() {},
+    hasAttribute: name => attrs.has(name),
+    setAttribute: (name, value) => attrs.set(name, String(value)),
+    removeAttribute: name => attrs.delete(name),
+  };
+}
+
+(async () => {
+  console.log('\n── General tab: API token form ──');
+
+  {
+    const t = await setup({ ok: true, body: {
+      status: 'success', message: 'Token created',
+      data: { token: 'lmx_secret', record: { id: 't1', name: 'Home Assistant', prefix: 'lmx_sec' } },
+    } });
+    const form = dirtyForm();
+    await t.general.createToken(t.ctx, form);
+    ok('the new token is shown', t.elements['#web-login-new-token-value'].textContent === 'lmx_secret');
+    ok('a created token leaves the form clean (no "Leave site?" on reload)',
+       !form.hasAttribute('data-dirty'));
+  }
+
+  {
+    const t = await setup({ ok: false, body: { status: 'error', message: 'Name is required' } });
+    const form = dirtyForm();
+    await t.general.createToken(t.ctx, form);
+    ok('a refused request reports the error', t.notes.some(([m, type]) => type === 'error' && /Name is required/.test(m)),
+       t.notes);
+    ok('...and keeps the form dirty: nothing was saved', form.hasAttribute('data-dirty'));
+  }
+
+  console.log(`\n${pass} passed, ${fail} failed\n`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.log('HARNESS ERROR: ' + e.stack); process.exit(1); });

test/js/unit/test_github_url_install.js

@@ -0,0 +1,93 @@
+// Plugin Manager > Install from GitHub > Install Single Plugin: one click,
+// one request, no errors.
+//
+// The Install button carried an inline onclick calling
+// window.handleGitHubPluginInstall, and attachInstallButtonHandler also gave
+// it a click listener that installs. Both ran on every click. The inline one
+// threw a ReferenceError (it called isGithubUrl, which lives inside the
+// plugin-manager IIFE, from outside it), so only the listener's request went
+// out -- and fixing that scope alone would have sent every install twice.
+// The button now has the listener only.
+//
+// Runs the whole of plugins_manager.js in the sandbox, with the button as
+// partials/plugins.html ships it.
+
+const { create, templateAttributes } = require('../plugins_manager_sandbox');
+
+let pass = 0, fail = 0;
+const ok = (label, cond, extra) => cond
+  ? (pass++, console.log('  ok   ' + label))
+  : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  -> ' + JSON.stringify(extra).slice(0, 400) : '')));
+
+const URL = 'https://github.com/someone/ledmatrix-demo';
+
+function route(method, url) {
+  if (method === 'POST' && url === '/api/v3/plugins/install-from-url') {
+    return { json: { status: 'success', message: 'Plugin demo installed successfully', plugin_id: 'demo' } };
+  }
+  if (url.startsWith('/api/v3/plugins/installed')) return { json: { status: 'success', data: { plugins: [] } } };
+  return { json: { status: 'success' } };
+}
+
+function page() {
+  const sb = create({ route });
+  const button = templateAttributes('install-plugin-from-url');
+  sb.el('install-plugin-from-url', button.tag, button.attrs);
+  sb.el('github-plugin-url', 'input');
+  sb.el('github-plugin-status');
+  sb.el('plugin-branch-input', 'input');
+  return sb;
+}
+
+const installs = sb => sb.requests.filter(r => r.url === '/api/v3/plugins/install-from-url');
+
+(async () => {
+  console.log('\nthe template');
+  {
+    const { attrs } = templateAttributes('install-plugin-from-url');
+    ok('the Install button has no inline onclick', !('onclick' in attrs), attrs.onclick);
+  }
+
+  console.log('\na click');
+  {
+    const sb = page();
+    sb.window.attachInstallButtonHandler();
+    // htmx:afterSettle runs it again on every swap; that must not add a handler.
+    sb.window.attachInstallButtonHandler();
+    sb.el('github-plugin-url').value = URL;
+    sb.window.document.getElementById('install-plugin-from-url').click();
+    await sb.settle();
+    ok('raises no error', sb.errors.length === 0, sb.errors.map(String));
+    ok('sends exactly one install request', installs(sb).length === 1, installs(sb));
+    ok('for the URL typed', installs(sb)[0] && installs(sb)[0].body.repo_url === URL, installs(sb));
+    ok('and reports the result', /Successfully installed: demo/.test(sb.el('github-plugin-status').innerHTML),
+       sb.el('github-plugin-status').innerHTML);
+  }
+
+  console.log('\nEnter in the URL field');
+  {
+    const sb = page();
+    sb.window.attachInstallButtonHandler();
+    const input = sb.el('github-plugin-url');
+    input.value = URL;
+    input.dispatch('keypress', { key: 'Enter' });
+    await sb.settle();
+    ok('raises no error', sb.errors.length === 0, sb.errors.map(String));
+    ok('sends exactly one install request', installs(sb).length === 1, installs(sb));
+  }
+
+  console.log('\na URL that is not GitHub');
+  {
+    const sb = page();
+    sb.window.attachInstallButtonHandler();
+    sb.el('github-plugin-url').value = 'https://example.com/x';
+    sb.window.document.getElementById('install-plugin-from-url').click();
+    await sb.settle();
+    ok('is refused without a request or an error',
+       installs(sb).length === 0 && sb.errors.length === 0 && /valid GitHub URL/.test(sb.el('github-plugin-status').innerHTML),
+       { errors: sb.errors.map(String), status: sb.el('github-plugin-status').innerHTML });
+  }
+
+  console.log(`\n${pass} passed, ${fail} failed`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.error(e); process.exit(1); });

test/js/unit/test_install_polling.js

@@ -0,0 +1,89 @@
+// How long the store's Install waits for a queued install, and what it says
+// when it stops waiting.
+//
+// It polled the operation 60 times, a second apart, then reported "Install
+// operation timed out" as an error and did nothing else. The server is
+// allowed far longer: the plugin's dependency install alone may take 300 s
+// (install_requirements_file in src/plugin_system/store_install.py), after
+// a download that fetches the plugin one file at a time. So an install that
+// went on to succeed was reported as failed, never enabled, and missing from
+// the installed list until the page was reloaded.
+//
+// Runs the whole of plugins_manager.js in the sandbox; its timers ignore
+// their delays, so each poll here stands for one second on a real page.
+
+const { create } = require('../plugins_manager_sandbox');
+
+let pass = 0, fail = 0;
+const ok = (label, cond, extra) => cond
+  ? (pass++, console.log('  ok   ' + label))
+  : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  -> ' + JSON.stringify(extra).slice(0, 400) : '')));
+
+// The server's dependency-install timeout, in polls (one a second).
+const DEPENDENCY_INSTALL_TIMEOUT_POLLS = 300;
+
+function server(completesAfterPolls) {
+  const state = { polls: 0, installed: [] };
+  state.route = (method, url, body) => {
+    if (url.startsWith('/api/v3/plugins/installed')) {
+      return { json: { status: 'success', data: { plugins: state.installed.map(p => ({ ...p })) } } };
+    }
+    if (method === 'POST' && url === '/api/v3/plugins/install') {
+      return { json: { status: 'success', message: 'queued', data: { operation_id: 'op-1' } } };
+    }
+    if (url === '/api/v3/plugins/operation/op-1') {
+      state.polls++;
+      if (completesAfterPolls === null || state.polls < completesAfterPolls) {
+        return { json: { status: 'success', data: { status: 'running' } } };
+      }
+      state.installed = [{ id: 'clock-simple', name: 'Clock', enabled: false }];
+      return { json: { status: 'success', data: { status: 'completed',
+        result: { success: true, message: 'installed', plugin_id: 'clock-simple' } } } };
+    }
+    if (method === 'POST' && url === '/api/v3/plugins/toggle') {
+      return { json: { status: 'success', message: 'enabled' } };
+    }
+    return { json: { status: 'success' } };
+  };
+  return state;
+}
+
+(async () => {
+  console.log('\nan install that takes longer than a minute');
+  {
+    // 200 s: well inside what the server allows.
+    const srv = server(200);
+    const sb = create({ route: srv.route });
+    sb.window.installPlugin('clock-simple');
+    await sb.until(() => sb.toasts.some(t => /installed and enabled|enabling it failed|timed out|still/i.test(t.message)),
+                   'the install to finish');
+    await sb.settle();
+    ok('is waited for until it completes', srv.polls === 200, srv.polls);
+    ok('is not reported as an error', !sb.toasts.some(t => t.type === 'error'), sb.toasts);
+    ok('and is enabled', sb.requests.some(r => r.url === '/api/v3/plugins/toggle' && r.body.plugin_id === 'clock-simple'),
+       sb.requests.filter(r => r.method === 'POST'));
+  }
+
+  console.log('\nan install that never reports back');
+  {
+    const srv = server(null);
+    const sb = create({ route: srv.route });
+    sb.window.installPlugin('clock-simple');
+    await sb.until(() => sb.toasts.length >= 3, 'the poller to give up');
+    await sb.settle();
+    ok(`is polled for at least the ${DEPENDENCY_INSTALL_TIMEOUT_POLLS} s dependency-install timeout`,
+       srv.polls >= DEPENDENCY_INSTALL_TIMEOUT_POLLS, srv.polls);
+    ok('...but not forever', srv.polls <= 1200, srv.polls);
+    const lastPoll = sb.requests.map(r => r.url).lastIndexOf('/api/v3/plugins/operation/op-1');
+    ok('then the installed list is reloaded, to show what actually happened',
+       sb.requests.slice(lastPoll + 1).some(r => r.url === '/api/v3/plugins/installed'),
+       sb.requests.slice(lastPoll + 1).map(r => r.url));
+    const last = sb.toasts[sb.toasts.length - 1];
+    ok('it says the install may still be running, as a warning, not a failure',
+       last && last.type === 'warning' && !/fail|timed out/i.test(last.message), sb.toasts);
+    ok('nothing is enabled on a guess', !sb.requests.some(r => r.url === '/api/v3/plugins/toggle'));
+  }
+
+  console.log(`\n${pass} passed, ${fail} failed`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.error(e); process.exit(1); });

test/js/unit/test_overview_reconciliation_poll.js

@@ -0,0 +1,137 @@
+// The Overview's "Plugin Config Warning" poll must end.
+//
+// The banner script in partials/overview.html asks
+// /api/v3/plugins/reconciliation-status every 2 s until startup reconciliation
+// says it is done. The route answers done: false whenever its status file is
+// missing -- reconciliation raised before writing it, or /tmp was cleaned
+// under a long-running web service -- so the poll used to run every 2 s for
+// as long as the page stayed open, on every tab. It now gives up after a
+// bounded number of tries and runs only while the Overview is on screen
+// (LEDVisibility, like the other partials' pollers).
+//
+// Runs the shipped inline script in a vm with fake timers, fetch and DOM --
+// no jsdom and no server needed.
+
+const fs = require('fs');
+const path = require('path');
+const vm = require('vm');
+
+const PARTIAL = path.resolve(__dirname, '../../../web_interface/templates/v3/partials/overview.html');
+
+let pass = 0, fail = 0;
+const ok = (label, cond, extra) => cond
+  ? (pass++, console.log('  ok   ' + label))
+  : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  ' + JSON.stringify(extra) : '')));
+
+function bannerScript() {
+  const html = fs.readFileSync(PARTIAL, 'utf8');
+  const scripts = [...html.matchAll(/<script\b[^>]*>([\s\S]*?)<\/script[^>]*>/gi)].map(m => m[1]);
+  const found = scripts.find(s => s.includes('ledmatrix-recon-dismissed'));
+  if (!found) throw new Error('reconciliation banner script not found in overview.html');
+  return found;
+}
+
+const flush = async () => { for (let i = 0; i < 10; i++) await new Promise(r => setImmediate(r)); };
+
+function load({ payload, visibility = true }) {
+  const timers = new Map();
+  let nextId = 1;
+  const calls = [];
+  const banner = { style: { setProperty() {} }, dataset: {} };
+  const text = { textContent: '' };
+  const registrations = [];
+  const window = {};
+  if (visibility) {
+    window.LEDVisibility = {
+      onActive(tab, start, stop, key) { registrations.push({ tab, start, stop, key }); start(); },
+    };
+  }
+  const context = {
+    window,
+    document: {
+      getElementById: id => ({ 'reconciliation-banner': banner, 'reconciliation-banner-text': text })[id] || null,
+    },
+    sessionStorage: { getItem: () => null, setItem() {} },
+    fetch: (url) => {
+      calls.push(url);
+      return Promise.resolve({ json: () => Promise.resolve(payload()) });
+    },
+    setTimeout: (fn) => { const id = nextId++; timers.set(id, fn); return id; },
+    clearTimeout: (id) => { timers.delete(id); },
+  };
+  vm.createContext(context);
+  vm.runInContext(bannerScript(), context);
+  const fireTimers = async () => {
+    const due = [...timers.entries()];
+    timers.clear();
+    due.forEach(([, fn]) => fn());
+    await flush();
+  };
+  return { calls, timers, registrations, banner, text, window, fireTimers };
+}
+
+(async () => {
+  console.log('\n── Overview reconciliation poll ──');
+
+  // 1. A status file that never says done: the poll stops on its own.
+  {
+    const t = load({ payload: () => ({ status: 'success', data: { done: false, unresolved: [] } }) });
+    await flush();
+    for (let i = 0; i < 200; i++) await t.fireTimers();
+    ok('a status that never turns done stops being polled', t.timers.size === 0,
+       { pending: t.timers.size, requests: t.calls.length });
+    ok('...after a bounded number of requests (at most 30, a minute at 2 s)',
+       t.calls.length > 1 && t.calls.length <= 30, t.calls.length);
+  }
+
+  // 2. Runs only while the Overview is on screen.
+  {
+    const t = load({ payload: () => ({ status: 'success', data: { done: false, unresolved: [] } }) });
+    await flush();
+    const reg = t.registrations[0];
+    ok('registers with LEDVisibility for the overview tab', !!reg && reg.tab === 'overview', reg && reg.tab);
+    ok('under its own key, so it does not replace another overview poller',
+       !!reg && !!reg.key && reg.key !== 'overview', reg && reg.key);
+    ok('first request goes out at once', t.calls.length === 1, t.calls.length);
+    if (reg) {
+      reg.stop();
+      ok('leaving the tab cancels the pending retry', t.timers.size === 0, t.timers.size);
+      for (let i = 0; i < 5; i++) await t.fireTimers();
+      ok('no requests while another tab is active', t.calls.length === 1, t.calls.length);
+      reg.start();
+      await flush();
+      ok('coming back asks again at once', t.calls.length === 2, t.calls.length);
+      ok('...and keeps polling', t.timers.size === 1, t.timers.size);
+    }
+  }
+
+  // 3. A finished reconciliation with findings shows the banner and stops.
+  {
+    let done = false;
+    const t = load({ payload: () => (done
+      ? { status: 'success', data: { done: true, unresolved: [{ plugin_id: 'clock', type: 'plugin_missing_on_disk' }] } }
+      : { status: 'success', data: { done: false, unresolved: [] } }) });
+    await flush();
+    await t.fireTimers();
+    done = true;
+    await t.fireTimers();
+    ok('the banner names the finding once reconciliation is done',
+       t.text.textContent.includes('clock'), t.text.textContent);
+    const before = t.calls.length;
+    for (let i = 0; i < 5; i++) await t.fireTimers();
+    ok('no more requests once it is done', t.calls.length === before && t.timers.size === 0,
+       { before, after: t.calls.length, pending: t.timers.size });
+  }
+
+  // 4. Without LEDVisibility (base.html always has it) it still runs, bounded.
+  {
+    const t = load({ visibility: false, payload: () => ({ status: 'success', data: { done: false } }) });
+    await flush();
+    ok('runs without LEDVisibility', t.calls.length === 1, t.calls.length);
+    for (let i = 0; i < 200; i++) await t.fireTimers();
+    ok('...and is still bounded', t.timers.size === 0 && t.calls.length <= 30, t.calls.length);
+  }
+
+  console.log(`\n${pass} passed, ${fail} failed\n`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.log('HARNESS ERROR: ' + e.stack); process.exit(1); });

test/js/unit/test_plugin_order_list.js

@@ -0,0 +1,189 @@
+// The shared plugin order list (widgets/plugin-order-list.js) keeps what it
+// does not show.
+//
+// It lists enabled plugins only, and rewrites its hidden inputs from those
+// rows as soon as it has drawn them. A disabled plugin's place in the order
+// and its Vegas exclusion used to vanish from the inputs on that rewrite, so
+// any later save of the Display or Rotation & Durations tab stored them
+// without it: re-enabled, the plugin came back at the end of the rotation and
+// scrolling in Vegas again. An uninstalled plugin's id is still dropped, as
+// before, so the lists don't collect ids nothing can show. Runs the shipped
+// widget in a vm with a minimal fake DOM -- no jsdom and no server needed, so
+// it runs under test/test_js_unit_suites.py too.
+
+const fs = require('fs');
+const path = require('path');
+const vm = require('vm');
+const WIDGET = path.resolve(__dirname, '../../../web_interface/static/v3/js/widgets/plugin-order-list.js');
+
+let pass = 0, fail = 0;
+const ok = (label, cond, extra) => cond
+  ? (pass++, console.log('  ok   ' + label))
+  : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  ' + JSON.stringify(extra) : '')));
+const same = (a, b) => JSON.stringify(a) === JSON.stringify(b);
+
+class FakeElement {
+  constructor(tag) {
+    this.tagName = tag.toUpperCase();
+    this.children = [];
+    this.parent = null;
+    this.dataset = {};
+    this.style = {};
+    this.className = '';
+    this.value = '';
+    this.checked = false;
+    this.listeners = {};
+    this._text = '';
+  }
+  appendChild(child) {
+    if (child.parent) child.parent.children = child.parent.children.filter(c => c !== child);
+    child.parent = this;
+    this.children.push(child);
+    return child;
+  }
+  insertBefore(child, ref) {
+    if (!ref) return this.appendChild(child);
+    if (child.parent) child.parent.children = child.parent.children.filter(c => c !== child);
+    child.parent = this;
+    this.children.splice(this.children.indexOf(ref), 0, child);
+    return child;
+  }
+  get previousElementSibling() {
+    const siblings = this.parent ? this.parent.children : [];
+    return siblings[siblings.indexOf(this) - 1] || null;
+  }
+  get nextElementSibling() {
+    const siblings = this.parent ? this.parent.children : [];
+    const i = siblings.indexOf(this);
+    return i < 0 ? null : siblings[i + 1] || null;
+  }
+  set textContent(value) { this._text = value; this.children = []; }
+  get textContent() { return this._text; }
+  setAttribute() {}
+  focus() {}
+  addEventListener(type, fn) { (this.listeners[type] ||= []).push(fn); }
+  fire(type, event) { (this.listeners[type] || []).forEach(fn => fn.call(this, event || {})); }
+  descendants() { return this.children.flatMap(c => [c, ...c.descendants()]); }
+  querySelectorAll(selector) {
+    const cls = selector.replace(/^\./, '');
+    return this.descendants().filter(e => e.className.split(/\s+/).includes(cls));
+  }
+  querySelector(selector) { return this.querySelectorAll(selector)[0] || null; }
+}
+
+/** Run the widget over `plugins` with the given saved inputs; resolves once it has drawn. */
+async function mount({ plugins, order, excluded, fetchFails }) {
+  const els = {
+    list: new FakeElement('div'),
+    order: Object.assign(new FakeElement('input'), { value: JSON.stringify(order) }),
+  };
+  if (excluded !== undefined) {
+    els.excluded = Object.assign(new FakeElement('input'), { value: JSON.stringify(excluded) });
+  }
+  const context = {
+    // The widget logs a failed list; expected there, so kept off the output.
+    console: fetchFails ? Object.assign({}, console, { error: () => {} }) : console,
+    window: {},
+    document: {
+      getElementById: (id) => els[id] || null,
+      createElement: (tag) => new FakeElement(tag),
+      createTextNode: (text) => new FakeElement('#text'),
+    },
+    fetch: () => (fetchFails ? Promise.reject(new Error('service restarting')) : Promise.resolve({
+      json: () => Promise.resolve({ status: 'success', data: { plugins } }),
+    })),
+  };
+  vm.createContext(context);
+  vm.runInContext(fs.readFileSync(WIDGET, 'utf8'), context);
+  context.window.PluginOrderList.init({
+    containerId: 'list', orderInputId: 'order',
+    excludedInputId: excluded !== undefined ? 'excluded' : undefined,
+  });
+  await new Promise(resolve => setTimeout(resolve, 0));
+  const rows = () => els.list.querySelectorAll('.plugin-order-item');
+  return {
+    rows,
+    rowIds: () => rows().map(r => r.dataset.pluginId),
+    order: () => JSON.parse(els.order.value),
+    excluded: () => JSON.parse(els.excluded.value),
+    row: (id) => rows().find(r => r.dataset.pluginId === id),
+  };
+}
+
+const PLUGINS = [
+  { id: 'weather', name: 'Weather', enabled: true },
+  { id: 'clock', name: 'Clock', enabled: false },
+  { id: 'stocks', name: 'Stocks', enabled: true },
+];
+
+(async () => {
+  console.log('\nVegas: a disabled plugin keeps its place and its exclusion');
+  {
+    const t = await mount({ plugins: PLUGINS, order: ['weather', 'clock', 'stocks'], excluded: ['clock'] });
+    ok('only enabled plugins get a row', same(t.rowIds(), ['weather', 'stocks']), t.rowIds());
+    ok('drawing the list keeps the disabled plugin in the order, in its place',
+       same(t.order(), ['weather', 'clock', 'stocks']), t.order());
+    ok('drawing the list keeps its exclusion', same(t.excluded(), ['clock']), t.excluded());
+
+    // Move Stocks up: the rows swap, and Clock stays in its saved slot.
+    const up = t.row('stocks').querySelectorAll('.plugin-order-move')[0];
+    up.fire('click');
+    ok('reordering the rows fills the other slots in the new order',
+       same(t.order(), ['stocks', 'clock', 'weather']), t.order());
+
+    const include = t.row('weather').querySelector('.plugin-order-include');
+    include.checked = false;
+    include.fire('change');
+    ok('unchecking a row adds it, and the disabled exclusion stays',
+       same([...t.excluded()].sort(), ['clock', 'weather']), t.excluded());
+    include.checked = true;
+    include.fire('change');
+    ok('checking it again removes only that one', same(t.excluded(), ['clock']), t.excluded());
+  }
+
+  console.log('\nRotation order: the same, without exclusions');
+  {
+    const plugins = [
+      { id: 'clock', enabled: true },
+      { id: 'off', enabled: false },
+      { id: 'weather', enabled: true },
+      { id: 'new', enabled: true },
+    ];
+    const t = await mount({ plugins, order: ['clock', 'off', 'weather'] });
+    ok('the disabled plugin keeps its slot; a plugin not in the saved order goes last',
+       same(t.order(), ['clock', 'off', 'weather', 'new']), t.order());
+  }
+
+  console.log('\nAn uninstalled plugin is dropped; a failed list keeps everything');
+  {
+    const t = await mount({ plugins: PLUGINS, order: ['weather', 'gone', 'clock', 'stocks'],
+                            excluded: ['gone', 'clock'] });
+    ok('the disabled plugin is kept and the uninstalled one dropped from the order',
+       same(t.order(), ['weather', 'clock', 'stocks']), t.order());
+    ok('and from the exclusions', same(t.excluded(), ['clock']), t.excluded());
+  }
+  {
+    const t = await mount({ plugins: PLUGINS, order: ['weather', 'gone', 'clock', 'stocks'],
+                            excluded: ['gone', 'clock'], fetchFails: true });
+    // No installed list, so nothing can be told apart: no rows, and the
+    // inputs keep what was saved, uninstalled ids included.
+    ok('a failed plugin list draws no rows', t.rowIds().length === 0, t.rowIds());
+    ok('and leaves the saved order as it was',
+       same(t.order(), ['weather', 'gone', 'clock', 'stocks']), t.order());
+    ok('and the saved exclusions', same(t.excluded(), ['gone', 'clock']), t.excluded());
+  }
+
+  console.log('\nOnly what the server would accept is carried over');
+  {
+    const t = await mount({ plugins: PLUGINS, order: ['weather', 7, 'clock', null, 'clock', 'stocks'],
+                            excluded: ['clock', 3, 'clock'] });
+    // /config/main refuses a list holding anything but strings, which would
+    // block every later Display save; a repeated id is kept once.
+    ok('non-string and repeated saved ids are dropped from the order',
+       same(t.order(), ['weather', 'clock', 'stocks']), t.order());
+    ok('and from the exclusions', same(t.excluded(), ['clock']), t.excluded());
+  }
+
+  console.log(`\n${pass} passed, ${fail} failed`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.error(e); process.exit(1); });

test/js/unit/test_restart_banner.js

@@ -19,7 +19,7 @@ const ok = (label, cond, extra) => cond
   ? (pass++, console.log('  ok   ' + label))
   : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  ' + JSON.stringify(extra) : '')));
 
-function load() {
+function load(notes) {
   const handlers = {};
   const listen = (target) => (type, fn) => { (handlers[target + ':' + type] ||= []).push(fn); };
   const banner = { style: { display: 'none' } };
@@ -43,14 +43,18 @@ function load() {
       removeItem: (k) => { delete store[k]; },
       getItem: (k) => (k in store ? store[k] : null),
     },
-    showNotification: () => {},
+    showNotification: (m, t) => { if (notes) notes.push([m, t]); },
     setTimeout: () => 0,
   };
   vm.createContext(context);
   vm.runInContext(fs.readFileSync(path.join(V3, 'app.js'), 'utf8'), context);
   const afterRequest = (handlers['body:htmx:afterRequest'] || [])[0];
-  const fire = ({ status = 200, body, path: reqPath = '/api/v3/anything', reportsItself = false }) => {
-    const elt = { closest: () => (reportsItself ? {} : null) };
+  // `marks`: the attribute selectors the requesting element (or its form)
+  // matches, for app.js's elt.closest(<selector list>).
+  const fire = ({ status = 200, body, path: reqPath = '/api/v3/anything', reportsItself = false, marks = [] }) => {
+    const elt = {
+      closest: (sel) => (reportsItself || sel.split(',').some(s => marks.includes(s.trim())) ? {} : null),
+    };
     afterRequest({
       target: { closest: () => null },
       detail: {
@@ -100,5 +104,20 @@ console.log('\nhtmx after-request follows the flag, not the URL');
   ok('a flagged answer raises it, even from a form that reports itself', t.banner.style.display === 'block');
 }
 
+console.log('\nthe server message toast');
+{
+  const notes = [];
+  const t = load(notes);
+  const answer = { status: 'success', message: 'Schedule saved' };
+  t.fire({ body: answer });
+  ok('a plain htmx request shows the server message', notes.length === 1 && notes[0][0] === 'Schedule saved', notes);
+  t.fire({ body: answer, marks: ['[hx-on\\:htmx\\:after-request]'] });
+  ok('a form with its own hx-on after-request handler does not', notes.length === 1, notes);
+  // Page modules (js/pages/schedule.js) report a form's save from a listener
+  // and mark the form data-reports-result instead of an hx-on attribute.
+  t.fire({ body: answer, marks: ['[data-reports-result]'] });
+  ok('nor does a form a page module reports for (data-reports-result)', notes.length === 1, notes);
+}
+
 console.log(`\n${pass} passed, ${fail} failed`);
 process.exit(fail ? 1 : 0);

test/js/unit/test_store_categories.js

@@ -0,0 +1,105 @@
+// The Plugin Store's category filter offers the categories its plugins have.
+//
+// The template listed seven fixed categories. The registry uses about
+// twenty (productivity, utility, transit, finance, ...), so roughly a third
+// of the store could not be filtered to at all, and "Financial" missed the
+// plugin filed under "finance". The options are now built from the store's
+// plugins, as the Starlark section builds its own; the template ships only
+// "All Categories".
+//
+// Runs the whole of plugins_manager.js in the sandbox.
+
+const fs = require('fs');
+const path = require('path');
+const { create, templateAttributes } = require('../plugins_manager_sandbox');
+
+let pass = 0, fail = 0;
+const ok = (label, cond, extra) => cond
+  ? (pass++, console.log('  ok   ' + label))
+  : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  -> ' + JSON.stringify(extra).slice(0, 400) : '')));
+
+const STORE = [
+  { id: 'nfl', name: 'NFL', category: 'sports' },
+  { id: 'nba', name: 'NBA', category: 'Sports' },
+  { id: 'todo', name: 'Todo', category: 'productivity' },
+  { id: 'stocks', name: 'Stocks', category: 'finance' },
+  { id: 'crypto', name: 'Crypto', category: 'financial' },
+  { id: 'bus', name: 'Bus', category: 'transit' },
+  { id: 'mystery', name: 'Mystery' },
+];
+
+function route(method, url) {
+  if (url.startsWith('/api/v3/plugins/store/list')) return { json: { status: 'success', data: { plugins: STORE } } };
+  if (url.startsWith('/api/v3/plugins/installed')) return { json: { status: 'success', data: { plugins: [] } } };
+  if (url.startsWith('/api/v3/plugins/store/github-status')) {
+    return { json: { status: 'success', data: { token_status: 'valid', authenticated: true, rate_limit: 5000 } } };
+  }
+  if (url.startsWith('/api/v3/plugins/saved-repositories')) {
+    return { json: { status: 'success', data: { repositories: [] } } };
+  }
+  if (url.startsWith('/api/v3/display/on-demand/status')) {
+    return { json: { status: 'success', data: { state: {}, service: {} } } };
+  }
+  return { json: { status: 'success' } };
+}
+
+const options = sel => sel.children.map(o => o.value);
+const cardIds = sb => [...sb.el('plugin-store-grid').innerHTML.matchAll(/<h4[^>]*>([^<]*)<\/h4>/g)].map(m => m[1]);
+
+(async () => {
+  console.log('\nthe template');
+  {
+    const html = fs.readFileSync(path.resolve(__dirname,
+      '../../../web_interface/templates/v3/partials/plugins.html'), 'utf8');
+    const start = html.indexOf('<select id="plugin-category"');
+    const block = html.slice(start, html.indexOf('</select>', start));
+    const shipped = [...block.matchAll(/<option value="([^"]*)"/g)].map(m => m[1]);
+    ok('ships only "All Categories"', JSON.stringify(shipped) === JSON.stringify(['']), shipped);
+  }
+
+  const sb = create({ route });
+  const attrs = templateAttributes('plugin-category').attrs;
+  const select = sb.el('plugin-category', 'select', attrs);
+  sb.el('plugin-store-grid');
+  sb.el('installed-plugins-grid');
+  sb.window.initPluginsPage();
+  await sb.until(() => sb.requests.some(r => r.url.startsWith('/api/v3/plugins/store/list')), 'the store list');
+  await sb.settle();
+
+  console.log('\noptions come from the store\'s plugins');
+  ok('"All Categories" is still the first choice', /<option value="">All Categories<\/option>/.test(select.innerHTML),
+     select.innerHTML);
+  ok('every category a plugin has is offered once, whatever its case',
+     JSON.stringify(options(select)) === JSON.stringify(['finance', 'financial', 'productivity', 'sports', 'transit']),
+     options(select));
+  ok('labels are capitalised',
+     (select.children.find(o => o.value === 'productivity') || {}).textContent === 'Productivity');
+
+  console.log('\nchoosing one filters to it');
+  select.value = 'productivity';
+  select.dispatch('change');
+  ok('productivity shows its plugin', JSON.stringify(cardIds(sb)) === JSON.stringify(['Todo']), cardIds(sb));
+  select.value = 'finance';
+  select.dispatch('change');
+  ok('finance is not lost to "financial"', JSON.stringify(cardIds(sb)) === JSON.stringify(['Stocks']), cardIds(sb));
+  select.value = 'sports';
+  select.dispatch('change');
+  ok('one option covers both spellings of sports',
+     JSON.stringify(cardIds(sb).sort()) === JSON.stringify(['NBA', 'NFL']), cardIds(sb));
+
+  console.log('\nthe partial is swapped back in (tab switch)');
+  {
+    // A fresh <select> from the template, the store list still cached.
+    const fresh = new sb.FakeElement('plugin-category', 'select', attrs);
+    select.parentNode.replaceChild(fresh, select);
+    sb.window.searchPluginStore(false);
+    await sb.settle();
+    ok('the new select is filled from the cache',
+       JSON.stringify(options(fresh)) === JSON.stringify(['finance', 'financial', 'productivity', 'sports', 'transit']),
+       options(fresh));
+    ok('keeping the chosen category', fresh.value === 'sports', fresh.value);
+  }
+
+  console.log(`\n${pass} passed, ${fail} failed`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.error(e); process.exit(1); });

test/js/unit/test_store_install.js

@@ -0,0 +1,138 @@
+// The store's Install button: which plugin it enables afterwards, and when.
+//
+//  1. Weather, Music, Stocks and Leaderboard are registry entries (`weather`)
+//     whose manifests declare another id (`ledmatrix-weather`). The plugin
+//     list, its config section and /plugins/toggle know them by that id, but
+//     the button enabled the registry id: /plugins/toggle answered 404
+//     "Plugin not found" and the plugin stayed disabled behind "installed,
+//     but enabling it failed". It now enables the id the install answer
+//     names (`plugin_id`), or, from an answer without one, the installed
+//     entry the store entry matches (its id, plugin_path name or aliases).
+//
+//  2. Reinstall (the same button on an installed plugin) enabled it too, so
+//     reinstalling a plugin the user had switched off switched it back on.
+//     Only a fresh install enables.
+//
+// Runs the whole of plugins_manager.js in the sandbox against a fake API.
+
+const { create } = require('../plugins_manager_sandbox');
+
+let pass = 0, fail = 0;
+const ok = (label, cond, extra) => cond
+  ? (pass++, console.log('  ok   ' + label))
+  : (fail++, console.log('  FAIL ' + label + (extra !== undefined ? '  -> ' + JSON.stringify(extra).slice(0, 400) : '')));
+
+const STORE = [
+  { id: 'weather', name: 'Weather', category: 'weather', plugin_path: 'plugins/ledmatrix-weather',
+    aliases: ['ledmatrix-weather'] },
+  { id: 'clock-simple', name: 'Clock', category: 'time', plugin_path: 'plugins/clock-simple', aliases: [] },
+];
+
+// A server with one install in flight. `queue` false answers the install
+// directly; `names` false leaves plugin_id out of the answer (an older
+// server); `installsAs` is the id the installed manifest declares.
+function server({ installed = [], queue = true, names = true, installsAs }) {
+  const state = { installed: installed.map(p => ({ ...p })), polls: 0 };
+  const done = (id) => {
+    if (!state.installed.some(p => p.id === installsAs)) {
+      state.installed.push({ id: installsAs, name: id, enabled: false });
+    }
+    const result = { success: true, message: `Plugin ${id} installed successfully`, restart_required: false };
+    if (names) result.plugin_id = installsAs;
+    return result;
+  };
+  state.route = (method, url, body) => {
+    if (url.startsWith('/api/v3/plugins/store/list')) {
+      return { json: { status: 'success', data: { plugins: STORE } } };
+    }
+    if (url.startsWith('/api/v3/plugins/installed')) {
+      return { json: { status: 'success', data: { plugins: state.installed.map(p => ({ ...p })) } } };
+    }
+    if (method === 'POST' && url === '/api/v3/plugins/install') {
+      if (queue) return { json: { status: 'success', message: 'queued', data: { operation_id: 'op-1' } } };
+      return { json: { status: 'success', message: 'Plugin installed successfully', ...done(body.plugin_id) } };
+    }
+    if (url === '/api/v3/plugins/operation/op-1') {
+      state.polls++;
+      if (state.polls < 3) return { json: { status: 'success', data: { status: 'running' } } };
+      return { json: { status: 'success', data: { status: 'completed', result: done('weather') } } };
+    }
+    if (method === 'POST' && url === '/api/v3/plugins/toggle') {
+      const plugin = state.installed.find(p => p.id === body.plugin_id);
+      if (!plugin) return { status: 404, json: { status: 'error', message: 'Plugin not found' } };
+      plugin.enabled = body.enabled;
+      return { json: { status: 'success', message: `Plugin ${body.plugin_id} enabled successfully` } };
+    }
+    return { json: { status: 'success' } };
+  };
+  return state;
+}
+
+async function install(pluginId, opts) {
+  const srv = server(opts);
+  const sb = create({ route: srv.route });
+  sb.window.searchPluginStore();
+  await sb.until(() => sb.requests.some(r => r.url.startsWith('/api/v3/plugins/store/list')), 'store list');
+  await sb.window.pluginManager.loadInstalledPlugins(true);
+  await sb.settle();
+  sb.requests.length = 0;
+  sb.toasts.length = 0;
+  sb.window.installPlugin(pluginId);
+  await sb.until(() => sb.toasts.some(t => /installed and enabled|enabling it failed|reinstalled/.test(t.message)),
+                 'the install to finish');
+  await sb.settle();
+  const toggles = sb.requests.filter(r => r.url === '/api/v3/plugins/toggle').map(r => r.body);
+  return { sb, srv, toggles };
+}
+
+(async () => {
+  console.log('\n1. a fresh install enables the id the plugin was installed as');
+  {
+    const { srv, toggles, sb } = await install('weather', { installsAs: 'ledmatrix-weather' });
+    ok('enables ledmatrix-weather, not the registry id',
+       JSON.stringify(toggles) === JSON.stringify([{ plugin_id: 'ledmatrix-weather', enabled: true }]), toggles);
+    ok('...which the server enabled', srv.installed.find(p => p.id === 'ledmatrix-weather').enabled === true, srv.installed);
+    ok('says so', sb.toasts.some(t => t.type === 'success' && /installed and enabled/.test(t.message)), sb.toasts);
+    ok('no "Plugin not found"', !sb.toasts.some(t => /not found|failed/.test(t.message)), sb.toasts);
+    const lastList = sb.requests.map(r => r.url).lastIndexOf('/api/v3/plugins/installed');
+    const toggleAt = sb.requests.findIndex(r => r.url === '/api/v3/plugins/toggle');
+    ok('the installed list is reloaded before enabling, so the new card is there to update',
+       lastList >= 0 && lastList < toggleAt, sb.requests.map(r => r.method + ' ' + r.url));
+  }
+  {
+    const { toggles } = await install('weather', { installsAs: 'ledmatrix-weather', names: false });
+    ok('an answer without plugin_id: the installed entry the store entry matches (its alias)',
+       JSON.stringify(toggles) === JSON.stringify([{ plugin_id: 'ledmatrix-weather', enabled: true }]), toggles);
+  }
+  {
+    const { toggles } = await install('weather', { installsAs: 'ledmatrix-weather', queue: false });
+    ok('without the operation queue, from the direct answer',
+       JSON.stringify(toggles) === JSON.stringify([{ plugin_id: 'ledmatrix-weather', enabled: true }]), toggles);
+  }
+  {
+    const { toggles } = await install('clock-simple', { installsAs: 'clock-simple', names: false });
+    ok('a plugin installed under its registry id is enabled by that id',
+       JSON.stringify(toggles) === JSON.stringify([{ plugin_id: 'clock-simple', enabled: true }]), toggles);
+  }
+
+  console.log('\n2. a reinstall leaves the plugin as the user had it');
+  {
+    const { srv, toggles, sb } = await install('weather', {
+      installsAs: 'ledmatrix-weather', installed: [{ id: 'ledmatrix-weather', name: 'Weather', enabled: false }],
+    });
+    ok('sends no toggle', toggles.length === 0, toggles);
+    ok('the plugin stays disabled', srv.installed.find(p => p.id === 'ledmatrix-weather').enabled === false);
+    ok('says it was reinstalled', sb.toasts.some(t => t.type === 'success' && /reinstalled/.test(t.message)), sb.toasts);
+    ok('and reloads the list',
+       sb.requests.some(r => r.url === '/api/v3/plugins/installed'), sb.requests.map(r => r.url));
+  }
+  {
+    const { toggles } = await install('weather', {
+      installsAs: 'ledmatrix-weather', installed: [{ id: 'ledmatrix-weather', name: 'Weather', enabled: true }],
+    });
+    ok('an enabled plugin is not toggled either', toggles.length === 0, toggles);
+  }
+
+  console.log(`\n${pass} passed, ${fail} failed`);
+  process.exit(fail ? 1 : 0);
+})().catch(e => { console.error(e); process.exit(1); });

test/js/unit/test_store_registry_fields.js

@@ -52,7 +52,8 @@ global.installedPlugins = [];
 // eslint-disable-next-line no-eval
 eval([
   'function escapeHtml(text) {', 'function escapeAttribute(text) {', 'function jsStringAttr(value) {',
-  'function isStorePluginInstalled(pluginIdOrPlugin) {', 'function renderPluginStore(plugins) {',
+  'function isStorePluginInstalled(pluginIdOrPlugin) {',
+  'function findInstalledStorePlugin(pluginIdOrPlugin) {', 'function renderPluginStore(plugins) {',
 ].map(extract).join('\n') + '\nglobal.renderPluginStore = renderPluginStore;'
   + '\nglobal.isStorePluginInstalled = isStorePluginInstalled;');
 

test/js/unit/test_update_all.js

@@ -52,7 +52,7 @@ function fakeApi(behaviour = {}) {
   };
 }
 
-function setup(api, { stateList, windowList } = {}) {
+function setup(api, { stateList, windowList, pluginManager } = {}) {
   global.window = {
     PluginAPI: api,
     installedPlugins: windowList,
@@ -60,6 +60,7 @@ function setup(api, { stateList, windowList } = {}) {
       installedPlugins: stateList,
       loadInstalledPlugins: async () => stateList,
     },
+    pluginManager,
   };
 }
 
@@ -92,12 +93,68 @@ const noSleep = { sleep: async () => {} };
     ok('progress total counts only what is sent',
        progress.length === EXPECTED.length && progress.every(([, n]) => n === EXPECTED.length), progress);
   }
+  {
+    // A page without the plugin manager has no window.installedPlugins.
+    const api = fakeApi();
+    setup(api, { stateList: INSTALLED });
+    await Manager.updateAll(null, noSleep);
+    ok('the PluginStateManager list (no live list) is filtered the same way',
+       JSON.stringify(api.calls) === JSON.stringify(EXPECTED), api.calls);
+  }
+
+  console.log('\na second run sends the live list, not the first run\'s snapshot');
+  {
+    // Run 1 leaves PluginStateManager holding a, b, c. Then c is uninstalled
+    // and d installed: plugins_manager.js publishes that only as
+    // window.installedPlugins. Run 2 used to send a, b, c -- c failed as
+    // "plugin not found" and d, which had an update waiting, was skipped.
+    const api = fakeApi({
+      c: () => { throw { error_code: 'PLUGIN_UPDATE_FAILED', message: 'Plugin update failed: plugin not found' }; },
+    });
+    const stale = [{ id: 'a' }, { id: 'b' }, { id: 'c' }];
+    setup(api, { stateList: stale, windowList: [{ id: 'a' }, { id: 'b' }, { id: 'd' }] });
+    const results = await Manager.updateAll(null, noSleep);
+    ok('sends exactly what is installed now',
+       JSON.stringify(api.calls) === JSON.stringify(['a', 'b', 'd']), api.calls);
+    ok('...so nothing fails over an uninstalled plugin', results.every(r => r.success), results);
+  }
   {
     const api = fakeApi();
     setup(api, { stateList: INSTALLED, windowList: [] });
+    const results = await Manager.updateAll(null, noSleep);
+    ok('an empty live list means nothing is installed: nothing is sent',
+       api.calls.length === 0 && results.length === 0, api.calls);
+  }
+
+  console.log('\nthe end-of-run refresh redraws the installed grid');
+  {
+    // PluginStateManager's refresh replaced window.installedPlugins and
+    // nothing else: the cards kept "Update to vX" and the Updates badge
+    // kept its count. The plugin manager's load renders the grid.
+    const loads = [];
+    let stateLoads = 0;
+    const pluginManager = { loadInstalledPlugins: async (force) => { loads.push(force); } };
+    setup(fakeApi(), { stateList: INSTALLED, windowList: INSTALLED, pluginManager });
+    window.PluginStateManager.loadInstalledPlugins = async () => { stateLoads++; };
     await Manager.updateAll(null, noSleep);
-    ok('the PluginStateManager list is filtered the same way',
-       JSON.stringify(api.calls) === JSON.stringify(EXPECTED), api.calls);
+    ok('reloads through the plugin manager once, forced past its caches',
+       JSON.stringify(loads) === JSON.stringify([true]), loads);
+    ok('...instead of PluginStateManager', stateLoads === 0, stateLoads);
+  }
+  {
+    const pluginManager = { loadInstalledPlugins: async () => { throw new Error('offline'); } };
+    const answer = { status: 'success', data: { update_status: 'updated' }, restart_required: true };
+    setup(fakeApi({ 'ledmatrix-flights': () => answer }), { windowList: INSTALLED, pluginManager });
+    const warn = console.warn;
+    console.warn = () => {};
+    let results;
+    try {
+      results = await Manager.updateAll(null, noSleep);
+    } finally {
+      console.warn = warn;
+    }
+    ok('a failed plugin-manager reload still returns the results with their restart flag',
+       Array.isArray(results) && Manager.restartRequest(results) === answer);
   }
   {
     const api = fakeApi();

test/test_api_v3_install_reports_installed_id.py

@@ -0,0 +1,104 @@
+"""POST /plugins/install says which id the plugin was installed as.
+
+A registry entry can install under another id: `weather` (aliases
+`ledmatrix-weather`) installs a directory whose manifest declares
+`ledmatrix-weather`, and that is the id the plugin list, the plugin's config
+section and /plugins/toggle know it by. The store's Install button enabled
+the new plugin by the registry id, which /plugins/toggle answered with 404
+"Plugin not found", so Weather, Music, Stocks and Leaderboard installed
+disabled behind an "enabling it failed" warning.
+
+The answer -- the queued operation's result, or the direct response --
+carries `plugin_id`: the id the installed manifest declares, found the way
+the store's update and uninstall find an install.
+"""
+
+import json
+from unittest.mock import MagicMock
+
+import pytest
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401
+
+INSTALL = "/api/v3/plugins/install"
+
+
+@pytest.fixture
+def store(api_v3_module, tmp_path):
+    manager = api_v3_module.api_v3.plugin_store_manager
+    manager.install_plugin.return_value = True
+    manager.get_registry_info.return_value = None
+    manager._find_plugin_path.return_value = None
+
+    def installed_as(directory, manifest):
+        path = tmp_path / directory
+        path.mkdir()
+        (path / "manifest.json").write_text(json.dumps(manifest), encoding="utf-8")
+        manager._find_plugin_path.side_effect = (
+            lambda pid: path if pid == "weather" else None)
+        return path
+
+    manager.installed_as = installed_as
+    return manager
+
+
+@pytest.fixture
+def queued(api_v3_module):
+    queue = MagicMock()
+
+    def enqueue(operation_type, plugin_id, operation_callback=None):
+        queue.callback_result = operation_callback(MagicMock())
+        return "op-1"
+
+    queue.enqueue_operation.side_effect = enqueue
+    api_v3_module.api_v3.operation_queue = queue
+    return queue
+
+
+class TestDirectInstall:
+    def test_an_aliased_entry_reports_the_manifest_id(self, api_v3_client, store):
+        store.installed_as("ledmatrix-weather", {"id": "ledmatrix-weather"})
+        body = api_v3_client.post(INSTALL, json={"plugin_id": "weather"}).get_json()
+        assert body["status"] == "success"
+        assert body["plugin_id"] == "ledmatrix-weather"
+        store._find_plugin_path.assert_called_with("weather")
+
+    def test_an_entry_installed_under_its_own_id_reports_that(self, api_v3_client, store):
+        store.installed_as("weather", {"id": "weather"})
+        body = api_v3_client.post(INSTALL, json={"plugin_id": "weather"}).get_json()
+        assert body["plugin_id"] == "weather"
+
+    def test_an_install_that_cannot_be_found_reports_the_requested_id(self, api_v3_client, store):
+        body = api_v3_client.post(INSTALL, json={"plugin_id": "weather"}).get_json()
+        assert body["status"] == "success"
+        assert body["plugin_id"] == "weather"
+
+    def test_a_manifest_id_that_is_not_a_plain_name_is_not_passed_on(self, api_v3_client, store):
+        store.installed_as("ledmatrix-weather", {"id": "../elsewhere"})
+        body = api_v3_client.post(INSTALL, json={"plugin_id": "weather"}).get_json()
+        assert body["plugin_id"] == "weather"
+
+    def test_an_unreadable_manifest_reports_the_requested_id(self, api_v3_client, store):
+        path = store.installed_as("ledmatrix-weather", {})
+        (path / "manifest.json").write_text("[not json", encoding="utf-8")
+        body = api_v3_client.post(INSTALL, json={"plugin_id": "weather"}).get_json()
+        assert body["plugin_id"] == "weather"
+
+    def test_the_restart_fields_are_still_sent(self, api_v3_client, store):
+        store.installed_as("ledmatrix-weather", {"id": "ledmatrix-weather"})
+        body = api_v3_client.post(INSTALL, json={"plugin_id": "weather"}).get_json()
+        assert "restart_required" in body
+
+
+class TestQueuedInstall:
+    def test_the_operation_result_names_the_manifest_id(self, api_v3_client, store, queued):
+        store.installed_as("ledmatrix-weather", {"id": "ledmatrix-weather"})
+        body = api_v3_client.post(INSTALL, json={"plugin_id": "weather"}).get_json()
+        assert body["data"]["operation_id"] == "op-1"
+        assert queued.callback_result["success"] is True
+        assert queued.callback_result["plugin_id"] == "ledmatrix-weather"
+
+    def test_an_install_that_cannot_be_found_names_the_requested_id(
+            self, api_v3_client, store, queued):
+        api_v3_client.post(INSTALL, json={"plugin_id": "weather"})
+        assert queued.callback_result["plugin_id"] == "weather"

test/test_api_v3_installed_display_modes.py

@@ -0,0 +1,59 @@
+"""GET /api/v3/plugins/installed carries each plugin's ``display_modes``.
+
+The on-demand modal (plugins_manager.js) fills its Display Mode list from
+``plugin.display_modes``, but the route never included the field, so every
+plugin offered one option -- its own id -- under "This plugin exposes a
+single display mode". The display turns that id into the plugin's first
+mode, so a multi-mode plugin could only be started, and pinned, on that one.
+
+The modes come from the plugin catalog (the manifests the web process
+discovered), the same source /display/modes and on-demand/start use.
+"""
+
+from unittest.mock import MagicMock
+
+import pytest
+
+from test._api_v3_test_helpers import (  # noqa: F401 - fixtures
+    api_v3_client, api_v3_module,
+)
+
+
+@pytest.fixture
+def installed(api_v3_module, api_v3_client, tmp_path):
+    def _get(declared_modes):
+        api = api_v3_module.api_v3
+        # The listing's own metadata says nothing about modes: what the
+        # route reports must come from the catalog.
+        info = {'id': 'football-scoreboard', 'name': 'Football', 'version': '1.0.0'}
+        api.plugin_catalog.plugins_dir = str(tmp_path)  # no manifest on disk
+        api.plugin_catalog.get_all_plugin_info = MagicMock(return_value=[info])
+        api.plugin_catalog.get_plugin_display_modes = MagicMock(return_value=declared_modes)
+        api.plugin_store_manager.get_cached_registry_info = MagicMock(return_value=None)
+        api.config_manager.load_config = MagicMock(return_value={})
+        response = api_v3_client.get('/api/v3/plugins/installed')
+        assert response.status_code == 200
+        plugins = [p for p in response.get_json()['data']['plugins']
+                   if p['id'] == 'football-scoreboard']
+        assert len(plugins) == 1
+        api.plugin_catalog.get_plugin_display_modes.assert_any_call('football-scoreboard')
+        return plugins[0]
+    return _get
+
+
+def test_every_declared_mode_is_listed_in_order(installed):
+    modes = ['nfl_live', 'nfl_recent', 'nfl_upcoming']
+    assert installed(modes)['display_modes'] == modes
+
+
+def test_a_single_mode_plugin_lists_its_one_mode(installed):
+    assert installed(['clock-simple'])['display_modes'] == ['clock-simple']
+
+
+def test_no_declared_modes_is_an_empty_list(installed):
+    # The modal falls back to the plugin id for an empty list.
+    assert installed([])['display_modes'] == []
+
+
+def test_a_hand_edited_manifest_cannot_put_non_strings_in_the_list(installed):
+    assert installed(['nfl_live', 7, None, {'x': 1}])['display_modes'] == ['nfl_live']

test/test_api_v3_installed_plugin_icon.py

@@ -22,7 +22,7 @@ def installed(api_v3_module, api_v3_client, tmp_path):
         info.update(manifest_extra)
         api.plugin_catalog.plugins_dir = str(tmp_path)  # no manifest on disk
         api.plugin_catalog.get_all_plugin_info = MagicMock(return_value=[info])
-        api.plugin_store_manager.get_registry_info = MagicMock(return_value=None)
+        api.plugin_store_manager.get_cached_registry_info = MagicMock(return_value=None)
         api.config_manager.load_config = MagicMock(return_value={})
         response = api_v3_client.get('/api/v3/plugins/installed')
         assert response.status_code == 200

test/test_api_v3_on_demand_restart.py

@@ -37,6 +37,7 @@ from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401
 START_URL = "/api/v3/display/on-demand/start"
 STOP_URL = "/api/v3/display/on-demand/stop"
 MAILBOX = "display_on_demand_request"
+DISPLAY = "web_interface.blueprints.api_v3.display"
 
 
 @pytest.fixture
@@ -150,6 +151,102 @@ class TestStartWhileTheServiceIsStopped:
         assert response.get_json()["status"] == "error"
 
 
+class _Mailbox:
+    """The CacheManager calls the routes make, over a dict."""
+
+    def __init__(self):
+        self.entries = {}
+
+    def set(self, key, value, ttl=None):
+        self.entries[key] = value
+
+    def get(self, key, max_age=300, memory_ttl=None):
+        return self.entries.get(key)
+
+    def delete(self, key):
+        self.entries.pop(key, None)
+
+
+class TestARefusedStartLeavesNoRequestBehind:
+    """A start the route answers with an error must not run later.
+
+    The request was posted (to the mailbox, with the display stopped) before
+    the route refused it, and the display reads the mailbox for an hour
+    without looking at a request's age. So "Display service is not running"
+    (start_service off) or "Failed to start display service" left the
+    request waiting, and the next time the display started -- minutes later,
+    by hand -- it ran that plugin, pinned if the request said so.
+
+    A socket acknowledgement is the other side of it: the display answered,
+    so it is running and has the request, whatever systemd says (a display
+    run by hand or in the emulator has no active unit). That is a success,
+    not "not running", and no unit is started beside it.
+    """
+
+    @pytest.fixture
+    def mailbox(self, api_v3_module, service):
+        box = _Mailbox()
+        api_v3_module.api_v3.cache_manager = box
+        service["state"]["active"] = False
+        return box
+
+    @pytest.mark.parametrize("body", [
+        {"plugin_id": "weather", "start_service": False},
+        {"plugin_id": "weather"},                           # start_service defaults on
+    ])
+    def test_a_socket_ack_is_a_success_whatever_systemd_says(
+            self, api_v3_client, service, mailbox, body):
+        with patch(f"{DISPLAY}.control_client.on_demand_start",
+                   side_effect=lambda request_id, *a: {"accepted": True}):
+            response = api_v3_client.post(START_URL, json=body)
+        assert response.status_code == 200, response.get_json()
+        assert response.get_json()["data"]["transport"] == "socket"
+        assert MAILBOX not in mailbox.entries
+        assert _systemctl_verbs(service["systemctl"]) == [], (
+            "a unit was started beside a display that answered the socket")
+
+    def test_without_start_service_the_request_is_taken_back(
+            self, api_v3_client, service, mailbox):
+        response = api_v3_client.post(START_URL, json={
+            "plugin_id": "weather", "pinned": True, "start_service": False})
+        assert response.status_code == 400
+        assert response.get_json()["status"] == "error"
+        assert MAILBOX not in mailbox.entries
+
+    def test_a_start_that_fails_takes_its_request_back(self, api_v3_client, service, mailbox):
+        service["systemctl"].side_effect = lambda args: {
+            "returncode": 1, "stdout": "", "stderr": "denied"}
+        response = api_v3_client.post(START_URL, json={"plugin_id": "weather"})
+        assert response.status_code == 500
+        assert MAILBOX not in mailbox.entries
+
+    def test_a_newer_request_is_left_alone_on_the_400(self, api_v3_client, service, mailbox):
+        newer = {"request_id": "someone-else", "action": "start", "plugin_id": "clock"}
+
+        def stopped_and_another_post_lands(*args):
+            mailbox.entries[MAILBOX] = newer
+            return {"active": False}
+
+        with patch(f"{DISPLAY}._get_display_service_status",
+                   side_effect=stopped_and_another_post_lands):
+            response = api_v3_client.post(START_URL, json={
+                "plugin_id": "weather", "start_service": False})
+        assert response.status_code == 400
+        assert mailbox.entries[MAILBOX] is newer
+
+    def test_a_newer_request_is_left_alone_on_the_500(self, api_v3_client, service, mailbox):
+        newer = {"request_id": "someone-else", "action": "start", "plugin_id": "clock"}
+
+        def start_fails_after_another_post(args):
+            mailbox.entries[MAILBOX] = newer
+            return {"returncode": 1, "stdout": "", "stderr": "denied"}
+
+        service["systemctl"].side_effect = start_fails_after_another_post
+        response = api_v3_client.post(START_URL, json={"plugin_id": "weather"})
+        assert response.status_code == 500
+        assert mailbox.entries[MAILBOX] is newer
+
+
 class TestStop:
     def test_stop_posts_a_stop_request_and_leaves_the_service_running(
             self, api_v3_client, service):

test/test_api_v3_on_demand_socket.py

@@ -1,10 +1,13 @@
 """POST /display/on-demand/start and /stop: control socket first, mailbox fallback.
 
 The routes hand the request to the display over the control socket
-(src/ipc) and get an acknowledgement. On any failure -- no socket (a stopped
-display, or one older than the socket), a timeout, a refusal, a bug in the
-client -- they write the file mailbox exactly as they did before the socket
-existed. These tests pin both paths, that exactly one of them is used, that
+(src/ipc) and get an acknowledgement. When the socket could not carry the
+request -- no socket (a stopped display, or one older than the socket), a
+refused or timed-out connect, a display too old to know the command, a bug
+in the client -- they write the file mailbox exactly as they did before the
+socket existed. When the display had the request and failed it (a full
+queue, bad arguments, no answer in time) the route says so and writes
+nothing. These tests pin each path, that at most one of them is used, that
 the response says which, and that the request id is the same either way (the
 display deduplicates on it).
 
@@ -101,12 +104,15 @@ class TestSocketPath:
 class TestMailboxFallback:
     @pytest.mark.parametrize("reason", [
         "no_socket", "refused", "timeout", "closed", "bad_response", "invalid_request",
-        "busy", "unknown_command", "unsupported_version", "disabled", "unsupported",
+        "busy", "forbidden", "unknown_command", "unsupported_version", "disabled",
+        "unsupported",
     ])
-    def test_any_socket_failure_writes_the_mailbox_as_before(
+    def test_a_request_the_socket_never_carried_writes_the_mailbox(
             self, api_v3_client, service, reason):
+        # sent=False: the display never had it (no socket, a refused or
+        # timed-out connect, turned away at the door).
         with patch(f"{CLIENT}.on_demand_start",
-                   side_effect=control_client.ControlError(reason, "x")):
+                   side_effect=control_client.ControlError(reason, "x", sent=False)):
             resp = api_v3_client.post(START_URL, json={
                 "plugin_id": "weather", "mode": "weather_current",
                 "duration": 60, "pinned": True})
@@ -168,6 +174,60 @@ class TestMailboxFallback:
         assert data["socket_error"] in ("disabled", "unsupported")   # Linux, Windows
 
 
+class TestTheDisplayHadIt:
+    """Once the display has the request, its answer stands: no mailbox copy.
+
+    A busy queue, a refusal or silence after the request was sent mean the
+    display may have applied it, or would refuse the mailbox copy too, so
+    the route reports the failure instead of posting it a second time.
+    """
+
+    @pytest.mark.parametrize("reason,status", [
+        ("busy", 503), ("internal", 503), ("timeout", 503), ("closed", 503),
+        ("bad_response", 503), ("invalid_args", 400),
+    ])
+    def test_start_is_answered_with_the_failure(self, api_v3_client, service, reason, status):
+        with patch(f"{CLIENT}.on_demand_start",
+                   side_effect=control_client.ControlError(reason, "x", sent=True)):
+            resp = api_v3_client.post(START_URL, json={"plugin_id": "weather"})
+        assert resp.status_code == status
+        body = resp.get_json()
+        assert body["status"] == "error"
+        assert body["data"]["transport"] == "socket"
+        assert body["data"]["socket_error"] == reason
+        assert _mailbox_writes(service["cache"]) == []
+        assert not [call for call in service["calls"] if call[0] == "systemctl"]
+
+    def test_stop_is_answered_with_the_failure(self, api_v3_client, service):
+        with patch(f"{CLIENT}.on_demand_stop",
+                   side_effect=control_client.ControlError("busy", "x", sent=True)):
+            resp = api_v3_client.post(STOP_URL, json={})
+        assert resp.status_code == 503
+        assert _mailbox_writes(service["cache"]) == []
+
+    def test_a_stop_with_stop_service_still_stops_the_service(self, api_v3_client, service):
+        with patch(f"{CLIENT}.on_demand_stop",
+                   side_effect=control_client.ControlError("timeout", "x", sent=True)), \
+             patch("web_interface.blueprints.api_v3.display._stop_display_service",
+                   return_value={"active": False}) as stop:
+            resp = api_v3_client.post(STOP_URL, json={"stop_service": True})
+        assert resp.status_code == 200
+        data = resp.get_json()["data"]
+        assert data["transport"] == "socket" and data["socket_error"] == "timeout"
+        stop.assert_called_once()
+        assert _mailbox_writes(service["cache"]) == []
+
+    @pytest.mark.parametrize("reason", ["unknown_command", "unsupported_version"])
+    def test_an_older_display_that_does_not_speak_it_gets_the_mailbox(
+            self, api_v3_client, service, reason):
+        # The upgrade case: new web interface, display still on an old build.
+        with patch(f"{CLIENT}.on_demand_start",
+                   side_effect=control_client.ControlError(reason, "x", sent=True)):
+            data = api_v3_client.post(START_URL, json={"plugin_id": "weather"}).get_json()["data"]
+        assert data["transport"] == "mailbox" and data["socket_error"] == reason
+        assert len(_mailbox_writes(service["cache"])) == 1
+
+
 @pytest.mark.skipif(not c.socket_supported(), reason="AF_UNIX sockets are Linux/macOS only")
 class TestRealSocket:
     @pytest.fixture
@@ -204,3 +264,23 @@ class TestRealSocket:
         data = api_v3_client.post(START_URL, json={"plugin_id": "weather"}).get_json()["data"]
         assert data["transport"] == "mailbox" and data["socket_error"] == "no_socket"
         assert len(_mailbox_writes(service["cache"])) == 1
+
+    def test_a_full_queue_is_reported_not_mailed(self, api_v3_client, service, monkeypatch):
+        import shutil
+        import tempfile
+        from src.ipc.server import ControlServer
+        d = tempfile.mkdtemp(prefix="lmipc-")
+        path = os.path.join(d, "control.sock")
+        server = ControlServer(path, status_provider=dict, queue_size=1)
+        assert server.start()
+        monkeypatch.setenv(c.SOCKET_PATH_ENV, path)
+        try:
+            first = api_v3_client.post(START_URL, json={"plugin_id": "weather"})
+            assert first.get_json()["data"]["transport"] == "socket"
+            second = api_v3_client.post(START_URL, json={"plugin_id": "weather"})
+            assert second.status_code == 503
+            assert second.get_json()["data"]["socket_error"] == "busy"
+            assert _mailbox_writes(service["cache"]) == []
+        finally:
+            server.close()
+            shutil.rmtree(d, ignore_errors=True)

test/test_api_v3_operation_status_pending.py

@@ -0,0 +1,83 @@
+"""GET /api/v3/plugins/operation/<id> answers for an operation still waiting.
+
+PluginOperationQueue keeps an operation's callback in its parameters, under
+``_callback``, until the worker takes it to run. PluginOperation.to_dict()
+returned the parameters as they were, so for a pending operation the route
+handed jsonify a function and answered 500 "A system error occurred". That
+is every poll of an install queued behind another plugin's: the second of
+two installs read as broken until the first one finished.
+"""
+
+import json
+import sys
+import threading
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+from src.plugin_system.operation_queue import PluginOperationQueue  # noqa: E402
+from src.plugin_system.operation_types import (  # noqa: E402
+    OperationType, PluginOperation,
+)
+
+
+def _callback(op):
+    return {"success": True, "message": "done"}
+
+
+class TestToDict:
+    def test_private_parameters_are_left_out(self):
+        op = PluginOperation(OperationType.INSTALL, "demo",
+                             parameters={"_callback": _callback, "branch": "main"})
+        assert op.to_dict()["parameters"] == {"branch": "main"}
+        json.dumps(op.to_dict())   # serializable
+
+    def test_the_operation_keeps_its_callback_for_the_worker(self):
+        op = PluginOperation(OperationType.INSTALL, "demo",
+                             parameters={"_callback": _callback})
+        op.to_dict()
+        assert op.parameters["_callback"] is _callback
+
+    def test_the_other_fields_are_unchanged(self):
+        op = PluginOperation(OperationType.UNINSTALL, "demo", operation_id="op-1")
+        assert op.to_dict() == {
+            "operation_id": "op-1", "operation_type": "uninstall", "plugin_id": "demo",
+            "parameters": {}, "status": "pending", "progress": 0.0, "message": "",
+            "error": None, "result": None,
+            "created_at": op.created_at.isoformat(), "started_at": None,
+            "completed_at": None,
+        }
+
+
+class TestTheRoute:
+    @pytest.fixture
+    def busy_queue(self, api_v3_module):
+        """A real queue whose worker is held by another plugin's operation."""
+        queue = PluginOperationQueue(max_history=10)
+        api_v3_module.api_v3.operation_queue = queue
+        started, release = threading.Event(), threading.Event()
+
+        def blocker(op):
+            started.set()
+            release.wait(10)
+            return {"success": True, "message": "done"}
+
+        queue.enqueue_operation(OperationType.INSTALL, "busy", operation_callback=blocker)
+        assert started.wait(5)
+        yield queue
+        release.set()
+        queue.shutdown()
+
+    def test_a_pending_operation_reports_pending(self, api_v3_client, busy_queue):
+        op_id = busy_queue.enqueue_operation(
+            OperationType.INSTALL, "demo", operation_callback=_callback)
+        response = api_v3_client.get(f"/api/v3/plugins/operation/{op_id}")
+        assert response.status_code == 200, response.get_json()
+        data = response.get_json()["data"]
+        assert data["status"] == "pending"
+        assert data["plugin_id"] == "demo"
+        assert "_callback" not in data["parameters"]

test/test_api_v3_partial_main_save.py

@@ -253,6 +253,32 @@ class TestVegasCycleDurations:
         assert saved['config']['display']['display_durations'] == {'clock': 45}
 
 
+class TestMalformedBody:
+    """A JSON body that does not parse is the caller's mistake: a 400.
+
+    get_json() raised Werkzeug's BadRequest inside the handler's try, whose
+    catch-all answered 500 CONFIG_SAVE_FAILED with "check file permissions"
+    advice and logged a traceback at ERROR.
+    """
+
+    def test_is_a_400_in_the_raw_routes_shape(self, api_v3_client, saved, api_v3_module):
+        api_v3_module.api_v3.config_manager.get_raw_file_content.return_value = {}
+        resp = api_v3_client.post('/api/v3/config/main', data='{not json',
+                                  content_type='application/json')
+        assert resp.status_code == 400
+        assert resp.get_json() == {'status': 'error', 'message': 'Invalid JSON in request body'}
+        assert 'config' not in saved
+        raw = api_v3_client.post('/api/v3/config/raw/main', data='{not json',
+                                 content_type='application/json')
+        assert (raw.status_code, raw.get_json()) == (400, resp.get_json())
+
+    def test_an_empty_json_post_is_still_no_data(self, api_v3_client, saved):
+        resp = api_v3_client.post('/api/v3/config/main', data='',
+                                  content_type='application/json')
+        assert resp.status_code == 400
+        assert resp.get_json()['message'] == 'No data provided'
+
+
 class TestRawSaveStartsAutoUpdateSetup:
     @pytest.fixture
     def raw_env(self, api_v3_module, monkeypatch):

test/test_api_v3_plugin_action_params.py

@@ -0,0 +1,93 @@
+"""POST /api/v3/plugins/action hands ``params`` to the plugin's script intact.
+
+The route runs the script through a generated wrapper, and the params went
+into that wrapper as Python source: ``params = {json.dumps(params)}``. JSON is
+not Python. ``true``, ``false`` and ``null`` are undefined names there, so any
+params holding a boolean or a null died with a NameError before the script
+ran. The plugin file manager's category toggle sends ``{"category_name": ...,
+"enabled": true}``, so of-the-day's category toggle failed every time with
+"Action failed".
+
+The script's side of the contract is unchanged and pinned here too: the
+params arrive on stdin as one JSON document, LEDMATRIX_ROOT is set, and what
+the script prints to stdout is what the route parses.
+"""
+
+import json
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+ACTION_URL = "/api/v3/plugins/action"
+
+# The action script: report what it was handed, as JSON on stdout.
+ECHO_SCRIPT = (
+    "import json, os, sys\n"
+    "raw = sys.stdin.read()\n"
+    "print(json.dumps({'status': 'success', 'got': json.loads(raw),\n"
+    "                  'root': os.environ.get('LEDMATRIX_ROOT')}))\n"
+)
+
+
+@pytest.fixture
+def echo_plugin(tmp_path, api_v3_module, monkeypatch):
+    plugin_dir = tmp_path / "demo"
+    plugin_dir.mkdir()
+    (plugin_dir / "manifest.json").write_text(json.dumps({
+        "id": "demo",
+        "web_ui_actions": [{"id": "toggle", "type": "script", "script": "echo.py"}],
+    }), encoding="utf-8")
+    (plugin_dir / "echo.py").write_text(ECHO_SCRIPT, encoding="utf-8")
+    api_v3_module.api_v3.plugin_catalog.get_plugin_directory.return_value = str(plugin_dir)
+
+    # The route runs `python3`; use this interpreter, so the test does not
+    # depend on what that name resolves to here.
+    real_run = subprocess.run
+
+    def run(cmd, *args, **kwargs):
+        if isinstance(cmd, list) and cmd and cmd[0] == "python3":
+            cmd = [sys.executable] + cmd[1:]
+        return real_run(cmd, *args, **kwargs)
+
+    monkeypatch.setattr(subprocess, "run", run)
+    return plugin_dir
+
+
+@pytest.mark.parametrize("params", [
+    {"category_name": "jokes", "enabled": True},   # the file manager's toggle
+    {"category_name": "jokes", "enabled": False},
+    {"filename": None},
+    {"nested": {"list": [1, None, True, 2.5], "empty": {}}},
+    {"text": "café ✓ \U0001F600"},
+    {"text": "he said \"hi\" and 'bye' \\ ''' \"\"\" \n\t end"},
+], ids=["true", "false", "null", "nested", "unicode", "quotes"])
+def test_the_script_receives_the_params_it_was_sent(api_v3_client, echo_plugin, params):
+    response = api_v3_client.post(ACTION_URL, json={
+        "plugin_id": "demo", "action_id": "toggle", "params": params})
+    body = response.get_json()
+    assert response.status_code == 200, body
+    assert body["got"] == params
+
+
+def test_a_param_cannot_run_code_in_the_wrapper(api_v3_client, echo_plugin, tmp_path):
+    marker = tmp_path / "PWNED"
+    hostile = "\"}\nopen(%r, 'w').write('ran')\n#" % str(marker)
+    params = {"name": hostile, "flag": True}
+    response = api_v3_client.post(ACTION_URL, json={
+        "plugin_id": "demo", "action_id": "toggle", "params": params})
+    assert response.status_code == 200, response.get_json()
+    assert response.get_json()["got"] == params
+    assert not marker.exists(), "a param value ran as code"
+
+
+def test_the_script_still_gets_ledmatrix_root(api_v3_client, echo_plugin, api_v3_module):
+    response = api_v3_client.post(ACTION_URL, json={
+        "plugin_id": "demo", "action_id": "toggle", "params": {"enabled": True}})
+    assert response.status_code == 200, response.get_json()
+    assert response.get_json()["root"] == str(api_v3_module.PROJECT_ROOT)

test/test_api_v3_plugin_operation_conflict.py

@@ -0,0 +1,89 @@
+"""A second install or uninstall while one is in progress is a 409, not a 500.
+
+PluginOperationQueue refuses a second operation for a plugin that already
+has one waiting or running (test_operation_queue_pending_and_trim.py), and
+says so by raising ValueError. /plugins/install let that escape to the
+blueprint's catch-all, so a double-clicked Install answered 500 "An error
+occurred; see logs for details" while the first install carried on.
+/plugins/uninstall caught it in its own catch-all: a 500 "Failed to
+uninstall plugin", and an "uninstall failed" entry in the operation
+history for an uninstall that never started.
+"""
+
+import sys
+import threading
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+from src.plugin_system.operation_queue import PluginOperationQueue  # noqa: E402
+
+INSTALL = "/api/v3/plugins/install"
+UNINSTALL = "/api/v3/plugins/uninstall"
+
+
+@pytest.fixture
+def installing(api_v3_module, tmp_path):
+    """A real queue with an install of "clock" running and held there."""
+    queue = PluginOperationQueue(max_history=10)
+    api_v3_module.api_v3.operation_queue = queue
+    started, release = threading.Event(), threading.Event()
+
+    def slow_install(plugin_id, branch=None):
+        started.set()
+        release.wait(10)
+        return True
+
+    store = api_v3_module.api_v3.plugin_store_manager
+    store.install_plugin.side_effect = slow_install
+    store.get_registry_info.return_value = None
+    store.plugins_dir = str(tmp_path)
+    api_v3_module.api_v3.plugin_catalog.get_plugin_directory.return_value = None
+    yield {"queue": queue, "started": started, "store": store}
+    release.set()
+    queue.shutdown()
+
+
+def _start_first_install(client, installing):
+    response = client.post(INSTALL, json={"plugin_id": "clock"})
+    assert response.status_code == 200, response.get_json()
+    assert installing["started"].wait(5)
+
+
+def _failed_history(api_v3_module):
+    return [c for c in api_v3_module.api_v3.operation_history.record_operation.call_args_list
+            if c.kwargs.get("status") == "failed"]
+
+
+def test_a_second_install_click_is_a_conflict(api_v3_client, api_v3_module, installing):
+    _start_first_install(api_v3_client, installing)
+    response = api_v3_client.post(INSTALL, json={"plugin_id": "clock"})
+    assert response.status_code == 409, response.get_json()
+    body = response.get_json()
+    assert body["status"] == "error"
+    assert body["error_code"] == "PLUGIN_OPERATION_CONFLICT"
+    assert "clock" in body["message"]
+    assert installing["store"].install_plugin.call_count == 1
+    assert _failed_history(api_v3_module) == []
+
+
+def test_an_uninstall_during_the_install_is_a_conflict(api_v3_client, api_v3_module,
+                                                        installing):
+    _start_first_install(api_v3_client, installing)
+    response = api_v3_client.post(UNINSTALL, json={"plugin_id": "clock"})
+    assert response.status_code == 409, response.get_json()
+    assert response.get_json()["error_code"] == "PLUGIN_OPERATION_CONFLICT"
+    assert _failed_history(api_v3_module) == [], (
+        "an uninstall that never started was recorded as failed")
+    api_v3_module.api_v3.plugin_store_manager.uninstall_plugin.assert_not_called()
+
+
+def test_another_plugin_is_still_queued(api_v3_client, installing):
+    _start_first_install(api_v3_client, installing)
+    response = api_v3_client.post(INSTALL, json={"plugin_id": "weather"})
+    assert response.status_code == 200, response.get_json()
+    assert response.get_json()["data"]["operation_id"]

test/test_api_v3_plugin_static_files.py

@@ -0,0 +1,73 @@
+"""GET /api/v3/plugins/<plugin_id>/static/<path> serves binary files too.
+
+The route opened every file as UTF-8 text, so an image -- what the API
+reference says it is for, plugin previews and icons -- failed to decode and
+answered 500 "UnicodeDecodeError". Files are now sent as bytes. The text
+types the route always set are unchanged, and the path checks are pinned in
+test_path_traversal_guards.py::TestServePluginStatic.
+"""
+
+import json
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+PNG = (b"\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x00\x01\x00\x00\x00\x01"
+       b"\x08\x06\x00\x00\x00\x1f\x15\xc4\x89")
+
+
+@pytest.fixture
+def plugin_dir(tmp_path, api_v3_module):
+    d = tmp_path / "demo"
+    (d / "web_ui").mkdir(parents=True)
+    (d / "manifest.json").write_text(json.dumps({"id": "demo"}), encoding="utf-8")
+    api_v3_module.api_v3.plugin_catalog.get_plugin_directory.side_effect = (
+        lambda pid: str(d) if pid == "demo" else None)
+    return d
+
+
+def _get(client, path):
+    return client.get(f"/api/v3/plugins/demo/static/{path}")
+
+
+def test_an_image_is_served_as_its_bytes(api_v3_client, plugin_dir):
+    (plugin_dir / "web_ui" / "icon.png").write_bytes(PNG)
+    response = _get(api_v3_client, "web_ui/icon.png")
+    assert response.status_code == 200, response.get_json(silent=True)
+    assert response.mimetype == "image/png"
+    assert response.data == PNG
+
+
+def test_an_unknown_binary_file_is_served_too(api_v3_client, plugin_dir):
+    blob = bytes(range(256))
+    (plugin_dir / "data.bin").write_bytes(blob)
+    response = _get(api_v3_client, "data.bin")
+    assert response.status_code == 200, response.get_json(silent=True)
+    assert response.data == blob
+
+
+@pytest.mark.parametrize("name,mimetype", [
+    ("page.html", "text/html"),
+    ("app.js", "application/javascript"),
+    ("style.css", "text/css"),
+    ("data.json", "application/json"),
+    ("notes.txt", "text/plain"),
+    ("README.md", "text/plain"),
+    ("helper.py", "text/plain"),
+])
+def test_text_files_keep_their_types(api_v3_client, plugin_dir, name, mimetype):
+    content = "caf\u00e9 \u2713 <p>hi</p>\n"
+    (plugin_dir / name).write_bytes(content.encode("utf-8"))
+    response = _get(api_v3_client, name)
+    assert response.status_code == 200
+    assert response.mimetype == mimetype
+    assert response.data == content.encode("utf-8")
+
+
+def test_a_missing_file_is_still_a_404(api_v3_client, plugin_dir):
+    assert _get(api_v3_client, "nope.png").status_code == 404

test/test_api_v3_status_accuracy.py

@@ -0,0 +1,326 @@
+"""Four web answers that disagreed with the rig they describe (found on ledpi).
+
+1. POST /config/schedule refused the schedule GET returns on a fresh install
+   (config.template.json: per-day, every day off, schedule disabled) with
+   "At least one day must be enabled", as did /config/dim-schedule. A
+   disabled schedule needs no enabled day.
+2. A brightness-only POST /config/main answered ``restart_required: true``,
+   though the display applies brightness live (brightness.set over the
+   socket, and the config watcher). The flag now says whether anything
+   changed that the running display does not pick up by itself.
+3. /health stayed "healthy" with the display service stopped: only the
+   sub-checks changed. Service inactive, no socket and no live heartbeat
+   is now ``display_loop: stopped`` and "degraded".
+4. /display/current-status kept answering ``is_display_active: true`` from
+   the cache for up to 120 s after the display stopped. With no socket and
+   no live heartbeat it is now unknown.
+"""
+
+import copy
+import json
+import os
+import sys
+import time
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+from src import display_watchdog  # noqa: E402
+from src.ipc import client as control_client  # noqa: E402
+from web_interface import display_state  # noqa: E402
+
+REPO = Path(__file__).resolve().parent.parent
+TEMPLATE = json.loads((REPO / 'config' / 'config.template.json').read_text(encoding='utf-8'))
+
+
+@pytest.fixture
+def store(api_v3_module, monkeypatch):
+    state = {'config': {}, 'saves': 0}
+    api_v3_module.api_v3.config_manager.load_config.side_effect = \
+        lambda *a, **k: copy.deepcopy(state['config'])
+
+    def fake_save(_manager, config, **_kwargs):
+        state['config'] = copy.deepcopy(config)
+        state['saves'] += 1
+        return True, ''
+
+    monkeypatch.setattr(api_v3_module, '_save_config_atomic', fake_save)
+    return state
+
+
+# --- 1. schedules ---------------------------------------------------------------
+
+SCHEDULE_ROUTES = [('/api/v3/config/schedule', 'schedule'),
+                   ('/api/v3/config/dim-schedule', 'dim_schedule')]
+
+
+@pytest.mark.parametrize('route,section', SCHEDULE_ROUTES)
+def test_the_templates_disabled_per_day_schedule_saves_back(api_v3_client, store,
+                                                            route, section):
+    stored = copy.deepcopy(TEMPLATE[section])
+    stored['mode'] = 'per-day'
+    assert stored['enabled'] is False
+    assert not any(day['enabled'] for day in stored['days'].values())
+    store['config'] = {section: copy.deepcopy(stored)}
+
+    read = api_v3_client.get(route).get_json()['data']
+    resp = api_v3_client.post(route, json=read)
+
+    assert resp.status_code == 200, resp.get_json()
+    saved = store['config'][section]
+    assert saved['enabled'] is False and saved['mode'] == 'per-day'
+    # The disabled days keep their times: switching one on finds them.
+    assert saved['days'] == stored['days']
+
+
+@pytest.mark.parametrize('route,section', SCHEDULE_ROUTES)
+def test_an_enabled_per_day_schedule_still_needs_a_day(api_v3_client, store, route, section):
+    body = copy.deepcopy(TEMPLATE[section])
+    body.update(enabled=True, mode='per-day')
+    resp = api_v3_client.post(route, json=body)
+    assert resp.status_code == 400
+    assert 'At least one day must be enabled' in resp.get_json()['message']
+    assert store['saves'] == 0
+
+
+@pytest.mark.parametrize('route', [r for r, _ in SCHEDULE_ROUTES])
+def test_the_pickers_form_post_with_every_day_off_saves(api_v3_client, store, route):
+    """What schedule-picker.js posts: flat hidden inputs, booleans as strings,
+    times for every day."""
+    body = {'enabled': 'false', 'mode': 'per_day', 'start_time': '07:00', 'end_time': '23:00'}
+    for day in ('monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday'):
+        body.update({f'{day}_enabled': 'false', f'{day}_start': '06:30', f'{day}_end': '22:15'})
+    resp = api_v3_client.post(route, json=body)
+    assert resp.status_code == 200, resp.get_json()
+
+
+def test_an_invalid_time_on_a_disabled_day_is_dropped_not_refused(api_v3_client, store):
+    body = {'enabled': False, 'mode': 'per-day',
+            'days': {'monday': {'enabled': False, 'start_time': 'soon', 'end_time': '22:00'}}}
+    resp = api_v3_client.post('/api/v3/config/schedule', json=body)
+    assert resp.status_code == 200, resp.get_json()
+    assert store['config']['schedule']['days']['monday'] == {'enabled': False,
+                                                             'end_time': '22:00'}
+
+
+# --- 2. restart_required on /config/main ------------------------------------------
+
+STORED_MAIN = {
+    'timezone': 'America/Chicago',
+    'display': {
+        'hardware': {'rows': 32, 'cols': 64, 'chain_length': 2, 'brightness': 90,
+                     'disable_hardware_pulsing': False, 'inverse_colors': False,
+                     'show_refresh_rate': False},
+        'runtime': {'gpio_slowdown': 4},
+        'display_durations': {'clock': 15},
+        'use_short_date_format': False,
+    },
+}
+
+
+@pytest.fixture
+def main_store(store):
+    store['config'] = copy.deepcopy(STORED_MAIN)
+    return store
+
+
+def _save_main(client, body):
+    with patch('web_interface.blueprints.api_v3.control_client.brightness_set',
+               side_effect=control_client.ControlError('no_socket', 'x')):
+        resp = client.post('/api/v3/config/main', data=json.dumps(body),
+                           content_type='application/json')
+    assert resp.status_code == 200, resp.get_json()
+    return resp.get_json()
+
+
+def test_a_brightness_only_save_needs_no_restart(api_v3_client, main_store):
+    body = _save_main(api_v3_client, {'brightness': 40})
+    assert main_store['config']['display']['hardware']['brightness'] == 40
+    assert body['restart_required'] is False
+
+
+def test_a_brightness_save_on_a_config_without_a_display_section(api_v3_client, store):
+    """The route creates display.hardware and display.runtime on the way;
+    empty sections are not a change."""
+    store['config'] = {}
+    assert _save_main(api_v3_client, {'brightness': 40})['restart_required'] is False
+
+
+def test_the_display_form_with_only_brightness_changed_needs_no_restart(api_v3_client,
+                                                                       main_store):
+    hw = STORED_MAIN['display']['hardware']
+    body = {'__form_section': 'display', 'rows': 32, 'cols': 64, 'chain_length': 2,
+            'brightness': 55, 'gpio_slowdown': 4}
+    body.update({k: 'on' for k in ('disable_hardware_pulsing', 'inverse_colors',
+                                   'show_refresh_rate') if hw[k]})
+    assert _save_main(api_v3_client, body)['restart_required'] is False
+
+
+def test_a_mode_duration_needs_no_restart(api_v3_client, main_store):
+    body = _save_main(api_v3_client, {'duration__clock': 40})
+    assert main_store['config']['display']['display_durations']['clock'] == 40
+    assert body['restart_required'] is False
+
+
+@pytest.mark.parametrize('change', [{'rows': 64}, {'brightness': 40, 'chain_length': 3},
+                                    {'gpio_slowdown': 2}, {'timezone': 'UTC'}])
+def test_a_setting_the_display_reads_at_startup_still_needs_one(api_v3_client, main_store,
+                                                                change):
+    assert _save_main(api_v3_client, change)['restart_required'] is True
+
+
+def test_restart_needed_compares_leaves():
+    from web_interface.blueprints.api_v3.config import restart_needed
+    before = {'display': {'hardware': {'brightness': 90, 'rows': 32}}}
+    assert not restart_needed(before, copy.deepcopy(before))
+    assert not restart_needed(before, {'display': {'hardware': {'brightness': 10, 'rows': 32},
+                                                   'runtime': {}}})
+    assert restart_needed(before, {'display': {'hardware': {'brightness': 90}}})  # removed
+    assert not restart_needed({}, {'clock': {'enabled': True}}, live_paths=[('clock',)])
+    assert restart_needed({}, {'clockwork': {'enabled': True}}, live_paths=[('clock',)])
+
+
+# --- 3 and 4. a stopped display -----------------------------------------------------
+
+@pytest.fixture
+def no_display(monkeypatch, tmp_path):
+    """A Pi whose display service has stopped: the socket is expected here
+    but does not answer, and systemd took the heartbeat's directory away."""
+    monkeypatch.setattr(display_state, 'socket_supported', lambda: True)
+    monkeypatch.setattr(display_state, 'client_socket_paths', lambda: [str(tmp_path / 'gone')])
+    monkeypatch.setattr(display_state, 'read_state', lambda: None)
+    path = tmp_path / 'display-heartbeat.json'
+    monkeypatch.setattr(display_watchdog, 'HEARTBEAT_PATH', str(path))
+
+    def beat(age, pid=None):
+        path.write_text(json.dumps({'pid': os.getpid() if pid is None else pid,
+                                    'mono': time.monotonic() - age,
+                                    'wall': time.time() - age}))
+    return beat
+
+
+@pytest.fixture
+def service(monkeypatch):
+    status = {'active': False, 'returncode': 3, 'stdout': 'inactive', 'stderr': ''}
+    monkeypatch.setattr('web_interface.blueprints.api_v3.misc._get_display_service_status',
+                        lambda: dict(status))
+    return status
+
+
+@pytest.fixture
+def fresh_preview(tmp_path, monkeypatch):
+    """The preview frame the display left behind, under 60 s old: on its own
+    it kept the hardware check "connected"."""
+    from web_interface import display_preview
+    snapshot = tmp_path / 'preview.png'
+    snapshot.write_bytes(b'png')
+    monkeypatch.setattr(display_preview, 'SNAPSHOT_PATH', str(snapshot))
+
+
+def _health(client):
+    resp = client.get('/api/v3/health')
+    assert resp.status_code == 200, resp.get_json()
+    return resp.get_json()['data']
+
+
+class TestHealth:
+    def test_a_stopped_display_service_is_degraded(self, api_v3_client, no_display, service,
+                                                   fresh_preview):
+        data = _health(api_v3_client)
+        assert data['services']['display_service']['status'] == 'inactive'
+        assert data['checks']['display_loop']['status'] == 'stopped'
+        assert data['status'] == 'degraded'
+
+    def test_a_service_still_starting_is_not(self, api_v3_client, no_display, service,
+                                             fresh_preview):
+        """Active, before its socket and first heartbeat: not stopped."""
+        service.update(active=True, stdout='active', returncode=0)
+        data = _health(api_v3_client)
+        assert data['checks']['display_loop']['status'] == 'not_reported'
+        assert data['status'] == 'healthy'
+
+    def test_a_display_run_by_hand_is_not_stopped(self, api_v3_client, no_display, service,
+                                                  fresh_preview):
+        """The service is off but a display process beats (sudo python3 run.py)."""
+        no_display(age=2)
+        data = _health(api_v3_client)
+        assert data['checks']['display_loop']['status'] == 'running'
+        assert data['status'] == 'healthy'
+
+    @pytest.mark.parametrize('platform', ['no_unix_sockets', 'socket_off'])
+    def test_without_a_socket_to_expect_nothing_changes(self, api_v3_client, no_display,
+                                                        service, fresh_preview, monkeypatch,
+                                                        platform):
+        """Windows and the dev server (no systemd unit), or the socket
+        deliberately off: no heartbeat is no signal, as before."""
+        if platform == 'no_unix_sockets':
+            monkeypatch.setattr(display_state, 'socket_supported', lambda: False)
+        else:
+            monkeypatch.setattr(display_state, 'client_socket_paths', lambda: [])
+        service.update(returncode=-1, stdout='', stderr='systemctl not found')
+        data = _health(api_v3_client)
+        assert data['checks']['display_loop']['status'] == 'not_reported'
+        assert data['status'] == 'healthy'
+
+    def test_the_status_only_answer_says_degraded(self, api_v3_client, no_display, service,
+                                                  fresh_preview, monkeypatch):
+        monkeypatch.setattr('web_interface.blueprints.api_v3.misc.request_is_authenticated',
+                            lambda: False)
+        resp = api_v3_client.get('/api/v3/health')
+        assert resp.get_json()['data'] == {'status': 'degraded'}
+
+
+class TestCurrentStatus:
+    CACHED = {'mode': 'clock', 'plugin_id': 'clock', 'is_display_active': True,
+              'on_demand_active': False, 'last_updated': None}
+
+    @pytest.fixture
+    def cached(self, api_v3_module):
+        entry = dict(self.CACHED, last_updated=time.time() - 30)
+        cache = api_v3_module.api_v3.cache_manager
+        cache.get.side_effect = lambda key, *a, **kw: (
+            dict(entry) if key == 'display_current_state' else None)
+        return entry
+
+    def _status(self, client):
+        resp = client.get('/api/v3/display/current-status')
+        assert resp.status_code == 200
+        return resp.get_json()['data']
+
+    def test_a_stopped_display_is_not_reported_active(self, api_v3_client, no_display, cached):
+        data = self._status(api_v3_client)
+        assert not data.get('is_display_active')
+        assert data['mode'] is None and data['last_updated'] is None
+        assert data['source'] == 'cache'
+
+    def test_a_stale_heartbeat_is_not_active_either(self, api_v3_client, no_display, cached):
+        no_display(age=display_watchdog.HEARTBEAT_STALE_SECONDS + 5)
+        assert self._status(api_v3_client)['mode'] is None
+
+    @pytest.mark.skipif(os.name != 'posix', reason='process_exists answers only on POSIX')
+    def test_a_heartbeat_from_a_dead_process_is_not_active(self, api_v3_client, no_display,
+                                                           cached):
+        no_display(age=1, pid=2 ** 22 + 12345)
+        assert self._status(api_v3_client)['mode'] is None
+
+    def test_a_live_heartbeat_without_a_socket_reads_the_cache(self, api_v3_client,
+                                                               no_display, cached):
+        """An older display with no socket, still running."""
+        no_display(age=2)
+        data = self._status(api_v3_client)
+        assert data['mode'] == 'clock' and data['is_display_active'] is True
+
+    @pytest.mark.parametrize('platform', ['no_unix_sockets', 'socket_off'])
+    def test_without_a_socket_to_expect_the_cache_answers(self, api_v3_client, no_display,
+                                                          cached, monkeypatch, platform):
+        if platform == 'no_unix_sockets':
+            monkeypatch.setattr(display_state, 'socket_supported', lambda: False)
+        else:
+            monkeypatch.setattr(display_state, 'client_socket_paths', lambda: [])
+        data = self._status(api_v3_client)
+        assert data['mode'] == 'clock' and data['is_display_active'] is True

test/test_async_plugin_updates.py

@@ -13,6 +13,7 @@ The invariants that keep this change safe:
    inline path exactly.
 """
 
+import asyncio
 import os
 import sys
 import threading
@@ -209,6 +210,32 @@ class TestFailurePaths:
         assert pm.get_plugin_lock(plugin_id).acquire(blocking=False) is True
         pm.get_plugin_lock(plugin_id).release()
 
+    @pytest.mark.parametrize("raised", [asyncio.CancelledError, SystemExit])
+    def test_update_raising_a_base_exception_still_releases_the_plugin(self, pm, raised):
+        """asyncio.CancelledError and SystemExit derive from BaseException,
+        not Exception. Raised from update() on the worker, one skipped the
+        bookkeeping entirely: the plugin kept its lock and stayed RUNNING for
+        the life of the process -- never updated again, and every display()
+        skipped as busy."""
+        class CancellingPlugin(SlowPlugin):
+            def update(self):
+                self.update_calls += 1
+                raise raised()
+
+        plugin_id = _install(pm, CancellingPlugin())
+        pm.run_scheduled_updates()
+        deadline = time.monotonic() + 3
+        while pm.plugins[plugin_id].update_calls == 0 and time.monotonic() < deadline:
+            time.sleep(0.05)
+        time.sleep(0.2)
+
+        assert pm.get_plugin_lock(plugin_id).acquire(blocking=False) is True
+        pm.get_plugin_lock(plugin_id).release()
+        assert pm.state_manager.can_execute(plugin_id) is True
+        assert pm.plugin_last_update.get(plugin_id, 0) > 0
+        error = pm.state_manager.get_error_info(plugin_id)
+        assert error is not None and error["error_type"] == raised.__name__
+
     def test_unloaded_while_queued_is_harmless(self, pm):
         """Exercise the public unload_plugin() lifecycle rather than
         deleting pm.plugins directly: queue the target's update behind a

test/test_cache_long_keys.py

@@ -0,0 +1,99 @@
+"""A cache key too long to be a filename still gets a cache file.
+
+The calendar plugin's key joins every calendar id the user picked; on a real
+install it passed 300 bytes, and since ext4 caps a filename at 255 every write
+failed with ENAMETOOLONG -- logged as "permission denied", every update.
+"""
+
+import logging
+import os
+from unittest.mock import patch
+
+from src.cache.disk_cache import DiskCache, _MAX_KEY_FILENAME_BYTES, _filename_stem
+from src.cache_manager import CacheManager
+
+# The shape of the key that failed on hdpi, ids anonymised.
+CALENDAR_KEY = (
+    "calendar_events_someone@example.com_en.usa#holiday@group.v.calendar.google.com_"
+    "family13997378751670666433@group.calendar.google.com_ncaaf_-m-07kbp5_"
+    "%47eorgia+%42ulldogs+football#sports@group.v.calendar.google.com_nfl_-m-07l24_"
+    "%54ampa+%42ay+%42uccaneers#sports@group.v.calendar.google.com_primary"
+)
+
+# ext4/xfs/btrfs NAME_MAX; set()'s temp file adds 15 bytes to the stem.
+NAME_MAX = 255
+TEMP_OVERHEAD = len(".") + len(".json") + len(".") + 8
+
+
+def test_the_real_key_was_too_long_to_write():
+    assert len((CALENDAR_KEY + ".json").encode()) > NAME_MAX - 10
+
+
+def test_a_long_key_round_trips(tmp_path):
+    cache = DiskCache(str(tmp_path))
+    cache.set(CALENDAR_KEY, {"events": [1, 2, 3]})
+
+    assert cache.get(CALENDAR_KEY, max_age=None) == {"events": [1, 2, 3]}
+    path = cache.get_cache_path(CALENDAR_KEY)
+    assert os.path.isfile(path)
+    stem = os.path.basename(path)[:-len(".json")]
+    assert len(stem.encode()) + TEMP_OVERHEAD <= NAME_MAX
+
+
+def test_short_keys_keep_their_filename(tmp_path):
+    cache = DiskCache(str(tmp_path))
+    exactly = "k" * _MAX_KEY_FILENAME_BYTES
+    assert cache.get_cache_path("weather_current") == str(tmp_path / "weather_current.json")
+    assert cache.get_cache_path(exactly) == str(tmp_path / f"{exactly}.json")
+    assert cache.get_cache_path(exactly + "k") != str(tmp_path / f"{exactly}k.json")
+
+
+def test_long_keys_sharing_a_prefix_stay_apart(tmp_path):
+    cache = DiskCache(str(tmp_path))
+    first, second = CALENDAR_KEY + "_a", CALENDAR_KEY + "_b"
+    cache.set(first, {"which": "a"})
+    cache.set(second, {"which": "b"})
+
+    assert cache.get_cache_path(first) != cache.get_cache_path(second)
+    assert cache.get(first, max_age=None) == {"which": "a"}
+    assert cache.get(second, max_age=None) == {"which": "b"}
+
+
+def test_the_prefix_never_splits_a_character():
+    key = "news_" + "é" * 300  # two bytes each, so the cut lands mid-character
+    stem = _filename_stem(key)
+
+    assert stem.startswith("news_é")
+    assert len(stem.encode("utf-8")) <= _MAX_KEY_FILENAME_BYTES
+    stem.encode("utf-8").decode("utf-8")  # well-formed
+
+
+def test_a_stem_listed_by_the_web_ui_deletes_the_same_file(tmp_path):
+    with patch('src.cache_manager.CacheManager._get_writable_cache_dir', return_value=str(tmp_path)):
+        manager = CacheManager()
+    try:
+        manager.save_cache(CALENDAR_KEY, {"events": []})
+
+        listed = [entry["key"] for entry in manager.list_cache_files()]
+        assert len(listed) == 1
+        manager.clear_cache(listed[0])
+
+        assert [n for n in os.listdir(tmp_path) if n.endswith(".json")] == []
+    finally:
+        manager.stop_cleanup_thread()
+
+
+def test_a_failed_write_names_the_real_error(tmp_path, monkeypatch, caplog):
+    blocker = tmp_path / "a-file"
+    blocker.write_text("")
+    # No writable fallback either, so set() gives up and says why.
+    monkeypatch.setattr(os.path, "expanduser", lambda _p: str(blocker / "home"))
+    cache = DiskCache(str(tmp_path / "missing"))
+
+    with caplog.at_level(logging.WARNING):
+        cache.set("weather_current", {"t": 1})
+
+    gave_up = [r.getMessage() for r in caplog.records if "Could not write cache" in r.getMessage()]
+    assert len(gave_up) == 1
+    assert "permission denied" not in gave_up[0]
+    assert os.strerror(2) in gave_up[0]  # ENOENT: the directory does not exist

test/test_cache_memory_tier_age.py

@@ -0,0 +1,95 @@
+"""The memory tier never serves a record older than the reader asked for.
+
+A record read from disk went into the memory tier timed from the read, not
+from when it was written, so get(max_age=300) could hand out data up to twice
+that old: after a restart, after the memory sweep, or in a second process that
+loaded a record once and kept serving it.
+"""
+
+import time
+from unittest.mock import patch
+
+import pytest
+
+from src.cache_manager import CacheManager
+
+
+class Clock:
+    def __init__(self, now):
+        self.now = now
+
+    def __call__(self):
+        return self.now
+
+
+@pytest.fixture
+def clock(monkeypatch):
+    fake = Clock(1_800_000_000.0)
+    monkeypatch.setattr(time, "time", fake)
+    return fake
+
+
+def _manager(path):
+    # No disk sweep: it judges files by their real mtime against the fake
+    # clock and would delete them as months old.
+    with patch('src.cache_manager.CacheManager._get_writable_cache_dir',
+               return_value=str(path)), \
+            patch('src.cache_manager.CacheManager.start_cleanup_thread'):
+        return CacheManager()
+
+
+def test_a_record_loaded_late_expires_on_its_own_timestamp(tmp_path, clock):
+    writer = _manager(tmp_path)
+    writer.set("weather_current", {"t": 1})
+
+    reader = _manager(tmp_path)  # a restart, or the other process
+    clock.now += 250
+    assert reader.get("weather_current", max_age=300) == {"t": 1}
+
+    clock.now += 100  # the data is 350 s old; it sat in memory for 100 s
+    assert reader.get("weather_current", max_age=300) is None
+
+
+def test_a_stored_ttl_bounds_the_memory_copy_too(tmp_path, clock):
+    writer = _manager(tmp_path)
+    writer.set("odds_espn_football_nfl_401", {"spread": 6.5}, ttl=60)
+
+    reader = _manager(tmp_path)
+    clock.now += 55
+    assert reader.get("odds_espn_football_nfl_401", max_age=3600) == {"spread": 6.5}
+
+    clock.now += 60
+    assert reader.get("odds_espn_football_nfl_401", max_age=3600) is None
+
+
+def test_a_stale_memory_copy_gives_way_to_a_newer_write_on_disk(tmp_path, clock):
+    writer = _manager(tmp_path)
+    reader = _manager(tmp_path)
+    writer.set("stocks_AAPL", {"price": 1})
+    assert reader.get("stocks_AAPL", max_age=300) == {"price": 1}
+
+    clock.now += 280
+    writer.set("stocks_AAPL", {"price": 2})
+    clock.now += 40  # reader's copy: 40 s in memory, 320 s old
+
+    assert reader.get("stocks_AAPL", max_age=300) == {"price": 2}
+
+
+def test_fresh_records_are_still_served_from_memory(tmp_path, clock):
+    manager = _manager(tmp_path)
+    manager.set("news_NFL", {"items": []})
+    clock.now += 100
+
+    with patch.object(manager._disk_cache_component, "get") as disk_get:
+        assert manager.get("news_NFL", max_age=300) == {"items": []}
+    disk_get.assert_not_called()
+
+
+def test_max_age_none_and_records_without_a_timestamp_never_expire(tmp_path, clock):
+    manager = _manager(tmp_path)
+    manager.set("plugin_health_x", {"ok": True})
+    manager.save_cache("raw_record", {"no": "timestamp"})
+    clock.now += 10 ** 6
+
+    assert manager.get("plugin_health_x", max_age=None) == {"ok": True}
+    assert manager.get_cached_data("raw_record", max_age=None) == {"no": "timestamp"}

test/test_config_load_cache.py

@@ -58,7 +58,8 @@ class TestFastPath:
         for _ in range(10):
             again = m.load_config()
         assert counts["n"] == 0, "fast path must not re-open any config file"
-        assert again is first  # same aliasing semantics as the full path
+        assert again == first
+        assert again is not first  # each caller gets its own copy, see below
 
     def test_config_change_triggers_reload(self, mgr):
         m, config, secrets, template = mgr
@@ -98,6 +99,33 @@ class TestFastPath:
         assert m.load_config()["timezone"] == "America/New_York"
 
 
+class TestCallersGetACopy:
+    """A web handler edits what load_config returned, then validates. When
+    validation failed, the edit stayed in the cache the fast path serves, and
+    the next unrelated save wrote it -- a nested secret included, in plain
+    text, because it had never reached config_secrets.json to be stripped."""
+
+    def test_editing_a_loaded_config_does_not_change_the_next_load(self, mgr):
+        m, config, secrets, template = mgr
+        loaded = m.load_config()
+        loaded["display"]["brightness"] = 1
+        loaded["weather"]["api_key"] = "typed-but-never-saved"
+        again = m.load_config()
+        assert again["display"]["brightness"] == 90
+        assert again["weather"]["api_key"] == "sek"
+
+    def test_the_full_path_also_returns_a_copy(self, mgr):
+        m, config, secrets, template = mgr
+        m.load_config()["display"]["brightness"] = 1  # first load: full path
+        assert m.load_config()["display"]["brightness"] == 90
+
+    def test_an_edit_never_reaches_a_later_save(self, mgr):
+        m, config, secrets, template = mgr
+        m.load_config()["display"]["new_secret"] = "hunter2"  # then bailed out
+        m.save_config(m.load_config())  # some other handler saves
+        assert "hunter2" not in config.read_text()
+
+
 class TestSaveCoherence:
     def test_save_config_then_load_returns_saved_data(self, mgr, monkeypatch):
         m, config, secrets, template = mgr
@@ -111,6 +139,15 @@ class TestSaveCoherence:
         assert loaded["weather"]["api_key"] == "sek"  # secrets survive in memory
         assert counts["n"] == 0  # signature refreshed by save; no re-read
 
+    def test_the_saved_dict_does_not_become_the_cache(self, mgr):
+        m, config, secrets, template = mgr
+        m.load_config()
+        new = {"display": {"brightness": 42}, "timezone": "UTC",
+               "weather": {"api_key": "sek"}}
+        m.save_config(new)
+        new["display"]["brightness"] = 7  # the caller keeps using its dict
+        assert m.load_config()["display"]["brightness"] == 42
+
     def test_cross_process_save_is_picked_up(self, mgr):
         """Another process writing config.json (different mtime) must bust
         this process's fast path — the core cross-process guarantee."""

test/test_config_manager_secrets.py

@@ -143,7 +143,10 @@ class TestLoadFastPath:
         manager = make_manager(tmp_path, config={"timezone": "UTC"})
         first = manager.load_config()
         second = manager.load_config()
-        assert second is first  # same aliased dict, no re-read
+        # A copy of the cached dict, never the dict itself; that it is not
+        # re-read is test_config_load_cache's test_unchanged_files_are_not_reread
+        assert second == first
+        assert second is not first
 
     def test_touching_secrets_file_invalidates_cache(self, tmp_path):
         manager = make_manager(

test/test_config_service_notify.py

@@ -0,0 +1,199 @@
+"""ConfigService notifies subscribers outside its lock, in order.
+
+Subscribers ran while _load_config held the service's lock. The display's
+per-plugin subscriber is PluginManager.apply_config_change, which waits up to
+PLUGIN_LOCK_TIMEOUT (5 s) for a busy plugin. The same save that toggles a
+plugin's ``enabled`` flags a reconcile, and the render thread runs it: its
+get_config() -- and the unsubscribe() of a plugin it disables -- waited behind
+every slow callback, freezing the panel for up to 5 s per busy plugin.
+
+What callers could rely on before still holds: one reload's notifications
+finish before the next reload's start, and a callback unsubscribe() removed is
+not running, and will not run, once unsubscribe() returns.
+"""
+
+import itertools
+import json
+import os
+import threading
+import time
+
+import pytest
+
+from src.config_manager import ConfigManager
+from src.config_service import ConfigService
+
+SLOW = 2.0  # how long a blocked callback waits before giving up
+
+
+@pytest.fixture
+def service(tmp_path):
+    config_path = tmp_path / "config.json"
+    config_path.write_text(json.dumps({"display": {"brightness": 50},
+                                       "weather": {"enabled": True}}),
+                           encoding="utf-8")
+    manager = ConfigManager(str(config_path), str(tmp_path / "config_secrets.json"))
+    manager.template_path = str(tmp_path / "no-template.json")
+    svc = ConfigService(manager, enable_hot_reload=False)
+    yield svc, config_path
+    svc.shutdown()
+
+
+_saves = itertools.count(1)
+
+
+def _save(config_path, **sections):
+    config = json.loads(config_path.read_text(encoding="utf-8"))
+    config.update(sections)
+    config_path.write_text(json.dumps(config), encoding="utf-8")
+    # ConfigManager re-reads only when (mtime, size) moves. Two quick saves of
+    # the same size can share an mtime tick (about 16 ms on Windows), so step
+    # it forward explicitly.
+    st = config_path.stat()
+    os.utime(config_path, ns=(st.st_atime_ns, st.st_mtime_ns + next(_saves) * 50_000_000))
+
+
+def _reload_in_background(svc):
+    thread = threading.Thread(target=svc._load_config, daemon=True)
+    thread.start()
+    return thread
+
+
+def test_get_config_does_not_wait_for_a_slow_subscriber(service):
+    svc, config_path = service
+    entered, release = threading.Event(), threading.Event()
+
+    def slow(_old, _new):
+        entered.set()
+        release.wait(SLOW)
+
+    svc.subscribe(slow, plugin_id="weather")
+    _save(config_path, weather={"enabled": False})
+    reload = _reload_in_background(svc)
+    assert entered.wait(SLOW)
+
+    start = time.monotonic()
+    config = svc.get_config()
+    waited = time.monotonic() - start
+    release.set()
+    reload.join(SLOW)
+
+    assert waited < 0.5
+    # Swapped before anyone was told: a subscriber that reads it sees the new one.
+    assert config["weather"]["enabled"] is False
+
+
+def test_unsubscribing_another_callback_does_not_wait(service):
+    svc, config_path = service
+    entered, release = threading.Event(), threading.Event()
+
+    def slow(_old, _new):
+        entered.set()
+        release.wait(SLOW)
+
+    def other(_old, _new):
+        pass
+
+    svc.subscribe(slow, plugin_id="weather")
+    svc.subscribe(other, plugin_id="clock")
+    _save(config_path, weather={"enabled": False})
+    reload = _reload_in_background(svc)
+    assert entered.wait(SLOW)
+
+    start = time.monotonic()
+    svc.unsubscribe(other, plugin_id="clock")
+    waited = time.monotonic() - start
+    release.set()
+    reload.join(SLOW)
+
+    assert waited < 0.5
+
+
+def test_a_callback_unsubscribed_mid_notification_is_not_called(service):
+    svc, config_path = service
+    entered, release = threading.Event(), threading.Event()
+    called = []
+
+    def slow_global(_old, _new):  # global subscribers are notified first
+        entered.set()
+        release.wait(SLOW)
+
+    def weather(_old, _new):
+        called.append("weather")
+
+    svc.subscribe(slow_global)
+    svc.subscribe(weather, plugin_id="weather")
+    _save(config_path, weather={"enabled": False})
+    reload = _reload_in_background(svc)
+    assert entered.wait(SLOW)
+
+    svc.unsubscribe(weather, plugin_id="weather")
+    release.set()
+    reload.join(SLOW)
+
+    assert called == []
+
+
+def test_unsubscribe_waits_for_its_own_callback_to_return(service):
+    svc, config_path = service
+    entered, release = threading.Event(), threading.Event()
+    returned = threading.Event()
+
+    def slow(_old, _new):
+        entered.set()
+        release.wait(SLOW)
+        returned.set()
+
+    svc.subscribe(slow, plugin_id="weather")
+    _save(config_path, weather={"enabled": False})
+    reload = _reload_in_background(svc)
+    assert entered.wait(SLOW)
+
+    threading.Timer(0.2, release.set).start()
+    svc.unsubscribe(slow, plugin_id="weather")
+
+    assert returned.is_set()
+    reload.join(SLOW)
+
+
+def test_a_callback_may_read_config_and_unsubscribe_itself(service):
+    svc, config_path = service
+    seen = []
+
+    def once(_old, _new):
+        seen.append(svc.get_config()["weather"]["enabled"])
+        svc.unsubscribe(once, plugin_id="weather")
+
+    svc.subscribe(once, plugin_id="weather")
+    _save(config_path, weather={"enabled": False})
+    reload = _reload_in_background(svc)
+    reload.join(SLOW)
+
+    assert not reload.is_alive()
+    assert seen == [False]
+
+
+def test_two_reloads_notify_in_order(service):
+    svc, config_path = service
+    entered, release = threading.Event(), threading.Event()
+    seen = []
+
+    def record(old, new):
+        seen.append((old["brightness"], new["brightness"]))
+        if len(seen) == 1:
+            entered.set()
+            release.wait(SLOW)
+
+    svc.subscribe(record, plugin_id="display")
+    _save(config_path, display={"brightness": 60})
+    first = _reload_in_background(svc)
+    assert entered.wait(SLOW)
+
+    _save(config_path, display={"brightness": 100})
+    second = _reload_in_background(svc)
+    time.sleep(0.2)
+    release.set()
+    first.join(SLOW)
+    second.join(SLOW)
+
+    assert seen == [(50, 60), (60, 100)]

test/test_display_arbiter.py

@@ -9,6 +9,7 @@ that overrides the schedule and ends (#714).
 """
 
 import itertools
+from dataclasses import replace
 import os
 from unittest.mock import MagicMock, patch
 
@@ -19,6 +20,7 @@ os.environ.setdefault("EMULATOR", "true")
 from src import display_arbiter  # noqa: E402
 from src.display_arbiter import (  # noqa: E402
     SCHEDULED_OFF_DWELL,
+    SCREEN_PREEMPTERS,
     WIFI_NOTICE_DWELL,
     Arbiter,
     ArbiterInputs,
@@ -26,6 +28,9 @@ from src.display_arbiter import (  # noqa: E402
     ScreenPlan,
     Source,
     WifiNotice,
+    live_pick,
+    live_takeover,
+    on_demand_bound,
     wifi_notice_preempts,
 )
 
@@ -34,7 +39,9 @@ NOTICE = WifiNotice(message="Connected to HomeNet", expires_at=1_000.0)
 OFF = Source.SCHEDULED_OFF
 FOLLOW = Source.FOLLOWER
 WIFI = Source.WIFI
+ONDEM = Source.ON_DEMAND
 LEGACY = Source.LEGACY
+ROTATION = Source.ROTATION
 
 # (schedule_on, on_demand_active, follower_active, notice) -> Source.
 # Every combination of the stage-2 inputs: 2 x 2 x 2 x 2 = 16 rows.
@@ -46,17 +53,17 @@ DECIDE_TABLE = [
     (False, False, True, None, OFF),
     (False, False, True, NOTICE, OFF),
     # Scheduled off, but on-demand overrides the gate.
-    (False, True, False, None, LEGACY),       # on-demand: run() decides
-    (False, True, False, NOTICE, LEGACY),     # on-demand outranks WiFi
+    (False, True, False, None, ONDEM),        # on-demand overrides the gate
+    (False, True, False, NOTICE, ONDEM),      # on-demand outranks WiFi
     (False, True, True, None, FOLLOW),        # follower outranks on-demand
     (False, True, True, NOTICE, FOLLOW),
     # Scheduled on.
-    (True, False, False, None, LEGACY),       # live / Vegas / rotation
+    (True, False, False, None, ROTATION),     # live / Vegas / rotation
     (True, False, False, NOTICE, WIFI),
     (True, False, True, None, FOLLOW),
     (True, False, True, NOTICE, FOLLOW),      # follower outranks WiFi
-    (True, True, False, None, LEGACY),
-    (True, True, False, NOTICE, LEGACY),      # on-demand outranks WiFi
+    (True, True, False, None, ONDEM),
+    (True, True, False, NOTICE, ONDEM),       # on-demand outranks WiFi
     (True, True, True, None, FOLLOW),
     (True, True, True, NOTICE, FOLLOW),
 ]
@@ -95,8 +102,15 @@ class TestDecide:
         elif expected is WIFI:
             assert plan == ScreenPlan(WIFI, max_duration=WIFI_NOTICE_DWELL,
                                       notice=NOTICE)
+        elif expected is ONDEM:
+            # An empty state: a session with no modes, which the
+            # controller ends (see TestOnDemand for real sessions).
+            assert plan == ScreenPlan(ONDEM)
+        elif expected is ROTATION:
+            # No live scan and Vegas off: the rotation's (empty) mode.
+            assert plan == ScreenPlan(ROTATION, preemptible_by=SCREEN_PREEMPTERS)
         else:
-            # A follower paces itself; LEGACY is run()'s existing code.
+            # A follower paces itself.
             assert plan == ScreenPlan(expected)
 
     def test_dwells_are_todays(self):
@@ -224,16 +238,389 @@ class TestControllerSnapshot:
             assert (plan.source is OFF) is (not dc.is_display_active), time_str
             return plan.source
 
-        assert step("22:59:30") is LEGACY
+        assert step("22:59:30") is ROTATION
         assert step("23:00:00") is OFF                 # window ends
         dc.on_demand_active = True
-        assert step("23:00:10") is LEGACY              # on-demand overrides
+        assert step("23:00:10") is ONDEM               # on-demand overrides
         assert dc.on_demand_schedule_override is True
-        assert step("23:01:00") is LEGACY              # next minute, still on
+        assert step("23:01:00") is ONDEM               # next minute, still on
         dc._reset_on_demand_fields()                   # session ends
         assert step("23:01:20") is OFF                 # same minute: blanks
         dc.on_demand_active = True
-        assert step("06:59:00") is LEGACY
-        assert step("07:00:00") is LEGACY              # schedule back on mid-session
+        assert step("06:59:00") is ONDEM
+        assert step("07:00:00") is ONDEM               # schedule back on mid-session
         dc._reset_on_demand_fields()
-        assert step("07:00:30") is LEGACY
+        assert step("07:00:30") is ROTATION
+
+
+# -- OnDemand (stage 3) ---------------------------------------------------
+
+ON = ArbiterInputs(schedule_on=True, on_demand_active=True, follower_active=False)
+
+
+def _session(modes=("a", "b", "c"), index=0, expires_at=None, current=None):
+    return ArbiterState(current_mode=current, on_demand_modes=tuple(modes),
+                        on_demand_index=index, on_demand_expires_at=expires_at)
+
+
+class TestOnDemand:
+
+    # (modes, index, expires_at, now) -> (mode, max_duration)
+    TABLE = [
+        (("a", "b", "c"), 0, None, 100.0, "a", None),       # untimed
+        (("a", "b", "c"), 2, None, 100.0, "c", None),
+        (("a", "b", "c"), 3, None, 100.0, "a", None),       # past the end: 0
+        (("a", "b", "c"), 9, None, 100.0, "a", None),
+        (("a",), 0, 130.0, 100.0, "a", 30.0),               # 30 s left
+        (("a",), 0, 130.0, 130.0, "a", 0.0),                # none left
+        (("a",), 0, 130.0, 200.0, "a", 0.0),                # never negative
+    ]
+
+    @pytest.mark.parametrize("modes,index,expires_at,now,mode,max_duration", TABLE)
+    def test_current_mode_and_time_left(self, modes, index, expires_at, now, mode,
+                                        max_duration):
+        plan = Arbiter.decide(_session(modes, index, expires_at), ON, now)
+        assert plan.source is ONDEM
+        assert plan.mode == mode
+        assert plan.max_duration == max_duration
+        assert plan.deadline == expires_at
+
+    def test_no_modes_left_is_a_plan_with_no_mode(self):
+        plan = Arbiter.decide(_session(modes=()), ON, 0.0)
+        assert plan == ScreenPlan(ONDEM)
+
+    def test_preemptible_by_the_schedule_a_reload_and_its_own_changes(self):
+        plan = Arbiter.decide(_session(), ON, 0.0)
+        assert {Source.SCHEDULED_OFF, ONDEM, Source.RELOAD} <= plan.preemptible_by
+        assert Source.FOLLOWER not in plan.preemptible_by
+
+    @pytest.mark.parametrize("index,expected_index,expected_mode", [
+        (0, 1, "b"), (1, 2, "c"), (2, 0, "a")])
+    def test_next_on_demand_wraps(self, index, expected_index, expected_mode):
+        nxt = _session(index=index).next_on_demand()
+        assert (nxt.on_demand_index, nxt.current_mode) == (expected_index, expected_mode)
+
+    def test_showing_a_plan_resets_an_index_past_the_end(self):
+        state = _session(index=5, current="x")
+        plan = Arbiter.decide(state, ON, 0.0)
+        shown = state.showing(plan)
+        assert (shown.on_demand_index, shown.current_mode) == (0, "a")
+        assert state.on_demand_index == 5            # not mutated
+
+
+# (min, max, deadline, now) -> bounds. The bound applied after the first frame.
+BOUND_TABLE = [
+    (10.0, 20.0, None, 0.0, (10.0, 20.0)),      # untimed: unchanged
+    (10.0, 20.0, 100.0, 50.0, (10.0, 20.0)),    # plenty left
+    (10.0, 20.0, 100.0, 85.0, (10.0, 15.0)),    # max cut to what is left
+    (10.0, 20.0, 100.0, 95.0, (5.0, 5.0)),      # both cut
+    (10.0, 20.0, 100.0, 100.0, None),           # nothing left
+    (10.0, 20.0, 100.0, 150.0, None),
+]
+
+
+@pytest.mark.parametrize("min_d,max_d,deadline,now,expected", BOUND_TABLE)
+def test_on_demand_bound(min_d, max_d, deadline, now, expected):
+    assert on_demand_bound(min_d, max_d, deadline, now) == expected
+
+
+# -- Live (stage 3) -------------------------------------------------------
+
+LIVE = Source.LIVE
+
+# (live_modes, current_mode, advance) -> pick. _check_live_priority's rule.
+PICK_TABLE = [
+    ((), "clock", True, None),
+    (None, "clock", True, None),
+    (("nfl",), "clock", True, "nfl"),                 # not on a live mode: first
+    (("nfl", "nhl"), "clock", True, "nfl"),
+    (("nfl", "nhl"), "clock", False, "nfl"),
+    (("nfl", "nhl"), "nfl", True, "nhl"),             # round-robin
+    (("nfl", "nhl"), "nhl", True, "nfl"),             # wraps
+    (("nfl", "nhl"), "nhl", False, "nhl"),            # a peek stays put
+    (("nfl",), "nfl", True, "nfl"),                   # one game: itself
+]
+
+
+@pytest.mark.parametrize("live,current,advance,expected", PICK_TABLE)
+def test_live_pick(live, current, advance, expected):
+    assert live_pick(live, current, advance) == expected
+
+
+def _below(live=None, vegas=False, keeps=False, yielded=False, on_demand=False):
+    """Inputs for the Sources below the notice (no notice, no follower)."""
+    return ArbiterInputs(schedule_on=True, on_demand_active=on_demand,
+                         follower_active=False, live_modes=live, vegas_enabled=vegas,
+                         vegas_live_in_ticker=keeps, vegas_yielded=yielded)
+
+
+ROT = ("clock", "weather", "nfl_live", "nhl_live")
+
+
+def _rot(current="clock", index=0, resume=None, unshown=False):
+    return ArbiterState(current_mode=current, rotation=ROT, rotation_index=index,
+                        live_resume_index=resume, live_takeover_unshown=unshown)
+
+
+class TestLive:
+
+    # (state, inputs) -> (source, mode, ends_live)
+    TABLE = [
+        # Nothing live, nothing to resume.
+        (_rot(), _below(live=()), "below", None, False),
+        # Not scanned (on-demand, or the ticker keeps live content).
+        (_rot(), _below(live=None), "below", None, False),
+        # A game is live: it takes the panel.
+        (_rot(), _below(live=("nfl_live",)), LIVE, "nfl_live", False),
+        # Two: round-robin from the one showing.
+        (_rot("nfl_live", 2), _below(live=("nfl_live", "nhl_live")), LIVE, "nhl_live", False),
+        # ... unless a mid-screen takeover chose it and it has not shown yet.
+        (_rot("nfl_live", 2, resume=0, unshown=True),
+         _below(live=("nfl_live", "nhl_live")), LIVE, "nfl_live", False),
+        # Vegas keeps live content in its ticker: Live has no say at all,
+        # not even the resume.
+        (_rot(), _below(live=("nfl_live",), vegas=True, keeps=True), "below", None, False),
+        (_rot("nfl_live", 2, resume=1),
+         _below(live=(), vegas=True, keeps=True), "below", None, False),
+        # Vegas that yields to live content: Live outranks it.
+        (_rot(), _below(live=("nfl_live",), vegas=True), LIVE, "nfl_live", False),
+        # The game ended: the interrupted rotation resumes.
+        (_rot("nfl_live", 2, resume=1), _below(live=()), "below", None, True),
+        (_rot("nfl_live", 2, resume=1), _below(live=(), vegas=True), "below", None, True),
+        # On-demand outranks Live.
+        (ArbiterState(on_demand_modes=("x",)), _below(live=("nfl_live",), on_demand=True),
+         ONDEM, "x", False),
+    ]
+
+    @pytest.mark.parametrize("state,inputs,source,mode,ends_live", TABLE)
+    def test_decide(self, state, inputs, source, mode, ends_live):
+        plan = Arbiter.decide(state, inputs, 0.0)
+        if source == "below":
+            assert plan.source not in (LIVE, ONDEM, OFF, FOLLOW, WIFI)
+        else:
+            assert plan.source is source
+            assert plan.mode == mode
+        assert plan.ends_live is ends_live
+
+    def test_a_live_plan_has_no_durations_until_its_first_frame(self):
+        plan = Arbiter.decide(_rot(), _below(live=("nfl_live",)), 0.0)
+        assert (plan.min_duration, plan.max_duration, plan.frame_policy) == (None, None, None)
+
+
+class TestLiveTransitions:
+
+    def test_claim_saves_where_the_rotation_was(self):
+        nxt = _rot("weather", 1).claim_live("nfl_live")
+        assert (nxt.current_mode, nxt.rotation_index, nxt.live_resume_index) == ("nfl_live", 2, 1)
+
+    def test_a_second_claim_keeps_the_first_resume_point(self):
+        nxt = _rot("nfl_live", 2, resume=1).claim_live("nhl_live")
+        assert (nxt.current_mode, nxt.rotation_index, nxt.live_resume_index) == ("nhl_live", 3, 1)
+
+    def test_claiming_the_mode_showing_changes_nothing(self):
+        state = _rot("nfl_live", 2, resume=1)
+        assert state.claim_live("nfl_live") is state
+
+    def test_a_live_mode_outside_the_rotation_keeps_the_index(self):
+        nxt = _rot("weather", 1).claim_live("mlb_live")
+        assert (nxt.current_mode, nxt.rotation_index, nxt.live_resume_index) == ("mlb_live", 1, 1)
+
+    def test_release_resumes_and_forgets(self):
+        nxt = _rot("nhl_live", 3, resume=1).release_live()
+        assert (nxt.current_mode, nxt.rotation_index, nxt.live_resume_index) == ("weather", 1, None)
+
+    def test_release_wraps_a_resume_point_past_a_shortened_rotation(self):
+        nxt = _rot("nhl_live", 3, resume=6).release_live()
+        assert (nxt.current_mode, nxt.rotation_index) == ("nfl_live", 2)   # 6 % 4
+
+    def test_release_with_nothing_to_resume_changes_nothing(self):
+        state = _rot("clock", 0)
+        assert state.release_live() is state
+        empty = ArbiterState(current_mode="x", live_resume_index=2)
+        assert empty.release_live() is empty      # no rotation to resume into
+
+
+# -- Vegas and Rotation (stage 3) -----------------------------------------
+
+class TestVegasAndRotation:
+
+    # (state, inputs) -> (source, mode, ends_live). LEGACY now means Vegas only.
+    TABLE = [
+        (_rot("weather", 1), _below(live=()), ROTATION, "weather", False),
+        (_rot("weather", 1), _below(live=None), ROTATION, "weather", False),
+        (_rot("weather", 1), _below(live=(), vegas=True), LEGACY, None, False),
+        (_rot("weather", 1), _below(live=None, vegas=True, keeps=True), LEGACY, None, False),
+        # The iteration yielded: the screen it fell through to.
+        (_rot("weather", 1), _below(live=(), vegas=True, yielded=True),
+         ROTATION, "weather", False),
+        (_rot("weather", 1), _below(live=("nfl_live",), vegas=True, yielded=True),
+         LIVE, "nfl_live", False),
+        # Live priority just ended: the rotation resumes where it was cut.
+        (_rot("nhl_live", 3, resume=1), _below(live=()), ROTATION, "weather", True),
+        # ... and Vegas carries the resume through to its own pass.
+        (_rot("nhl_live", 3, resume=1), _below(live=(), vegas=True), LEGACY, None, True),
+        # A rotation that something moved off its list carries on from there.
+        (ArbiterState(current_mode=None, rotation=ROT), _below(live=()), ROTATION, None, False),
+    ]
+
+    @pytest.mark.parametrize("state,inputs,source,mode,ends_live", TABLE)
+    def test_decide(self, state, inputs, source, mode, ends_live):
+        plan = Arbiter.decide(state, inputs, 0.0)
+        assert (plan.source, plan.mode, plan.ends_live) == (source, mode, ends_live)
+
+    def test_a_rotation_plan_may_be_preempted_by_everything_a_screen_watches(self):
+        plan = Arbiter.decide(_rot(), _below(live=()), 0.0)
+        assert plan.preemptible_by == SCREEN_PREEMPTERS
+        assert {OFF, ONDEM, WIFI, LIVE, ROTATION, Source.RELOAD} == SCREEN_PREEMPTERS
+
+
+class _End:
+    def __init__(self, on_demand_active=False, still_live=False):
+        self.on_demand_active = on_demand_active
+        self.still_live = still_live
+
+
+class TestAfter:
+    """ArbiterState.after: _advance_after_screen's step."""
+
+    def test_the_rotation_advances(self):
+        nxt = _rot("weather", 1).after(_End())
+        assert (nxt.current_mode, nxt.rotation_index) == ("nfl_live", 2)
+
+    def test_it_wraps(self):
+        nxt = _rot("nhl_live", 3).after(_End())
+        assert (nxt.current_mode, nxt.rotation_index) == ("clock", 0)
+
+    def test_a_live_mode_still_live_holds(self):
+        state = _rot("nfl_live", 2)
+        assert state.after(_End(still_live=True)) is state
+
+    def test_an_on_demand_session_moves_to_its_next_mode(self):
+        state = replace(_session(index=1, current="b"), rotation=ROT, rotation_index=1)
+        nxt = state.after(_End(on_demand_active=True))
+        assert (nxt.current_mode, nxt.on_demand_index, nxt.rotation_index) == ("c", 2, 1)
+
+    def test_a_session_with_no_modes_is_left_to_the_controller(self):
+        state = ArbiterState(current_mode="x", rotation=ROT)
+        assert state.after(_End(on_demand_active=True)) is state
+
+    def test_no_rotation_no_step(self):
+        state = ArbiterState(current_mode="x")
+        assert state.after(_End()) is state
+
+
+# -- Mid-screen: decide(..., running=plan) (stage 3) ----------------------
+#
+# What the ScreenRunner asks at each service point. These rows are what
+# _check_live_takeover, _screen_preempted and _wifi_notice_pending answered
+# between frames before stage 3, written out.
+
+CLOCK = Arbiter.decide(ArbiterState(current_mode="clock"), _below(live=()), 0.0)
+NFL = Arbiter.decide(ArbiterState(current_mode="clock"), _below(live=("nfl_live",)), 0.0)
+OD = Arbiter.decide(_session(modes=("x", "y")), ON, 0.0)
+FRESH = WifiNotice(message="AP mode", expires_at=1_000.0)
+
+HELD = "held"
+
+
+def _mid(on_demand=False, schedule_on=True, live=None, notice=None, reload=False):
+    return ArbiterInputs(schedule_on=schedule_on, on_demand_active=on_demand,
+                         follower_active=False, live_modes=live, wifi_notice=notice,
+                         reload_pending=reload)
+
+
+# (running, current_mode, inputs, now) -> HELD or (source, mode)
+MID_TABLE = [
+    # Nothing changed.
+    (CLOCK, "clock", _mid(), 500.0, HELD),
+    (CLOCK, "clock", _mid(live=()), 500.0, HELD),
+    # A game went live: it takes the panel (the first live mode).
+    (CLOCK, "clock", _mid(live=("nfl_live", "nhl_live")), 500.0, (LIVE, "nfl_live")),
+    # ... even with a notice pending: the claim is made now, and the next
+    # pass shows the notice first (top-of-pass order), then the game.
+    (CLOCK, "clock", _mid(live=("nfl_live",), notice=FRESH), 500.0, (LIVE, "nfl_live")),
+    # ... but not over the schedule or an on-demand session.
+    (CLOCK, "clock", _mid(live=("nfl_live",), schedule_on=False), 500.0, (OFF, None)),
+    (CLOCK, "x", _mid(live=("nfl_live",), on_demand=True), 500.0, (ONDEM, "x")),
+    # A screen already on a live mode is not taken over by another.
+    (CLOCK, "nfl_live", _mid(live=("nfl_live", "nhl_live")), 500.0, (ROTATION, "nfl_live")),
+    (NFL, "nfl_live", _mid(live=("nhl_live",)), 500.0, HELD),
+    # The mode moved under the screen: on-demand started, or ended, or the
+    # rotation was rebuilt.
+    (CLOCK, "x", _mid(on_demand=True), 500.0, (ONDEM, "x")),
+    (OD, "weather", _mid(), 500.0, (ROTATION, "weather")),
+    (CLOCK, "weather", _mid(), 500.0, (ROTATION, "weather")),
+    # An on-demand session that ends on the same mode keeps the screen.
+    (OD, "x", _mid(), 500.0, HELD),
+    # The schedule: off ends it; an on-demand override holds.
+    (CLOCK, "clock", _mid(schedule_on=False), 500.0, (OFF, None)),
+    (OD, "x", _mid(on_demand=True, schedule_on=False), 500.0, HELD),
+    # A WiFi notice, compared with its expiry; on-demand outranks it.
+    (CLOCK, "clock", _mid(notice=FRESH), 999.9, (WIFI, None)),
+    (CLOCK, "clock", _mid(notice=FRESH), 1_000.0, HELD),
+    (NFL, "nfl_live", _mid(notice=FRESH), 500.0, (WIFI, None)),
+    (OD, "x", _mid(on_demand=True, notice=FRESH), 500.0, HELD),
+    # A plugin reload waits at the top of the loop.
+    (CLOCK, "clock", _mid(reload=True), 500.0, (Source.RELOAD, None)),
+    (OD, "x", _mid(on_demand=True, reload=True), 500.0, (Source.RELOAD, None)),
+    # The order between them: a moved mode before the schedule, the
+    # schedule before a notice, a notice before a reload.
+    (CLOCK, "weather", _mid(schedule_on=False), 500.0, (ROTATION, "weather")),
+    (CLOCK, "clock", _mid(schedule_on=False, notice=FRESH), 500.0, (OFF, None)),
+    (CLOCK, "clock", _mid(notice=FRESH, reload=True), 500.0, (WIFI, None)),
+]
+
+
+class TestMidScreen:
+
+    @pytest.mark.parametrize("running,current,inputs,now,expected", MID_TABLE)
+    def test_decide(self, running, current, inputs, now, expected):
+        state = ArbiterState(current_mode=current)
+        plan = Arbiter.decide(state, inputs, now, running=running)
+        if expected == HELD:
+            assert plan is running
+        else:
+            assert plan is not running
+            assert (plan.source, plan.mode) == expected
+
+    def test_the_running_plans(self):
+        assert (CLOCK.source, CLOCK.mode) == (ROTATION, "clock")
+        assert (NFL.source, NFL.mode) == (LIVE, "nfl_live")
+        assert LIVE not in NFL.preemptible_by
+        assert (OD.source, OD.mode) == (ONDEM, "x")
+
+    def test_a_follower_and_vegas_never_preempt(self):
+        for plan in (CLOCK, NFL, OD):
+            assert FOLLOW not in plan.preemptible_by
+            assert LEGACY not in plan.preemptible_by
+
+    def test_nothing_in_preemptible_by_means_nothing_preempts(self):
+        bare = replace(CLOCK, preemptible_by=frozenset())
+        inputs = _mid(live=("nfl_live",), schedule_on=False, notice=FRESH, reload=True)
+        assert Arbiter.decide(ArbiterState(current_mode="weather"), inputs, 0.0,
+                              running=bare) is bare
+
+    def test_mid_screen_decide_reads_no_clock(self):
+        boom = MagicMock(side_effect=AssertionError("decide read the clock"))
+        with patch("time.time", boom), patch("time.monotonic", boom):
+            for running, current, inputs, now, _ in MID_TABLE:
+                Arbiter.decide(ArbiterState(current_mode=current), inputs, now,
+                               running=running)
+
+
+# (current, inputs) -> live_takeover. The mode a mid-screen check claims.
+TAKEOVER_TABLE = [
+    ("clock", _mid(live=("nfl_live",)), "nfl_live"),
+    ("clock", _mid(live=()), None),
+    ("clock", _mid(live=None), None),                       # no scan was due
+    ("nfl_live", _mid(live=("nfl_live",)), None),
+    ("clock", _mid(live=("nfl_live",), on_demand=True), None),
+    ("clock", _mid(live=("nfl_live",), schedule_on=False), None),
+    ("clock", replace(_mid(live=("nfl_live",)), vegas_enabled=True,
+                      vegas_live_in_ticker=True), None),
+]
+
+
+@pytest.mark.parametrize("current,inputs,expected", TAKEOVER_TABLE)
+def test_live_takeover(current, inputs, expected):
+    assert live_takeover(ArbiterState(current_mode=current), inputs) == expected

test/test_display_duration_not_a_number.py

@@ -0,0 +1,112 @@
+"""A plugin duration that is not a number must not stop the display.
+
+Several plugins return their ``display_duration`` setting as it is in
+config.json (``return self.config.get('display_duration', 15.0)``), so a
+value saved as ``"20"`` or ``null`` -- from the raw config editor, or by
+hand -- reached run() as a string or None. _resolve_durations then compared
+it with 0, the TypeError went past every handler in the loop, and the
+display service exited; systemd restarted it into the same screen and the
+same crash.
+"""
+
+import logging
+import math
+import os
+from unittest.mock import MagicMock
+
+os.environ.setdefault("EMULATOR", "true")
+
+import pytest
+
+from src.display_controller import DisplayController
+from test._run_loop_harness import FakePlugin, RunLoopHarness
+
+
+def _controller(plugin_modes):
+    dc = object.__new__(DisplayController)
+    dc.config = {}
+    dc.plugin_modes = plugin_modes
+    return dc
+
+
+def _plugin(duration, plugin_id='clock-simple'):
+    plugin = MagicMock()
+    plugin.plugin_id = plugin_id
+    plugin.get_display_duration.return_value = duration
+    return plugin
+
+
+class TestPluginDurationIsCoerced:
+    @pytest.mark.parametrize('value, expected', [
+        ('20', 20.0), (' 7.5 ', 7.5), (12, 12.0), (12.5, 12.5)])
+    def test_numbers_and_numeric_strings_are_used(self, value, expected):
+        dc = _controller({'clock': _plugin(value)})
+        duration = dc._get_display_duration('clock')
+        assert duration == expected and isinstance(duration, float)
+
+    @pytest.mark.parametrize('value', [
+        None, '', 'twenty', True, False, float('nan'), float('inf'), 'inf',
+        [20], {'seconds': 20}])
+    def test_anything_but_a_finite_number_gets_the_default(self, value):
+        dc = _controller({'clock': _plugin(value)})
+        assert dc._get_display_duration('clock') == 30
+
+    @pytest.mark.parametrize('value', [0, -5, '-5', '0'])
+    def test_a_number_not_above_zero_still_gets_the_15s_rule(self, value):
+        """Unchanged: _resolve_durations turns it into 15 s, with its warning."""
+        plugin = _plugin(value)
+        dc = _controller({'clock': plugin})
+        base = dc._get_display_duration('clock')
+        assert dc._resolve_durations(plugin, 'clock', base, False)[1] == 15.0
+
+    def test_a_raising_get_display_duration_gets_the_default(self):
+        plugin = _plugin(None)
+        plugin.get_display_duration.side_effect = KeyError('display_duration')
+        assert _controller({'clock': plugin})._get_display_duration('clock') == 30
+
+    def test_the_result_feeds_resolve_durations(self):
+        """The two calls run() makes back to back, for one screen."""
+        plugin = _plugin('bad')
+        dc = _controller({'clock': plugin})
+        base = dc._get_display_duration('clock')
+        assert dc._resolve_durations(plugin, 'clock', base, False) == (30, 30)
+
+    def test_logged_once_per_plugin(self, caplog):
+        dc = _controller({'clock': _plugin('twenty'),
+                          'clock_big': _plugin('twenty'),
+                          'calendar': _plugin(None, plugin_id='calendar')})
+        # clock_big is a second mode of the same plugin.
+        dc.plugin_modes['clock_big'].plugin_id = 'clock-simple'
+        with caplog.at_level(logging.WARNING, logger='src.display_controller'):
+            for _ in range(3):
+                for mode in ('clock', 'clock_big', 'calendar'):
+                    dc._get_display_duration(mode)
+        warnings = [r for r in caplog.records if 'display duration' in r.getMessage()]
+        assert len(warnings) == 2
+        assert {'clock-simple', 'calendar'} == {
+            next(p for p in ('clock-simple', 'calendar') if p in r.getMessage())
+            for r in warnings}
+
+    def test_a_good_value_after_a_bad_one_is_used(self):
+        plugin = _plugin(None)
+        dc = _controller({'clock': plugin})
+        assert dc._get_display_duration('clock') == 30
+        plugin.get_display_duration.return_value = 45
+        assert dc._get_display_duration('clock') == 45.0
+
+
+class TestRunLoopSurvives:
+    """Through the real run() on the harness's fake clock."""
+
+    @pytest.mark.parametrize('duration, shown_for', [('20', 20.0), (None, 30.0),
+                                                     ('twenty', 30.0)])
+    def test_the_screen_runs_and_the_rotation_goes_on(self, tmp_path, duration, shown_for):
+        harness = RunLoopHarness(tmp_path, horizon=120)
+        harness.add_plugin(FakePlugin("weather", ["weather"], duration=30))
+        harness.add_plugin(FakePlugin("clock-simple", ["clock"], duration=duration))
+        # Before the fix run() returned at t=30, when the clock came up, and
+        # the harness raised "run() returned ... before the horizon".
+        rows = harness.run()["screens"]
+        clock = next(row for row in rows if row[1] == "clock")
+        assert math.isclose(clock[2], shown_for, abs_tol=1.0)
+        assert [row[1] for row in rows][:3] == ["weather", "clock", "weather"]

test/test_display_hold_report.py

@@ -0,0 +1,142 @@
+"""The report of a scrolling screen held by its plugin's update().
+
+While a plugin's update() runs it holds the plugin's lock, and its screen's
+frames are skipped -- on a scroller, a frozen strip -- with nothing logged.
+_note_display_hold times each such run and reports one of
+DISPLAY_HOLD_REPORT_SECONDS or more.
+"""
+
+import threading
+import types
+from unittest.mock import MagicMock
+
+import pytest
+
+
+class _Clock:
+    """display_controller's clock: moves only when run() sleeps or a test says."""
+
+    def __init__(self, start=10_000.0):
+        self.t = start
+
+    def now(self):
+        return self.t
+
+    def sleep(self, seconds):
+        self.t += max(seconds, 0.0005)
+
+    def module(self):
+        return types.SimpleNamespace(time=self.now, monotonic=self.now,
+                                     perf_counter=self.now, sleep=self.sleep)
+
+
+@pytest.fixture
+def clock(monkeypatch):
+    c = _Clock()
+    monkeypatch.setattr("src.display_controller.time", c.module())
+    return c
+
+
+class _Locks:
+    """get_plugin_lock for one plugin, whose lock the test can hold."""
+
+    def __init__(self):
+        self.lock = threading.Lock()
+
+    def __call__(self, plugin_id):
+        return self.lock
+
+
+@pytest.fixture
+def held(test_display_controller):
+    c = test_display_controller
+    locks = _Locks()
+    c.plugin_manager.get_plugin_lock = locks
+    c.plugin_manager._warn_rate_limited = MagicMock()
+    c.plugin_manager.health_tracker = MagicMock()
+    c._display_hold = None
+    return c, locks.lock
+
+
+def _plugin(plugin_id):
+    p = MagicMock()
+    p.plugin_id = plugin_id
+    p.display.return_value = True
+    return p
+
+
+class TestTheDisplayHoldReport:
+    def test_a_long_hold_is_reported_when_it_ends(self, held, clock):
+        c, lock = held
+        ticker = _plugin("ticker")
+        lock.acquire()                         # update() running
+        assert c._display_once(ticker, "ticker", False, report_hold=True) is True
+        clock.t += 0.2
+        assert c._display_once(ticker, "ticker", False, report_hold=True) is True
+        assert ticker.display.call_count == 0
+        c.plugin_manager._warn_rate_limited.assert_not_called()
+        clock.t += 0.2
+        lock.release()                         # update() done
+        c._display_once(ticker, "ticker", False, report_hold=True)
+        assert ticker.display.call_count == 1
+        key, message, plugin_id, ms = c.plugin_manager._warn_rate_limited.call_args[0]
+        assert key == "display-hold:ticker" and plugin_id == "ticker"
+        assert "held" in message and ms == pytest.approx(400.0)
+        c.plugin_manager.health_tracker.record_busy_skip.assert_called_once_with(
+            "ticker", "display hold", pytest.approx(0.4))
+
+    def test_a_short_hold_is_not(self, held, clock):
+        c, lock = held
+        ticker = _plugin("ticker")
+        lock.acquire()
+        c._display_once(ticker, "ticker", False, report_hold=True)
+        clock.t += 0.1
+        lock.release()
+        c._display_once(ticker, "ticker", False, report_hold=True)
+        c.plugin_manager._warn_rate_limited.assert_not_called()
+        c.plugin_manager.health_tracker.record_busy_skip.assert_not_called()
+
+    def test_a_hold_that_ends_on_another_plugins_screen_is_not_blamed_on_it(
+            self, held, clock):
+        c, lock = held
+        lock.acquire()
+        c._display_once(_plugin("ticker"), "ticker", False, report_hold=True)
+        clock.t += 1.0
+        lock.release()
+        c._display_once(_plugin("clock"), "clock", False, report_hold=True)
+        c.plugin_manager._warn_rate_limited.assert_not_called()
+        assert c._display_hold is None
+
+    def test_frames_that_draw_report_nothing(self, held, clock):
+        c, _lock = held
+        ticker = _plugin("ticker")
+        for _ in range(5):
+            c._display_once(ticker, "ticker", False, report_hold=True)
+            clock.t += 0.5
+        c.plugin_manager._warn_rate_limited.assert_not_called()
+
+    def test_the_1hz_loop_reports_no_holds(self, held, clock):
+        # A static screen's frames are a second apart: one skipped frame is
+        # not a measured hold, and nothing on the panel froze. (On ledpi the
+        # first version reported every such skip as "held 1000 ms".)
+        c, lock = held
+        board = _plugin("board")
+        lock.acquire()
+        c._display_once(board, "board", False)
+        clock.t += 1.0
+        lock.release()
+        c._display_once(board, "board", False)
+        c.plugin_manager._warn_rate_limited.assert_not_called()
+        c.plugin_manager.health_tracker.record_busy_skip.assert_not_called()
+
+    def test_a_run_left_open_is_dropped_by_a_1hz_frame(self, held, clock):
+        c, lock = held
+        ticker = _plugin("ticker")
+        lock.acquire()
+        c._display_once(ticker, "ticker", False, report_hold=True)
+        lock.release()
+        c._display_once(ticker, "ticker", False)        # the 1 Hz loop draws
+        assert c._display_hold is None
+        clock.t += 5.0
+        c._display_once(ticker, "ticker", False, report_hold=True)
+        c.plugin_manager._warn_rate_limited.assert_not_called()

test/test_error_snapshot_cross_process.py

@@ -430,6 +430,157 @@ class TestClear:
         assert "clear request" in response.get_json()["message"]
 
 
+CLIENT = "web_interface.blueprints.api_v3.control_client"
+
+
+def _mailbox_file(shared_cache):
+    _, _, directory = shared_cache
+    return directory / f"{ERROR_CLEAR_REQUEST_KEY}.json"
+
+
+class TestClearOverTheSocket:
+    """``errors.clear``: the display applies the clear before it answers, and
+    the mailbox is written only when the socket could not carry it."""
+
+    @pytest.fixture
+    def socket_up(self, display, monkeypatch):
+        """The control socket, as the display serves it: errors_clear runs
+        the display's own handler against its publisher."""
+        from src.ipc import client as control_client
+        from src.ipc.contract import ErrorsClearArgs
+        _, publisher, _ = display
+        monkeypatch.setattr(errors, "_snapshot_publisher", publisher)
+        calls = []
+
+        def errors_clear(request_id, cutoff, **kw):
+            calls.append((request_id, cutoff))
+            return errors.apply_error_clear(request_id, ErrorsClearArgs(cutoff=cutoff))
+
+        monkeypatch.setattr(f"{CLIENT}.errors_clear", errors_clear)
+        assert control_client.errors_clear is errors_clear
+        return calls
+
+    def test_socket_clear_is_applied_before_the_answer(self, web, display, socket_up,
+                                                       shared_cache):
+        aggregator, publisher, _ = display
+        for _ in range(3):
+            _fail(aggregator)
+        publisher.tick()
+        response = web.post("/api/v3/errors/clear", json={"all": True})
+        assert response.status_code == 200
+        body = response.get_json()
+        data = body["data"]
+        assert data["transport"] == "socket" and data["applied"] is True
+        assert data["cleared_count"] == 3
+        assert body["message"] == "Cleared all errors"
+        [(request_id, _)] = socket_up
+        assert data["request_id"] == request_id
+        # Applied already: no display tick needed, nothing pending.
+        assert aggregator.get_error_summary()["total_errors"] == 0
+        summary = _summary(web)
+        assert summary["total_errors"] == 0 and summary["clear_pending"] is False
+        # And no mailbox file.
+        assert not _mailbox_file(shared_cache).exists()
+
+    def test_an_older_mailbox_request_does_not_read_as_pending(self, web, display, socket_up,
+                                                               shared_cache, monkeypatch):
+        # A clear that went to the mailbox while the socket was down, then a
+        # wider one over the socket: the old request has nothing left to hide.
+        from unittest.mock import patch
+        from src.ipc import client as control_client
+        aggregator, publisher, _ = display
+        _fail(aggregator)
+        publisher.tick()
+        with patch(f"{CLIENT}.errors_clear",
+                   side_effect=control_client.ControlError("no_socket")):
+            data = web.post("/api/v3/errors/clear", json={"max_age_hours": 1}).get_json()["data"]
+        assert data["transport"] == "mailbox"
+        assert _mailbox_file(shared_cache).exists()
+        data = web.post("/api/v3/errors/clear", json={"all": True}).get_json()["data"]
+        assert data["transport"] == "socket"
+        assert _summary(web)["clear_pending"] is False
+
+    @pytest.mark.parametrize("reason", ["no_socket", "refused", "disabled", "unsupported"])
+    def test_no_socket_writes_the_mailbox(self, web, display, shared_cache, monkeypatch, reason):
+        from src.ipc import client as control_client
+        monkeypatch.setattr(f"{CLIENT}.errors_clear", MagicMock(
+            side_effect=control_client.ControlError(reason, sent=False)))
+        aggregator, publisher, _ = display
+        _fail(aggregator)
+        publisher.tick()
+        data = web.post("/api/v3/errors/clear", json={"all": True}).get_json()["data"]
+        assert data["transport"] == "mailbox" and data["applied"] is False
+        assert _mailbox_file(shared_cache).exists()
+        assert _summary(web)["clear_pending"] is True
+        publisher.tick()
+        assert aggregator.get_error_summary()["total_errors"] == 0
+
+    def test_an_older_display_gets_the_mailbox(self, web, display, shared_cache, monkeypatch):
+        # The upgrade case: new web interface, a display from before errors.clear.
+        from src.ipc import client as control_client
+        monkeypatch.setattr(f"{CLIENT}.errors_clear", MagicMock(
+            side_effect=control_client.ControlError("unknown_command", sent=True)))
+        aggregator, publisher, _ = display
+        _fail(aggregator)
+        publisher.tick()
+        data = web.post("/api/v3/errors/clear", json={"all": True}).get_json()["data"]
+        assert data["transport"] == "mailbox"
+        publisher.tick()
+        assert aggregator.get_error_summary()["total_errors"] == 0
+
+    @pytest.mark.parametrize("reason", ["internal", "timeout", "busy", "invalid_args"])
+    def test_a_display_that_had_it_and_failed_is_an_error(self, web, display, shared_cache,
+                                                         monkeypatch, reason):
+        from src.ipc import client as control_client
+        monkeypatch.setattr(f"{CLIENT}.errors_clear", MagicMock(
+            side_effect=control_client.ControlError(reason, sent=True)))
+        response = web.post("/api/v3/errors/clear", json={"all": True})
+        assert response.status_code == 503
+        assert response.get_json()["context"]["socket_error"] == reason
+        assert not _mailbox_file(shared_cache).exists()
+
+
+class TestPublisherMailboxPoll:
+    def test_the_mailbox_is_read_only_when_its_file_changed(self, display, shared_cache):
+        _, publisher, _ = display
+        _, web_cache, _ = shared_cache
+        publisher.tick()
+        publisher.cache_manager = MagicMock(wraps=publisher.cache_manager)
+
+        def reads():
+            return [c for c in publisher.cache_manager.get.call_args_list
+                    if c.args[0] == ERROR_CLEAR_REQUEST_KEY]
+
+        for _ in range(5):
+            publisher.tick()
+        assert reads() == []          # no file: a stat per tick, no read
+        errors.request_error_clear(web_cache, 1.0)
+        publisher.tick()
+        assert len(reads()) == 1
+        for _ in range(5):
+            publisher.tick()
+        assert len(reads()) == 1      # unchanged file: not read again
+        errors.request_error_clear(web_cache, 2.0)
+        publisher.tick()
+        assert len(reads()) == 2
+
+    def test_clear_now_publishes_what_it_applied(self, display, shared_cache):
+        aggregator, publisher, _ = display
+        _, web_cache, _ = shared_cache
+        _fail(aggregator)
+        assert publisher.clear_now("sock-1", datetime.now().timestamp() + 1) == 1
+        snapshot = web_cache.get(ERROR_SNAPSHOT_KEY, max_age=None, memory_ttl=0)
+        assert snapshot["applied_clear_id"] == "sock-1"
+        assert snapshot["total_errors"] == 0
+        assert snapshot["applied_clear_cutoff"] is not None
+
+    def test_the_handler_needs_a_running_publisher(self, monkeypatch):
+        from src.ipc.contract import ErrorsClearArgs
+        monkeypatch.setattr(errors, "_snapshot_publisher", None)
+        with pytest.raises(RuntimeError):
+            errors.apply_error_clear("x", ErrorsClearArgs(cutoff=1.0))
+
+
 @pytest.mark.skipif(not hasattr(os, "fchmod") or os.name == "nt",
                     reason="POSIX file modes")
 def test_both_files_are_group_readable(web, display, shared_cache):

test/test_espn_dates.py

@@ -489,3 +489,171 @@ class TestConcurrency:
 
         assert live["peak"] <= espn_dates.ESPN_CHUNK_WORKERS
         assert live["peak"] > 1, "chunks should actually overlap"
+
+
+class TestEdgeMonths:
+    """A window's partial edge months are asked whole and trimmed.
+
+    The default scoreboard window -- a fortnight either side of today -- spans
+    two partial months, so it used to cost 29 day requests per league. ESPN's
+    ``dates=YYYYMMDD`` means a US Eastern day (verified against the live API
+    on 2026-10-03, 417 of 417 soccer events), so a month answer trimmed to
+    the window's Eastern days is what the day requests returned.
+    """
+
+    def test_a_fortnight_either_side_is_two_requests(self):
+        planned = espn_dates.espn_request_chunks(date(2026, 9, 20), date(2026, 10, 18))
+        assert planned == [
+            ("202609", (date(2026, 9, 20), date(2026, 9, 30))),
+            ("202610", (date(2026, 10, 1), date(2026, 10, 18))),
+        ]
+
+    def test_a_live_polls_two_days_stay_two_days(self):
+        planned = espn_dates.espn_request_chunks(date(2026, 10, 2), date(2026, 10, 3))
+        assert planned == [("20261002", None), ("20261003", None)]
+
+    def test_the_threshold_is_inclusive(self):
+        n = espn_dates.ESPN_MONTH_COVER_MIN_DAYS
+        short = espn_dates.espn_request_chunks(date(2026, 10, 1), date(2026, 10, n - 1))
+        assert [chunk for chunk, _ in short] == [
+            "202610%02d" % day for day in range(1, n)]
+        enough = espn_dates.espn_request_chunks(date(2026, 10, 1), date(2026, 10, n))
+        assert enough == [("202610", (date(2026, 10, 1), date(2026, 10, n)))]
+
+    def test_whole_months_and_short_edges_are_unchanged(self):
+        planned = espn_dates.espn_request_chunks(date(2026, 8, 30), date(2026, 10, 2))
+        assert planned == [
+            ("20260830", None), ("20260831", None), ("202609", None),
+            ("20261001", None), ("20261002", None),
+        ]
+
+    def test_without_time_zone_data_edges_stay_days(self, monkeypatch):
+        monkeypatch.setattr(espn_dates, "_EASTERN", None)
+        planned = espn_dates.espn_request_chunks(date(2026, 9, 20), date(2026, 10, 18))
+        assert len(planned) == 29
+        assert all(trim is None for _, trim in planned)
+
+    @pytest.mark.parametrize("start,end", [
+        (date(2026, 9, 20), date(2026, 10, 18)),
+        (date(2026, 1, 25), date(2026, 3, 3)),
+        (date(2026, 12, 20), date(2027, 1, 9)),
+        (date(2026, 10, 5), date(2026, 10, 9)),
+    ])
+    def test_the_planned_requests_still_cover_every_day_exactly_once(self, start, end):
+        covered = []
+        for chunk, trim in espn_dates.espn_request_chunks(start, end):
+            if trim is None:
+                covered.extend(days_covered_by([chunk]))
+            else:
+                assert chunk == trim[0].strftime("%Y%m") == trim[1].strftime("%Y%m")
+                covered.extend(trim[0] + timedelta(days=offset)
+                               for offset in range((trim[1] - trim[0]).days + 1))
+        expected = [start + timedelta(days=offset) for offset in range((end - start).days + 1)]
+        assert covered == expected
+
+    def test_a_trimmed_month_keeps_only_the_windows_eastern_days(self):
+        september = [
+            # 03:30Z on the 20th is still the 19th in New York: outside.
+            {"id": "before", "date": "2026-09-20T03:30Z"},
+            {"id": "first", "date": "2026-09-20T14:00Z"},
+            {"id": "late", "date": "2026-09-30T23:30Z"},
+        ]
+        october = [
+            {"id": "oct1", "date": "2026-10-01T19:00Z"},
+            # 03:30Z on the 19th is the evening of the 18th in New York: inside.
+            {"id": "last", "date": "2026-10-19T03:30Z"},
+            {"id": "after", "date": "2026-10-19T14:00Z"},
+            {"id": "undated"},
+        ]
+        session = FakeSession({"202609": september, "202610": october})
+
+        data = fetch_espn_date_chunks(session, URL, params={"dates": "20260920-20261018"})
+
+        assert sorted(call["dates"] for call in session.calls) == ["202609", "202610"]
+        # An event with no readable date is kept, never dropped on a guess.
+        assert [e["id"] for e in data["events"]] == ["first", "late", "oct1", "last", "undated"]
+
+    def test_eastern_standard_time_is_honoured_after_the_clocks_change(self):
+        # 2026-11-01 ends daylight saving: Eastern is UTC-5 from then on.
+        november = [
+            {"id": "out", "date": "2026-11-15T04:30Z"},  # Nov 14, 23:30 EST
+            {"id": "in", "date": "2026-11-15T05:30Z"},   # Nov 15, 00:30 EST
+        ]
+        session = FakeSession({"202611": november})
+        data = fetch_espn_date_chunks(session, URL, params={"dates": "20261115-20261121"})
+        assert [e["id"] for e in data["events"]] == ["in"]
+
+    def test_a_capped_edge_month_re_asks_only_the_windows_days(self):
+        full = [{"id": "cap%d" % i, "date": "2026-10-05T18:00Z"} for i in range(ESPN_MAX_LIMIT)]
+        by_chunk = {"202610": full}
+        by_chunk.update({"202610%02d" % day: [{"id": "o%02d" % day}] for day in range(1, 32)})
+        session = FakeSession(by_chunk)
+
+        data = fetch_espn_date_chunks(session, URL, params={"dates": "20261001-20261010"})
+
+        sent = [call["dates"] for call in session.calls]
+        assert sent[0] == "202610"
+        assert sorted(sent[1:]) == ["202610%02d" % day for day in range(1, 11)]
+        assert [e["id"] for e in data["events"]] == ["o%02d" % day for day in range(1, 11)]
+
+
+class TestProcessWideChunkCap:
+    """The chunk cap holds across windows, not per window.
+
+    A soccer board starting eight leagues fetches sixteen windows at once.
+    With a pool of ``ESPN_CHUNK_WORKERS`` each, ~40 requests were in flight
+    and every one past a session's pool opened a connection -- and a DNS
+    lookup. On ledpi that was ~90 NameResolutionErrors per start.
+    """
+
+    def test_concurrent_windows_share_one_budget(self):
+        live = {"now": 0, "peak": 0}
+        guard = threading.Lock()
+
+        class CountingSession(FakeSession):
+            def get(self, url, params=None, headers=None, timeout=None):
+                with guard:
+                    live["now"] += 1
+                    live["peak"] = max(live["peak"], live["now"])
+                try:
+                    time.sleep(0.01)
+                    return super().get(url, params=params, headers=headers, timeout=timeout)
+                finally:
+                    with guard:
+                        live["now"] -= 1
+
+        sessions = [CountingSession() for _ in range(6)]
+        # Six leagues, so the fetch service cannot merge them into one, on a
+        # host with no token bucket: earlier tests may have spent ESPN's
+        # burst, and a bucket paced at 20/s would serialise these by itself.
+        threads = [
+            threading.Thread(target=fetch_espn_date_chunks,
+                             args=(session, "https://scores.example.test/league%d" % index),
+                             kwargs={"params": {"dates": "20260101-20261231"}})
+            for index, session in enumerate(sessions)
+        ]
+        for thread in threads:
+            thread.start()
+        for thread in threads:
+            thread.join(timeout=30)
+
+        assert all(len(session.calls) == 12 for session in sessions)
+        assert live["peak"] <= espn_dates.ESPN_CHUNK_WORKERS
+        assert live["peak"] > 1, "chunks should still overlap"
+
+
+def test_a_fresh_process_skips_the_doomed_range_request():
+    """Every start used to spend one 400 per window learning that ranges are
+    still rejected -- eleven at once from a soccer board. A new process now
+    starts inside the retry period instead."""
+    import subprocess
+    import sys
+    from pathlib import Path
+
+    out = subprocess.run(
+        [sys.executable, "-c",
+         "import src.common.espn_dates as e; print(e._ranges_known_rejected())"],
+        cwd=str(Path(__file__).resolve().parents[1]),
+        capture_output=True, text=True, timeout=60,
+    )
+    assert out.stdout.strip() == "True", out.stderr

test/test_fetch_service.py

@@ -576,6 +576,42 @@ class TestCounters:
         assert snap["hosts"]["site.api.espn.com"]["requests"] == 1
         assert snap["totals"]["bytes"] == 3 * len(b'{"ok": 1}')
 
+    def test_wire_bytes_are_the_compressed_size(self, service):
+        # Built the way requests builds a real response: a urllib3
+        # HTTPResponse carrying a gzip body, decoded when .content is read.
+        import gzip
+        import io
+
+        from requests.adapters import HTTPAdapter
+        from urllib3.response import HTTPResponse
+
+        decoded = json.dumps({"events": [{"id": str(i), "name": "x" * 200}
+                                         for i in range(50)]}).encode()
+        wire = gzip.compress(decoded)
+
+        def handler(url, kwargs):
+            raw = HTTPResponse(body=io.BytesIO(wire), status=200,
+                               headers={"Content-Encoding": "gzip",
+                                        "Content-Type": "application/json"},
+                               preload_content=False, decode_content=True)
+            request = requests.Request("GET", url).prepare()
+            response = HTTPAdapter().build_response(request, raw)
+            response.content  # what Session.get does for a non-streamed call
+            return response
+
+        response = service.get(FakeSession(handler), "https://site.api.espn.com/x")
+        assert response.content == decoded
+        totals = _counters(service)
+        assert totals["bytes"] == len(decoded)
+        assert totals["wire_bytes"] == len(wire) < len(decoded)
+
+    def test_wire_bytes_fall_back_to_the_decoded_size(self, service):
+        # No urllib3 response behind it (a test double, another adapter):
+        # count what is known rather than nothing.
+        service.get(FakeSession(), "https://api.test/x")
+        totals = _counters(service)
+        assert totals["wire_bytes"] == totals["bytes"] == len(b'{"ok": 1}')
+
     def test_errors_and_http_errors(self, service):
         def handler(url, kwargs):
             if url.endswith("/down"):
@@ -670,14 +706,14 @@ class TestCallerIdentity:
         assert _counters(global_service, plugin="football-scoreboard")["requests"] == 1
 
     def test_espn_chunks_on_worker_threads_count_against_the_caller(self, global_service):
-        from src.common.espn_dates import espn_date_chunks, fetch_espn_date_chunks, parse_espn_date_range
+        from src.common.espn_dates import espn_request_chunks, fetch_espn_date_chunks, parse_espn_date_range
 
         session = FakeSession(lambda url, kw: make_response(body=b'{"events": []}', url=url))
         dates = "20260801-20261015"
         with plugin_scope("baseball-scoreboard"):
             fetch_espn_date_chunks(session, "https://site.api.espn.com/s/scoreboard",
                                    params={"dates": dates})
-        chunks = len(espn_date_chunks(*parse_espn_date_range(dates)))
+        chunks = len(espn_request_chunks(*parse_espn_date_range(dates)))
         assert chunks > 1
         assert len(session.calls) == chunks
         assert _counters(global_service, plugin="baseball-scoreboard")["requests"] == chunks

test/test_font_manager.py

@@ -185,6 +185,149 @@ class TestPluginFonts:
         assert fm.font_catalog["my-plugin::bundled"] == str(plugin_dir / "fonts" / "Bundled.ttf")
 
 
+class TestForgetPluginFonts:
+    """forget_plugin_fonts drops what a plugin's manifest registered. Before
+    it, unloading a plugin left its fonts resolvable and its cached font
+    objects alive until a restart."""
+
+    @staticmethod
+    def _register(fm, root, plugin_id, family="bundled"):
+        plugin_dir = root / plugin_id
+        (plugin_dir / "fonts").mkdir(parents=True, exist_ok=True)
+        font_file = plugin_dir / "fonts" / f"{family}.ttf"
+        if not font_file.exists():  # a loaded font may hold it open (Windows)
+            shutil.copy(resolve_asset_path("assets/fonts/PressStart2P-Regular.ttf"), font_file)
+        manifest = {"fonts": [{"family": family, "source": f"plugin://fonts/{family}.ttf"}]}
+        assert fm.register_plugin_fonts(plugin_id, manifest, plugin_dir=plugin_dir)
+        return plugin_dir
+
+    @staticmethod
+    def _entries_of(fm, plugin_id):
+        prefix = f"{plugin_id}::"
+        return {
+            "plugin_fonts": plugin_id in fm.plugin_fonts,
+            "plugin_font_catalogs": plugin_id in fm.plugin_font_catalogs,
+            "font_catalog": [k for k in fm.font_catalog if k.startswith(prefix)],
+            "font_cache": [k for k in fm.font_cache if k.startswith(prefix)],
+        }
+
+    NONE = {"plugin_fonts": False, "plugin_font_catalogs": False,
+            "font_catalog": [], "font_cache": []}
+
+    def test_unload_leaves_no_plugin_entries(self, fm, tmp_path):
+        self._register(fm, tmp_path, "alpha")
+        fm.resolve_font("alpha.title", "bundled", 8, plugin_id="alpha")
+        fm.get_font("alpha::bundled", 10)
+        assert self._entries_of(fm, "alpha")["font_cache"]  # cached before
+        gen = fm.cache_generation
+
+        assert fm.forget_plugin_fonts("alpha") is True
+
+        assert self._entries_of(fm, "alpha") == self.NONE
+        assert fm.cache_generation == gen + 1
+        # The family no longer resolves to the plugin's file.
+        assert fm.font_catalog.get("alpha::bundled") is None
+
+    def test_other_plugins_and_core_fonts_are_untouched(self, fm, tmp_path):
+        self._register(fm, tmp_path, "alpha")
+        self._register(fm, tmp_path, "beta")
+        # A plugin whose id is a prefix of another's must not take it along.
+        self._register(fm, tmp_path, "alpha-two")
+        for pid in ("alpha", "beta", "alpha-two"):
+            fm.get_font(f"{pid}::bundled", 8)
+        core_font = fm.get_font("press_start", 8)
+        beta_before = self._entries_of(fm, "beta")
+        alpha_two_before = self._entries_of(fm, "alpha-two")
+
+        fm.forget_plugin_fonts("alpha")
+
+        assert self._entries_of(fm, "beta") == beta_before
+        assert self._entries_of(fm, "alpha-two") == alpha_two_before
+        assert fm.get_font("press_start", 8) is core_font
+
+    def test_reload_re_registers_cleanly(self, fm, tmp_path):
+        plugin_dir = self._register(fm, tmp_path, "alpha")
+        old = fm.get_font("alpha::bundled", 8)
+        fm.forget_plugin_fonts("alpha")
+
+        self._register(fm, tmp_path, "alpha")
+
+        assert fm.font_catalog["alpha::bundled"] == str(plugin_dir / "fonts" / "bundled.ttf")
+        font = fm.resolve_font("alpha.title", "bundled", 8, plugin_id="alpha")
+        assert isinstance(font, ImageFont.FreeTypeFont)
+        assert font is not old  # loaded fresh, not the dropped cache entry
+
+    def test_a_family_the_new_manifest_drops_stops_resolving(self, fm, tmp_path):
+        self._register(fm, tmp_path, "alpha", family="old_face")
+        fm.forget_plugin_fonts("alpha")
+        self._register(fm, tmp_path, "alpha", family="new_face")
+
+        assert "alpha::old_face" not in fm.font_catalog
+        assert "alpha::new_face" in fm.font_catalog
+
+    def test_unknown_plugin_is_a_no_op(self, fm):
+        catalog = dict(fm.font_catalog)
+        gen = fm.cache_generation
+
+        assert fm.forget_plugin_fonts("never-registered") is False
+
+        assert fm.font_catalog == catalog
+        assert fm.cache_generation == gen
+
+
+class TestPluginManagerReloadFonts:
+    """Through PluginManager: unloading a plugin forgets its manifest fonts,
+    and reload_plugin (unload + load) registers them again so they resolve."""
+
+    PLUGIN_ID = "font-reload-demo"
+    MODULE = "plugin_font_reload_demo"
+
+    def test_unload_forgets_and_reload_resolves(self, tmp_path):
+        import sys
+        from src.plugin_system.plugin_manager import PluginManager
+
+        plugins_dir = tmp_path / "plugins"
+        plugin_dir = plugins_dir / self.PLUGIN_ID
+        (plugin_dir / "fonts").mkdir(parents=True)
+        shutil.copy(resolve_asset_path("assets/fonts/PressStart2P-Regular.ttf"),
+                    plugin_dir / "fonts" / "Bundled.ttf")
+        manifest = {"id": self.PLUGIN_ID, "name": "Demo", "class_name": "Demo",
+                    "entry_point": "manager.py",
+                    "fonts": {"fonts": [{"family": "bundled",
+                                         "source": "plugin://fonts/Bundled.ttf"}]}}
+        (plugin_dir / "manifest.json").write_text(json.dumps(manifest), encoding="utf-8")
+        (plugin_dir / "manager.py").write_text(
+            "class Demo:\n"
+            "    def __init__(self, plugin_id, config, display_manager, cache_manager, plugin_manager):\n"
+            "        self.enabled = True\n", encoding="utf-8")
+
+        pm = PluginManager(plugins_dir=str(plugins_dir))
+        fm = FontManager({})
+        pm.font_manager = fm
+        pm.plugin_manifests[self.PLUGIN_ID] = manifest
+        key = f"{self.PLUGIN_ID}::bundled"
+        try:
+            assert pm.load_plugin(self.PLUGIN_ID) is True
+            assert key in fm.font_catalog
+            fm.register_manager_font(self.PLUGIN_ID, "demo.title", "bundled", 8)
+            old = fm.resolve_font("demo.title", "bundled", 8, plugin_id=self.PLUGIN_ID)
+
+            assert pm.unload_plugin(self.PLUGIN_ID) is True
+            assert self.PLUGIN_ID not in fm.plugin_fonts
+            assert self.PLUGIN_ID not in fm.plugin_font_catalogs
+            assert key not in fm.font_catalog
+            assert not [k for k in fm.font_cache if k.startswith(f"{self.PLUGIN_ID}::")]
+            assert self.PLUGIN_ID not in fm.manager_fonts
+
+            assert pm.reload_plugin(self.PLUGIN_ID) is True
+            assert fm.font_catalog[key] == str(plugin_dir / "fonts" / "Bundled.ttf")
+            font = fm.resolve_font("demo.title", "bundled", 8, plugin_id=self.PLUGIN_ID)
+            assert isinstance(font, ImageFont.FreeTypeFont)
+            assert font is not old
+        finally:
+            sys.modules.pop(self.MODULE, None)
+
+
 class TestDownloadFont:
     """_download_font: plugin fonts declared by URL, cached in temp_font_dir."""
 

test/test_handover_scroll_state.py

@@ -709,6 +709,6 @@ class TestTheControllersOwnScreens:
         c._check_wifi_status_message.return_value = None
         inputs = DisplayController._arbiter_inputs(c)
         assert inputs.wifi_notice is None
-        assert Arbiter.decide(ArbiterState(), inputs, 0.0).source is Source.LEGACY
+        assert Arbiter.decide(ArbiterState(), inputs, 0.0).source is Source.ROTATION
         assert dm.is_currently_scrolling()
         assert dm._frame_hold == 2

test/test_installed_list_registry_offline.py

@@ -0,0 +1,188 @@
+"""GET /api/v3/plugins/installed never waits on the network for registry data.
+
+The route used `get_registry_info`, which goes through `fetch_registry`: on a
+cold (or expired) cache that downloads plugins.json from GitHub with a 10s
+timeout and three attempts -- and, with no registry to fall back on, every
+plugin's lookup repeated the whole cycle. The first plugin-list load after a
+restart waited on GitHub, and offline it waited out every timeout.
+
+Now the route reads the registry copy already in memory, however old, and a
+missing or expired copy only starts a background refresh. These tests block
+the network at the socket layer (DNS lookups hang, then fail) and assert the
+request returns quickly without a single network attempt on the request path.
+"""
+
+import functools
+import socket
+import threading
+import time
+from unittest.mock import MagicMock
+
+import pytest
+import requests
+
+from test._api_v3_test_helpers import (  # noqa: F401 - fixtures
+    api_v3_client, api_v3_module,
+)
+from src.plugin_system.store_manager import PluginStoreManager
+
+# How long a blocked lookup hangs before failing: long enough that a single
+# one on the request path blows the response budget below.
+HANG_SECONDS = 1.5
+FAST_SECONDS = 1.0
+
+REGISTRY = {'plugins': [
+    {'id': 'weather', 'name': 'Weather', 'verified': True, 'latest_version': '1.2.0'},
+]}
+
+
+@pytest.fixture
+def blocked_network(monkeypatch):
+    """Every DNS lookup hangs, then fails; records the thread it came from."""
+    attempts = []
+
+    def hang_then_fail(host, *args, **kwargs):
+        attempts.append((host, threading.current_thread().name))
+        time.sleep(HANG_SECONDS)
+        raise socket.gaierror(-3, 'Temporary failure in name resolution (blocked by test)')
+
+    monkeypatch.setattr(socket, 'getaddrinfo', hang_then_fail)
+    return attempts
+
+
+@pytest.fixture
+def store(tmp_path, monkeypatch):
+    store = PluginStoreManager(plugins_dir=str(tmp_path / 'plugins'))
+    # One attempt, no pause between attempts, so a background refresh against
+    # the blocked network ends within the test (teardown joins it).
+    monkeypatch.setattr(store, '_http_get_with_retries', functools.partial(
+        PluginStoreManager._http_get_with_retries, store, max_retries=1))
+    yield store
+    thread = getattr(store, '_registry_refresh_thread', None)
+    if thread is not None:
+        thread.join(timeout=30)
+
+
+@pytest.fixture
+def get_installed(api_v3_module, api_v3_client, store, tmp_path):
+    api = api_v3_module.api_v3
+    api.plugin_store_manager = store
+    api.plugin_catalog.plugins_dir = str(tmp_path / 'plugins')
+    api.plugin_catalog.get_all_plugin_info = MagicMock(return_value=[
+        {'id': 'weather', 'name': 'Weather', 'version': '1.0.0'},
+        {'id': 'clock', 'name': 'Clock', 'version': '2.0.0'},
+    ])
+    api.plugin_catalog.get_plugin_display_modes = MagicMock(return_value=[])
+    api.config_manager.load_config = MagicMock(return_value={})
+
+    def _get():
+        start = time.perf_counter()
+        response = api_v3_client.get('/api/v3/plugins/installed')
+        elapsed = time.perf_counter() - start
+        assert response.status_code == 200
+        plugins = {p['id']: p for p in response.get_json()['data']['plugins']}
+        return plugins, elapsed
+    return _get
+
+
+def _request_path_attempts(attempts):
+    return [a for a in attempts if a[1] != 'registry-refresh']
+
+
+def test_a_cold_cache_offline_returns_fast_without_registry_info(get_installed, blocked_network):
+    plugins, elapsed = get_installed()
+
+    assert _request_path_attempts(blocked_network) == []
+    assert elapsed < FAST_SECONDS, f"installed list took {elapsed:.2f}s with the network blocked"
+    weather = plugins['weather']
+    assert weather['latest_version'] == ''
+    assert weather['update_available'] is False
+    assert weather['verified'] is False
+
+
+def test_a_stale_cache_is_used_as_is_without_a_fetch(get_installed, store, blocked_network):
+    store.registry_cache = REGISTRY
+    store.registry_cache_time = time.time() - store.registry_cache_timeout - 3600
+
+    plugins, elapsed = get_installed()
+
+    assert _request_path_attempts(blocked_network) == []
+    assert elapsed < FAST_SECONDS
+    weather = plugins['weather']
+    assert weather['latest_version'] == '1.2.0'
+    assert weather['update_available'] is True
+    assert weather['verified'] is True
+    assert plugins['clock']['latest_version'] == ''
+
+
+def test_a_fresh_cache_starts_no_refresh(get_installed, store, blocked_network):
+    store.registry_cache = REGISTRY
+    store.registry_cache_time = time.time()
+
+    plugins, _ = get_installed()
+
+    assert blocked_network == []
+    assert store._registry_refresh_thread is None
+    assert plugins['weather']['update_available'] is True
+
+
+def test_a_cold_cache_is_filled_in_the_background_for_the_next_load(get_installed, store, monkeypatch):
+    response = MagicMock()
+    response.json.return_value = REGISTRY
+    fetched_on = []
+
+    def fake_get(url, **kwargs):
+        fetched_on.append(threading.current_thread().name)
+        return response
+
+    monkeypatch.setattr(store, '_http_get_with_retries', fake_get)
+
+    first, _ = get_installed()
+    assert first['weather']['update_available'] is False
+    store._registry_refresh_thread.join(timeout=10)
+
+    second, _ = get_installed()
+    assert second['weather']['latest_version'] == '1.2.0'
+    assert second['weather']['update_available'] is True
+    # One background fetch for the whole listing, none on the request path.
+    assert fetched_on == ['registry-refresh']
+
+
+def test_an_offline_background_refresh_backs_off(store, monkeypatch):
+    def offline(url, **kwargs):
+        raise requests.ConnectionError('blocked by test')
+
+    monkeypatch.setattr(store, '_http_get_with_retries', offline)
+
+    assert store.refresh_registry_in_background() is True
+    store._registry_refresh_thread.join(timeout=10)
+    assert store.registry_cache is None
+    # Offline: the next page load does not start another attempt straight away.
+    assert store.refresh_registry_in_background() is False
+    store._registry_refresh_retry_after = 0.0
+    assert store.refresh_registry_in_background() is True
+
+
+def test_only_one_background_refresh_runs_at_a_time(store, monkeypatch):
+    release = threading.Event()
+
+    def slow(url, **kwargs):
+        release.wait(10)
+        raise requests.ConnectionError('blocked by test')
+
+    monkeypatch.setattr(store, '_http_get_with_retries', slow)
+    try:
+        assert store.refresh_registry_in_background() is True
+        assert store.refresh_registry_in_background() is False
+    finally:
+        release.set()
+
+
+def test_get_registry_info_still_fetches_for_the_store(store, monkeypatch):
+    """The store, install and update paths keep fetching a cold registry."""
+    response = MagicMock()
+    response.json.return_value = REGISTRY
+    monkeypatch.setattr(store, '_http_get_with_retries', MagicMock(return_value=response))
+
+    assert store.get_registry_info('weather')['latest_version'] == '1.2.0'
+    store._http_get_with_retries.assert_called_once()

test/test_ipc_contract.py

@@ -167,7 +167,8 @@ class TestOnDemandArgs:
     def test_every_command_has_an_argument_type(self, cmd):
         args = {Command.ON_DEMAND_START: {'plugin_id': 'p'},
                 Command.PLUGIN_RELOAD: {'plugin_id': 'p'},
-                Command.BRIGHTNESS_SET: {'brightness': 50}}.get(cmd, {})
+                Command.BRIGHTNESS_SET: {'brightness': 50},
+                Command.ERRORS_CLEAR: {'cutoff': 1790000000.0}}.get(cmd, {})
         c.parse_args(cmd, args)
 
     def test_hello_versions(self):

test/test_ipc_display_stage2.py

@@ -41,6 +41,15 @@ def _reload(plugin_id):
     return _command(Command.PLUGIN_RELOAD, PluginReloadArgs(plugin_id))
 
 
+def _screen(mode):
+    """A rotation screen of ``mode``, as the ScreenRunner hands it to the
+    1 Hz loop's frame wait."""
+    from src.display_arbiter import ArbiterState, rotation_plan
+    from src.screen_runner import Screen
+    plan = rotation_plan(ArbiterState(current_mode=mode))
+    return Screen(plan, plugin=None, accepts_display_mode=False, start=0.0)
+
+
 @pytest.fixture
 def dc(test_display_controller):
     c = test_display_controller
@@ -253,7 +262,8 @@ class TestRealTimeWake:
         dc.on_demand_active = False
         dc._activate_on_demand = MagicMock(
             side_effect=lambda request: setattr(dc, 'current_display_mode', 'weather'))
-        dc._wifi_notice_pending = MagicMock(return_value=False)
+        dc._wifi_notice_pending = MagicMock(return_value=False)   # the dwell's check
+        dc._read_wifi_notice = MagicMock(return_value=None)       # the frame wait's
         dc._tick_plugin_updates = MagicMock()
         dc._check_live_takeover = MagicMock()
         dc.cache_manager.get = MagicMock(return_value=None)
@@ -282,10 +292,10 @@ class TestRealTimeWake:
             dc.current_display_mode = 'clock'
             stamps = []
             t = self._post_later(server, self._start_line(f's{i}'), 0.05, stamps)
-            ended = dc._wait_frame_interval(1.0, 'clock')
+            ended = dc._wait_frame_interval(1.0, _screen('clock'))
             woke = time.monotonic()
             t.join()
-            assert ended is True
+            assert ended is not None
             latencies.append(woke - stamps[0])
         latencies.sort()
         print(f"static-screen wake latency: median {latencies[5] * 1000:.2f} ms, "
@@ -315,7 +325,7 @@ class TestRealTimeWake:
                            'args': {'brightness': 33}}).encode()
         started = time.monotonic()
         t = self._post_later(server, line, 0.1, stamps)
-        assert dc._wait_frame_interval(0.5, 'clock') is False
+        assert dc._wait_frame_interval(0.5, _screen('clock')) is None
         assert time.monotonic() - started >= 0.49
         t.join()
         dc.display_manager.set_brightness.assert_called_once_with(33)
@@ -323,7 +333,7 @@ class TestRealTimeWake:
     def test_without_a_socket_it_is_a_plain_sleep(self, dc):
         dc._control_server = None
         started = time.monotonic()
-        assert dc._wait_frame_interval(0.2, 'clock') is False
+        assert dc._wait_frame_interval(0.2, _screen('clock')) is None
         assert time.monotonic() - started >= 0.19
 
 

test/test_ipc_stage4.py

@@ -0,0 +1,509 @@
+"""Stage 4 of the control socket: the file mailboxes are only a fallback.
+
+* The client knows whether the display had the request (``ControlError.sent``)
+  and ``should_fall_back`` allows a mailbox write only when it did not, or
+  when the display is too old to know the command (the upgrade case).
+* ``errors.clear`` is answered on the connection thread by a handler the
+  display registers; a display without one answers like an older display.
+* The display looks at the on-demand mailbox once a second while the socket
+  is up (0.25 s without it), reads it only when its file changed, never
+  touches it for a socket command, and logs who still writes it.
+* ``CacheManager.file_signature`` / ``MailboxWatch`` make a look one stat().
+
+The web routes are covered in test_api_v3_on_demand_socket.py and
+test_error_snapshot_cross_process.py.
+"""
+
+import json
+import logging
+import os
+import socket
+import time
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from src.cache_manager import CacheManager, MailboxWatch
+from src.ipc import client
+from src.ipc import contract as c
+from src.ipc.contract import Command, ErrorsClearArgs, OnDemandStartArgs, ProtocolError
+from src.ipc.server import ControlServer, QueuedCommand
+
+MAILBOX = 'display_on_demand_request'
+
+
+# -- the client: was the request sent? ---------------------------------------------
+
+class FakeSock:
+    """Stands in for a connected socket in client._exchange."""
+
+    def __init__(self, replies=(), send_error=None, recv_error=None):
+        self.replies = list(replies)
+        self.send_error = send_error
+        self.recv_error = recv_error
+        self.sent = b''
+
+    def settimeout(self, _t):
+        pass
+
+    def sendall(self, data):
+        if self.send_error is not None:
+            raise self.send_error
+        self.sent += data
+
+    def recv(self, _n):
+        if self.recv_error is not None:
+            raise self.recv_error
+        return self.replies.pop(0) if self.replies else b''
+
+    def close(self):
+        pass
+
+
+def _reply(request_id, **body):
+    return (json.dumps(dict({'v': 1, 'id': request_id}, **body)) + '\n').encode()
+
+
+def _call(sock=None, connect_error=None, request_id='rid-1'):
+    with patch.object(client, 'socket_supported', return_value=True), \
+         patch.object(client, '_connect',
+                      side_effect=connect_error, return_value=sock):
+        return client.request(Command.PING, {}, request_id=request_id, paths=['/x.sock'])
+
+
+def _error(**kw):
+    with pytest.raises(client.ControlError) as e:
+        _call(**kw)
+    return e.value
+
+
+class TestSent:
+    def test_an_answer_is_returned(self):
+        assert _call(FakeSock([_reply('rid-1', ok=True, result={'pong': True})])) == {'pong': True}
+
+    @pytest.mark.parametrize('reason', ['no_socket', 'refused', 'timeout', 'busy'])
+    def test_a_failed_connect_was_not_sent(self, reason):
+        e = _error(connect_error=client.ControlError(reason))
+        assert e.reason == reason and e.sent is False
+        assert client.should_fall_back(e)
+
+    def test_a_send_that_timed_out_was_not_sent(self):
+        e = _error(sock=FakeSock(send_error=socket.timeout()))
+        assert e.reason == 'timeout' and e.sent is False
+        assert client.should_fall_back(e)
+
+    def test_silence_after_the_request_was_sent(self):
+        e = _error(sock=FakeSock(recv_error=socket.timeout()))
+        assert e.reason == 'timeout' and e.sent is True
+        assert not client.should_fall_back(e)
+
+    def test_a_hang_up_after_the_request_was_sent(self):
+        e = _error(sock=FakeSock([]))
+        assert e.reason == 'closed' and e.sent is True
+        assert not client.should_fall_back(e)
+
+    def test_a_garbled_reply(self):
+        e = _error(sock=FakeSock([b'not json\n']))
+        assert e.reason == 'bad_response' and e.sent is True
+        assert not client.should_fall_back(e)
+
+    @pytest.mark.parametrize('code', ['busy', 'invalid_args', 'internal', 'pending', 'failed'])
+    def test_a_display_error_with_an_id_was_sent(self, code):
+        sock = FakeSock([_reply('rid-1', ok=False, error={'code': code, 'message': 'x'})])
+        e = _error(sock=sock)
+        assert e.reason == code and e.sent is True
+        assert not client.should_fall_back(e)
+
+    @pytest.mark.parametrize('code', ['forbidden', 'busy'])
+    def test_a_refusal_at_the_door_was_not_sent(self, code):
+        # forbidden, or too many connections: answered before the request
+        # was read, so with no id.
+        sock = FakeSock([(json.dumps({'v': 1, 'id': None, 'ok': False,
+                                      'error': {'code': code, 'message': 'x'}}) + '\n').encode()])
+        e = _error(sock=sock)
+        assert e.reason == code and e.sent is False
+        assert client.should_fall_back(e)
+
+    @pytest.mark.parametrize('code', ['unknown_command', 'unsupported_version'])
+    def test_an_older_display_is_fallen_back_from(self, code):
+        sock = FakeSock([_reply('rid-1', ok=False, error={'code': code, 'message': 'x'})])
+        e = _error(sock=sock)
+        assert e.sent is True
+        assert client.should_fall_back(e)
+
+    def test_a_request_refused_locally_never_left(self):
+        with pytest.raises(client.ControlError) as e:
+            client.request(Command.ERRORS_CLEAR, {'cutoff': 'soon'}, paths=['/x.sock'])
+        assert e.value.reason == 'invalid_request' and e.value.sent is False
+        assert client.should_fall_back(e.value)
+
+    def test_a_client_bug_falls_back(self):
+        assert client.should_fall_back(RuntimeError('boom'))
+
+
+# -- errors.clear on the server ------------------------------------------------------
+
+def _line(cmd, args, rid='r1'):
+    return c.encode_message({'v': 1, 'id': rid, 'cmd': cmd, 'args': args})
+
+
+class TestErrorsClearOnTheServer:
+    def test_the_handler_answers_it(self, tmp_path):
+        seen = []
+
+        def handler(request_id, args):
+            seen.append((request_id, args))
+            return {'request_id': request_id, 'cutoff': args.cutoff, 'cleared': 4}
+
+        server = ControlServer(str(tmp_path / 's.sock'),
+                               handlers={Command.ERRORS_CLEAR: handler})
+        response = server.handle_line(_line(Command.ERRORS_CLEAR, {'cutoff': 123}))
+        assert response.ok and response.result == {'request_id': 'r1', 'cutoff': 123.0,
+                                                   'cleared': 4}
+        assert seen == [('r1', ErrorsClearArgs(cutoff=123.0))]
+        assert not server.has_pending   # not queued for the render thread
+
+    def test_a_display_without_a_handler_answers_like_an_older_one(self, tmp_path):
+        server = ControlServer(str(tmp_path / 's.sock'))
+        response = server.handle_line(_line(Command.ERRORS_CLEAR, {'cutoff': 1}))
+        assert not response.ok and response.error.code == c.ErrorCode.UNKNOWN_COMMAND
+
+    def test_only_direct_commands_take_a_handler(self, tmp_path):
+        server = ControlServer(str(tmp_path / 's.sock'),
+                               handlers={Command.ON_DEMAND_START: lambda *a: {}})
+        response = server.handle_line(_line(Command.ON_DEMAND_START, {'plugin_id': 'p'}))
+        assert response.ok and response.result['accepted'] is True   # still queued
+        assert server.has_pending
+
+    def test_a_handler_error_is_contained(self, tmp_path):
+        def boom(*_a):
+            raise ValueError('disk gone')
+
+        server = ControlServer(str(tmp_path / 's.sock'), handlers={Command.ERRORS_CLEAR: boom})
+        response = server.handle_line(_line(Command.ERRORS_CLEAR, {'cutoff': 1}))
+        assert response.error.code == c.ErrorCode.INTERNAL
+        assert 'disk gone' not in response.error.message
+
+    def test_a_handler_can_refuse_with_a_code(self, tmp_path):
+        def refuse(*_a):
+            raise ProtocolError(c.ErrorCode.BUSY, 'later')
+
+        server = ControlServer(str(tmp_path / 's.sock'), handlers={Command.ERRORS_CLEAR: refuse})
+        assert server.handle_line(
+            _line(Command.ERRORS_CLEAR, {'cutoff': 1})).error.code == c.ErrorCode.BUSY
+
+    @pytest.mark.parametrize('cutoff', ['1', None, True, float('inf'), -1])
+    def test_bad_cutoffs_are_refused(self, cutoff):
+        with pytest.raises(ProtocolError) as e:
+            ErrorsClearArgs.from_dict({'cutoff': cutoff})
+        assert e.value.code == c.ErrorCode.INVALID_ARGS
+
+    def test_hello_lists_it(self, tmp_path):
+        server = ControlServer(str(tmp_path / 's.sock'))
+        result = server.handle_line(_line(Command.HELLO, {'versions': [1]})).result
+        assert Command.ERRORS_CLEAR in result['commands']
+
+
+# -- the display's mailbox poll ------------------------------------------------------
+
+class SignedCache:
+    """The slice of CacheManager the poll uses, counting what it costs."""
+
+    def __init__(self):
+        self.data = {}
+        self.writes = 0
+        self.version = {}
+        self.reads = []
+        self.stats = 0
+        self.deletes = []
+        self.sets = []
+
+    def file_signature(self, key):
+        self.stats += 1
+        return (self.version[key], 0, 0) if key in self.data else None
+
+    def get(self, key, *a, **kw):
+        self.reads.append(key)
+        return self.data.get(key)
+
+    def set(self, key, value, *a, **kw):
+        self.sets.append(key)
+        self.data[key] = value
+        self.writes += 1
+        self.version[key] = self.writes
+
+    def delete(self, key):
+        self.deletes.append(key)
+        self.data.pop(key, None)
+
+
+class FakeServer:
+    def __init__(self):
+        self.commands = []
+
+    @property
+    def has_pending(self):
+        return bool(self.commands)
+
+    def drain(self):
+        out, self.commands = self.commands, []
+        return out
+
+
+class Clock:
+    def __init__(self):
+        self.t = 1000.0
+
+    def __call__(self):
+        return self.t
+
+
+@pytest.fixture
+def controller(test_display_controller, monkeypatch):
+    dc = test_display_controller
+    dc.cache_manager = SignedCache()
+    dc._activate_on_demand = MagicMock()
+    dc.on_demand_active = False
+    dc.on_demand_request_id = None
+    dc._last_on_demand_poll = None
+    dc._on_demand_mailbox = None
+    dc._mailbox_writers_logged = frozenset()
+    clock = Clock()
+    monkeypatch.setattr('src.display_controller.time.monotonic', clock)
+    dc.clock = clock
+    return dc
+
+
+def _post(dc, rid, action='start', **fields):
+    dc.cache_manager.set(MAILBOX, dict({'request_id': rid, 'action': action}, **fields))
+
+
+def _poll_for(dc, seconds, step=1 / 16):   # exact in binary: no drift past a floor
+    end = dc.clock.t + seconds
+    while dc.clock.t < end:
+        dc._poll_on_demand_requests()
+        dc.clock.t += step
+
+
+class TestMailboxCadence:
+    def test_without_a_socket_it_is_looked_at_every_quarter_second(self, controller):
+        controller._control_server = None
+        _poll_for(controller, 10.0)
+        assert 38 <= controller.cache_manager.stats <= 42
+
+    def test_with_a_socket_it_is_looked_at_once_a_second(self, controller):
+        controller._control_server = FakeServer()
+        _poll_for(controller, 10.0)
+        assert 9 <= controller.cache_manager.stats <= 11
+
+    def test_a_look_that_finds_nothing_reads_nothing(self, controller):
+        controller._control_server = FakeServer()
+        _poll_for(controller, 10.0)
+        assert controller.cache_manager.reads == []
+
+    def test_an_unchanged_mailbox_is_not_read_again(self, controller):
+        # An already-processed start the delete could not remove, say.
+        controller._control_server = FakeServer()
+        controller.cache_manager.delete = MagicMock()   # the file stays
+        _post(controller, 'once', plugin_id='clock')
+        _poll_for(controller, 10.0)
+        assert controller.cache_manager.reads.count(MAILBOX) <= 2   # the read + the re-check
+        controller._activate_on_demand.assert_called_once()
+
+    def test_a_mailbox_request_lands_within_a_second_with_the_socket_up(self, controller):
+        # The upgrade case the other way round: a new display, and a web
+        # interface (or a plugin) that still writes the mailbox.
+        controller._control_server = FakeServer()
+        controller._poll_on_demand_requests()
+        controller.clock.t += 0.1
+        _post(controller, 'old-web', plugin_id='clock')
+        posted = controller.clock.t
+        while not controller._activate_on_demand.called:
+            controller._poll_on_demand_requests()
+            controller.clock.t += 0.05
+            assert controller.clock.t - posted < 1.5
+        assert controller.clock.t - posted <= controller.MAILBOX_POLL_INTERVAL_WITH_SOCKET + 0.06
+        assert MAILBOX in controller.cache_manager.deletes   # consumed
+
+    def test_socket_commands_still_land_at_once(self, controller):
+        server = controller._control_server = FakeServer()
+        controller._poll_on_demand_requests()
+        server.commands.append(QueuedCommand('sock', Command.ON_DEMAND_START,
+                                             OnDemandStartArgs(plugin_id='clock'), time.time()))
+        controller._poll_on_demand_requests()   # inside the mailbox interval
+        controller._activate_on_demand.assert_called_once()
+
+
+class TestSocketCommandsLeaveTheMailboxAlone:
+    def test_a_socket_start_reads_and_deletes_no_mailbox(self, controller):
+        server = controller._control_server = FakeServer()
+        controller._poll_on_demand_requests()
+        before = list(controller.cache_manager.reads)
+        server.commands.append(QueuedCommand('s1', Command.ON_DEMAND_START,
+                                             OnDemandStartArgs(plugin_id='clock'), time.time()))
+        controller._poll_on_demand_requests()
+        controller._activate_on_demand.assert_called_once()
+        assert MAILBOX not in controller.cache_manager.reads[len(before):]
+        assert controller.cache_manager.deletes == []
+
+    def test_a_socket_stop_reads_and_deletes_no_mailbox(self, controller):
+        from src.ipc.contract import OnDemandStopArgs
+        controller.on_demand_active = True
+        controller._clear_on_demand = MagicMock()
+        server = controller._control_server = FakeServer()
+        server.commands.append(QueuedCommand('s2', Command.ON_DEMAND_STOP,
+                                             OnDemandStopArgs(), time.time()))
+        controller.clock.t += 5
+        controller._drain_control_commands()
+        controller._clear_on_demand.assert_called_once()
+        assert MAILBOX not in controller.cache_manager.reads
+        assert controller.cache_manager.deletes == []
+
+    def test_a_mailbox_copy_of_a_socket_command_is_dropped(self, controller):
+        # An older web interface timed out after the display queued the
+        # command, then wrote the mailbox too.
+        server = controller._control_server = FakeServer()
+        server.commands.append(QueuedCommand('both', Command.ON_DEMAND_START,
+                                             OnDemandStartArgs(plugin_id='clock'), time.time()))
+        controller._poll_on_demand_requests()
+        _post(controller, 'both', plugin_id='clock')
+        _poll_for(controller, 2.0)
+        controller._activate_on_demand.assert_called_once()
+        assert MAILBOX not in controller.cache_manager.data
+
+
+class TestDeprecationLog:
+    def test_each_mailbox_writer_is_logged_once(self, controller, caplog):
+        controller._control_server = FakeServer()
+        caplog.set_level(logging.INFO, logger='src.display_controller')
+        for i, plugin in enumerate(['on-air', 'on-air', 'pomodoro-timer']):
+            _post(controller, f'r{i}', plugin_id=plugin)
+            _poll_for(controller, 1.2)
+        lines = [r.getMessage() for r in caplog.records if 'file mailbox' in r.getMessage()]
+        assert len(lines) == 2
+        assert 'on-air' in lines[0] and 'pomodoro-timer' in lines[1]
+
+    def test_nothing_is_logged_without_a_socket(self, controller, caplog):
+        controller._control_server = None
+        caplog.set_level(logging.INFO, logger='src.display_controller')
+        _post(controller, 'r', plugin_id='on-air')
+        _poll_for(controller, 1.0)
+        controller._activate_on_demand.assert_called_once()
+        assert not [r for r in caplog.records if 'file mailbox' in r.getMessage()]
+
+
+# -- file_signature and MailboxWatch -------------------------------------------------
+
+@pytest.fixture
+def real_cache(tmp_path, monkeypatch):
+    monkeypatch.setattr(CacheManager, '_get_writable_cache_dir', lambda self: str(tmp_path))
+    cache = CacheManager()
+    yield cache
+    cache.stop_cleanup_thread()
+
+
+class TestFileSignature:
+    def test_absent_key(self, real_cache):
+        assert real_cache.file_signature('nothing') is None
+
+    def test_every_write_is_a_new_signature(self, real_cache):
+        seen = set()
+        for i in range(20):
+            # Same size each time, written as fast as possible.
+            real_cache.set(MAILBOX, {'request_id': f'r{i:02d}'})
+            sig = real_cache.file_signature(MAILBOX)
+            assert isinstance(sig, tuple)
+            seen.add(sig)
+        assert len(seen) == 20
+
+    def test_gone_after_a_delete(self, real_cache):
+        real_cache.set(MAILBOX, {'a': 1})
+        real_cache.delete(MAILBOX)
+        assert real_cache.file_signature(MAILBOX) is None
+
+
+class TestMailboxWatch:
+    def test_reads_once_per_write(self, real_cache):
+        watch = MailboxWatch(MAILBOX)
+        assert watch.changed(real_cache) is False       # no file
+        real_cache.set(MAILBOX, {'request_id': 'a'})
+        assert watch.changed(real_cache) is True
+        assert watch.changed(real_cache) is False
+        real_cache.set(MAILBOX, {'request_id': 'b'})
+        assert watch.changed(real_cache) is True
+
+    def test_forget_reads_again(self, real_cache):
+        watch = MailboxWatch(MAILBOX)
+        real_cache.set(MAILBOX, {'request_id': 'a'})
+        assert watch.changed(real_cache) is True
+        watch.forget()
+        assert watch.changed(real_cache) is True
+
+    def test_a_rewrite_after_a_delete_is_seen(self, real_cache):
+        watch = MailboxWatch(MAILBOX)
+        real_cache.set(MAILBOX, {'request_id': 'a'})
+        assert watch.changed(real_cache)
+        real_cache.delete(MAILBOX)
+        assert watch.changed(real_cache) is False
+        real_cache.set(MAILBOX, {'request_id': 'a'})
+        assert watch.changed(real_cache) is True
+
+    def test_a_cache_that_cannot_tell_is_read_every_time(self):
+        watch = MailboxWatch(MAILBOX)
+        assert watch.changed(MagicMock()) is True
+        assert watch.changed(MagicMock()) is True
+        assert watch.changed(object()) is True
+
+
+# -- end to end over a real socket ---------------------------------------------------
+
+@pytest.mark.skipif(not c.socket_supported(), reason='AF_UNIX sockets are Linux/macOS only')
+class TestOverTheSocket:
+    @pytest.fixture
+    def sock_path(self):
+        import shutil
+        import tempfile
+        d = tempfile.mkdtemp(prefix='lmipc-')
+        yield os.path.join(d, 'control.sock')
+        shutil.rmtree(d, ignore_errors=True)
+
+    def test_errors_clear_round_trip(self, sock_path):
+        def handler(request_id, args):
+            return {'request_id': request_id, 'cutoff': args.cutoff, 'cleared': 2}
+
+        server = ControlServer(sock_path, handlers={Command.ERRORS_CLEAR: handler})
+        assert server.start()
+        try:
+            result = client.errors_clear('clr-1', 1790000000.0, paths=[sock_path])
+            assert result == {'request_id': 'clr-1', 'cutoff': 1790000000.0, 'cleared': 2}
+        finally:
+            server.close()
+
+    def test_an_older_display_is_an_upgrade_fallback(self, sock_path):
+        server = ControlServer(sock_path)   # no errors.clear handler
+        assert server.start()
+        try:
+            with pytest.raises(client.ControlError) as e:
+                client.errors_clear('clr-2', 1.0, paths=[sock_path])
+            assert e.value.reason == 'unknown_command' and e.value.sent is True
+            assert client.should_fall_back(e.value)
+        finally:
+            server.close()
+
+    def test_no_display_is_a_fallback(self, sock_path):
+        with pytest.raises(client.ControlError) as e:
+            client.errors_clear('clr-3', 1.0, paths=[sock_path])
+        assert e.value.reason == 'no_socket' and e.value.sent is False
+        assert client.should_fall_back(e.value)
+
+    def test_a_full_queue_is_not_a_fallback(self, sock_path):
+        server = ControlServer(sock_path, queue_size=1)
+        assert server.start()
+        try:
+            client.on_demand_start('q1', 'clock', None, paths=[sock_path])
+            with pytest.raises(client.ControlError) as e:
+                client.on_demand_start('q2', 'clock', None, paths=[sock_path])
+            assert e.value.reason == 'busy' and e.value.sent is True
+            assert not client.should_fall_back(e.value)
+        finally:
+            server.close()

test/test_ipc_state_stream.py

@@ -96,6 +96,27 @@ class TestStateHub:
         assert hub.snapshot(since=1, epoch='other')['changed'] is True
         assert hub.snapshot(since=1)['changed'] is True
 
+    def test_the_short_answer_carries_the_latest_volatile_values(self, hub):
+        """A version that stays put must not freeze the timestamps a reader
+        judges freshness by: the short answer (a tick) carries them."""
+        hub.publish('on_demand', {'active': False, 'last_updated': 2.0, 'remaining': 0.0},
+                    volatile=('last_updated', 'remaining'))
+        hub.publish('brightness', {'brightness': 50})
+        version = hub.version
+        assert not hub.publish('display', _display(updated=1234.5), volatile=('last_updated',))
+        short = hub.snapshot(since=version, epoch='e1')
+        assert short['changed'] is False and 'state' not in short
+        assert short['volatile'] == {'display': {'last_updated': 1234.5},
+                                     'on_demand': {'last_updated': 2.0, 'remaining': 0.0}}
+        # The full answer has them in place already.
+        assert 'volatile' not in hub.snapshot()
+
+    def test_volatile_values_skip_sections_without_any(self):
+        hub = StateHub(epoch='e1')
+        hub.publish('brightness', {'brightness': 50})
+        hub.publish('plugins', None, volatile=('published_at',))
+        assert hub.snapshot(since=hub.version, epoch='e1')['volatile'] == {}
+
     def test_each_display_run_has_its_own_epoch(self):
         assert StateHub().epoch != StateHub().epoch
 
@@ -276,6 +297,40 @@ class TestSubscriptionStore:
         assert latest['state']['loop']['heartbeat_age_seconds'] == 70.0
         assert latest['received_mono'] == clock.now
 
+    def test_a_tick_refreshes_the_volatile_timestamps(self, hub):
+        """The bug from the ledpi rig: the same mode on screen for minutes
+        left the reader's display.last_updated at the last real change."""
+        clock = FakeClock()
+        sub = client.StateSubscription(paths=['/nowhere'], clock=clock)
+        sub._store(hub.snapshot(), full=True)
+        hub.publish('display', _display(updated=9999.0), volatile=('last_updated',))
+        sub._store(hub.snapshot(since=1, epoch='e1'), full=False)
+        latest = sub.latest()
+        assert latest['state']['display']['last_updated'] == 9999.0
+        assert latest['state']['display']['mode'] == 'clock'
+        assert latest['version'] == 1
+
+    def test_a_tick_adds_no_section_or_key_and_ignores_another_version(self, hub):
+        clock = FakeClock()
+        sub = client.StateSubscription(paths=['/nowhere'], clock=clock)
+        snap = hub.snapshot()
+        sub._store(snap, full=True)
+        updated = snap['state']['display']['last_updated']
+        sub._store({'version': 1, 'epoch': 'e1',
+                    'volatile': {'display': {'new_key': 1}, 'plugins': {'published_at': 5.0},
+                                 'on_demand': 'junk'}}, full=False)
+        state = sub.latest()['state']
+        assert 'new_key' not in state['display'] and state['plugins'] is None
+        assert state['on_demand'] is None
+        # A tick for a version this copy is not at says nothing about it.
+        sub._store({'version': 7, 'epoch': 'e1',
+                    'volatile': {'display': {'last_updated': 5.0}}}, full=False)
+        assert sub.latest()['state']['display']['last_updated'] == updated
+        # A display from before ticks carried them: the loop still refreshes.
+        sub._store({'version': 1, 'epoch': 'e1', 'loop': {'heartbeat_age_seconds': 3.0}},
+                   full=False)
+        assert sub.latest()['loop'] == {'heartbeat_age_seconds': 3.0}
+
     def test_a_tick_from_another_epoch_is_ignored(self, hub):
         clock = FakeClock()
         sub = client.StateSubscription(paths=['/nowhere'], clock=clock)
@@ -291,6 +346,52 @@ class TestSubscriptionStore:
         assert client.snapshot_loop_age(snap, now_mono=104.0) is None
 
 
+class TestReconnectBackoff:
+    """StateSubscription._run's waits between connections, without a socket."""
+
+    def test_a_connection_that_got_a_snapshot_starts_the_backoff_over(self, hub,
+                                                                       monkeypatch):
+        """Three failed tries, then the display is back twice, restarting
+        each time, then gone again. Each restart is retried after the
+        shortest wait, not after whatever the waits had grown to."""
+        sub = client.StateSubscription(paths=['/nowhere'])
+        script = ['refused', 'refused', 'refused', 'snapshot', 'snapshot', 'refused']
+        waits = []
+
+        def follow():
+            step = script.pop(0)
+            if step == 'snapshot':      # subscribed, then the display restarted
+                sub._store(hub.snapshot(), full=True)
+                raise client.ControlError('closed', 'the display closed the connection')
+            raise client.ControlError(step)
+
+        def wait(seconds):
+            waits.append(seconds)
+            return not script           # True ends _run, as stop() would
+
+        monkeypatch.setattr(sub, '_follow', follow)
+        monkeypatch.setattr(sub._stop, 'wait', wait)
+        sub._run()
+        first = client._RECONNECT_MIN_SECONDS
+        assert waits == [first, 2 * first, 4 * first, first, first, 2 * first]
+
+    def test_a_display_without_the_stream_is_still_retried_slowly(self, monkeypatch):
+        sub = client.StateSubscription(paths=['/nowhere'])
+        waits = []
+
+        def follow():
+            raise client.ControlError('unknown_command')
+
+        def wait(seconds):
+            waits.append(seconds)
+            return len(waits) == 2
+
+        monkeypatch.setattr(sub, '_follow', follow)
+        monkeypatch.setattr(sub._stop, 'wait', wait)
+        sub._run()
+        assert waits == [client._RECONNECT_MAX_SECONDS] * 2
+
+
 # --- a real socket ------------------------------------------------------------------
 
 def _wait_until(predicate, timeout=5.0):
@@ -369,6 +470,33 @@ class TestLiveStream:
         assert kinds == ['tick', 'tick', 'tick']
         sock.close()
 
+    def test_ticks_carry_the_timestamps_the_version_ignores(self, live, path):
+        _, hub = live
+        sock, reader = self._subscribe(path)
+        pending = []
+        self._next(sock, reader, pending)
+        hub.publish('display', _display(updated=4242.0), volatile=('last_updated',))
+        for _ in range(3):   # a tick already on its way may predate the publish
+            tick = self._next(sock, reader, pending)
+            assert tick['event'] == 'tick'
+            if tick['result']['volatile'] == {'display': {'last_updated': 4242.0}}:
+                break
+        else:
+            pytest.fail(f'no tick carried the new last_updated: {tick}')
+        sock.close()
+
+    def test_a_subscription_keeps_last_updated_current(self, live, path):
+        _, hub = live
+        sub = client.StateSubscription(paths=[path]).start()
+        try:
+            assert _wait_until(lambda: sub.latest() is not None)
+            hub.publish('display', _display(updated=4242.0), volatile=('last_updated',))
+            assert _wait_until(lambda: (sub.latest() or {}).get('state', {})
+                               .get('display', {}).get('last_updated') == 4242.0)
+            assert sub.snapshots == 1        # ticks, not new snapshots
+        finally:
+            sub.stop()
+
     def test_a_burst_is_coalesced_to_the_latest(self, live, path):
         _, hub = live
         sock, reader = self._subscribe(path)

test/test_live_display_modes.py

@@ -0,0 +1,252 @@
+"""The web interface sees the display modes the display actually registered (#668).
+
+A plugin may compute its modes from its config: soccer-scoreboard registers
+``soccer_<league>_live/recent/upcoming`` for every league the user adds under
+``custom_leagues``, and no manifest can list those ahead of time. The display
+always rotated them -- DisplayController._register_loaded_plugin prefers
+``plugin.modes`` -- but the web process reads plugins as files, so its mode
+listing (/display/modes, the on-demand dialog) and find_plugin_for_mode
+(/display/on-demand/start with a mode and no plugin_id) saw only manifests.
+
+The display now records each plugin's registered modes in its plugin state,
+the runtime snapshot carries them, and PluginCatalog prefers them while the
+snapshot is live, falling back to the manifest when it is not.
+"""
+import json
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from src.cache_manager import CacheManager  # noqa: E402
+from src.plugin_system import plugin_runtime as rt  # noqa: E402
+from src.plugin_system.plugin_catalog import PluginCatalog  # noqa: E402
+from src.plugin_system.plugin_runtime import (  # noqa: E402
+    PluginRuntimePublisher, build_runtime_snapshot, read_plugin_runtime,
+    view_from_snapshot,
+)
+from src.plugin_system.plugin_state import PluginState, PluginStateManager  # noqa: E402
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+DECLARED = ["soccer_eng.1_live", "soccer_eng.1_recent", "soccer_eng.1_upcoming"]
+CUSTOM = ["soccer_sco.1_live", "soccer_sco.1_recent", "soccer_sco.1_upcoming"]
+REGISTERED = DECLARED + CUSTOM
+
+
+def _loaded_states(modes=None):
+    states = PluginStateManager()
+    states.set_state("soccer-scoreboard", PluginState.ENABLED)
+    states.record_loaded("soccer-scoreboard", "2.24.1")
+    if modes is not None:
+        states.record_modes("soccer-scoreboard", modes)
+    return states
+
+
+@pytest.fixture
+def shared_cache(tmp_path, monkeypatch):
+    """Two cache managers over one directory: the display's and the web's."""
+    monkeypatch.setattr(CacheManager, "_get_writable_cache_dir",
+                        lambda self: str(tmp_path / "cache"))
+    (tmp_path / "cache").mkdir()
+    display_cache, web_cache = CacheManager(), CacheManager()
+    yield display_cache, web_cache
+    display_cache.stop_cleanup_thread()
+    web_cache.stop_cleanup_thread()
+
+
+@pytest.fixture
+def plugins_dir(tmp_path):
+    root = tmp_path / "plugins"
+    for plugin_id, modes in (("soccer-scoreboard", DECLARED), ("clock-simple", ["clock"])):
+        (root / plugin_id).mkdir(parents=True)
+        (root / plugin_id / "manifest.json").write_text(json.dumps({
+            "id": plugin_id, "name": plugin_id, "version": "1.0.0",
+            "class_name": "P", "display_modes": modes}), encoding="utf-8")
+    return root
+
+
+# --- The display records what it registered ---------------------------------
+
+class TestStateManagerRecordsModes:
+    def test_runtime_records_carry_them(self):
+        assert _loaded_states(REGISTERED).runtime_records()[
+            "soccer-scoreboard"]["modes"] == REGISTERED
+
+    def test_none_until_registered(self):
+        assert _loaded_states().runtime_records()["soccer-scoreboard"]["modes"] is None
+
+    def test_a_new_list_is_a_change_the_same_one_is_not(self):
+        """change_count drives the publisher: re-registering an unchanged
+        plugin must not cost an SD-card write."""
+        states = _loaded_states(DECLARED)
+        before = states.change_count
+        states.record_modes("soccer-scoreboard", list(DECLARED))
+        assert states.change_count == before
+        states.record_modes("soccer-scoreboard", REGISTERED)
+        assert states.change_count == before + 1
+
+    def test_ignored_for_a_plugin_that_is_not_loaded(self):
+        states = PluginStateManager()
+        states.record_modes("ghost", ["ghost"])
+        assert "ghost" not in states.runtime_records()
+
+    def test_unload_forgets_them(self):
+        states = _loaded_states(REGISTERED)
+        states.clear_state("soccer-scoreboard")
+        assert "soccer-scoreboard" not in states.runtime_records()
+
+    def test_a_reload_starts_without_them_until_registered_again(self):
+        states = _loaded_states(REGISTERED)
+        states.record_loaded("soccer-scoreboard", "2.25.0")
+        assert states.runtime_records()["soccer-scoreboard"]["modes"] is None
+
+
+class TestControllerRecordsOnRegistration:
+    def test_plugin_modes_reach_the_state_manager(self, test_display_controller):
+        """_register_loaded_plugin is the one path every load, enable and
+        reload goes through."""
+        c = test_display_controller
+        states = _loaded_states()
+        plugin = MagicMock()
+        plugin.modes = list(REGISTERED)
+        c.plugin_manager.state_manager = states
+        c.plugin_manager.get_plugin = MagicMock(return_value=plugin)
+        c.plugin_manager.plugin_manifests = {"soccer-scoreboard": {"display_modes": DECLARED}}
+
+        c._register_loaded_plugin("soccer-scoreboard")
+
+        assert states.runtime_records()["soccer-scoreboard"]["modes"] == REGISTERED
+
+    def test_a_failing_state_manager_does_not_break_registration(self, test_display_controller):
+        c = test_display_controller
+        plugin = MagicMock()
+        plugin.modes = ["clock"]
+        c.plugin_manager.state_manager.record_modes = MagicMock(side_effect=RuntimeError("x"))
+        c.plugin_manager.get_plugin = MagicMock(return_value=plugin)
+        c.plugin_manager.plugin_manifests = {}
+
+        assert c._register_loaded_plugin("clock-simple") == ["clock"]
+        assert c.mode_to_plugin_id["clock"] == "clock-simple"
+
+
+# --- The snapshot carries them; only a live view reports them ---------------
+
+class TestSnapshotAndView:
+    NOW = 1_800_000_000.0
+
+    def _view(self, states, running=True, published_at=None):
+        snapshot = build_runtime_snapshot(states, started_at=1.0, now=self.NOW,
+                                          running=running)
+        if published_at is not None:
+            snapshot["published_at"] = published_at
+        return view_from_snapshot(snapshot, now=self.NOW)
+
+    def test_live_view_reports_the_registered_modes(self):
+        assert self._view(_loaded_states(REGISTERED)).display_modes(
+            "soccer-scoreboard") == REGISTERED
+
+    def test_stale_and_stopped_views_report_nothing(self):
+        states = _loaded_states(REGISTERED)
+        assert self._view(states, published_at=self.NOW - 10_000).display_modes(
+            "soccer-scoreboard") is None
+        assert self._view(states, running=False).display_modes("soccer-scoreboard") is None
+
+    def test_unregistered_or_unknown_plugins_report_nothing(self):
+        view = self._view(_loaded_states())
+        assert view.display_modes("soccer-scoreboard") is None
+        assert view.display_modes("not-loaded") is None
+
+    def test_a_runaway_list_is_bounded(self):
+        modes = [f"m{i}" for i in range(1000)] + ["x" * 500]
+        snapshot = build_runtime_snapshot(_loaded_states(modes), started_at=1.0, now=self.NOW)
+        published = snapshot["plugins"]["soccer-scoreboard"]["modes"]
+        assert len(published) == rt._MAX_MODES
+
+    def test_non_strings_from_a_hand_made_snapshot_are_dropped(self):
+        snapshot = {"schema": rt.SNAPSHOT_SCHEMA, "running": True,
+                    "published_at": self.NOW, "plugins": {
+                        "p": {"loaded": True, "modes": ["a", 3, None]}}}
+        assert view_from_snapshot(snapshot, now=self.NOW).display_modes("p") == ["a"]
+
+
+# --- The web's catalog prefers them -------------------------------------------
+
+class TestCatalog:
+    def _catalog(self, plugins_dir, web_cache):
+        catalog = PluginCatalog(plugins_dir,
+                                runtime_source=lambda: read_plugin_runtime(web_cache))
+        catalog.discover_plugins()
+        return catalog
+
+    def test_live_display_modes_win_over_the_manifest(self, plugins_dir, shared_cache):
+        display_cache, web_cache = shared_cache
+        PluginRuntimePublisher(display_cache, _loaded_states(REGISTERED)).tick()
+        catalog = self._catalog(plugins_dir, web_cache)
+        assert catalog.get_plugin_display_modes("soccer-scoreboard") == REGISTERED
+
+    def test_a_custom_league_mode_resolves_to_its_plugin(self, plugins_dir, shared_cache):
+        """What /display/on-demand/start does with a mode and no plugin_id."""
+        display_cache, web_cache = shared_cache
+        PluginRuntimePublisher(display_cache, _loaded_states(REGISTERED)).tick()
+        catalog = self._catalog(plugins_dir, web_cache)
+        assert catalog.find_plugin_for_mode("SOCCER_SCO.1_LIVE") == "soccer-scoreboard"
+
+    def test_a_plugin_the_display_has_not_loaded_falls_back_to_its_manifest(
+            self, plugins_dir, shared_cache):
+        display_cache, web_cache = shared_cache
+        PluginRuntimePublisher(display_cache, _loaded_states(REGISTERED)).tick()
+        catalog = self._catalog(plugins_dir, web_cache)
+        assert catalog.get_plugin_display_modes("clock-simple") == ["clock"]
+        assert catalog.find_plugin_for_mode("clock") == "clock-simple"
+
+    def test_a_stopped_display_falls_back_to_manifests(self, plugins_dir, shared_cache):
+        display_cache, web_cache = shared_cache
+        publisher = PluginRuntimePublisher(display_cache, _loaded_states(REGISTERED))
+        publisher.tick()
+        publisher.stop()
+        catalog = self._catalog(plugins_dir, web_cache)
+        assert catalog.get_plugin_display_modes("soccer-scoreboard") == DECLARED
+        assert catalog.find_plugin_for_mode("soccer_sco.1_live") is None
+
+    def test_no_runtime_source_is_manifests_only(self, plugins_dir):
+        catalog = PluginCatalog(plugins_dir)
+        catalog.discover_plugins()
+        assert catalog.get_plugin_display_modes("soccer-scoreboard") == DECLARED
+
+    def test_a_failing_runtime_source_is_manifests_only(self, plugins_dir):
+        def broken():
+            raise OSError("cache gone")
+        catalog = PluginCatalog(plugins_dir, runtime_source=broken)
+        catalog.discover_plugins()
+        assert catalog.get_plugin_display_modes("soccer-scoreboard") == DECLARED
+
+    def test_one_listing_reads_the_view_once(self, plugins_dir):
+        source = MagicMock(return_value=None)
+        catalog = PluginCatalog(plugins_dir, runtime_source=source)
+        catalog.discover_plugins()
+        for _ in range(10):
+            catalog.get_plugin_display_modes("soccer-scoreboard")
+            catalog.find_plugin_for_mode("clock")
+        assert source.call_count == 1
+
+
+class TestDisplayModesRoute:
+    def test_lists_the_custom_league_modes(self, api_v3_module, api_v3_client,  # noqa: F811
+                                           plugins_dir, shared_cache):
+        display_cache, web_cache = shared_cache
+        PluginRuntimePublisher(display_cache, _loaded_states(REGISTERED)).tick()
+        api = api_v3_module.api_v3
+        api.plugin_catalog = PluginCatalog(
+            plugins_dir, runtime_source=lambda: read_plugin_runtime(web_cache))
+        api.config_manager.load_config = MagicMock(return_value={
+            "soccer-scoreboard": {"enabled": True}})
+
+        response = api_v3_client.get("/api/v3/display/modes")
+
+        assert response.status_code == 200, response.get_data(as_text=True)
+        modes = {m["mode"]: m for m in response.get_json()["data"]["modes"]}
+        assert set(modes) == set(REGISTERED)
+        assert modes["soccer_sco.1_live"]["plugin_id"] == "soccer-scoreboard"

test/test_mqtt_bridge_config_endpoint.py

@@ -136,3 +136,22 @@ class TestCleartextCredentialsNeedAnExplicitOptIn:
                              "allow_insecure_mqtt": "false"})
         assert r.status_code == 400
 
+    def test_the_settings_read_reports_the_opt_in(self, client, monkeypatch):
+        """The Tools form prefills its "Allow without TLS" box from the GET.
+
+        Off until someone saves it on, so an untouched form sends false and
+        the guard above still refuses a cleartext password.
+        """
+        c, _ = client
+        monkeypatch.setattr(misc, "_mqtt_bridge_service_state",
+                            lambda: {"installed": False, "active": False, "enabled": False})
+
+        def read():
+            return c.get("/api/v3/integrations/mqtt-bridge").get_json()["data"]["config"]
+
+        assert read()["allow_insecure_mqtt"] is False
+        r = c.put(URL, json={"mqtt_password": "hunter2", "mqtt_tls": False,
+                             "allow_insecure_mqtt": True})
+        assert r.status_code == 200, r.get_json()
+        assert read()["allow_insecure_mqtt"] is True
+

test/test_on_demand_live_and_restore.py

@@ -0,0 +1,164 @@
+"""Two on-demand edges seen on a rig.
+
+  * A request naming a ``*_live`` mode got HTTP 200 and a different mode on
+    the panel. The session's mode list kept live modes only when the plugin's
+    has_live_content() said so, and that is the live-priority question,
+    which the sports plugins answer for favourite teams only: fifteen college
+    games on, no favourite playing, and ``ncaa_fb_live`` became
+    ``nfl_recent``.
+  * A restart during a session whose plugin then failed to load (its config
+    no longer validated) logged "No valid display modes found ... after
+    restoration" and left the session active with no modes: published as
+    active for a plugin that was not running, with its cached request kept
+    for the next restart.
+"""
+
+from unittest.mock import MagicMock
+
+import pytest
+
+SPORTS_MODES = ['nfl_live', 'nfl_recent', 'nfl_upcoming',
+                'ncaa_fb_live', 'ncaa_fb_recent', 'ncaa_fb_upcoming']
+
+
+def _sports_plugin(has_live_content=False):
+    plugin = MagicMock(spec=['display', 'has_live_content', 'has_live_priority',
+                             'get_live_modes'])
+    plugin.has_live_content.return_value = has_live_content
+    plugin.has_live_priority.return_value = True
+    plugin.get_live_modes.return_value = []
+    return plugin
+
+
+def _register(controller, plugin_id, modes, plugin):
+    controller.plugin_display_modes[plugin_id] = list(modes)
+    for mode in modes:
+        controller.plugin_modes[mode] = plugin
+        controller.mode_to_plugin_id[mode] = plugin_id
+        if mode not in controller.available_modes:
+            controller.available_modes.append(mode)
+
+
+@pytest.fixture
+def football(test_display_controller):
+    c = test_display_controller
+    _register(c, 'football-scoreboard', SPORTS_MODES, _sports_plugin())
+    return c
+
+
+class TestANamedLiveModeIsShown:
+
+    def test_it_is_the_first_screen(self, football):
+        football._activate_on_demand({'plugin_id': 'football-scoreboard',
+                                      'mode': 'ncaa_fb_live'})
+        assert football.on_demand_active
+        assert football.current_display_mode == 'ncaa_fb_live'
+        assert football.on_demand_mode == 'ncaa_fb_live'
+
+    def test_the_plugins_other_modes_follow_it(self, football):
+        football._activate_on_demand({'plugin_id': 'football-scoreboard',
+                                      'mode': 'ncaa_fb_live'})
+        assert football.on_demand_modes[0] == 'ncaa_fb_live'
+        assert set(football.on_demand_modes[1:]) == {
+            'nfl_recent', 'nfl_upcoming', 'ncaa_fb_recent', 'ncaa_fb_upcoming'}
+
+    def test_pinned_holds_it(self, football):
+        football._activate_on_demand({'plugin_id': 'football-scoreboard',
+                                      'mode': 'ncaa_fb_live', 'pinned': True})
+        assert football.on_demand_modes == ['ncaa_fb_live']
+
+    def test_a_bare_plugin_request_still_skips_quiet_live_modes(self, football):
+        """Only a mode asked for by name is kept: a plugin-only request
+        resolves to the plugin's first mode (nfl_live), and opening on an
+        empty live screen there is what the ordering exists to avoid."""
+        football._activate_on_demand({'plugin_id': 'football-scoreboard'})
+        assert not any(m.endswith('_live') for m in football.on_demand_modes)
+
+    def test_a_named_second_live_mode_with_content_leads(self, test_display_controller):
+        """With live content both live modes are kept, nfl_live first; a
+        request naming ncaa_fb_live must still open on it, not rotate away."""
+        c = test_display_controller
+        _register(c, 'football-scoreboard', SPORTS_MODES, _sports_plugin(has_live_content=True))
+        c._activate_on_demand({'plugin_id': 'football-scoreboard', 'mode': 'ncaa_fb_live'})
+        assert c.on_demand_modes[0] == 'ncaa_fb_live'
+        assert c.on_demand_modes.count('ncaa_fb_live') == 1
+        assert 'nfl_live' in c.on_demand_modes[1:]
+
+    def test_the_named_mode_survives_a_restart(self, football):
+        football._activate_on_demand({'plugin_id': 'football-scoreboard',
+                                      'mode': 'ncaa_fb_live'})
+        # The last on-demand config write, not the last write of any key: the
+        # font-usage publisher thread writes its own key at its own pace.
+        saved = [c for c in football.cache_manager.set.call_args_list
+                 if c.args and c.args[0] == 'display_on_demand_config'][-1]
+        config = saved.args[1]
+        assert config['named_mode'] == 'ncaa_fb_live'
+
+        football._reset_on_demand_fields()
+        football._select_startup_plugins(['football-scoreboard'], config)
+        football._populate_on_demand_modes_from_plugin()
+        assert football.on_demand_modes[football.on_demand_mode_index] == 'ncaa_fb_live'
+
+
+class TestARestoreWithNothingToResume:
+
+    @pytest.fixture
+    def restored(self, test_display_controller):
+        c = test_display_controller
+        c.config['clock-simple'] = {'enabled': True}
+        c._select_startup_plugins(['clock-simple'],
+                                  {'plugin_id': 'clock-simple', 'mode': 'clock-simple'})
+        assert c.on_demand_active
+        # The plugin's load then fails: nothing is registered for it.
+        c.cache_manager.clear_cache.reset_mock()
+        c._populate_on_demand_modes_from_plugin()
+        return c
+
+    def test_the_session_ends(self, restored):
+        assert not restored.on_demand_active
+        assert restored.on_demand_plugin_id is None
+        assert not restored.on_demand_schedule_override
+
+    def test_it_is_reported_as_an_error(self, restored):
+        assert restored.on_demand_status == 'error'
+        assert restored.on_demand_last_error == 'restore-failed'
+        # The last on-demand state write, not the last write of any key: the
+        # font-usage publisher thread writes its own key at its own pace.
+        published = [c for c in restored.cache_manager.set.call_args_list
+                     if c.args and c.args[0] == 'display_on_demand_state'][-1]
+        assert published.args[1]['status'] == 'error'
+        assert published.args[1]['error'] == 'restore-failed'
+
+    def test_the_cached_request_is_dropped(self, restored):
+        restored.cache_manager.clear_cache.assert_any_call('display_on_demand_config')
+
+
+def test_a_plugin_system_failure_ends_a_cached_session_not_yet_restored(
+        mock_config_manager, mock_display_manager, mock_cache_manager,
+        test_config_with_plugins, emulator_mode):
+    """Initialization can fail before the cached session is read, with
+    on_demand_active still False: the session must still end, visibly."""
+    from unittest.mock import patch
+    from src.display_controller import DisplayController
+
+    mock_config_manager.get_config.return_value = test_config_with_plugins
+    mock_config_manager.load_config.return_value = test_config_with_plugins
+    mock_cache_manager._memory_cache['display_on_demand_config'] = {
+        'plugin_id': 'clock-simple', 'mode': 'clock-simple'}
+    with patch('src.display_controller.ConfigManager', return_value=mock_config_manager), \
+         patch('src.display_controller.DisplayManager', return_value=mock_display_manager), \
+         patch('src.display_controller.CacheManager', return_value=mock_cache_manager), \
+         patch('src.display_controller.FontManager'), \
+         patch('src.plugin_system.PluginManager', side_effect=RuntimeError("boom")):
+        controller = DisplayController()
+        try:
+            assert controller.plugin_manager is None
+            assert not controller.on_demand_active
+            assert controller.on_demand_status == 'error'
+            assert controller.on_demand_last_error == 'restore-failed'
+            mock_cache_manager.clear_cache.assert_any_call('display_on_demand_config')
+        finally:
+            try:
+                controller.cleanup()
+            except Exception:
+                pass

test/test_plugin_loader_reload_isolation.py

@@ -58,3 +58,83 @@ def test_a_reloaded_plugin_still_gets_its_own_bare_module(plugins):
     assert reloaded.WHO == "alpha"
     assert sys.path.index(str(plugins["alpha"])) < sys.path.index(str(plugins["beta"]))
     assert sys.path.count(str(plugins["alpha"])) == 1
+
+
+# -- sub-packages ------------------------------------------------------------
+#
+# A plugin that keeps helpers in a package (``providers/feed.py``, imported as
+# ``from providers.feed import ...``) leaves dotted entries in sys.modules.
+# Only the bare ``providers`` used to be tracked, so ``providers.feed`` outlived
+# the plugin: a reload after a store update re-ran the new manager.py against
+# the old feed.py, until the display restarted. Elections (providers/),
+# flights (enrichment/) and olympics (data/, renderers/) ship packages.
+
+
+@pytest.fixture
+def package_plugin(tmp_path):
+    before_path = list(sys.path)
+    before_modules = set(sys.modules)
+    plugin_dir = tmp_path / "pkgdemo"
+    (plugin_dir / "providers").mkdir(parents=True)
+    (plugin_dir / "providers" / "__init__.py").write_text("", encoding="utf-8")
+    (plugin_dir / "providers" / "feed.py").write_text("VERSION = 'v1'\n", encoding="utf-8")
+    (plugin_dir / "manager.py").write_text(
+        "from providers.feed import VERSION\n", encoding="utf-8")
+    yield plugin_dir
+    sys.path[:] = before_path
+    for key in set(sys.modules) - before_modules:
+        sys.modules.pop(key, None)
+
+
+def test_a_reloaded_plugin_runs_its_updated_subpackage_module(package_plugin):
+    loader = PluginLoader()
+    assert loader.load_module("pkgdemo", package_plugin, "manager.py").VERSION == "v1"
+
+    _unload(loader, "pkgdemo")
+    # The store update: a different size, so no cached bytecode can match.
+    (package_plugin / "providers" / "feed.py").write_text(
+        "VERSION = 'v2 from the update'\n", encoding="utf-8")
+    reloaded = loader.load_module("pkgdemo", package_plugin, "manager.py")
+
+    assert reloaded.VERSION == "v2 from the update"
+
+
+def test_unload_drops_the_plugins_subpackage_modules(package_plugin):
+    loader = PluginLoader()
+    loader.load_module("pkgdemo", package_plugin, "manager.py")
+    # Still importable while the plugin runs, as before.
+    assert "providers.feed" in sys.modules
+
+    _unload(loader, "pkgdemo")
+
+    assert not [k for k in sys.modules if k.startswith("providers")]
+
+
+def test_a_failed_load_leaves_no_subpackage_module_behind(package_plugin):
+    (package_plugin / "manager.py").write_text(
+        "from providers.feed import VERSION\nraise RuntimeError('broken')\n",
+        encoding="utf-8")
+    loader = PluginLoader()
+
+    with pytest.raises(RuntimeError):
+        loader.load_module("pkgdemo", package_plugin, "manager.py")
+
+    assert not [k for k in sys.modules if k.startswith("providers")]
+
+
+def test_unload_leaves_packages_from_outside_the_plugin_alone(package_plugin, tmp_path):
+    # A library the plugin imports is not the plugin's to drop.
+    lib_root = tmp_path / "site"
+    (lib_root / "extlib").mkdir(parents=True)
+    (lib_root / "extlib" / "__init__.py").write_text("", encoding="utf-8")
+    (lib_root / "extlib" / "sub.py").write_text("X = 1\n", encoding="utf-8")
+    sys.path.append(str(lib_root))
+    (package_plugin / "manager.py").write_text(
+        "import extlib.sub\nfrom providers.feed import VERSION\n", encoding="utf-8")
+    loader = PluginLoader()
+    loader.load_module("pkgdemo", package_plugin, "manager.py")
+
+    _unload(loader, "pkgdemo")
+
+    assert "extlib.sub" in sys.modules
+    assert "extlib" in sys.modules

test/test_plugin_loader_symlinked_dir.py

@@ -0,0 +1,81 @@
+"""A dev plugin linked in under a name its checkout does not share still loads.
+
+``scripts/dev/dev_plugin_setup.sh`` links a checkout into the plugins
+directory under the plugin's id: ``link-github foo <url>`` clones
+``ledmatrix-foo`` (the repository naming convention) and links it as
+``plugins/foo``. ``contained_plugin_dir`` resolved the link and looked for the
+*target's* folder name, ``ledmatrix-foo``, among the plugins directory's
+entries. There is none, so ``install_dependencies`` refused the plugin as
+outside the plugins directory and the load failed with "Dependency
+installation failed" -- even with no requirements.txt at all.
+
+The containment it exists for still holds: the answer is always rebuilt from
+an entry enumerated under the plugins directory.
+
+Skipped where this process cannot create a symlink (Windows without the
+privilege).
+"""
+
+import os
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from src.plugin_system.plugin_loader import PluginLoader, contained_plugin_dir
+
+
+def _symlink_or_skip(target, link):
+    try:
+        os.symlink(target, link, target_is_directory=True)
+    except (OSError, NotImplementedError) as e:
+        pytest.skip(f"cannot create a symlink here: {e}")
+
+
+@pytest.fixture
+def linked(tmp_path):
+    checkout = tmp_path / "dev-plugins" / "ledmatrix-foo"
+    checkout.mkdir(parents=True)
+    plugins_dir = tmp_path / "plugins"
+    plugins_dir.mkdir()
+    link = plugins_dir / "foo"
+    _symlink_or_skip(checkout, link)
+    return plugins_dir, link, checkout
+
+
+def test_a_link_resolves_to_its_own_entry_in_the_plugins_dir(linked):
+    plugins_dir, link, _checkout = linked
+
+    assert contained_plugin_dir(link, plugins_dir) == os.path.join(
+        os.path.realpath(plugins_dir), "foo")
+
+
+def test_a_linked_plugin_without_requirements_needs_no_install(linked):
+    plugins_dir, link, _checkout = linked
+
+    with patch("subprocess.run") as pip:
+        assert PluginLoader().install_dependencies(link, "foo", plugins_dir=plugins_dir) is True
+    pip.assert_not_called()
+
+
+@patch("src.plugin_system.plugin_loader.requirements_are_satisfied", return_value=False)
+def test_a_linked_plugins_requirements_are_installed_through_the_link(_satisfied, linked):
+    plugins_dir, link, checkout = linked
+    (checkout / "requirements.txt").write_text("package1==1.0.0\n", encoding="utf-8")
+
+    with patch("subprocess.run", return_value=MagicMock(returncode=0, stderr="")) as pip:
+        assert PluginLoader().install_dependencies(link, "foo", plugins_dir=plugins_dir) is True
+
+    argv = pip.call_args[0][0]
+    assert argv[argv.index("-r") + 1] == os.path.join(
+        os.path.realpath(plugins_dir), "foo", "requirements.txt")
+
+
+def test_a_link_outside_the_plugins_dir_is_still_refused(linked, tmp_path):
+    plugins_dir, _link, checkout = linked
+    elsewhere = tmp_path / "elsewhere"
+    elsewhere.mkdir()
+    stray = elsewhere / "bar"
+    _symlink_or_skip(checkout, stray)
+
+    assert contained_plugin_dir(stray, plugins_dir) is None
+    assert contained_plugin_dir(plugins_dir / ".." / "elsewhere" / "bar", plugins_dir) is None

test/test_plugin_manager_failed_load_cleanup.py

@@ -69,6 +69,7 @@ def test_fixed_plugin_loads_new_code_after_failed_load(plugin_env, first_source)
     assert MODULE_NAME not in sys.modules
     assert PLUGIN_ID not in pm.plugin_loader._loaded_modules
     pm.font_manager.forget_manager_fonts.assert_called_with(PLUGIN_ID)
+    pm.font_manager.forget_plugin_fonts.assert_called_with(PLUGIN_ID)
 
     (plugin_dir / "manager.py").write_text(_FIXED, encoding="utf-8")
     assert pm.load_plugin(PLUGIN_ID) is True

test/test_plugin_on_demand_api.py

@@ -0,0 +1,418 @@
+"""Plugins asking for the screen in-process: BasePlugin.request_on_demand()
+and end_on_demand().
+
+A plugin running in the display process used to write the
+``display_on_demand_request`` mailbox, which the display reads once a second
+while the control socket is up. These tests pin the way in that replaces it:
+
+* BasePlugin -> PluginManager -> DisplayController.submit_plugin_on_demand,
+  which only queues, from any thread;
+* the render thread applies the queue where it applies socket commands,
+  through the mailbox's own handler, without the mailbox's read floor, and
+  woken by the control socket when it is up;
+* a plugin's stop ends only its own session;
+* no display to ask (the web interface's plugin manager, an old core's
+  plugin manager) answers None, which is a plugin's cue to fall back to the
+  mailbox;
+* the mailbox still works for plugins that write it.
+"""
+
+import logging
+import threading
+import time
+from unittest.mock import MagicMock
+
+import pytest
+
+from src.ipc.server import ControlServer
+from src.plugin_system.base_plugin import BasePlugin
+from src.plugin_system.plugin_manager import PluginManager
+
+
+class _Plugin(BasePlugin):
+    def update(self):
+        pass
+
+    def display(self, force_clear=False):
+        pass
+
+
+def _plugin(plugin_id, manager):
+    plugin = _Plugin.__new__(_Plugin)
+    plugin.plugin_id = plugin_id
+    plugin.plugin_manager = manager
+    return plugin
+
+
+def _manager(handler=None):
+    manager = PluginManager.__new__(PluginManager)
+    manager.logger = logging.getLogger('test.plugin_on_demand')
+    if handler is not None:
+        manager.set_on_demand_handler(handler)
+    return manager
+
+
+class _WakeServer:
+    """The parts of ControlServer the controller uses, with no socket."""
+
+    def __init__(self):
+        self.woken = 0
+        self.has_pending = False
+
+    def wake(self):
+        self.woken += 1
+        self.has_pending = True
+
+    def drain(self):
+        self.has_pending = False
+        return []
+
+
+@pytest.fixture
+def controller(test_display_controller):
+    c_ = test_display_controller
+    c_.on_demand_active = False
+    c_.on_demand_request_id = None
+    c_._last_on_demand_poll = None
+    mailbox = {'value': None}
+
+    def fake_get(key, *a, **kw):
+        if key == 'display_on_demand_request':
+            return mailbox['value']
+        return None
+
+    c_.cache_manager.get = MagicMock(side_effect=fake_get)
+    c_.cache_manager.set = MagicMock()
+    c_.cache_manager.delete = MagicMock()
+    c_._activate_on_demand = MagicMock()
+    c_.mailbox = mailbox
+    return c_
+
+
+@pytest.fixture
+def wired(controller):
+    """A real PluginManager wired to the controller, as __init__ wires it."""
+    manager = _manager(controller.submit_plugin_on_demand)
+    return controller, manager
+
+
+class TestWiring:
+    def test_the_controller_wires_its_plugin_manager(self, controller):
+        controller.plugin_manager.set_on_demand_handler.assert_called_once_with(
+            controller.submit_plugin_on_demand)
+
+    def test_a_start_reaches_the_mailbox_handler(self, wired):
+        controller, manager = wired
+        rid = _plugin('pomodoro-timer', manager).request_on_demand(
+            mode='pomodoro', duration=30, pinned=True)
+        assert isinstance(rid, str) and rid
+        controller._activate_on_demand.assert_not_called()   # only queued
+        controller._poll_on_demand_requests()
+        controller._activate_on_demand.assert_called_once()
+        request = controller._activate_on_demand.call_args.args[0]
+        assert request['request_id'] == rid
+        assert request['action'] == 'start'
+        assert request['plugin_id'] == 'pomodoro-timer'
+        assert request['mode'] == 'pomodoro'
+        assert request['duration'] == 30.0 and request['pinned'] is True
+        assert request['source'] == 'plugin'
+        assert controller.on_demand_request_id == rid
+
+    def test_a_plugin_request_never_touches_the_mailbox(self, wired):
+        controller, manager = wired
+        _plugin('on-air', manager).request_on_demand(mode='on_air')
+        controller._drain_control_commands()
+        controller._activate_on_demand.assert_called_once()
+        mailbox_reads = [call for call in controller.cache_manager.get.call_args_list
+                         if call.args[0] == 'display_on_demand_request']
+        assert mailbox_reads == []
+        controller.cache_manager.delete.assert_not_called()
+
+    def test_requests_apply_in_order(self, wired):
+        controller, manager = wired
+        seen = []
+        controller._activate_on_demand = MagicMock(
+            side_effect=lambda r: seen.append(r['mode']))
+        plugin = _plugin('p', manager)
+        for mode in ('a', 'b', 'c'):
+            plugin.request_on_demand(mode=mode)
+        controller._poll_on_demand_requests()
+        assert seen == ['a', 'b', 'c']
+
+    def test_the_mailbox_still_works_for_older_plugins(self, wired):
+        controller, manager = wired
+        controller.mailbox['value'] = {'request_id': 'mb', 'action': 'start',
+                                       'plugin_id': 'birdnet-go'}
+        _plugin('on-air', manager).request_on_demand()
+        controller._poll_on_demand_requests()
+        ids = [call.args[0]['request_id'] for call in controller._activate_on_demand.call_args_list]
+        assert 'mb' in ids and len(ids) == 2
+
+    def test_a_failing_request_is_contained(self, wired):
+        controller, manager = wired
+        calls = []
+
+        def activate(request):
+            calls.append(request['mode'])
+            if request['mode'] == 'bad':
+                raise RuntimeError('plugin exploded')
+
+        controller._activate_on_demand = MagicMock(side_effect=activate)
+        plugin = _plugin('p', manager)
+        plugin.request_on_demand(mode='bad')
+        plugin.request_on_demand(mode='good')
+        controller._poll_on_demand_requests()
+        assert calls == ['bad', 'good']
+
+
+class TestPromptness:
+    def test_a_plugin_request_skips_the_pending_changes_floor(self, wired):
+        controller, manager = wired
+        controller._control_server = None
+        controller._service_pending_changes()
+        _plugin('p', manager).request_on_demand()
+        controller._service_pending_changes()        # well inside the 0.25 s floor
+        controller._activate_on_demand.assert_called_once()
+
+    def test_a_plugin_request_skips_the_mailbox_floor(self, wired):
+        controller, manager = wired
+        controller._control_server = _WakeServer()
+        controller._poll_on_demand_requests()        # sets the 1 s mailbox floor
+        _plugin('p', manager).request_on_demand()
+        controller._poll_on_demand_requests()
+        controller._activate_on_demand.assert_called_once()
+
+    def test_it_wakes_the_control_socket_wait(self, wired):
+        controller, manager = wired
+        server = ControlServer('/nonexistent/control.sock')   # never started
+        controller._control_server = server
+        assert not server.wait_for_command(0)
+        _plugin('p', manager).request_on_demand()
+        assert server.has_pending
+        assert controller._wait_for_control(5.0) is True     # returns at once
+        assert controller._control_command_pending()
+        controller._poll_on_demand_requests()
+        controller._activate_on_demand.assert_called_once()
+        assert not server.has_pending
+        assert not controller._control_command_pending()
+
+    def test_without_a_socket_a_waiting_request_cuts_the_sleep(self, wired):
+        controller, manager = wired
+        controller._control_server = None
+        _plugin('p', manager).request_on_demand()
+        started = time.monotonic()
+        assert controller._wait_for_control(5.0) is True
+        assert time.monotonic() - started < 1.0
+        assert controller._control_command_pending()
+
+    def test_nothing_waiting_keeps_the_floor(self, controller):
+        controller._control_server = None
+        controller._poll_on_demand_requests = MagicMock()
+        controller._service_pending_changes()
+        controller._service_pending_changes()
+        assert controller._poll_on_demand_requests.call_count == 1
+
+
+class TestThreads:
+    def test_requests_from_many_threads_all_land_in_order_per_thread(self, wired):
+        controller, manager = wired
+        seen = []
+        controller._activate_on_demand = MagicMock(
+            side_effect=lambda r: seen.append(r['mode']))
+        controller.PLUGIN_ON_DEMAND_QUEUE_SIZE = 10_000
+        threads_n, each = 8, 50
+        barrier = threading.Barrier(threads_n)
+
+        def ask(n):
+            plugin = _plugin(f'p{n}', manager)
+            barrier.wait()
+            for i in range(each):
+                assert plugin.request_on_demand(mode=f'{n}:{i}')
+
+        threads = [threading.Thread(target=ask, args=(n,)) for n in range(threads_n)]
+        for t in threads:
+            t.start()
+        # Drain while they ask, as the render thread would.
+        while any(t.is_alive() for t in threads):
+            controller._drain_control_commands()
+        for t in threads:
+            t.join()
+        controller._drain_control_commands()
+        assert len(seen) == threads_n * each
+        for n in range(threads_n):
+            mine = [int(m.split(':')[1]) for m in seen if m.startswith(f'{n}:')]
+            assert mine == list(range(each))
+
+    def test_a_full_queue_refuses(self, wired, caplog):
+        controller, manager = wired
+        controller.PLUGIN_ON_DEMAND_QUEUE_SIZE = 2
+        plugin = _plugin('p', manager)
+        assert plugin.request_on_demand()
+        assert plugin.request_on_demand()
+        assert plugin.request_on_demand() is None
+        assert 'queue full' in caplog.text
+        controller._poll_on_demand_requests()
+        assert controller._activate_on_demand.call_count == 2
+        assert plugin.request_on_demand()              # room again
+
+
+class TestStop:
+    def test_a_plugin_ends_its_own_session(self, wired):
+        controller, manager = wired
+        controller.on_demand_active = True
+        controller.on_demand_plugin_id = 'on-air'
+        controller._clear_on_demand = MagicMock()
+        assert _plugin('on-air', manager).end_on_demand()
+        controller._poll_on_demand_requests()
+        controller._clear_on_demand.assert_called_once_with(reason='requested-stop')
+        controller.cache_manager.delete.assert_not_called()
+
+    def test_a_plugin_cannot_end_another_plugins_session(self, wired):
+        controller, manager = wired
+        controller.on_demand_active = True
+        controller.on_demand_plugin_id = 'clock'       # the user started it
+        controller.on_demand_request_id = 'user'
+        controller._clear_on_demand = MagicMock()
+        _plugin('pomodoro-timer', manager).end_on_demand()
+        controller._poll_on_demand_requests()
+        controller._clear_on_demand.assert_not_called()
+        assert controller.on_demand_request_id == 'user'
+
+    def test_a_stop_with_no_session_does_nothing(self, wired):
+        controller, manager = wired
+        controller.on_demand_status = 'error'
+        controller._clear_on_demand = MagicMock()
+        _plugin('on-air', manager).end_on_demand()
+        controller._poll_on_demand_requests()
+        controller._clear_on_demand.assert_not_called()
+
+    def test_a_mailbox_stop_still_ends_any_session(self, wired):
+        controller, _ = wired
+        controller.on_demand_active = True
+        controller.on_demand_plugin_id = 'clock'
+        controller._clear_on_demand = MagicMock()
+        controller.mailbox['value'] = {'request_id': 's', 'action': 'stop',
+                                       'plugin_id': 'on-air'}
+        controller._poll_on_demand_requests()
+        controller._clear_on_demand.assert_called_once_with(reason='requested-stop')
+
+    def test_start_then_stop_from_one_thread_ends_the_session(self, wired):
+        controller, manager = wired
+
+        def activate(request):
+            controller.on_demand_active = True
+            controller.on_demand_plugin_id = request['plugin_id']
+
+        controller._activate_on_demand = MagicMock(side_effect=activate)
+        controller._clear_on_demand = MagicMock()
+        plugin = _plugin('pomodoro-timer', manager)
+        plugin.request_on_demand(mode='pomodoro', pinned=True)
+        plugin.end_on_demand()
+        controller._poll_on_demand_requests()
+        controller._activate_on_demand.assert_called_once()
+        controller._clear_on_demand.assert_called_once_with(reason='requested-stop')
+
+
+class TestNoDisplay:
+    """None is a plugin's cue to write the mailbox instead."""
+
+    def test_a_manager_with_no_handler_answers_none(self):
+        plugin = _plugin('p', _manager())
+        assert plugin.request_on_demand() is None
+        assert plugin.end_on_demand() is None
+
+    def test_no_plugin_manager_answers_none(self):
+        plugin = _plugin('p', None)
+        assert plugin.request_on_demand() is None
+        assert plugin.end_on_demand() is None
+
+    def test_an_old_cores_plugin_manager_answers_none(self):
+        class OldManager:
+            plugin_manifests = {}
+
+        plugin = _plugin('p', OldManager())
+        assert plugin.request_on_demand() is None
+        assert plugin.end_on_demand() is None
+
+    def test_a_handler_that_raises_answers_none(self):
+        def broken(request):
+            raise RuntimeError('boom')
+
+        plugin = _plugin('p', _manager(broken))
+        assert plugin.request_on_demand() is None
+        assert plugin.end_on_demand() is None
+
+    def test_a_handler_that_refuses_answers_none(self):
+        plugin = _plugin('p', _manager(lambda request: False))
+        assert plugin.request_on_demand() is None
+
+    def test_a_controller_built_without_init_refuses(self):
+        from src.display_controller import DisplayController
+        bare = DisplayController.__new__(DisplayController)
+        assert bare.submit_plugin_on_demand({'action': 'start'}) is False
+        assert bare._plugin_on_demand_pending() is False
+        bare._drain_plugin_on_demand()                 # nothing to do, no error
+
+    def test_the_feature_detection_pattern(self):
+        """The hasattr pattern from docs/PLUGIN_API_REFERENCE.md."""
+        writes = []
+
+        class OldCorePlugin:     # an older core's BasePlugin has no such method
+            pass
+
+        for plugin, expect_mailbox in ((OldCorePlugin(), True),
+                                       (_plugin('p', _manager()), True),
+                                       (_plugin('p', _manager(lambda r: True)), False)):
+            writes.clear()
+            if not (hasattr(plugin, 'request_on_demand')
+                    and plugin.request_on_demand(mode='m')):
+                writes.append('mailbox')
+            assert (writes == ['mailbox']) is expect_mailbox
+
+
+class TestArguments:
+    def test_the_manager_shapes_the_request(self):
+        got = []
+        plugin = _plugin('p', _manager(lambda r: got.append(r) or True))
+        plugin.request_on_demand()
+        plugin.end_on_demand()
+        start, stop = got
+        assert start['plugin_id'] == 'p' and start['mode'] is None
+        assert start['duration'] is None and start['pinned'] is False
+        assert start['source'] == 'plugin' and start['timestamp'] > 0
+        assert stop == {'action': 'stop', 'plugin_id': 'p', 'request_id': stop['request_id'],
+                        'timestamp': stop['timestamp'], 'source': 'plugin'}
+        assert start['request_id'] != stop['request_id']
+
+    @pytest.mark.parametrize('duration', [0, -5, float('inf'), float('nan')])
+    def test_no_positive_duration_means_no_limit(self, duration):
+        got = []
+        _plugin('p', _manager(lambda r: got.append(r) or True)).request_on_demand(
+            duration=duration)
+        assert got[0]['duration'] is None
+
+    @pytest.mark.parametrize('kwargs', [{'mode': 5}, {'mode': ''}, {'duration': '30'},
+                                        {'duration': True}])
+    def test_bad_arguments_raise(self, kwargs):
+        plugin = _plugin('p', _manager(lambda r: True))
+        with pytest.raises(ValueError):
+            plugin.request_on_demand(**kwargs)
+
+
+class TestMockManagers:
+    def test_a_magicmock_manager_reads_as_not_taken(self):
+        """A plugin's test with a MagicMock manager keeps its mailbox path."""
+        plugin = _plugin('p', MagicMock())
+        assert plugin.request_on_demand(mode='m') is None
+        assert plugin.end_on_demand() is None
+        plugin.plugin_manager.request_on_demand.assert_called_once_with(
+            'p', mode='m', duration=None, pinned=False)
+        plugin.plugin_manager.end_on_demand.assert_called_once_with('p')
+
+    def test_a_mocked_id_is_passed_through(self):
+        manager = MagicMock()
+        manager.request_on_demand.return_value = 'rid'
+        manager.end_on_demand.return_value = 'rid2'
+        plugin = _plugin('p', manager)
+        assert plugin.request_on_demand() == 'rid'
+        assert plugin.end_on_demand() == 'rid2'

test/test_plugin_runtime_snapshot.py

@@ -162,7 +162,7 @@ class TestPublisher:
         assert snapshot["stale_after"] == rt.STALE_AFTER
         assert snapshot["plugins"] == {"clock": {
             "loaded": True, "state": "enabled", "error": None,
-            "version": "1.0.0", "loaded_at": 10.0}}
+            "version": "1.0.0", "loaded_at": 10.0, "modes": None}}
 
     def test_changes_are_throttled_and_quiet_displays_refresh(self):
         cache = MagicMock()
@@ -423,7 +423,7 @@ def web_listing(api_v3_module, api_v3_client, shared_cache, tmp_path):  # noqa:
         {"id": "clock", "name": "Clock", "version": "1.1.0"},
         {"id": "weather", "name": "Weather", "version": "3.0.0"},
     ])
-    api.plugin_store_manager.get_registry_info = MagicMock(return_value=None)
+    api.plugin_store_manager.get_cached_registry_info = MagicMock(return_value=None)
     api.plugin_store_manager._get_local_git_info = MagicMock(return_value=None)
     api.config_manager.load_config = MagicMock(return_value={
         "clock": {"enabled": True}, "weather": {"enabled": True}})

test/test_plugin_system.py

@@ -189,6 +189,24 @@ class TestPluginExecutor:
         
         assert result is False
 
+    def test_a_base_exception_is_a_failure_not_a_timeout(self):
+        """asyncio.CancelledError derives from BaseException. Uncaught on
+        the executor's thread it ended the thread with the call never marked
+        complete, so a call that failed at once was reported, and recorded,
+        as timing out."""
+        import asyncio
+        import pytest
+        from src.exceptions import PluginError
+        from src.plugin_system.plugin_executor import PluginExecutor
+        executor = PluginExecutor(default_timeout=5.0)
+
+        def cancelled():
+            raise asyncio.CancelledError()
+
+        with pytest.raises(PluginError) as raised:
+            executor.execute_with_timeout(cancelled, plugin_id="test_plugin")
+        assert isinstance(raised.value.__cause__, asyncio.CancelledError)
+
 
 class TestPluginHealth:
     """Test plugin health monitoring."""