feat(plugins): request_on_demand() / end_on_demand() -- plugins ask for the screen in-process (#768)

* feat(plugins): request_on_demand() / end_on_demand() -- plugins ask for the screen in-process

Four plugins (birdnet-go, mqtt-notifications, on-air, pomodoro-timer) take
the screen by writing the display_on_demand_request mailbox, which the
display reads once a second while the control socket is up and which stage 5
removes. This is the in-process way in that stage needed.

- BasePlugin.request_on_demand(mode=None, duration=None, pinned=False) and
  end_on_demand(), safe from any thread, go through PluginManager to
  DisplayController.submit_plugin_on_demand, which only queues (at most 32)
  and wakes the render thread through ControlServer.wake(). The render
  thread applies them in _drain_control_commands, after socket commands,
  through _handle_on_demand_request, so they land within a frame; without a
  socket, on the next pending-changes pass.
- A plugin's stop ends only its own session; a mailbox stop still ends any.
- Both answer the request id, or None with no display in the process (web
  interface, check_plugin.py), a full queue, or a mock manager -- a plugin's
  cue to write the mailbox, which the display still reads.
- docs/PLUGIN_API_REFERENCE.md documents the hasattr pattern for plugins
  that must keep working on older cores; IPC_CONTROL_SOCKET.md and the
  CHANGELOG are updated.

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

* fix(display): wire the on-demand handler only on a manager that has it

Tests and the golden traces stand in simpler plugin managers.

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

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -19,6 +19,135 @@ 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
@@ -45,6 +174,18 @@ accepts both, but the store flags the old spelling as deprecated
   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
 

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.
 

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
@@ -367,7 +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
@@ -390,7 +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.
 
@@ -418,7 +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
@@ -436,11 +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
 
@@ -457,9 +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
@@ -576,15 +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
 
@@ -599,7 +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

@@ -464,7 +464,7 @@ 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
@@ -489,10 +489,19 @@ 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
 
@@ -2248,13 +2257,11 @@ 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
 {
@@ -2262,17 +2269,30 @@ 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`.
 
 ---
 

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
 
@@ -250,37 +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
 
@@ -345,3 +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/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
@@ -72,6 +72,43 @@ def _outlived(record: Any, max_age: Optional[float], now: float) -> bool:
         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."""
 
@@ -296,6 +333,24 @@ class CacheManager:
         """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.
 

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/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."""
+        """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/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)

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})
@@ -565,8 +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]
@@ -581,6 +613,7 @@ _ARG_TYPES: Dict[str, Any] = {
     Command.PLUGIN_RELOAD: PluginReloadArgs,
     Command.STATE_GET: StateGetArgs,
     Command.STATE_SUBSCRIBE: StateSubscribeArgs,
+    Command.ERRORS_CLEAR: ErrorsClearArgs,
 }
 
 
@@ -653,6 +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?
 

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.
@@ -552,6 +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.
@@ -569,9 +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)
@@ -759,8 +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:
@@ -1028,6 +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
@@ -1055,6 +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.
 
@@ -1079,7 +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
@@ -1091,7 +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/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]]] = {}
@@ -1844,3 +1848,73 @@ 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/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

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)

test/js/README.md

@@ -60,7 +60,7 @@ server has none.
 | `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 | `window.webLogin.createToken` from `partials/general.html`, run in a vm: 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_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 |
@@ -69,6 +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_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/run_all.js

@@ -36,7 +36,8 @@ const UNIT = ['unit/test_list_filter.js', 'unit/test_render_cards.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_general_web_login_token.js

@@ -3,32 +3,24 @@
 // 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 (window.webLogin.createToken in partials/general.html), 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.
+// 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.
 //
-// Runs the shipped inline script in a vm with a fake fetch and DOM -- no jsdom
-// and no server needed.
+// Imports the shipped page module and runs createToken with a fake fetch and
+// DOM -- no jsdom and no server needed.
 
-const fs = require('fs');
 const path = require('path');
-const vm = require('vm');
+const { pathToFileURL } = require('url');
 
-const PARTIAL = path.resolve(__dirname, '../../../web_interface/templates/v3/partials/general.html');
+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 webLoginScript() {
-  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('window.webLogin = {'));
-  if (!found) throw new Error('webLogin script not found in general.html');
-  return found;
-}
-
 function el() {
   const classes = new Set(['hidden']);
   return {
@@ -38,29 +30,28 @@ function el() {
   };
 }
 
-function load(answer) {
+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(),
+    '#web-login-tokens': el(),
+    '#web-login-new-token-value': el(),
+    '#web-login-new-token': el(),
   };
   const notes = [];
-  const window = { showNotification: (m, t) => notes.push([m, t]), alert() {}, confirm: () => true };
-  const context = {
-    window, console,
-    document: {
-      getElementById: id => elements[id] || null,
-      createElement: () => el(),
-      querySelectorAll: () => [],
-    },
-    fetch: () => Promise.resolve({
+  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,
-      json: () => Promise.resolve(answer.body),
-    }),
+    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]),
   };
-  vm.createContext(context);
-  vm.runInContext(webLoginScript(), context);
-  return { webLogin: context.window.webLogin, elements, notes };
+  return { general, ctx, elements, notes };
 }
 
 function dirtyForm() {
@@ -74,29 +65,25 @@ function dirtyForm() {
   };
 }
 
-const flush = async () => { for (let i = 0; i < 10; i++) await new Promise(r => setImmediate(r)); };
-
 (async () => {
   console.log('\n── General tab: API token form ──');
 
   {
-    const t = load({ ok: true, body: {
+    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();
-    t.webLogin.createToken(form);
-    await flush();
-    ok('the new token is shown', t.elements['web-login-new-token-value'].textContent === 'lmx_secret');
+    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 = load({ ok: false, body: { status: 'error', message: 'Name is required' } });
+    const t = await setup({ ok: false, body: { status: 'error', message: 'Name is required' } });
     const form = dirtyForm();
-    t.webLogin.createToken(form);
-    await flush();
+    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'));

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/test_api_v3_installed_display_modes.py

@@ -29,7 +29,7 @@ def installed(api_v3_module, api_v3_client, tmp_path):
         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_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_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_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_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_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_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_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

@@ -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_screen_runner.py

@@ -0,0 +1,455 @@
+"""ScreenRunner (src/screen_runner.py) on a scripted host and a fake clock.
+
+The golden traces (test_run_loop_golden.py) run it inside the real
+DisplayController; these pin down its own contract: which ExitReason each
+way of ending gives, the order it calls its host in, how the 125 Hz loop
+paces, and which service point asks what.
+"""
+
+from typing import Any, List, Optional, Tuple
+
+import pytest
+
+from src.display_arbiter import (
+    RELOAD_PLAN, SCREEN_PREEMPTERS, FramePolicy, ScreenPlan, Source,
+)
+from src.screen_runner import (
+    AFTER_COMPLETED_LOOP, AFTER_LOOP, DYNAMIC_GRACE, FINAL, FRAME, HIGH_FPS_INTERVAL,
+    Checkpoint, ExitReason, FirstFrame, NoticeRead, Screen, ScreenRunner,
+)
+
+WIFI_PLAN = ScreenPlan(Source.WIFI)
+
+
+class Clock:
+    """time/perf_counter read ``now``; sleep advances it."""
+
+    def __init__(self):
+        self.now = 0.0
+        self.sleeps: List[float] = []
+
+    def time(self) -> float:
+        return self.now
+
+    def perf_counter(self) -> float:
+        return self.now
+
+    def sleep(self, seconds: float) -> None:
+        self.sleeps.append(round(seconds, 6))
+        self.now += seconds
+
+
+class Host:
+    """A ScreenHost whose answers are scripted; records every call."""
+
+    def __init__(self, clock: Clock, *, shown=True, raised=False, minimum=10.0,
+                 maximum=10.0, dynamic=False, policy=FramePolicy.STATIC,
+                 completed=True, draws=None, checks=None, work=0.0,
+                 cycle_complete_at=None, dwell_to=None):
+        self.clock = clock
+        self.calls: List[Tuple[Any, ...]] = []
+        self.shown, self.raised = shown, raised
+        self.minimum, self.maximum = minimum, maximum
+        self.dynamic, self.policy, self.completed = dynamic, policy, completed
+        #: display() results for the frames after the first, in order.
+        self.draws = list(draws or [])
+        #: (checkpoint name, frame number) -> plan, or a callable(screen, cp).
+        self.checks = checks or {}
+        self.work = work
+        self.cycle_complete_at = cycle_complete_at
+        self.dwell_to = dwell_to
+        self.frames = 0
+
+    def first_frame(self, plan, plugin):
+        self.calls.append(("first", plan.mode))
+        return FirstFrame(self.shown, self.raised, False)
+
+    def complete_plan(self, plan, plugin):
+        self.calls.append(("complete",))
+        if not self.completed:
+            return None
+        return ScreenPlan(plan.source, mode=plan.mode, min_duration=self.minimum,
+                          max_duration=self.maximum, dynamic=self.dynamic,
+                          frame_policy=self.policy, preemptible_by=plan.preemptible_by)
+
+    def draw(self, screen):
+        self.frames += 1
+        self.calls.append(("draw", self.frames))
+        self.clock.now += self.work
+        return self.draws.pop(0) if self.draws else True
+
+    def after_frame(self, screen):
+        self.calls.append(("after_frame",))
+
+    def tick(self):
+        self.calls.append(("tick",))
+
+    def service(self, screen):
+        self.calls.append(("service",))
+        return ("scan", self.frames)
+
+    def wait_frame(self, interval, screen):
+        self.calls.append(("wait", interval))
+        self.clock.sleep(interval)
+        return self._scripted("wait", screen)
+
+    def check(self, screen, checkpoint, live_scan=None):
+        self.calls.append(("check", checkpoint.name, live_scan))
+        return self._scripted(checkpoint.name, screen, checkpoint)
+
+    def _scripted(self, name, screen, checkpoint=None):
+        answer = self.checks.get((name, self.frames))
+        if callable(answer):
+            return answer(screen, checkpoint)
+        return answer
+
+    def dwell(self, seconds):
+        self.calls.append(("dwell", round(seconds, 6)))
+        self.clock.now = self.dwell_to if self.dwell_to is not None else self.clock.now + seconds
+
+    def cycle_complete(self, screen):
+        self.calls.append(("cycle?",))
+        return self.cycle_complete_at is not None and self.clock.now >= self.cycle_complete_at
+
+
+PLAN = ScreenPlan(Source.ROTATION, mode="clock", preemptible_by=SCREEN_PREEMPTERS)
+
+
+def _run(**kwargs) -> Tuple[Any, Host, Clock]:
+    clock = Clock()
+    host = Host(clock, **kwargs)
+    outcome = ScreenRunner(clock, host).run(PLAN, plugin=object())
+    return outcome, host, clock
+
+
+def _names(host, *kinds):
+    return [c for c in host.calls if c[0] in kinds]
+
+
+class TestFirstFrame:
+
+    def test_no_plugin_is_empty_without_a_dispatch(self):
+        clock = Clock()
+        host = Host(clock)
+        outcome = ScreenRunner(clock, host).run(PLAN, plugin=None)
+        assert outcome.exit_reason is ExitReason.EMPTY
+        assert host.calls == []
+
+    @pytest.mark.parametrize("raised,reason", [(False, ExitReason.EMPTY),
+                                               (True, ExitReason.ERROR)])
+    def test_nothing_shown(self, raised, reason):
+        outcome, host, _ = _run(shown=False, raised=raised)
+        assert outcome.exit_reason is reason
+        assert host.calls == [("first", "clock")]
+
+    def test_an_on_demand_session_with_no_time_left(self):
+        outcome, host, _ = _run(completed=False)
+        assert outcome.exit_reason is ExitReason.PREEMPTED
+        assert outcome.preempted_by is None
+        assert host.calls == [("first", "clock"), ("complete",)]
+
+
+class TestStaticLoop:
+
+    def test_runs_its_duration_one_frame_a_second(self):
+        outcome, host, clock = _run(maximum=5.0)
+        assert outcome.exit_reason is ExitReason.DURATION
+        assert outcome.elapsed == 5.0
+        # Frames at 1..4 s; the wait that reaches 5 s ends it before a fifth.
+        assert host.frames == 4
+        assert clock.sleeps == [1.0] * 5
+        # Each frame: wait, tick, draw, follower frame, service, the check.
+        assert host.calls[2:9] == [("wait", 1.0), ("tick",), ("draw", 1), ("after_frame",),
+                                   ("service",), ("check", "frame", ("scan", 1)), ("wait", 1.0)]
+        # A completed loop: the after-loop look reads no notice, then FINAL.
+        assert host.calls[-2:] == [("check", "after-completed-loop", None), ("check", "final", None)]
+
+    def test_preempted_between_frames(self):
+        by = ScreenPlan(Source.ON_DEMAND, mode="x")
+        outcome, host, _ = _run(maximum=30.0, checks={("frame", 3): by})
+        assert outcome.exit_reason is ExitReason.PREEMPTED
+        assert outcome.preempted_by is by
+        assert outcome.elapsed == 3.0
+        # Decided at the service point: no second look, no dwell.
+        assert host.calls[-1] == ("check", "frame", ("scan", 3))
+
+    def test_preempted_by_a_socket_command_in_the_frame_wait(self):
+        outcome, host, _ = _run(maximum=30.0, checks={("wait", 2): WIFI_PLAN})
+        assert outcome.exit_reason is ExitReason.PREEMPTED
+        assert host.calls[-1] == ("wait", 1.0)
+
+    def test_display_false_makes_up_the_minimum(self):
+        outcome, host, _ = _run(maximum=12.0, draws=[True, False])
+        assert outcome.exit_reason is ExitReason.DISPLAY_FALSE
+        # The loop ended early: the after-loop look may read a notice, then
+        # the dwell makes up the rest of the 12 s.
+        assert _names(host, "check", "dwell")[-4:] == [
+            ("check", "after-loop", None), ("dwell", 10.0),
+            ("check", "after-dwell", None), ("check", "final", None)]
+        assert outcome.elapsed == 12.0
+
+    def test_a_notice_that_cuts_the_dwell_short_ends_the_screen(self):
+        def notice(screen, checkpoint):
+            assert checkpoint.notice is NoticeRead.ALWAYS
+            return WIFI_PLAN if checkpoint.notice_counts else None
+        outcome, _, _ = _run(maximum=12.0, draws=[False], dwell_to=6.0,
+                             checks={("after-dwell", 1): notice})
+        assert outcome.exit_reason is ExitReason.PREEMPTED
+
+    def test_a_notice_after_a_full_dwell_does_not(self):
+        def notice(screen, checkpoint):
+            return WIFI_PLAN if checkpoint.notice_counts else None
+        outcome, _, _ = _run(maximum=12.0, draws=[False],
+                             checks={("after-dwell", 1): notice})
+        assert outcome.exit_reason is ExitReason.DISPLAY_FALSE
+
+    def test_a_reload_ends_the_loop_but_the_screen_counts(self):
+        outcome, host, _ = _run(maximum=30.0, checks={("frame", 2): RELOAD_PLAN})
+        assert outcome.exit_reason is ExitReason.RELOAD
+        # Not decided at the service point: the after-loop look, the dwell
+        # (which returns at once while a reload waits) and FINAL follow.
+        assert ("check", "after-loop", None) in host.calls
+        assert ("check", "final", None) in host.calls
+
+    def test_a_change_after_the_loop_preempts(self):
+        by = ScreenPlan(Source.ROTATION, mode="weather")
+        outcome, _, _ = _run(maximum=3.0, checks={("final", 2): by})
+        assert outcome.exit_reason is ExitReason.PREEMPTED
+        assert outcome.preempted_by is by
+
+    def test_a_dynamic_screen_keeps_going_on_false(self):
+        outcome, host, _ = _run(minimum=3.0, maximum=8.0, dynamic=True,
+                                draws=[False, False, False])
+        assert outcome.exit_reason is ExitReason.DURATION
+        assert host.frames == 7
+
+
+class TestHighFpsLoop:
+
+    def test_paces_to_the_deadline(self):
+        outcome, host, clock = _run(maximum=0.05, policy=FramePolicy.HIGH_FPS, work=0.003)
+        assert outcome.exit_reason is ExitReason.DURATION
+        # 3 ms of drawing leaves 5 ms of an 8 ms frame to sleep.
+        assert set(clock.sleeps) == {round(HIGH_FPS_INTERVAL - 0.003, 6)}
+
+    def test_an_overrun_frame_still_yields(self):
+        _, _, clock = _run(maximum=0.05, policy=FramePolicy.HIGH_FPS, work=0.02)
+        assert set(clock.sleeps) == {0.001}
+
+    def test_service_before_the_sleep_check_after(self):
+        _, host, clock = _run(maximum=0.016, policy=FramePolicy.HIGH_FPS)
+        first = host.calls[2:7]
+        assert first == [("draw", 1), ("after_frame",), ("tick",), ("service",),
+                         ("check", "frame", ("scan", 1))]
+        assert clock.sleeps[0] == HIGH_FPS_INTERVAL
+
+    def test_preempted_after_the_frames_sleep(self):
+        outcome, _, clock = _run(maximum=30.0, policy=FramePolicy.HIGH_FPS,
+                                 checks={("frame", 3): WIFI_PLAN})
+        assert outcome.exit_reason is ExitReason.PREEMPTED
+        assert clock.now == pytest.approx(3 * HIGH_FPS_INTERVAL)
+
+    def test_display_false_has_no_make_up_dwell(self):
+        outcome, host, _ = _run(maximum=30.0, policy=FramePolicy.HIGH_FPS,
+                                draws=[True, False])
+        assert outcome.exit_reason is ExitReason.DISPLAY_FALSE
+        assert not _names(host, "dwell")
+
+
+class TestDynamicDuration:
+
+    def test_cycle_complete_after_the_minimum_and_grace(self):
+        outcome, host, _ = _run(minimum=3.0, maximum=20.0, dynamic=True,
+                                cycle_complete_at=1.0)
+        assert outcome.exit_reason is ExitReason.CYCLE_COMPLETE
+        # Not asked before minimum + grace (3.5 s): the 1 Hz loop's first
+        # frame at or past it is the one at 4 s.
+        assert outcome.elapsed == 4.0
+        assert DYNAMIC_GRACE == 0.5
+
+    def test_capped_at_the_maximum(self):
+        outcome, host, _ = _run(minimum=3.0, maximum=6.0, dynamic=True)
+        assert outcome.exit_reason is ExitReason.DURATION
+        # The end-of-screen log asks the plugin once more, before FINAL.
+        assert host.calls[-3:] == [("check", "after-completed-loop", None), ("cycle?",),
+                                   ("check", "final", None)]
+
+    def test_high_fps_cycle_complete(self):
+        outcome, _, _ = _run(minimum=0.02, maximum=1.0, dynamic=True,
+                             policy=FramePolicy.HIGH_FPS, cycle_complete_at=0.0)
+        assert outcome.exit_reason is ExitReason.CYCLE_COMPLETE
+        assert outcome.elapsed >= 0.02 + DYNAMIC_GRACE
+
+
+class TestCheckpoints:
+
+    @pytest.mark.parametrize("checkpoint,notice,reload", [
+        (FRAME, NoticeRead.IF_UNDECIDED, True),
+        (AFTER_LOOP, NoticeRead.IF_UNDECIDED, False),
+        (AFTER_COMPLETED_LOOP, NoticeRead.NEVER, False),
+        (FINAL, NoticeRead.NEVER, False),
+    ])
+    def test_what_each_service_point_considers(self, checkpoint, notice, reload):
+        """A reload counts only between frames; the notice file is read
+        where the loop read it before stage 3."""
+        assert isinstance(checkpoint, Checkpoint)
+        assert (checkpoint.notice, checkpoint.reload) == (notice, reload)
+
+    def test_the_screen_carries_the_completed_plan(self):
+        seen: List[Optional[Screen]] = []
+
+        def grab(screen, checkpoint):
+            seen.append(screen)
+        _run(maximum=2.0, checks={("frame", 1): grab})
+        assert seen[0].plan.frame_policy is FramePolicy.STATIC
+        assert seen[0].mode == "clock"
+
+
+class TestControllerServicePoint:
+    """DisplayController._screen_check: the reads it makes and what it claims,
+    on a controller built by the run-loop harness."""
+
+    @pytest.fixture
+    def dc(self, tmp_path):
+        import os
+        os.environ.setdefault("EMULATOR", "true")
+        from test._run_loop_harness import FakePlugin, RunLoopHarness
+        h = RunLoopHarness(tmp_path, horizon=10)
+        h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
+        h.add_plugin(FakePlugin("sports", ["sports_live"], duration=20,
+                                live=(0, 100), live_priority=True))
+        dc = h.controller
+        dc.current_display_mode = "clock"
+        dc.current_mode_index = 0
+        dc.reads = []
+
+        def read():
+            dc.reads.append(1)
+            return {"message": "AP mode", "expires_at": 1e12}
+        dc._check_wifi_status_message = read
+        return dc
+
+    @staticmethod
+    def _screen(mode="clock"):
+        from src.display_arbiter import ArbiterState, rotation_plan
+        return Screen(rotation_plan(ArbiterState(current_mode=mode)), plugin=None,
+                      accepts_display_mode=False, start=0.0)
+
+    def test_a_pending_notice_is_read_and_ends_the_screen(self, dc):
+        by = dc._screen_check(self._screen(), FRAME)
+        assert by.source is Source.WIFI and len(dc.reads) == 1
+
+    def test_not_read_once_the_mode_has_moved(self, dc):
+        dc.current_display_mode = "sports_live"
+        by = dc._screen_check(self._screen(), FRAME)
+        assert by.source is Source.ROTATION and dc.reads == []
+
+    def test_not_read_while_scheduled_off(self, dc):
+        dc.is_display_active = False
+        by = dc._screen_check(self._screen(), FRAME)
+        assert by.source is Source.SCHEDULED_OFF and dc.reads == []
+
+    def test_not_read_during_on_demand(self, dc):
+        dc.on_demand_active = True
+        dc.on_demand_schedule_override = True
+        assert dc._screen_check(self._screen(), FRAME) is None
+        assert dc.reads == []
+
+    def test_a_live_takeover_is_claimed_before_the_notice(self, dc):
+        by = dc._screen_check(self._screen(), FRAME, live_scan=("sports_live",))
+        assert by.source is Source.LIVE and dc.reads == []
+        assert dc.current_display_mode == "sports_live"
+        assert dc._live_takeover_unshown is True and dc._live_resume_index == 0
+
+    def test_after_a_completed_loop_the_notice_is_not_read(self, dc):
+        assert dc._screen_check(self._screen(), AFTER_COMPLETED_LOOP) is None
+        assert dc.reads == []
+
+    def test_after_a_full_dwell_it_is_read_but_does_not_count(self, dc):
+        from src.screen_runner import after_dwell
+        assert dc._screen_check(self._screen(), after_dwell(False)) is None
+        assert len(dc.reads) == 1
+
+    def test_a_reload_counts_only_between_frames(self, dc):
+        dc._check_wifi_status_message = lambda: None
+        dc._pending_plugin_reloads = ("pending",)
+        assert dc._screen_check(self._screen(), FRAME) is RELOAD_PLAN
+        assert dc._screen_check(self._screen(), AFTER_LOOP) is None
+
+    def test_an_on_demand_index_past_a_shortened_list_starts_again(self, dc):
+        """_take_plan writes the shown index back, so the session's next
+        step goes on from the mode actually shown."""
+        from src.display_arbiter import Arbiter, ArbiterInputs
+        dc.on_demand_active = True
+        dc.on_demand_modes = ["clock", "sports_live"]
+        dc.on_demand_mode_index = 5            # the list shrank under it
+        inputs = ArbiterInputs(schedule_on=True, on_demand_active=True,
+                               follower_active=False)
+        plan = dc._take_plan(Arbiter.decide(dc._arbiter_state(), inputs, 0.0))
+        assert plan.mode == "clock" and dc.on_demand_mode_index == 0
+        dc._advance_on_demand()
+        assert dc.current_display_mode == "sports_live"
+
+
+@pytest.mark.parametrize("policy,report_hold", [(FramePolicy.HIGH_FPS, True),
+                                                (FramePolicy.STATIC, False)])
+def test_only_the_high_fps_loop_reports_a_held_frame(policy, report_hold):
+    """#758's report_hold: the 125 Hz loop times frames held by update();
+    the 1 Hz loop's frames are a second apart and must not."""
+    from unittest.mock import MagicMock
+    from src.display_controller import _ScreenHost
+    controller = MagicMock()
+    plan = ScreenPlan(Source.ROTATION, mode="ticker", frame_policy=policy)
+    plugin = object()
+    _ScreenHost(controller).draw(Screen(plan, plugin, True, 0.0))
+    controller._display_once.assert_called_once_with(plugin, "ticker", True,
+                                                     report_hold=report_hold)
+
+
+def _rows(tmp_path, horizon, build):
+    import os
+    os.environ.setdefault("EMULATOR", "true")
+    from test._run_loop_harness import RunLoopHarness
+    h = RunLoopHarness(tmp_path, horizon=horizon)
+    build(h)
+    return h.run()["screens"]
+
+
+class TestThroughRun:
+    """Service points that only the full loop reaches, on the harness."""
+
+    def test_a_notice_pending_when_a_later_frame_is_empty_ends_the_screen(self, tmp_path):
+        """The after-loop look reads the notice when the loop ended early: a
+        1 Hz screen whose second frame has nothing to show must not sit in
+        its make-up dwell (which only notices a notice that arrives during
+        it) while the notice expires."""
+        from test._run_loop_harness import FakePlugin
+
+        def build(h):
+            h.add_plugin(FakePlugin("flaky", ["flaky"], duration=12, first_frame_only=True))
+            h.add_plugin(FakePlugin("clock", ["clock"], duration=12))
+            h.wifi_message(0.5, "Connected to HomeNet", duration=5)
+        rows = _rows(tmp_path, 30, build)
+        assert rows[0][1] == "flaky" and rows[0][2] == 1.0
+        assert rows[1][1] == "<wifi>"
+        # ... and the mode it cut short comes back, not the next one.
+        after = next(row for row in rows[1:] if row[1] != "<wifi>")
+        assert after[1] == "flaky"
+
+    def test_vegas_yielding_to_a_follower_shows_a_rotation_screen_first(self, tmp_path):
+        """Pins today's behaviour (docs/RUN_LOOP_REDESIGN.md, "may be
+        wrong"): the interrupt check stops the ticker for a follower, but
+        the yield path never looks at one, so a rotation screen runs its
+        full duration before the next pass hands the panel to the leader."""
+        from test._run_loop_harness import FakePlugin
+
+        def build(h):
+            h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
+            h.add_plugin(FakePlugin("weather", ["weather"], duration=20))
+            h.enable_vegas(cycle=30)
+            h.sync.follower_windows = [(10, 60)]
+        rows = _rows(tmp_path, 50, build)
+        assert rows[0][1] == "<vegas>" and rows[0][3] == "vegas-interrupt"
+        assert 10.0 <= rows[0][0] + rows[0][2] <= 10.2
+        assert rows[1][1] == "clock" and rows[1][2] == 20.0
+        assert rows[2][1] == "<follower>"

test/test_vegas_participation.py

@@ -446,7 +446,7 @@ class TestInstalledPluginsApi:
                     **(manifest_extra or {})}
             api.plugin_catalog.get_all_plugin_info = MagicMock(return_value=[info])
             api.plugin_catalog.get_plugin_directory = MagicMock(return_value=None)
-            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={'demo': config})
             response = api_v3_client.get('/api/v3/plugins/installed')
             assert response.status_code == 200

test/test_web_api.py

@@ -551,7 +551,7 @@ class TestPluginsAPI:
         mock_plugin_catalog.get_all_plugin_info.return_value = [
             {'id': 'weather', 'name': 'Weather Plugin'}
         ]
-        api_v3.plugin_store_manager.get_registry_info.return_value = None
+        api_v3.plugin_store_manager.get_cached_registry_info.return_value = None
 
         response = client.get('/api/v3/plugins/installed')
 
@@ -571,7 +571,7 @@ class TestPluginsAPI:
             {'id': 'weather', 'name': 'Weather', 'version': '1.0.0'}
         ]
         # Registry advertises a newer version than the installed one.
-        api_v3.plugin_store_manager.get_registry_info.return_value = {
+        api_v3.plugin_store_manager.get_cached_registry_info.return_value = {
             'verified': True, 'latest_version': '1.2.0'
         }
 
@@ -592,7 +592,7 @@ class TestPluginsAPI:
         mock_plugin_catalog.get_all_plugin_info.return_value = [
             {'id': 'weather', 'name': 'Weather', 'version': '1.2.0'}
         ]
-        api_v3.plugin_store_manager.get_registry_info.return_value = {
+        api_v3.plugin_store_manager.get_cached_registry_info.return_value = {
             'verified': True, 'latest_version': '1.2.0'
         }
 

test/test_web_plugin_dir_resolution.py

@@ -59,7 +59,7 @@ class TestInstalledList:
         info = {"id": "demo", "name": "Demo", "version": "1.0.0",
                 "description": "stale cached copy", "loaded": False}
         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.plugin_store_manager._get_local_git_info = MagicMock(return_value=None)
         api.config_manager.load_config = MagicMock(return_value={})
 

test/web_interface/test_es_modules.py

@@ -43,7 +43,7 @@ def _url(path):
 def test_the_module_directories_hold_modules():
     assert {p.name for p in MODULES} >= {"boot.js", "registry.js", "api.js", "facade.js", "cache.js",
                                          "durations.js", "operation-history.js", "raw-json.js",
-                                         "backup-restore.js"}
+                                         "backup-restore.js", "schedule.js", "general.js"}
     for directory in MODULE_DIRS:
         # node needs this to import them in the JS tests; browsers ignore it.
         assert '"type": "module"' in (directory / "package.json").read_text(encoding="utf-8")
@@ -104,6 +104,8 @@ CONVERTED = {
     "operation-history": ("operation_history.html", "/partials/operation-history"),
     "raw-json": ("raw_json.html", "/partials/raw-json"),
     "backup-restore": ("backup_restore.html", "/partials/backup-restore"),
+    "schedule": ("schedule.html", "/partials/schedule"),
+    "general": ("general.html", "/partials/general"),
 }
 
 # Old window.* names that moved into a page module. Each stays as a
@@ -114,6 +116,8 @@ ALIASES = {
                  "saveMainConfig", "saveSecretsConfig"],
     "backup-restore": ["exportBackup", "loadBackupList", "validateRestoreFile",
                        "clearRestore", "runRestore"],
+    "schedule": ["handleScheduleResponse", "handleDimScheduleResponse"],
+    "general": ["webLogin"],
 }
 
 
@@ -155,12 +159,15 @@ def test_moved_globals_stay_as_aliases(name):
         assert f"'{global_name}'" in boot, f"boot.js does not alias {global_name}"
         assert re.search(rf"^export (?:function|const) {global_name}\b", module, re.M), (
             f"pages/{name}.js does not export {global_name}")
-    # No template defines them any more.
+    # No template defines them any more, or calls them (an inline handler
+    # would reach the page only through the deprecated alias).
     for partial in PARTIALS.glob("*.html"):
         text = partial.read_text(encoding="utf-8")
         for global_name in ALIASES[name]:
             assert f"window.{global_name} =" not in text, partial.name
             assert f"function {global_name}(" not in text, partial.name
+            assert not re.search(rf"\b{global_name}\b", text), (
+                f"{partial.name} still names {global_name}")
 
 
 def test_every_registered_page_has_its_module_and_partial():
@@ -180,3 +187,32 @@ def test_converted_partials_carry_no_inline_script():
         if "data-page=" in text:
             assert "<script" not in text.lower(), (
                 f"{partial.name} is a page module now; its code belongs in js/pages/")
+
+
+def test_the_schedule_page_reads_its_config_back_intact():
+    """schedule.html hands both saved schedules to pages/schedule.js as JSON in
+    single-quoted data attributes; a value with quotes or markup must neither
+    end the attribute nor change on the way."""
+    from html.parser import HTMLParser
+    import json
+    import web_interface.app as web_app
+    from flask import render_template
+
+    hostile = {"mode": "per-day", "start_time": "07:00", "note": "it's a \"<b>\" & '</div>"}
+
+    class Root(HTMLParser):
+        attrs = None
+
+        def handle_starttag(self, tag, attrs):
+            if dict(attrs).get("data-page") == "schedule":
+                self.attrs = dict(attrs)
+
+    with web_app.app.test_request_context():
+        html = render_template("v3/partials/schedule.html", schedule_config=hostile,
+                               dim_schedule_config=None, normal_brightness=90)
+    parser = Root()
+    parser.feed(html)
+    assert parser.attrs is not None
+    assert json.loads(parser.attrs["data-schedule-config"]) == hostile
+    # A missing dim schedule arrives as null; the page treats that as {}.
+    assert json.loads(parser.attrs["data-dim-schedule-config"]) is None

test/web_interface/test_starlark_pixlet_routes.py

@@ -35,11 +35,35 @@ def client(monkeypatch):
     # and several tests below stub subprocess. Pin it: no test in this file
     # is about AP mode.
     monkeypatch.setattr(web_app, 'is_ap_mode_active', lambda: False)
+    # GET /plugins/installed looks up each plugin's registry entry, and on a
+    # cold cache that fetches plugins.json from GitHub -- so without a
+    # connection those tests sat in the HTTP retry loop. No test in this
+    # file is about the registry.
+    monkeypatch.setattr(web_app.plugin_store_manager, 'fetch_registry',
+                        lambda *args, **kwargs: {'plugins': []})
     app.config['TESTING'] = True
     with app.test_client() as c:
         yield c
 
 
+@pytest.fixture(autouse=True)
+def starlark_apps_dir(tmp_path, monkeypatch):
+    """Point every Starlark storage path at tmp_path for every test.
+
+    The manifest, its directory and the lock file are three separate module
+    constants. Fixtures that redirected the first two but not the lock left
+    the lock pointing at the repo, and on Linux (where the lock is taken)
+    each test created starlark-apps/manifest.json.lock in the checkout. The
+    directory is not created here; tests that need it make it.
+    """
+    from web_interface.blueprints import api_v3 as module
+    apps_dir = tmp_path / "starlark-apps"
+    monkeypatch.setattr(module, '_STARLARK_APPS_DIR', apps_dir)
+    monkeypatch.setattr(module, '_STARLARK_MANIFEST_FILE', apps_dir / 'manifest.json')
+    monkeypatch.setattr(module, '_STARLARK_MANIFEST_LOCK_FILE', apps_dir / 'manifest.json.lock')
+    return apps_dir
+
+
 class TestRoutesAreRegistered:
     """The failure was a missing route, so check the URL map directly.
 
@@ -398,13 +422,9 @@ class TestTheManifestSurvivesConcurrentWriters:
     """
 
     @pytest.fixture
-    def starlark_dir(self, tmp_path, monkeypatch):
-        from web_interface.blueprints import api_v3 as module
-        apps_dir = tmp_path / "starlark-apps"
-        apps_dir.mkdir()
-        monkeypatch.setattr(module, '_STARLARK_APPS_DIR', apps_dir)
-        monkeypatch.setattr(module, '_STARLARK_MANIFEST_FILE', apps_dir / 'manifest.json')
-        return apps_dir
+    def starlark_dir(self, starlark_apps_dir):
+        starlark_apps_dir.mkdir()
+        return starlark_apps_dir
 
     def test_each_writer_gets_its_own_temp_file(self, starlark_dir):
         from web_interface.blueprints import api_v3 as module
@@ -560,13 +580,9 @@ class TestTheManifestStaysRelocatable:
     """
 
     @pytest.fixture
-    def starlark_dir(self, tmp_path, monkeypatch):
-        from web_interface.blueprints import api_v3 as module
-        apps_dir = tmp_path / "starlark-apps"
-        apps_dir.mkdir()
-        monkeypatch.setattr(module, '_STARLARK_APPS_DIR', apps_dir)
-        monkeypatch.setattr(module, '_STARLARK_MANIFEST_FILE', apps_dir / 'manifest.json')
-        return apps_dir
+    def starlark_dir(self, starlark_apps_dir):
+        starlark_apps_dir.mkdir()
+        return starlark_apps_dir
 
     def _install(self, tmp_path):
         from web_interface.blueprints import api_v3 as module
@@ -606,13 +622,10 @@ class TestManifestLockPreventsLostUpdates:
     """
 
     @pytest.fixture
-    def starlark_dir(self, tmp_path, monkeypatch):
+    def starlark_dir(self, starlark_apps_dir):
         from web_interface.blueprints import api_v3 as module
-        apps_dir = tmp_path / "starlark-apps"
+        apps_dir = starlark_apps_dir
         apps_dir.mkdir()
-        monkeypatch.setattr(module, '_STARLARK_APPS_DIR', apps_dir)
-        monkeypatch.setattr(module, '_STARLARK_MANIFEST_FILE', apps_dir / 'manifest.json')
-        monkeypatch.setattr(module, '_STARLARK_MANIFEST_LOCK_FILE', apps_dir / 'manifest.json.lock')
         module._write_starlark_manifest({'apps': {}})
         return apps_dir
 
@@ -700,12 +713,10 @@ class TestConfigAndManifestStayInSync:
     """
 
     @pytest.fixture
-    def app_dir(self, tmp_path, monkeypatch):
+    def app_dir(self, starlark_apps_dir):
         from web_interface.blueprints import api_v3 as module
-        apps_dir = tmp_path / "starlark-apps"
+        apps_dir = starlark_apps_dir
         apps_dir.mkdir()
-        monkeypatch.setattr(module, '_STARLARK_APPS_DIR', apps_dir)
-        monkeypatch.setattr(module, '_STARLARK_MANIFEST_FILE', apps_dir / 'manifest.json')
         one_app_dir = apps_dir / 'demo'
         one_app_dir.mkdir()
         module._write_starlark_manifest({'apps': {'demo': {'name': 'Demo', 'enabled': True}}})
@@ -1049,13 +1060,18 @@ class TestTheStoreUsesTheTokenTheUserConfigured:
     /plugins/store/github-status reported `authenticated: true` with a
     rate_limit of 5000 while /starlark/repository/browse reported a limit of
     60 -- the store going blank was that 60 running out.
+
+    The managers are attributes web_interface/app.py hangs on the blueprint
+    when it is imported, so they exist only once some earlier test has
+    imported the app. Every patch here passes create=True: these tests must
+    not depend on which test ran before them.
     """
 
     def test_the_store_managers_token_is_used(self):
         from web_interface.blueprints import api_v3 as mod
 
         with patch.object(mod.api_v3, 'plugin_store_manager',
-                          MagicMock(github_token='ghp_configured')):
+                          MagicMock(github_token='ghp_configured'), create=True):
             assert mod._starlark_github_token() == 'ghp_configured'
 
     def test_a_hand_edited_config_key_still_works(self):
@@ -1064,8 +1080,8 @@ class TestTheStoreUsesTheTokenTheUserConfigured:
         cfg = MagicMock()
         cfg.load_config.return_value = {'github_token': 'ghp_by_hand'}
         with patch.object(mod.api_v3, 'plugin_store_manager',
-                          MagicMock(github_token=None)), \
-             patch.object(mod.api_v3, 'config_manager', cfg):
+                          MagicMock(github_token=None), create=True), \
+             patch.object(mod.api_v3, 'config_manager', cfg, create=True):
             assert mod._starlark_github_token() == 'ghp_by_hand'
 
     def test_no_token_anywhere_is_not_an_error(self):
@@ -1074,8 +1090,8 @@ class TestTheStoreUsesTheTokenTheUserConfigured:
         cfg = MagicMock()
         cfg.load_config.return_value = {}
         with patch.object(mod.api_v3, 'plugin_store_manager',
-                          MagicMock(github_token=None)), \
-             patch.object(mod.api_v3, 'config_manager', cfg):
+                          MagicMock(github_token=None), create=True), \
+             patch.object(mod.api_v3, 'config_manager', cfg, create=True):
             assert mod._starlark_github_token() is None
 
     def test_an_unreadable_config_does_not_take_the_store_down(self):
@@ -1084,8 +1100,8 @@ class TestTheStoreUsesTheTokenTheUserConfigured:
         cfg = MagicMock()
         cfg.load_config.side_effect = OSError("config.json is unreadable")
         with patch.object(mod.api_v3, 'plugin_store_manager',
-                          MagicMock(github_token=None)), \
-             patch.object(mod.api_v3, 'config_manager', cfg):
+                          MagicMock(github_token=None), create=True), \
+             patch.object(mod.api_v3, 'config_manager', cfg, create=True):
             assert mod._starlark_github_token() is None
 
     def test_browse_hands_the_token_to_the_repository(self, client):
@@ -1099,7 +1115,7 @@ class TestTheStoreUsesTheTokenTheUserConfigured:
         repo.return_value.get_rate_limit_info.return_value = {'remaining': 4999}
 
         with patch.object(mod.api_v3, 'plugin_store_manager',
-                          MagicMock(github_token='ghp_configured')), \
+                          MagicMock(github_token='ghp_configured'), create=True), \
              patch('web_interface.blueprints.api_v3._get_tronbyte_repository_class',
                    return_value=repo):
             client.get('/api/v3/starlark/repository/browse')
@@ -1189,15 +1205,13 @@ class TestStandaloneRenderUsesTheDeviceLocation:
     SCHEMA = {"schema": [{"typeOf": "location", "id": "location"}]}
 
     @pytest.fixture
-    def app_dir(self, tmp_path, monkeypatch):
+    def app_dir(self, starlark_apps_dir, monkeypatch):
         from web_interface.blueprints import api_v3 as module
-        apps_dir = tmp_path / "starlark-apps"
+        apps_dir = starlark_apps_dir
         app_dir = apps_dir / "weather"
         app_dir.mkdir(parents=True)
         (app_dir / "weather.star").write_text("# app")
         (app_dir / "schema.json").write_text(json.dumps(self.SCHEMA))
-        monkeypatch.setattr(module, '_STARLARK_APPS_DIR', apps_dir)
-        monkeypatch.setattr(module, '_STARLARK_MANIFEST_FILE', apps_dir / 'manifest.json')
         (apps_dir / 'manifest.json').write_text(json.dumps(
             {'apps': {'weather': {'star_file': 'weather.star'}}}))
         config_manager = MagicMock()

test/web_interface/test_web_process_runs_no_plugin_code.py

@@ -128,6 +128,7 @@ class Web:
         store = api.plugin_store_manager
         store.plugins_dir = str(self.plugins_dir)
         store.get_registry_info.return_value = None
+        store.get_cached_registry_info.return_value = None
         store.get_plugin_info.return_value = None
         store._get_local_git_info.return_value = None
         store.install_plugin.return_value = True

web_interface/blueprints/api_v3/display.py

@@ -33,16 +33,28 @@ def _cache_manager():
 
 
 
+class _NotDelivered(Exception):
+    """The display took an on-demand request over the socket and did not
+    accept it (``busy``, ``invalid_args``, ...) or did not answer in time."""
+
+    def __init__(self, reason):
+        super().__init__(reason)
+        self.reason = reason
+
+
 def _deliver_on_demand(payload):
     """Hand an on-demand request to the display: control socket, else mailbox.
 
     The socket (src/ipc) answers with an acknowledgement as soon as the
-    display has the command queued for its render thread. Any failure -- no
-    socket (the display is stopped or predates it), a timeout, a refusal --
-    writes the file mailbox instead, exactly as before the socket existed;
-    the display reads it within ON_DEMAND_POLL_INTERVAL. Both carry the same
-    request_id, so a request that reached the display both ways (a reply
-    that timed out after the command was queued) is still processed once.
+    display has the command queued for its render thread. The file mailbox
+    is written only when the socket could not carry the request at all
+    (``control_client.should_fall_back``): no socket (the display is stopped
+    or predates it), a refused connection, or a display too old to know the
+    command. The display reads it within its mailbox poll interval.
+
+    A display that had the request and refused it, or did not answer in
+    time, raises :class:`_NotDelivered`: a mailbox copy would be refused
+    the same way, or hide a stuck display behind a "success".
 
     Returns ``(transport, socket_error)``: ``'socket'`` and None, or
     ``'mailbox'`` and the socket failure's reason code.
@@ -57,6 +69,10 @@ def _deliver_on_demand(payload):
         return 'socket', None
     except control_client.ControlError as e:
         reason = _socket_reason_code(e.reason)
+        if not control_client.should_fall_back(e):
+            logger.warning("The display did not accept on-demand %s %s (%s)",
+                           payload['action'], payload['request_id'], e)
+            raise _NotDelivered(reason) from None
         if reason in _QUIET_SOCKET_REASONS:
             logger.debug("On-demand %s via the mailbox: %s", payload['action'], e)
         else:
@@ -69,6 +85,17 @@ def _deliver_on_demand(payload):
     return 'mailbox', reason
 
 
+def _not_delivered_response(request_id, action, reason):
+    """The answer when the display had the request and did not accept it."""
+    status = 400 if reason == 'invalid_args' else 503
+    return jsonify({
+        'status': 'error',
+        'message': (f'The display service did not accept the on-demand {action} '
+                    f'request ({reason})'),
+        'data': {'request_id': request_id, 'transport': 'socket', 'socket_error': reason},
+    }), status
+
+
 def _withdraw_on_demand(request_id):
     """Take a start request the route has refused back out of the mailbox.
 
@@ -277,7 +304,10 @@ def start_on_demand_display():
         'pinned': pinned,
         'timestamp': _pkg.time.time()
     }
+    try:
         transport, socket_error = _deliver_on_demand(request_payload)
+    except _NotDelivered as e:
+        return _not_delivered_response(request_id, 'start', e.reason)
 
     # A socket acknowledgement is the display itself answering: it is
     # running and has the request queued, whatever systemd says (a display
@@ -312,9 +342,10 @@ def start_on_demand_display():
     # MQTT on-demand command, which posts here with the default -- cold-
     # restarted the display process: every plugin reloaded and the panel was
     # blank for seconds. The restart bought nothing. The running process
-    # reads this mailbox 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, and a restarted one got the request the same way: the
+    # looks at this mailbox at least once a second, from its dwell sleep,
+    # its render loops and Vegas's interrupt check as well as the main loop
+    # (DisplayController._mailbox_poll_interval), and a restarted one got
+    # the request the same way: the
     # startup path only restores a session the display itself saved
     # (display_on_demand_config), so it loaded nothing it would not have had.
     service_result = None
@@ -365,7 +396,14 @@ def stop_on_demand_display():
         'action': 'stop',
         'timestamp': _pkg.time.time()
     }
+    try:
         transport, socket_error = _deliver_on_demand(request_payload)
+    except _NotDelivered as e:
+        if not stop_service:
+            return _not_delivered_response(request_id, 'stop', e.reason)
+        # Stopping the service ends on-demand too, whatever the display did
+        # with the request.
+        transport, socket_error = 'socket', e.reason
 
     service_result = None
     if stop_service:

web_interface/blueprints/api_v3/misc.py

@@ -374,6 +374,23 @@ def _read_errors():
     return snapshot, clear_request
 
 
+def _send_error_clear(request_id, cutoff):
+    """``errors.clear`` over the control socket: the display's answer, or None
+    when the socket could not carry it (no socket, or a display older than
+    the command) and the clear goes to the mailbox instead. A display that
+    took the request and failed raises ControlError (no second copy)."""
+    client = _pkg.control_client
+    try:
+        return client.errors_clear(request_id, cutoff)
+    except client.ControlError as e:
+        if not client.should_fall_back(e):
+            raise
+        _pkg._log_socket_failure('errors.clear', e, _pkg._socket_reason_code(e.reason))
+    except Exception:  # never let the socket path break the route
+        logger.exception("Control socket client failed clearing errors; using the mailbox")
+    return None
+
+
 @api_v3.route('/errors/summary', methods=['GET'])
 def get_error_summary():
     """
@@ -471,7 +488,17 @@ def clear_old_errors():
         now = _pkg.time.time()
         cutoff = now if clear_all else now - max_age_hours * 3600
         try:
-            result = _errors.request_error_clear(_errors_cache(), cutoff)
+            result = _errors.request_error_clear(_errors_cache(), cutoff,
+                                                 send=_send_error_clear)
+        except _pkg.control_client.ControlError as e:
+            reason = _pkg._socket_reason_code(e.reason)
+            logger.warning("The display did not apply the error clear: %s", e)
+            return error_response(
+                error_code=ErrorCode.SYSTEM_ERROR,
+                message="The display service did not apply the clear",
+                context={'socket_error': reason},
+                status_code=503
+            )
         except OSError as e:
             logger.error("Could not record an error clear request: %s", e)
             return error_response(
@@ -481,11 +508,12 @@ def clear_old_errors():
             )
 
         scope = "all errors" if clear_all else f"errors older than {max_age_hours} hours"
-        return success_response(
-            data=result,
-            message=(f"Clear of {scope} requested; the display service applies it "
+        if result.get('applied'):
+            message = f"Cleared {scope}"
+        else:
+            message = (f"Clear of {scope} requested; the display service applies it "
                        f"within about {int(_errors.SNAPSHOT_TICK_INTERVAL)} seconds")
-        )
+        return success_response(data=result, message=message)
     except Exception as e:
         logger.error(f"Error clearing old errors: {e}", exc_info=True)
         return error_response(

web_interface/blueprints/api_v3/plugins.py

@@ -106,8 +106,13 @@ def get_installed_plugins():
             plugin_config = {}
         enabled = bool(plugin_config.get('enabled', False))
 
-        # Verified + latest published version from registry (no network call)
-        store_info = api_v3.plugin_store_manager.get_registry_info(plugin_id)
+        # Verified + latest published version from the registry copy already
+        # in memory. Never a fetch: on a cold cache get_registry_info would
+        # download plugins.json, and offline wait out its timeout and retries
+        # for every plugin. With no copy yet these are absent (no update or
+        # verified badge) and a background refresh fills them in for a
+        # later load.
+        store_info = api_v3.plugin_store_manager.get_cached_registry_info(plugin_id)
         verified = store_info.get('verified', False) if store_info else False
         latest_version = store_info.get('latest_version', '') if store_info else ''
         installed_version = plugin_info.get('version', '')

web_interface/static/v3/app.js

@@ -57,11 +57,13 @@ document.body.addEventListener('htmx:afterRequest', function(event) {
     // Show the server's message, unless the element that made the request
     // (or its form) has its own after-request handler: every such handler in
     // the templates reports the result itself, and this used to repeat it,
-    // so each save showed two toasts.
+    // so each save showed two toasts. A form whose page module reports the
+    // result instead (a js/pages/*.js listener for htmx:afterRequest) is
+    // marked data-reports-result.
     const response = event.detail.xhr;
     const elt = event.detail.elt;
     const reportsItself = elt && elt.closest &&
-        elt.closest('[hx-on\\:\\:after-request], [hx-on\\:htmx\\:after-request]');
+        elt.closest('[hx-on\\:\\:after-request], [hx-on\\:htmx\\:after-request], [data-reports-result]');
     if (!reportsItself && response && response.responseText) {
         try {
             const data = JSON.parse(response.responseText);

web_interface/static/v3/js/core/boot.js

@@ -43,18 +43,33 @@ const pages = {
     'operation-history': page(function() { return import('../pages/operation-history.js'); }),
     'raw-json': page(function() { return import('../pages/raw-json.js'); }),
     'backup-restore': page(function() { return import('../pages/backup-restore.js'); }),
+    'schedule': page(function() { return import('../pages/schedule.js'); }),
+    'general': page(function() { return import('../pages/general.js'); }),
 };
 Object.keys(pages).forEach(function(name) { registry.register(name, pages[name]); });
 
-/** Keep window[name] working: forward to the page module's export of the same name. */
-function alias(pageName, name, replacement) {
+/** A function that calls `pick(module)` with its arguments, loading the page's module if needed. */
+function forward(pageName, pick) {
     const loader = pages[pageName];
-    facade.deprecate(name, function() {
+    return function() {
         const args = arguments;
         const module = loader.loaded();
-        if (module) return module[name].apply(null, args);
-        return loader().then(function(loaded) { return loaded[name].apply(null, args); });
-    }, replacement);
+        if (module) return pick(module).apply(null, args);
+        return loader().then(function(loaded) { return pick(loaded).apply(null, args); });
+    };
+}
+
+/** Keep window[name] working: forward to the page module's export of the same name. */
+function alias(pageName, name, replacement) {
+    facade.deprecate(name, forward(pageName, function(module) { return module[name]; }), replacement);
+}
+
+/** The same for an old global object of functions: each method forwards to the export's method. */
+function aliasObject(pageName, name, methods, replacement) {
+    const target = Object.fromEntries(methods.map(function(method) {
+        return [method, forward(pageName, function(module) { return module[name][method]; })];
+    }));
+    facade.deprecate(name, Object.freeze(target), replacement);
 }
 
 // Old globals the converted pages used to define.
@@ -65,5 +80,10 @@ alias('cache', 'deleteCacheFile', "the Cache tab's Delete buttons");
 ['exportBackup', 'loadBackupList', 'validateRestoreFile', 'clearRestore', 'runRestore'].forEach(function(name) {
     alias('backup-restore', name, "the Backup & Restore tab's buttons");
 });
+['handleScheduleResponse', 'handleDimScheduleResponse'].forEach(function(name) {
+    alias('schedule', name, "the Schedule tab's own save handling");
+});
+aliasObject('general', 'webLogin', ['setPassword', 'disable', 'createToken', 'copyToken', 'revoke'],
+            "the General tab's Security buttons");
 
 registry.start();

web_interface/static/v3/js/pages/general.js

@@ -0,0 +1,262 @@
+/*
+ * pages/general.js -- the General tab (templates/v3/partials/general.html).
+ *
+ * The settings form stays plain htmx (hx-post to /api/v3/config/main; its
+ * hx-on calls the shared showSaveResult). This module:
+ *   - draws the timezone-selector widget into #timezone_container, with the
+ *     saved zone from its data-timezone attribute
+ *   - runs the optional Security section (web login, #683): three forms and
+ *     two kinds of button, all marked data-action and handled by one
+ *     delegated submit and one delegated click listener on the page root, so
+ *     a token row added later needs no listener of its own
+ *
+ * Login changes are writes: they are not cancelled when the page is swapped
+ * away, so the server always finishes and the result is still reported, but
+ * nothing is drawn into a page that has gone. Token names reach the page as
+ * text.
+ *
+ * window.webLogin (setPassword, disable, createToken, copyToken, revoke) is a
+ * deprecated alias made in core/boot.js; it forwards to the webLogin export
+ * at the bottom of this file.
+ */
+
+const API = '/api/v3/auth';
+const RETRY_MS = 50;
+const MAX_TRIES = 200;
+
+// The mounted page, for the deprecated alias (boot.js).
+let active = null;
+
+function windowOf(ctx) {
+    return ctx.root.ownerDocument.defaultView;
+}
+
+function find(ctx, id) {
+    return ctx.root.querySelector('#' + id);
+}
+
+function field(form, name) {
+    const el = form.querySelector('[name="' + name + '"]');
+    return el ? el.value : '';
+}
+
+/**
+ * A login request. Resolves to {ok, d}: d is the JSON body, also for a
+ * refused request (its message is shown). A network failure rejects; the
+ * optional login's own "sign in again" answer resolves to null, since the
+ * page is already on its way to the login form.
+ */
+function send(ctx, method, url, body) {
+    return ctx.api.request(method, url, body === undefined ? {} : { json: body }).then(function(d) {
+        return { ok: true, d: d };
+    }, function(err) {
+        if (err && err.loginRequired) return null;
+        // Only an HTTP answer is a refusal; anything else is a failure.
+        if (!err || err.name !== 'ApiError' || err.network || !err.status) throw err;
+        return { ok: false, d: err.body && typeof err.body === 'object' ? err.body : {} };
+    });
+}
+
+function failed(ctx) {
+    return function(err) { ctx.notify('Request failed: ' + ((err && err.message) || err), 'error'); };
+}
+
+function reloadSection(ctx) {
+    if (ctx.signal.aborted) return; // already swapped for a fresh copy
+    const win = windowOf(ctx);
+    if (win.htmx) {
+        win.htmx.ajax('GET', '/v3/partials/general', { target: '#general-content', swap: 'innerHTML' });
+    } else {
+        win.location.reload();
+    }
+}
+
+function tokenRow(doc, record) {
+    const row = doc.createElement('div');
+    row.className = 'flex flex-wrap items-center justify-between gap-2 border border-gray-200 rounded-md px-4 py-2';
+    row.dataset.tokenId = record.id;
+    const text = doc.createElement('div');
+    text.className = 'text-sm';
+    [['font-semibold text-gray-900', record.name],
+     ['font-mono text-gray-600 ml-2', record.prefix + '…'],
+     ['text-gray-600 ml-2', 'created just now']].forEach(function(part) {
+        const span = doc.createElement('span');
+        span.className = part[0];
+        span.textContent = part[1];
+        text.appendChild(span);
+    });
+    const button = doc.createElement('button');
+    button.type = 'button';
+    button.className = 'text-sm text-red-600 hover:underline';
+    button.dataset.action = 'revoke-token';
+    button.dataset.tokenName = record.name;
+    button.textContent = 'Revoke';
+    row.appendChild(text);
+    row.appendChild(button);
+    return row;
+}
+
+/** The password form: set (or change) the password, then redraw the section. */
+export function setPassword(ctx, form) {
+    const next = field(form, 'new_password');
+    if (next !== field(form, 'confirm_password')) {
+        ctx.notify('The two new passwords do not match.', 'error');
+        return Promise.resolve(false);
+    }
+    const body = { new_password: next };
+    if (form.querySelector('[name="current_password"]')) body.current_password = field(form, 'current_password');
+    return send(ctx, 'POST', API + '/password', body).then(function(res) {
+        if (!res) return false;
+        ctx.notify(res.d.message || (res.ok ? 'Saved' : 'Could not save the password'), res.ok ? 'success' : 'error');
+        if (res.ok) reloadSection(ctx);
+        return res.ok;
+    }).catch(failed(ctx));
+}
+
+/** The "Turn login off" form. */
+export function disableLogin(ctx, form) {
+    if (!windowOf(ctx).confirm('Turn login off? Anyone on your network will be able to open this page.')) {
+        return Promise.resolve(false);
+    }
+    return send(ctx, 'POST', API + '/disable', { current_password: field(form, 'current_password') }).then(function(res) {
+        if (!res) return false;
+        ctx.notify(res.d.message || (res.ok ? 'Login is off' : 'Could not turn login off'), res.ok ? 'success' : 'error');
+        if (res.ok) reloadSection(ctx);
+        return res.ok;
+    }).catch(failed(ctx));
+}
+
+/** The "Create token" form: add the row and show the token once. */
+export function createToken(ctx, form) {
+    return send(ctx, 'POST', API + '/tokens', { name: field(form, 'name') }).then(function(res) {
+        if (!res) return false;
+        if (!res.ok) {
+            ctx.notify(res.d.message || 'Could not create the token', 'error');
+            return false;
+        }
+        const data = res.d.data || {};
+        // app.js marks a form dirty on input and clears the mark only after
+        // an htmx save; this one posts with fetch, so clear it here or a
+        // reload asks "Leave site?" about a saved token.
+        form.reset();
+        form.removeAttribute('data-dirty');
+        if (!ctx.signal.aborted) {
+            const list = find(ctx, 'web-login-tokens');
+            if (list && data.record) {
+                const empty = list.querySelector('[data-empty]');
+                if (empty) empty.remove();
+                list.appendChild(tokenRow(ctx.root.ownerDocument, data.record));
+            }
+            const value = find(ctx, 'web-login-new-token-value');
+            const box = find(ctx, 'web-login-new-token');
+            if (value) value.textContent = data.token;
+            if (box) box.classList.remove('hidden');
+        }
+        ctx.notify(res.d.message || 'Token created', 'success');
+        return true;
+    }).catch(failed(ctx));
+}
+
+/** The Copy button next to a new token. */
+export function copyToken(ctx) {
+    const win = windowOf(ctx);
+    const box = find(ctx, 'web-login-new-token-value');
+    if (!box) return;
+    if (win.navigator.clipboard && win.isSecureContext) {
+        win.navigator.clipboard.writeText(box.textContent).then(function() { ctx.notify('Token copied', 'success'); });
+        return;
+    }
+    // Plain http on a LAN is not a secure context: select it instead.
+    const range = ctx.root.ownerDocument.createRange();
+    range.selectNodeContents(box);
+    const selection = win.getSelection();
+    selection.removeAllRanges();
+    selection.addRange(range);
+    ctx.notify('Selected: press Ctrl+C (or Cmd+C) to copy.', 'info');
+}
+
+/** A token row's Revoke button. */
+export function revokeToken(ctx, id, name) {
+    if (!windowOf(ctx).confirm('Revoke the token "' + name + '"? Anything using it stops working.')) {
+        return Promise.resolve(false);
+    }
+    return send(ctx, 'DELETE', API + '/tokens/' + encodeURIComponent(id)).then(function(res) {
+        if (!res) return false;
+        ctx.notify(res.d.message || (res.ok ? 'Token revoked' : 'Could not revoke the token'), res.ok ? 'success' : 'error');
+        if (!res.ok) return false;
+        ctx.root.querySelectorAll('#web-login-tokens [data-token-id]').forEach(function(row) {
+            if (row.dataset.tokenId === id) row.remove();
+        });
+        return true;
+    }).catch(failed(ctx));
+}
+
+const FORM_ACTIONS = { 'set-password': setPassword, 'disable-login': disableLogin, 'create-token': createToken };
+
+function drawTimezone(root, ctx) {
+    const win = root.ownerDocument.defaultView;
+    let tries = 0;
+    function attempt() {
+        ctx.state.timer = null;
+        if (ctx.signal.aborted) return;
+        const container = root.querySelector('#timezone_container');
+        if (!container) return;
+        const widget = win.LEDMatrixWidgets && win.LEDMatrixWidgets.get('timezone-selector');
+        if (!widget) {
+            if (++tries < MAX_TRIES) ctx.state.timer = win.setTimeout(attempt, RETRY_MS);
+            else win.console.error('[General] timezone-selector widget not available');
+            return;
+        }
+        // Only render if container is empty (not already rendered)
+        if (container.children.length > 0) return;
+        widget.render(container, {
+            'x-options': { showOffset: true, placeholder: 'Select your timezone...' },
+        }, container.dataset.timezone || 'America/Chicago', {
+            fieldId: 'timezone',
+            name: 'timezone',
+        });
+    }
+    attempt();
+}
+
+export function init(root, ctx) {
+    const on = { signal: ctx.signal };
+    root.addEventListener('submit', function(event) {
+        const form = event.target;
+        const action = form && form.dataset ? FORM_ACTIONS[form.dataset.action] : null;
+        if (!action) return; // the settings form: htmx posts it
+        event.preventDefault();
+        action(ctx, form);
+    }, on);
+    root.addEventListener('click', function(event) {
+        const button = event.target.closest('button[data-action]');
+        if (!button || !root.contains(button)) return;
+        if (button.dataset.action === 'copy-token') {
+            copyToken(ctx);
+        } else if (button.dataset.action === 'revoke-token') {
+            const row = button.closest('[data-token-id]');
+            if (row) revokeToken(ctx, row.dataset.tokenId, button.dataset.tokenName);
+        }
+    }, on);
+    drawTimezone(root, ctx);
+    active = ctx;
+}
+
+export function destroy(root, ctx) {
+    if (ctx.state.timer) {
+        root.ownerDocument.defaultView.clearTimeout(ctx.state.timer);
+        ctx.state.timer = null;
+    }
+    if (active === ctx) active = null;
+}
+
+// ── the old global, kept as a deprecated alias (boot.js) ─────────────────────
+// window.webLogin's methods took the form (or the token's id and name) and
+// acted on the General tab on screen.
+export const webLogin = Object.freeze({
+    setPassword: function(form) { return active ? setPassword(active, form) : undefined; },
+    disable: function(form) { return active ? disableLogin(active, form) : undefined; },
+    createToken: function(form) { return active ? createToken(active, form) : undefined; },
+    copyToken: function() { return active ? copyToken(active) : undefined; },
+    revoke: function(id, name) { return active ? revokeToken(active, id, name) : undefined; },
+});

web_interface/static/v3/js/pages/schedule.js

@@ -0,0 +1,176 @@
+/*
+ * pages/schedule.js -- the Schedule tab (templates/v3/partials/schedule.html):
+ * when the display is on, and when it dims.
+ *
+ * Both forms stay plain htmx (hx-post with json-enc). This module:
+ *   - draws the two schedule-picker widgets from the saved config the
+ *     partial carries in data-schedule-config / data-dim-schedule-config
+ *   - reports each form's save in one notification. The forms used to call
+ *     window.handleScheduleResponse / handleDimScheduleResponse from an
+ *     hx-on attribute; now one htmx:afterRequest listener on the page root
+ *     does it, and the forms carry data-reports-result so app.js does not
+ *     show the server's message a second time
+ *   - keeps the "30%" label next to the dim brightness slider current
+ *
+ * The widget registry (LEDMatrixWidgets) and the schedule-picker widget are
+ * classic deferred scripts and normally load before this module runs; the
+ * short retry covers a page that arrives first anyway.
+ *
+ * The old globals are deprecated aliases made in core/boot.js; they forward
+ * to the exports of the same name at the bottom of this file.
+ */
+
+const DAYS = ['monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday'];
+const RETRY_MS = 100;
+const MAX_TRIES = 50;
+
+const PICKERS = [
+    {
+        label: 'Schedule', container: 'schedule_picker_container', data: 'data-schedule-config',
+        fieldId: 'schedule', start: '07:00', end: '23:00',
+        // The display schedule fills in days only when it has no "days" at
+        // all; the dim schedule also when "days" is empty.
+        fillEmptyDays: false,
+    },
+    {
+        label: 'DimSchedule', container: 'dim_schedule_picker_container', data: 'data-dim-schedule-config',
+        fieldId: 'dim_schedule', start: '20:00', end: '07:00',
+        fillEmptyDays: true,
+    },
+];
+
+const FORMS = {
+    schedule_form: { saved: 'Schedule settings saved', failed: 'Error saving schedule' },
+    dim_schedule_form: { saved: 'Dim schedule settings saved', failed: 'Error saving dim schedule' },
+};
+
+const WIDGET_OPTIONS = { showModeToggle: true, showEnableToggle: true, compactMode: false };
+
+// The mounted page, for the deprecated aliases (boot.js).
+let active = null;
+
+function readConfig(root, attribute) {
+    try {
+        const parsed = JSON.parse(root.getAttribute(attribute) || 'null');
+        return parsed && typeof parsed === 'object' ? parsed : {};
+    } catch {
+        return {};
+    }
+}
+
+/** The saved config, in the shape the schedule-picker widget takes. */
+export function widgetValue(config, spec) {
+    config = config || {};
+    let mode = 'global';
+    if (config.mode) {
+        // Normalize mode value (handle both 'per_day' and 'per-day')
+        mode = config.mode.replace('-', '_');
+    } else if (config.days) {
+        mode = 'per_day';
+    }
+    const value = {
+        enabled: config.enabled || false,
+        mode: mode,
+        start_time: config.start_time || spec.start,
+        end_time: config.end_time || spec.end,
+        days: config.days || {},
+    };
+    const noDays = !config.days || (spec.fillEmptyDays && Object.keys(config.days).length === 0);
+    if (noDays) {
+        value.days = Object.fromEntries(DAYS.map(function(day) {
+            return [day, { enabled: true, start_time: spec.start, end_time: spec.end }];
+        }));
+    }
+    return value;
+}
+
+/** One notification for a schedule form's answer. */
+function report(notify, xhr, labels) {
+    let response;
+    try {
+        response = JSON.parse(xhr.responseText);
+    } catch {
+        response = { status: 'error', message: 'Invalid response from server' };
+    }
+    if (!response || typeof response !== 'object') {
+        response = { status: 'error', message: 'Invalid response from server' };
+    }
+    const message = response.message || (response.status === 'success' ? labels.saved : labels.failed);
+    notify(message, response.status || 'info');
+}
+
+function drawPickers(root, ctx) {
+    const win = root.ownerDocument.defaultView;
+    let tries = 0;
+    function attempt() {
+        ctx.state.timer = null;
+        if (ctx.signal.aborted) return;
+        const registry = win.LEDMatrixWidgets;
+        const widget = registry && registry.get('schedule-picker');
+        if (!widget) {
+            if (++tries < MAX_TRIES) {
+                ctx.state.timer = win.setTimeout(attempt, RETRY_MS);
+            } else {
+                win.console.error(registry
+                    ? '[Schedule] schedule-picker widget not registered'
+                    : '[Schedule] LEDMatrixWidgets registry not available');
+            }
+            return;
+        }
+        PICKERS.forEach(function(spec) {
+            const container = root.querySelector('#' + spec.container);
+            if (!container) {
+                win.console.error('[' + spec.label + '] Container not found');
+                return;
+            }
+            widget.render(container, { 'x-options': WIDGET_OPTIONS },
+                          widgetValue(readConfig(root, spec.data), spec), { fieldId: spec.fieldId });
+        });
+    }
+    attempt();
+}
+
+export function init(root, ctx) {
+    const on = { signal: ctx.signal };
+
+    root.addEventListener('htmx:afterRequest', function(event) {
+        const form = event.target && event.target.closest ? event.target.closest('form') : null;
+        const labels = form && root.contains(form) ? FORMS[form.id] : null;
+        if (labels && event.detail && event.detail.xhr) report(ctx.notify, event.detail.xhr, labels);
+    }, on);
+
+    const slider = root.querySelector('#dim_brightness');
+    const label = root.querySelector('#dim_brightness_display');
+    if (slider && label) {
+        slider.addEventListener('input', function() { label.textContent = slider.value + '%'; }, on);
+    }
+
+    drawPickers(root, ctx);
+    active = ctx;
+}
+
+export function destroy(root, ctx) {
+    if (ctx.state.timer) {
+        root.ownerDocument.defaultView.clearTimeout(ctx.state.timer);
+        ctx.state.timer = null;
+    }
+    if (active === ctx) active = null;
+}
+
+// ── the old globals, kept as deprecated aliases (boot.js) ────────────────────
+function notifier(event) {
+    if (active) return active.notify;
+    const win = event && event.target && event.target.ownerDocument
+        ? event.target.ownerDocument.defaultView : globalThis;
+    return function(message, type) { return win.showNotification(message, type); };
+}
+
+/** window.handleScheduleResponse(event): an htmx:afterRequest event. */
+export function handleScheduleResponse(event) {
+    report(notifier(event), event.detail.xhr, FORMS.schedule_form);
+}
+
+/** window.handleDimScheduleResponse(event): an htmx:afterRequest event. */
+export function handleDimScheduleResponse(event) {
+    report(notifier(event), event.detail.xhr, FORMS.dim_schedule_form);
+}

web_interface/templates/v3/partials/general.html

@@ -1,4 +1,9 @@
 {% import 'v3/partials/_macros.html' as ui %}
+{# No inline script: static/v3/js/pages/general.js draws the timezone picker
+   and runs the Security section's forms and buttons (data-action). The page
+   registry (static/v3/js/core/registry.js) starts it when this root appears
+   and stops it when the partial is swapped away. #}
+<div data-page="general">
 <div class="bg-white rounded-lg shadow p-6">
     <div class="border-b border-gray-200 pb-4 mb-6">
         <h2 class="text-lg font-semibold text-gray-900">General Settings</h2>
@@ -88,7 +93,7 @@
         <!-- Timezone -->
         <div class="form-group" id="setting-general-timezone" data-setting-key="timezone">
             <label for="timezone" class="block text-sm font-medium text-gray-700">Timezone{{ ui.help_tip('Time zone used for clocks, schedules, and time-based content.\nChoose the zone where the display physically lives so on/off schedules fire at the correct local time.', 'Timezone') }}</label>
-            <div id="timezone_container" class="mt-1"></div>
+            <div id="timezone_container" class="mt-1" data-timezone="{{ main_config.timezone or 'America/Chicago' }}"></div>
         </div>
 
         <!-- Legacy scroll frame rate (device-wide). Core scrolling no longer reads it. -->
@@ -102,32 +107,6 @@
                    max="200"
                    class="form-control">
         </div>
-        <script>
-        (function() {
-            function initTimezoneWidget() {
-                if (!window.LEDMatrixWidgets) { setTimeout(initTimezoneWidget, 50); return; }
-                var widget = window.LEDMatrixWidgets.get('timezone-selector');
-                if (!widget) { setTimeout(initTimezoneWidget, 50); return; }
-                var container = document.getElementById('timezone_container');
-                if (!container) return;
-
-                // Only render if container is empty (not already rendered)
-                if (container.children.length > 0) return;
-
-                widget.render(container, {
-                    'x-options': { showOffset: true, placeholder: 'Select your timezone...' }
-                }, {{ (main_config.timezone or "America/Chicago")|tojson }}, {
-                    fieldId: 'timezone',
-                    name: 'timezone'
-                });
-            }
-            if (document.readyState === 'loading') {
-                document.addEventListener('DOMContentLoaded', initTimezoneWidget);
-            } else {
-                setTimeout(initTimezoneWidget, 50);
-            }
-        })();
-        </script>
 
         <!-- Location Information -->
         <div class="grid grid-cols-1 md:grid-cols-3 xl:grid-cols-3 2xl:grid-cols-3 gap-4">
@@ -216,7 +195,7 @@
                    the password inputs keep their own labels. #}
                 <label>{% if web_login.enabled %}Change the web interface password{% else %}Web interface password{% endif %}{{ ui.help_tip('Optional. With a password set, every page and API call needs a login or an API token.\nAlways allowed without one: this Pi itself (localhost), and the Wi-Fi setup page while the Pi is in access-point mode.\nForgot it? On the Pi run: sudo python3 ~/LEDMatrix/scripts/reset_web_password.py', 'Web interface password') }}</label>
             </h3>
-            <form class="space-y-4" onsubmit="window.webLogin.setPassword(this); return false;" autocomplete="off">
+            <form class="space-y-4" data-action="set-password" autocomplete="off">
                 {% if web_login.enabled %}
                 <div>
                     <label for="web-login-current" class="block text-sm font-medium text-gray-700">Current password</label>
@@ -251,7 +230,7 @@
         {% if web_login.enabled %}
         <div class="border-t border-gray-200 pt-6">
             <h3 class="text-lg font-semibold text-gray-900 mb-2">Turn login off</h3>
-            <form class="flex flex-wrap items-end gap-2" onsubmit="window.webLogin.disable(this); return false;" autocomplete="off">
+            <form class="flex flex-wrap items-end gap-2" data-action="disable-login" autocomplete="off">
                 <div class="flex-1">
                     <label for="web-login-disable-current" class="block text-sm font-medium text-gray-700">Current password</label>
                     <input type="password" id="web-login-disable-current" name="current_password" required
@@ -280,8 +259,7 @@
                         <span class="text-gray-600 ml-2">created {{ (token.created_at or '')[:10] }}</span>
                     </div>
                     <button type="button" class="text-sm text-red-600 hover:underline"
-                            data-token-name="{{ token.name }}"
-                            onclick="window.webLogin.revoke(this.closest('[data-token-id]').dataset.tokenId, this.dataset.tokenName)">
+                            data-action="revoke-token" data-token-name="{{ token.name }}">
                         Revoke
                     </button>
                 </div>
@@ -289,7 +267,7 @@
                 <p class="text-sm text-gray-600" data-empty>No tokens yet.</p>
                 {% endfor %}
             </div>
-            <form class="flex flex-wrap items-end gap-2" onsubmit="window.webLogin.createToken(this); return false;" autocomplete="off">
+            <form class="flex flex-wrap items-end gap-2" data-action="create-token" autocomplete="off">
                 <div class="flex-1">
                     <label for="web-login-token-name" class="block text-sm font-medium text-gray-700">New token name</label>
                     <input type="text" id="web-login-token-name" name="name" required maxlength="60"
@@ -304,7 +282,7 @@
                 <div class="flex flex-wrap items-center gap-2">
                     <code id="web-login-new-token-value" class="font-mono break-all bg-white border border-gray-200 rounded-md px-4 py-2 flex-1"></code>
                     <button type="button" class="btn bg-white border border-gray-300 text-gray-700 px-4 py-2 rounded-md"
-                            onclick="window.webLogin.copyToken()">
+                            data-action="copy-token">
                         <i class="fas fa-copy mr-2" aria-hidden="true"></i>Copy
                     </button>
                 </div>
@@ -312,131 +290,5 @@
         </div>
     </div>
 </div>
-<script>
-(function() {
-    var API = '/api/v3/auth';
-
-    function notify(message, type) {
-        if (typeof window.showNotification === 'function') window.showNotification(message, type);
-        else window.alert(message);
-    }
-
-    function send(method, url, body) {
-        return fetch(url, {
-            method: method,
-            headers: {'Content-Type': 'application/json'},
-            body: body === undefined ? undefined : JSON.stringify(body)
-        }).then(function(r) {
-            return r.json().catch(function() { return {}; }).then(function(d) { return {ok: r.ok, d: d}; });
-        });
-    }
-
-    function reloadSection() {
-        if (window.htmx) {
-            window.htmx.ajax('GET', '/v3/partials/general', {target: '#general-content', swap: 'innerHTML'});
-        } else {
-            window.location.reload();
-        }
-    }
-
-    function field(form, name) {
-        var el = form.querySelector('[name="' + name + '"]');
-        return el ? el.value : '';
-    }
-
-    function tokenRow(record) {
-        var row = document.createElement('div');
-        row.className = 'flex flex-wrap items-center justify-between gap-2 border border-gray-200 rounded-md px-4 py-2';
-        row.dataset.tokenId = record.id;
-        var text = document.createElement('div');
-        text.className = 'text-sm';
-        [['font-semibold text-gray-900', record.name],
-         ['font-mono text-gray-600 ml-2', record.prefix + '…'],
-         ['text-gray-600 ml-2', 'created just now']].forEach(function(part) {
-            var span = document.createElement('span');
-            span.className = part[0];
-            span.textContent = part[1];
-            text.appendChild(span);
-        });
-        var btn = document.createElement('button');
-        btn.type = 'button';
-        btn.className = 'text-sm text-red-600 hover:underline';
-        btn.textContent = 'Revoke';
-        btn.addEventListener('click', function() { window.webLogin.revoke(record.id, record.name); });
-        row.appendChild(text);
-        row.appendChild(btn);
-        return row;
-    }
-
-    window.webLogin = {
-        setPassword: function(form) {
-            var next = field(form, 'new_password');
-            if (next !== field(form, 'confirm_password')) {
-                notify('The two new passwords do not match.', 'error');
-                return;
-            }
-            var body = {new_password: next};
-            if (form.querySelector('[name="current_password"]')) body.current_password = field(form, 'current_password');
-            send('POST', API + '/password', body).then(function(res) {
-                notify(res.d.message || (res.ok ? 'Saved' : 'Could not save the password'), res.ok ? 'success' : 'error');
-                if (res.ok) reloadSection();
-            }).catch(function(err) { notify('Request failed: ' + err.message, 'error'); });
-        },
-        disable: function(form) {
-            if (!window.confirm('Turn login off? Anyone on your network will be able to open this page.')) return;
-            send('POST', API + '/disable', {current_password: field(form, 'current_password')}).then(function(res) {
-                notify(res.d.message || (res.ok ? 'Login is off' : 'Could not turn login off'), res.ok ? 'success' : 'error');
-                if (res.ok) reloadSection();
-            }).catch(function(err) { notify('Request failed: ' + err.message, 'error'); });
-        },
-        createToken: function(form) {
-            send('POST', API + '/tokens', {name: field(form, 'name')}).then(function(res) {
-                if (!res.ok) {
-                    notify(res.d.message || 'Could not create the token', 'error');
-                    return;
-                }
-                var list = document.getElementById('web-login-tokens');
-                if (list) {
-                    var empty = list.querySelector('[data-empty]');
-                    if (empty) empty.remove();
-                    list.appendChild(tokenRow(res.d.data.record));
-                }
-                document.getElementById('web-login-new-token-value').textContent = res.d.data.token;
-                document.getElementById('web-login-new-token').classList.remove('hidden');
-                form.reset();
-                // app.js marks a form dirty on input and clears the mark only
-                // after an htmx save; this one posts with fetch, so clear it
-                // here or a reload asks "Leave site?" about a saved token.
-                form.removeAttribute('data-dirty');
-                notify(res.d.message || 'Token created', 'success');
-            }).catch(function(err) { notify('Request failed: ' + err.message, 'error'); });
-        },
-        copyToken: function() {
-            var box = document.getElementById('web-login-new-token-value');
-            if (navigator.clipboard && window.isSecureContext) {
-                navigator.clipboard.writeText(box.textContent).then(function() { notify('Token copied', 'success'); });
-                return;
-            }
-            // Plain http on a LAN is not a secure context: select it instead.
-            var range = document.createRange();
-            range.selectNodeContents(box);
-            var sel = window.getSelection();
-            sel.removeAllRanges();
-            sel.addRange(range);
-            notify('Selected: press Ctrl+C (or Cmd+C) to copy.', 'info');
-        },
-        revoke: function(id, name) {
-            if (!window.confirm('Revoke the token "' + name + '"? Anything using it stops working.')) return;
-            send('DELETE', API + '/tokens/' + encodeURIComponent(id)).then(function(res) {
-                notify(res.d.message || (res.ok ? 'Token revoked' : 'Could not revoke the token'), res.ok ? 'success' : 'error');
-                if (!res.ok) return;
-                var rows = document.querySelectorAll('#web-login-tokens [data-token-id]');
-                Array.prototype.forEach.call(rows, function(row) {
-                    if (row.dataset.tokenId === id) row.remove();
-                });
-            }).catch(function(err) { notify('Request failed: ' + err.message, 'error'); });
-        }
-    };
-})();
-</script>
 {% endif %}
+</div>

web_interface/templates/v3/partials/schedule.html

@@ -1,4 +1,13 @@
 {% import 'v3/partials/_macros.html' as ui %}
+{# No inline script: static/v3/js/pages/schedule.js draws both schedule
+   pickers from the data-*-config attributes, reports each form's save and
+   keeps the dim brightness label current. The page registry
+   (static/v3/js/core/registry.js) starts it when this root appears and stops
+   it when the partial is swapped away. The forms carry data-reports-result so
+   app.js leaves the save notification to the page. #}
+<div data-page="schedule"
+     data-schedule-config='{{ schedule_config | tojson }}'
+     data-dim-schedule-config='{{ dim_schedule_config | tojson }}'>
 <div class="bg-white rounded-lg shadow p-6">
     <div class="border-b border-gray-200 pb-4 mb-6">
         <h2 class="text-lg font-semibold text-gray-900">Schedule Settings</h2>
@@ -12,7 +21,7 @@
           hx-ext="json-enc"
           hx-headers='{"Content-Type": "application/json"}'
           hx-swap="none"
-          hx-on:htmx:after-request="handleScheduleResponse(event)"
+          data-reports-result
           class="space-y-6">
 
         <!-- Schedule Picker Widget Container -->
@@ -41,7 +50,7 @@
           hx-ext="json-enc"
           hx-headers='{"Content-Type": "application/json"}'
           hx-swap="none"
-          hx-on:htmx:after-request="handleDimScheduleResponse(event)"
+          data-reports-result
           class="space-y-6">
 
         <!-- Dim Brightness Level -->
@@ -56,8 +65,7 @@
                        min="0"
                        max="100"
                        value="{{ dim_schedule_config.dim_brightness | default(30) }}"
-                       class="flex-1 h-2 bg-gray-200 rounded-lg appearance-none cursor-pointer accent-blue-600"
-                       oninput="document.getElementById('dim_brightness_display').textContent = this.value + '%'">
+                       class="flex-1 h-2 bg-gray-200 rounded-lg appearance-none cursor-pointer accent-blue-600">
                 <span id="dim_brightness_display" class="text-sm font-medium text-gray-700 w-12 text-right">
                     {{ dim_schedule_config.dim_brightness | default(30) }}%
                 </span>
@@ -77,198 +85,4 @@
         </div>
     </form>
 </div>
-
-<script>
-(function() {
-    'use strict';
-
-    // Initialize schedule picker widget when DOM is ready
-    function initSchedulePicker() {
-        const container = document.getElementById('schedule_picker_container');
-        if (!container) {
-            console.error('[Schedule] Container not found');
-            return;
-        }
-
-        // Check if widget registry is available
-        if (typeof window.LEDMatrixWidgets === 'undefined') {
-            console.error('[Schedule] LEDMatrixWidgets registry not available');
-            return;
-        }
-
-        const widget = window.LEDMatrixWidgets.get('schedule-picker');
-        if (!widget) {
-            console.error('[Schedule] schedule-picker widget not registered');
-            return;
-        }
-
-        // Get schedule config from template data (injected by Jinja2)
-        // Default to empty object if null/undefined
-        const scheduleConfig = {{ schedule_config | tojson | safe }} || {};
-
-        // Determine mode: prefer explicit mode, then infer from days, then default to global
-        let mode = 'global';
-        if (scheduleConfig.mode) {
-            // Normalize mode value (handle both 'per_day' and 'per-day')
-            mode = scheduleConfig.mode.replace('-', '_');
-        } else if (scheduleConfig.days) {
-            mode = 'per_day';
-        }
-
-        // Convert flat config to nested format expected by widget
-        const widgetValue = {
-            enabled: scheduleConfig.enabled || false,
-            mode: mode,
-            start_time: scheduleConfig.start_time || '07:00',
-            end_time: scheduleConfig.end_time || '23:00',
-            days: scheduleConfig.days || {}
-        };
-
-        // If we have per-day data in the old flat format, convert it
-        if (!scheduleConfig.days) {
-            widgetValue.days = {};
-            const days = ['monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday'];
-            days.forEach(function(day) {
-                widgetValue.days[day] = {
-                    enabled: true,
-                    start_time: '07:00',
-                    end_time: '23:00'
-                };
-            });
-        }
-
-        // Render the widget
-        widget.render(container, {
-            'x-options': {
-                showModeToggle: true,
-                showEnableToggle: true,
-                compactMode: false
-            }
-        }, widgetValue, {
-            fieldId: 'schedule'
-        });
-
-        debugLog('[Schedule] Schedule picker widget initialized');
-    }
-
-    // Handle form submission response
-    window.handleScheduleResponse = function(event) {
-        const xhr = event.detail.xhr;
-        let response;
-        try {
-            response = JSON.parse(xhr.responseText);
-        } catch (e) {
-            response = { status: 'error', message: 'Invalid response from server' };
-        }
-
-        const message = response.message || (response.status === 'success' ? 'Schedule settings saved' : 'Error saving schedule');
-        const type = response.status || 'info';
-
-        // Use global notification function if available
-        window.showNotification(message, type);
-    };
-
-    // Initialize when DOM is ready or if already loaded
-    if (document.readyState === 'loading') {
-        document.addEventListener('DOMContentLoaded', initSchedulePicker);
-    } else {
-        // Small delay to ensure widget scripts are loaded
-        setTimeout(initSchedulePicker, 50);
-    }
-})();
-
-// Dim Schedule Picker initialization
-(function() {
-    'use strict';
-
-    function initDimSchedulePicker() {
-        const container = document.getElementById('dim_schedule_picker_container');
-        if (!container) {
-            console.error('[DimSchedule] Container not found');
-            return;
-        }
-
-        // Check if widget registry is available
-        if (typeof window.LEDMatrixWidgets === 'undefined') {
-            console.error('[DimSchedule] LEDMatrixWidgets registry not available');
-            return;
-        }
-
-        const widget = window.LEDMatrixWidgets.get('schedule-picker');
-        if (!widget) {
-            console.error('[DimSchedule] schedule-picker widget not registered');
-            return;
-        }
-
-        // Get dim schedule config from template data (injected by Jinja2)
-        const dimScheduleConfig = {{ dim_schedule_config | tojson | safe }} || {};
-
-        // Determine mode
-        let mode = 'global';
-        if (dimScheduleConfig.mode) {
-            mode = dimScheduleConfig.mode.replace('-', '_');
-        } else if (dimScheduleConfig.days) {
-            mode = 'per_day';
-        }
-
-        // Convert config to widget format
-        const widgetValue = {
-            enabled: dimScheduleConfig.enabled || false,
-            mode: mode,
-            start_time: dimScheduleConfig.start_time || '20:00',
-            end_time: dimScheduleConfig.end_time || '07:00',
-            days: dimScheduleConfig.days || {}
-        };
-
-        // If no days config, initialize with defaults for dim schedule (20:00-07:00)
-        if (!dimScheduleConfig.days || Object.keys(dimScheduleConfig.days).length === 0) {
-            widgetValue.days = {};
-            const days = ['monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday'];
-            days.forEach(function(day) {
-                widgetValue.days[day] = {
-                    enabled: true,
-                    start_time: '20:00',
-                    end_time: '07:00'
-                };
-            });
-        }
-
-        // Render the widget with a different field ID
-        widget.render(container, {
-            'x-options': {
-                showModeToggle: true,
-                showEnableToggle: true,
-                compactMode: false
-            }
-        }, widgetValue, {
-            fieldId: 'dim_schedule'
-        });
-
-        debugLog('[DimSchedule] Dim schedule picker widget initialized');
-    }
-
-    // Handle dim schedule form submission response
-    window.handleDimScheduleResponse = function(event) {
-        const xhr = event.detail.xhr;
-        let response;
-        try {
-            response = JSON.parse(xhr.responseText);
-        } catch (e) {
-            response = { status: 'error', message: 'Invalid response from server' };
-        }
-
-        const message = response.message || (response.status === 'success' ? 'Dim schedule settings saved' : 'Error saving dim schedule');
-        const type = response.status || 'info';
-
-        // Use global notification function if available
-        window.showNotification(message, type);
-    };
-
-    // Initialize when DOM is ready
-    if (document.readyState === 'loading') {
-        document.addEventListener('DOMContentLoaded', initDimSchedulePicker);
-    } else {
-        setTimeout(initDimSchedulePicker, 100);
-    }
-})();
-</script>
+</div>