fix(display): pin one text layout engine, and give the 5x7 BDF face a size (#539)

* fix(display): pin one text layout engine, and give the 5x7 face a size

Two ways a font could render differently on two machines running the same
code, both found while diagnosing four plugins whose golden images passed on
the machine that generated them and failed everywhere else.

**Layout engine.** `ImageFont.truetype` picks its engine at load time: Raqm
where the host Pillow was built with libraqm, Basic otherwise. The two round
fractional glyph advances differently. `PressStart2P-Regular.ttf` at 8px has
whole-pixel advances, so they agree — which is why most of the fleet matched
everywhere and hid this. `4x6-font.ttf` at 6px does not: glyph positions drift
cumulatively along a run, and the four plugins that draw body text in it
(geochron, of-the-day, christmas-countdown, ledmatrix-weather's almanac) are
exactly the four whose goldens travelled badly.

Every core font load now goes through `src/common/font_layout.load_truetype`,
which pins the Basic engine, so a render depends on the font file and the size
and nothing else. Basic gives up complex-script shaping and kerning pairs;
neither applies to bitmap-grid faces on an LED panel. Output is unchanged on a
host without libraqm.

**Zero font height.** `DisplayManager` built the 5x7 BDF face with
`freetype.Face(path)` and never called `set_char_size`, so `face.size.height`
stayed 0 and `get_font_height()` returned 0 for it — callers stacking rows by
`prev_y + prev_height + gap` drew two lines on top of each other. The
start-up line `Calendar font size: 0 pixels` has been printing the symptom all
along. `font_manager._load_bdf_font` already called `set_char_size`, so
whether measurement worked depended on which path loaded the face.

`DisplayManager` now sets it too, and `get_font_height()` falls back to the
strike the file declares rather than returning a zero line height.

Fixes ChuckBuilds/ledmatrix-plugins#397
Refs ChuckBuilds/ledmatrix-plugins#371, #375, #378, #391

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* fix(display): give the startup banner a rung that fits a full address at 64px

CI caught what pinning the layout engine exposed rather than caused.
`_fitting_font` walks PressStart2P then 4x6 at 6px, and "255.255.255.255" --
the widest thing the startup banner ever shows -- measures 66px at 4x6/6px
against the 62 a 64x32 panel has to give. It used to squeak in only because
the measurement depended on which layout engine the host Pillow happened to
have; with the engine pinned it does not, so the rung the worst case actually
needs is now in the ladder instead of implied: 4x6 at 5px, which measures 51.

The fallback was wrong in the same place. When nothing in the ladder fit, it
returned `self.font` -- the *widest* option, and precisely how "Initializing"
came to run off the side of a 64px panel to begin with. It returns the
narrowest face that loaded now.

test/test_initializing_screen.py: 34 passed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* fix(display): name the exceptions the BDF strike read can raise

Codacy flagged the try/except/pass. It was already narrow in intent -- a
malformed strike table on the measurement path must degrade to "size unknown"
rather than take the display down -- but a bare `except Exception: pass` says
neither of those things and hides a genuinely broken font behind a silent 8px
fallback. It now catches what reading `available_sizes` can actually raise and
logs which face failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* chore: drop logo PNGs the render harness downloaded into the worktree

These are fetched at runtime by the logo cache; they are not source, and they
rode in on a `git add -A` while I was running check_plugin.py against this
branch. Nothing in the change needs them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

docs/REST_API_REFERENCE.md

@@ -33,7 +33,7 @@ All endpoints return JSON responses with a standard format:
 
 > The API blueprint is mounted at `/api/v3` (`web_interface/app.py:199`).
 > SSE stream endpoints (`/api/v3/stream/*`) are defined directly on the
-> Flask app at `app.py:799-809`. There are 94 routes total — see
+> Flask app at `app.py:799-809`. There are 111 routes total — see
 > `web_interface/blueprints/api_v3.py` for the canonical list.
 
 ---
@@ -223,6 +223,56 @@ Get the current display state and preview image.
 }
 ```
 
+### List Display Modes
+
+**GET** `/api/v3/display/modes`
+
+Every display mode that can be requested on-demand, with the plugin that owns
+it. This is the list the force-display dialog offers.
+
+Send the reported `plugin_id` alongside `mode` when starting an on-demand
+display: `/display/on-demand/start` falls back to `find_plugin_for_mode` when
+`plugin_id` is omitted, and that lookup only sees modes declared in a static
+manifest — a plugin whose modes are generated (each installed Starlark app is
+one) returns 404 there.
+
+Triggers plugin discovery, which is otherwise lazy — so a caller that never
+opens the dashboard still gets the full list.
+
+**Query Parameters**:
+- `include_disabled` (optional): `1` to include modes belonging to disabled
+  plugins. They are still valid on-demand targets — the controller enables the
+  plugin for the duration of the request — and are reported with
+  `"enabled": false`.
+
+**Response**:
+```json
+{
+  "status": "success",
+  "data": {
+    "modes": [
+      {
+        "mode": "nfl_live",
+        "plugin_id": "football-scoreboard",
+        "plugin_name": "Football Scoreboard",
+        "name": "nfl_live",
+        "enabled": true
+      },
+      {
+        "mode": "clock-simple",
+        "plugin_id": "clock-simple",
+        "plugin_name": "Simple Clock",
+        "name": "Simple Clock",
+        "enabled": true
+      }
+    ]
+  }
+}
+```
+
+`name` is a label for a dropdown: a single-mode plugin's own name, or the raw
+mode string for a multi-mode plugin, since there is no per-mode name anywhere.
+
 ### On-Demand Display Status
 
 **GET** `/api/v3/display/on-demand/status`

docs/SCROLL_PERFORMANCE.md

@@ -0,0 +1,266 @@
+# Scroll Performance
+
+How scrolling is paced on this hardware, what was wrong with it, and how to
+configure a plugin so its marquee is smooth.
+
+Measured on a Raspberry Pi 4 driving a 2×128×64 chain (256×64 logical) at
+`limit_refresh_rate_hz: 100`. Numbers below come from that panel.
+
+| | before | after |
+|---|---|---|
+| scroll frame rate | 44–46 fps | **100 fps, locked** |
+| frames ≥ 45 ms | 14–17% | none observed |
+| dominant frame time | 20 ms | **10 ms** |
+| disk cache write (~1 MB) | 14.8 ms | **5.4 ms** |
+
+---
+
+## The one rule that matters
+
+**Motion is smooth when the strip advances a whole number of pixels per panel
+refresh.**
+
+Advancing one pixel per refresh on a 100 Hz panel gives 100 px/s. Slower crisp
+speeds come from holding each frame for several refreshes -- 50 px/s is one
+pixel every second refresh -- which is covered under *Choosing a speed* below.
+A speed that lands on no such combination has to do one of two bad things:
+
+- **blend** two adjacent columns to render a half-step — on pixel-font text
+  this alternates crisp and smeared frames and reads as shimmer, or as the
+  text jumping a pixel ahead of itself;
+- **repeat** a frame — the strip stands still, then jumps, which reads as
+  judder.
+
+Neither is tunable away. Pick a speed that divides evenly.
+
+`src.common.scroll_config` solves this for you: `configure()` snaps a requested
+speed to the nearest one the panel can actually show in whole pixels, and
+`scripts/scroll_speeds.py` prints the full ladder for your hardware.
+
+## Choosing a speed
+
+The crisp speeds are not a fixed list -- they depend on how fast *your* panel
+refreshes, which depends on its size, `pwm_bits`, `gpio_slowdown` and the Pi
+model. A Pi Zero driving a long chain has a completely different set of good
+speeds from a Pi 4 driving a short one.
+
+```bash
+# what can this panel do? (reads your configured refresh rate)
+python3 scripts/scroll_speeds.py
+
+# what does it ACTUALLY manage, rather than what is configured?
+sudo systemctl stop ledmatrix
+sudo python3 scripts/scroll_speeds.py --measure
+sudo systemctl start ledmatrix
+
+# highlight the closest option to the speed you want
+python3 scripts/scroll_speeds.py --want 45
+
+# try one on the panel
+sudo systemctl stop ledmatrix
+sudo python3 scripts/scroll_speeds.py --demo 50
+sudo systemctl start ledmatrix
+```
+
+Sample ladder for a 100 Hz panel:
+
+```
+  20.0 px/s  (1px every 5 refreshes =  20.0 fps, slightly stepped)
+  25.0 px/s  (1px every 4 refreshes =  25.0 fps, slightly stepped)
+  33.3 px/s  (1px every 3 refreshes =  33.3 fps, smooth)
+  50.0 px/s  (1px every 2 refreshes =  50.0 fps, smooth)
+  66.7 px/s  (2px every 3 refreshes =  33.3 fps, smooth)
+ 100.0 px/s  (1px every 1 refresh  = 100.0 fps, smooth)
+```
+
+### How a slow speed stays crisp
+
+`SwapOnVSync(canvas, framerate_fraction)` holds each frame for N panel
+refreshes. **The panel keeps refreshing at its full rate either way**, so
+holding a frame costs nothing in flicker -- it only changes how often a *new*
+image is presented. That is what allows 50 px/s to be one whole pixel every
+second refresh, instead of half a pixel every refresh (which has no good
+rendering, only a choice between blur and judder).
+
+`scroll_config.configure()` snaps the requested speed to the nearest entry on
+the ladder and reports the hold that speed needs. It does **not** apply the
+hold: the hold belongs to a scroll, not to a plugin's lifetime, and plugins
+share one display manager -- one set at construction is reset the moment any
+other plugin finishes scrolling. Apply it yourself when the scroll starts:
+
+```python
+settings = scroll_config.configure(
+    self.scroll_helper,
+    plugin_config=self.config,
+    global_config=self.global_config,
+    display_manager=self.display_manager,   # supplies the panel refresh rate
+)
+
+# ...then, each time this plugin begins scrolling:
+self.display_manager.set_scrolling_state(True, frame_hold=settings.frame_hold)
+```
+
+Passing `display_manager` only lets `configure` read the true refresh rate from
+`display.hardware`, which a plugin config cannot see. Skipping the
+`set_scrolling_state` call is the mistake that matters: the speed still
+resolves, but the panel keeps presenting a new frame every refresh, so a slow
+snapped speed falls back to fractional pixels. Pass `snap_to_crisp=False` to
+keep an exact requested speed and accept the artefacts.
+
+Speeds slower than about 20 px/s are stepped no matter what, because a 1-pixel
+advance at 20 fps is simply a coarse increment. That is the pixel pitch, not a
+software limit; the only way to move in smaller increments is sub-pixel
+blending, which this display does not tolerate (see above).
+
+## Configuring a plugin
+
+Use the shared resolver rather than reading config keys yourself:
+
+```python
+from src.common import scroll_config
+
+settings = scroll_config.configure(
+    self.scroll_helper,
+    plugin_config=self.config,
+    global_config=self.global_config,
+    refresh_hz=scroll_config.refresh_hz_from_config(self.global_config),
+    plugin_logger=self.logger,
+)
+```
+
+It resolves every config shape in one place, applies the speed, and returns
+what it did. Precedence, highest first:
+
+1. `display_options.scroll_speed` + `scroll_delay` — **the recommended form**
+2. `display.scroll_speed` + `scroll_delay` — deprecated shape
+3. `scroll_speed` + `scroll_delay` at the root — legacy flat
+4. `scroll_pixels_per_second` — deprecated
+5. the global `display` block
+6. the built-in default (100 px/s)
+
+`scroll_speed` is pixels per frame and `scroll_delay` is the frame period in
+seconds, so the pair means `scroll_speed / scroll_delay` px/s. The recommended
+config for a 100 Hz panel:
+
+```json
+"display_options": { "scroll_speed": 1.0, "scroll_delay": 0.01 }
+```
+
+### Why the deprecated key ranks below the explicit pair
+
+Because some plugins give `scroll_pixels_per_second` a **schema default**, and
+schema defaults are merged into plugin config. Ranking it above the pair means
+it is always present and always wins, so the documented settings become
+unreachable. That is a real, shipped bug — see
+[ledmatrix-plugins#408](https://github.com/ChuckBuilds/ledmatrix-plugins/issues/408).
+
+If you are writing a plugin: do not give a deprecated key a schema default.
+
+## What was actually wrong
+
+Four independent faults, each found by measurement.
+
+### 1. The frame loop slept on top of a wait it had already done
+
+`display_controller.py` ran the high-FPS loop as `render → SwapOnVSync (blocks
+to the panel's refresh) → time.sleep(0.008) → plugin ticks`. The sleep was
+unconditional and added to a wait that had already happened. Render work
+measured ~4 ms, so each iteration cost ~12 ms against a 10 ms refresh grid —
+every swap missed a refresh and landed on the next one. The loop settled at
+exactly 50 fps while asking for 125, with no headroom, so ~14% of frames
+slipped a further refresh.
+
+Now the loop sleeps only the remainder of the frame budget, with a 1 ms floor
+so plugin threads still get the GIL.
+
+### 2. `SwapOnVSync` held the GIL while blocking
+
+The rgbmatrix binding declares it without `nogil` (unlike `SetPixel`, `Clear`
+and `Fill` immediately above it in `cppinc.pxd`), so the render thread held the
+GIL for the entire vsync wait — most of every frame. Background threads were
+starved into long uninterruptible bursts; a 1.5 MB API response costs ~17 ms to
+parse and ~18 ms to re-encode for the cache, and `json.raw_decode` cannot be
+preempted mid-document. Those bursts are what the render loop then waited on.
+
+Fixed by rebuilding the binding: `scripts/build_rgbmatrix_nogil.sh`.
+
+### 3. Sub-pixel blending was wrong for this display
+
+Enabling it made things worse, not better — see the rule at the top. It is off
+by default and only Vegas mode opts in via `set_sub_pixel_scrolling(True)`.
+
+### 4. Frame-based stepping raced the vsync clock
+
+Frame-based mode gated motion on a wall clock at `1/scroll_delay` steps per
+second. Plugins set `scroll_delay` to the frame period, which puts that
+comparison exactly on its own threshold: a frame arriving a hair early moved
+zero pixels and rendered an identical frame, which dirty-tracking skipped, so
+it returned in ~2 ms and the beat repeated. No `scroll_delay` value tunes this
+out — a shorter delay just trades stalled frames for periodic double-steps.
+
+`ScrollHelper` now accumulates elapsed time in both modes at the same
+configured speed, so position stays proportional to real time.
+
+## Diagnosing a juddery scroller
+
+**`Avg FPS` will lie to you.** It is a 100-frame moving average, and a 2 ms
+duplicate frame plus a 21 ms double-wait average to exactly 10 ms. A ticker
+that is stalling on half its frames still reports a healthy `100.0`.
+
+Look at the **distribution** instead:
+
+```bash
+journalctl -u ledmatrix --since "-10min" --no-pager \
+  | grep -oE "Frame time: [0-9.]+ms" | awk '{print $3}' | sed 's/ms//' \
+  | awk '{printf "%.0f\n", $1}' | sort -n | uniq -c
+```
+
+Reading it, on a 100 Hz panel:
+
+| you see | it means |
+|---|---|
+| everything at 10 ms | healthy |
+| a mode at ~2 ms | **duplicate frames** — the swap was skipped because the image did not change. The scroller is advancing less than one pixel per frame. |
+| a mode at 20/30/50 ms | frames missing refreshes — per-frame work is overrunning, or a background thread is holding the GIL |
+| `Avg FPS` above 100 | duplicates present, unless the scroll cycle has completed and is idling |
+
+Then confirm what the plugin actually loaded — config edits do not always reach
+the running code:
+
+```bash
+journalctl -u ledmatrix --since "-5min" --no-pager | grep -iE "px/s|px/frame"
+```
+
+If a plugin logs its scroll config **twice** with different modes, the second
+line is what is running.
+
+## Rebuilding the binding
+
+```bash
+bash scripts/build_rgbmatrix_nogil.sh              # build into a scratch dir
+sudo bash scripts/build_rgbmatrix_nogil.sh --install
+sudo bash scripts/build_rgbmatrix_nogil.sh --rollback
+```
+
+The build never touches the installed module. `--install` backs up the original
+to `~/rgbmatrix-core.so.ORIGINAL` first, and rolls back automatically if the
+service does not come back healthy. Requires `build-essential`; Cython is
+installed into a cached venv under `~/.cache/ledmatrix-cython`.
+
+Re-run it after upgrading `rpi-rgb-led-matrix`, since a library upgrade
+replaces the patched binding.
+
+## Faster JSON
+
+`src/cache/disk_cache.py` uses `orjson` when it is importable and falls back to
+the stdlib otherwise, so it is optional:
+
+```bash
+sudo pip3 install --break-system-packages orjson
+```
+
+Encoding is where it pays — about 7× on this hardware. Decoding gains far less
+(~1.3× on large payloads) because the cost there is building Python objects,
+not scanning text. That is also why moving parsing to a subprocess does not
+help: `pickle.loads` of the same payload costs 8.1 ms against `json.loads` at
+10.9 ms, so the work just moves rather than disappearing.

integrations/mqtt_bridge/.gitignore

@@ -0,0 +1 @@
+bridge_config.json

integrations/mqtt_bridge/README.md

@@ -0,0 +1,118 @@
+# Home Assistant MQTT Bridge
+
+Control the matrix from Home Assistant: force any plugin or mode on demand,
+turn the display on and off, and set brightness — as real HA entities, not
+hand-written `mqtt.publish` calls.
+
+The bridge owns no display logic. It subscribes to one command topic and
+turns each message into a call against the same `api_v3` routes the web UI
+uses, so behaviour lives in one place. It talks to the API over HTTP only —
+no filesystem access — so it can run on the Pi or anywhere that can reach
+the web interface.
+
+## What appears in Home Assistant
+
+On connect the bridge publishes [MQTT Discovery](https://www.home-assistant.io/integrations/mqtt/#mqtt-discovery)
+config, so the matrix shows up under **Settings → Devices & Services → MQTT**
+with no YAML:
+
+| Entity | Does |
+|---|---|
+| `select.ledmatrix_display_mode` | Every mode across enabled plugins. Choosing one force-displays it. |
+| `button.ledmatrix_stop_display` | Back to normal rotation. |
+| `switch.ledmatrix_power` | Starts/stops the display service. |
+| `number.ledmatrix_brightness` | 0–100. |
+
+State is read back from the API every 30 seconds, so the entities also track
+changes made from the web UI or an on-demand window expiring on its own.
+All four share an availability topic that is the bridge's MQTT last will:
+if the bridge dies, HA greys the controls out rather than leaving them
+looking live but inert.
+
+## Raw commands
+
+For anything the entities do not cover, publish JSON to the command topic
+(`ledmatrix/command` by default):
+
+```jsonc
+// Force a mode. plugin_id is optional — the bridge fills it in from
+// /api/v3/display/modes.
+{"action": "display", "mode": "nfl_live"}
+
+// duration is seconds; pinned holds this one mode instead of rotating
+// through every mode the plugin owns. Pin Starlark apps, where each mode
+// is an unrelated widget; leave a sports plugin unpinned so live/recent/
+// upcoming still cycle.
+{"action": "display", "plugin_id": "starlark-apps", "mode": "aquarium",
+ "duration": 300, "pinned": true}
+
+{"action": "stop_display"}
+{"action": "power", "state": "on"}
+{"action": "brightness", "value": 75}
+
+// Re-read the mode list and re-publish discovery, after installing a plugin
+{"action": "refresh"}
+```
+
+Every command publishes its outcome to `<command_topic>/status`, and current
+state to `<command_topic>/state`.
+
+## Requirements
+
+- A LEDMatrix install with its web interface reachable (default `http://localhost:5000`)
+- An MQTT broker that Home Assistant is also connected to
+- Python 3 with `paho-mqtt` 2.x and `requests`
+
+## Install
+
+```bash
+sudo ./scripts/install/install_mqtt_bridge.sh
+```
+
+That copies `bridge_config.example.json` to `bridge_config.json` on first
+run, installs the dependencies, and enables `ledmatrix-mqtt-bridge.service`.
+Edit the config with your broker details and re-run it.
+
+```json
+{
+  "mqtt_host": "192.168.1.10",
+  "mqtt_port": 8883,
+  "mqtt_username": "ledmatrix",
+  "mqtt_password": null,
+  "mqtt_topic": "ledmatrix/command",
+  "mqtt_tls": true,
+  "ledmatrix_api_base": "http://localhost:5000"
+}
+```
+
+**TLS is on by default.** Without it the broker password and every display
+command cross the network in cleartext. If your broker only listens on plain
+1883 — which the Mosquitto add-on does out of the box — set `"mqtt_tls": false`
+and `"mqtt_port": 1883`. The bridge logs a warning at startup when a password
+is configured without TLS.
+
+`bridge_config.json` is gitignored. Any key can also be supplied through the
+environment as `LEDMATRIX_MQTT_<KEY>` (`LEDMATRIX_MQTT_MQTT_PASSWORD`, say),
+which keeps a broker password out of a file on disk — put it in a systemd
+drop-in with `Environment=` or `EnvironmentFile=` instead.
+
+Set `mqtt_tls: true` for a broker with TLS. `mqtt_tls_insecure` skips
+certificate verification and exists only for a self-signed broker on a
+trusted LAN; it logs a warning when used.
+
+To run it in the foreground while setting things up:
+
+```bash
+python3 integrations/mqtt_bridge/ledmatrix_mqtt_bridge.py --config integrations/mqtt_bridge/bridge_config.json
+```
+
+## Notes
+
+- Only one thing can be on-demand at a time — the same constraint the web UI has.
+- Forcing a mode restarts the display service, so the panel blanks for a moment.
+- The mode list comes from `/api/v3/display/modes`, which triggers plugin
+  discovery itself. Discovery is lazy and normally happens because somebody
+  opened the dashboard; without that endpoint a bridge that never does would
+  see an empty list.
+- Brightness writes `display.hardware.brightness` through `/api/v3/config/main`.
+  The display service picks it up on its next restart, not instantly.

integrations/mqtt_bridge/bridge_config.example.json

@@ -0,0 +1,13 @@
+{
+  "mqtt_host": "192.168.1.10",
+  "mqtt_port": 8883,
+  "mqtt_username": "ledmatrix",
+  "mqtt_password": null,
+  "mqtt_client_id": "ledmatrix-mqtt-bridge",
+  "mqtt_topic": "ledmatrix/command",
+  "mqtt_tls": true,
+  "ledmatrix_api_base": "http://localhost:5000",
+  "request_timeout": 15,
+  "on_demand_duration": null,
+  "log_level": "INFO"
+}

integrations/mqtt_bridge/ledmatrix_mqtt_bridge.py

@@ -0,0 +1,548 @@
+#!/usr/bin/env python3
+"""Control a LEDMatrix display from Home Assistant over MQTT.
+
+The bridge owns no display logic. It subscribes to one command topic and
+turns each message into a call against the same api_v3 routes the web UI
+uses, so behaviour stays in one place and this stays a translation layer.
+
+On connect it publishes Home Assistant MQTT Discovery config, so a matrix
+appears in HA as real entities rather than something you drive with
+`mqtt.publish` by hand:
+
+    select.ledmatrix_display_mode   every mode across enabled plugins;
+                                    choosing one force-displays it
+    button.ledmatrix_stop_display   back to normal rotation
+    switch.ledmatrix_power          the display service, on or off
+    number.ledmatrix_brightness     0-100
+
+Anything the entities do not cover is still reachable by publishing JSON
+to the command topic:
+
+    {"action": "display", "mode": "nfl_live"}
+    {"action": "display", "plugin_id": "starlark-apps", "mode": "aquarium",
+     "duration": 300, "pinned": true}
+    {"action": "stop_display"}
+    {"action": "power", "state": "on" | "off"}
+    {"action": "brightness", "value": 75}
+    {"action": "refresh"}          re-publish discovery after installing a plugin
+
+Every command publishes its result to <command_topic>/status.
+
+Run it with `python3 ledmatrix_mqtt_bridge.py [--config PATH]`, or install
+ledmatrix-mqtt-bridge.service.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import logging
+import os
+import signal
+import sys
+import threading
+from typing import Any, Callable, Dict, List, Optional
+
+import requests
+
+logger = logging.getLogger("ledmatrix-mqtt-bridge")
+
+DISCOVERY_PREFIX = "homeassistant"
+DEVICE_ID = "ledmatrix"
+DEVICE_INFO = {
+    "identifiers": [DEVICE_ID],
+    "name": "LEDMatrix",
+    "manufacturer": "ChuckBuilds",
+    "model": "LEDMatrix Display",
+}
+
+DEFAULTS = {
+    "mqtt_host": "localhost",
+    "mqtt_port": 1883,
+    "mqtt_username": None,
+    "mqtt_password": None,  # nosec B105 - "no password configured", not a credential
+    "mqtt_client_id": "ledmatrix-mqtt-bridge",
+    "mqtt_topic": "ledmatrix/command",
+    "mqtt_tls": False,
+    "mqtt_tls_insecure": False,
+    "ledmatrix_api_base": "http://localhost:5000",
+    "request_timeout": 15,
+    "on_demand_duration": None,
+    "log_level": "INFO",
+}
+
+
+class ConfigError(Exception):
+    """The bridge cannot start with the configuration it was given."""
+
+
+def load_config(path: str) -> Dict[str, Any]:
+    """Read bridge_config.json, overlaid on DEFAULTS.
+
+    Every value may also come from the environment as LEDMATRIX_MQTT_<KEY>,
+    which is how a password stays out of a file that has to be world-readable
+    for the service user.
+    """
+    config = dict(DEFAULTS)
+    if os.path.isfile(path):
+        with open(path, encoding="utf-8") as handle:
+            try:
+                loaded = json.load(handle)
+            except json.JSONDecodeError as err:
+                raise ConfigError(f"{path} is not valid JSON: {err}") from err
+        if not isinstance(loaded, dict):
+            raise ConfigError(f"{path} must contain a JSON object")
+        config.update(loaded)
+    else:
+        logger.warning("No config file at %s - using defaults and environment", path)
+
+    for key in DEFAULTS:
+        env_value = os.environ.get(f"LEDMATRIX_MQTT_{key.upper()}")
+        if env_value is not None:
+            config[key] = env_value
+
+    for key in ("mqtt_port", "request_timeout"):
+        try:
+            config[key] = int(config[key])
+        except (TypeError, ValueError) as err:
+            raise ConfigError(f"{key} must be a whole number, got {config[key]!r}") from err
+    for key in ("mqtt_tls", "mqtt_tls_insecure"):
+        config[key] = str(config[key]).lower() in ("1", "true", "yes", "on")
+
+    if config.get("mqtt_password") == "REPLACE_WITH_YOUR_ACTUAL_MQTT_PASSWORD":
+        raise ConfigError(
+            "mqtt_password is still the example placeholder - set a real password, "
+            "or remove the key if your broker allows anonymous connections")
+    return config
+
+
+class LEDMatrixClient:
+    """The api_v3 calls the bridge needs, and nothing else.
+
+    Everything goes through the HTTP API rather than the filesystem, so the
+    bridge does not have to live on the Pi, does not need read access to
+    config.json, and cannot drift from the web UI's own behaviour.
+    """
+
+    def __init__(self, api_base: str, timeout: int = 15,
+                 session: Optional[requests.Session] = None):
+        self.api_base = api_base.rstrip("/")
+        self.timeout = timeout
+        self.session = session or requests.Session()
+
+    def _call(self, method: str, path: str, **kwargs) -> Dict[str, Any]:
+        url = f"{self.api_base}/api/v3{path}"
+        response = self.session.request(method, url, timeout=self.timeout, **kwargs)
+        try:
+            body = response.json()
+        except ValueError:
+            body = {}
+        if response.status_code >= 400 or body.get("status") == "error":
+            message = body.get("message") or f"HTTP {response.status_code}"
+            raise RuntimeError(f"{method} {path} failed: {message}")
+        return body.get("data", body)
+
+    def list_modes(self) -> List[Dict[str, Any]]:
+        """Every display mode that can be force-displayed, newest discovery.
+
+        /display/modes triggers plugin discovery itself, which matters because
+        discovery is lazy: a bridge that never opens the dashboard would
+        otherwise see nothing at all.
+        """
+        return self._call("GET", "/display/modes").get("modes", [])
+
+    def display_status(self) -> Dict[str, Any]:
+        return self._call("GET", "/display/on-demand/status")
+
+    def start_on_demand(self, mode: str, plugin_id: Optional[str] = None,
+                        duration: Optional[int] = None, pinned: bool = False) -> Dict[str, Any]:
+        payload: Dict[str, Any] = {"mode": mode, "pinned": pinned}
+        if plugin_id:
+            # find_plugin_for_mode only sees modes declared in a static
+            # manifest, so a plugin whose modes are generated -- each installed
+            # Starlark app is one -- 404s when plugin_id is omitted. Sending it
+            # skips that lookup. /display/modes reports it for every mode.
+            payload["plugin_id"] = plugin_id
+        if duration:
+            payload["duration"] = int(duration)
+        return self._call("POST", "/display/on-demand/start", json=payload)
+
+    def stop_on_demand(self) -> Dict[str, Any]:
+        return self._call("POST", "/display/on-demand/stop", json={})
+
+    def set_power(self, on: bool) -> Dict[str, Any]:
+        action = "start_display" if on else "stop_display"
+        return self._call("POST", "/system/action", json={"action": action})
+
+    def get_brightness(self) -> Optional[int]:
+        config = self._call("GET", "/config/main")
+        value = config.get("display", {}).get("hardware", {}).get("brightness")
+        try:
+            return int(value)
+        except (TypeError, ValueError):
+            return None
+
+    def set_brightness(self, value: int) -> Dict[str, Any]:
+        return self._call("POST", "/config/main", json={"brightness": int(value)})
+
+
+class CommandHandler:
+    """Turns one decoded MQTT payload into one API call.
+
+    Kept free of MQTT so it can be tested against a fake client: the failure
+    modes worth pinning are all in here (an unknown mode, an out-of-range
+    brightness, a mode name that needs its plugin_id attached).
+    """
+
+    def __init__(self, client: LEDMatrixClient, default_duration: Optional[int] = None):
+        self.client = client
+        self.default_duration = default_duration
+        self._modes_by_name: Dict[str, Dict[str, Any]] = {}
+
+    def refresh_modes(self) -> List[Dict[str, Any]]:
+        modes = self.client.list_modes()
+        self._modes_by_name = {m["mode"]: m for m in modes}
+        # Home Assistant's select shows labels, so accept them back as well --
+        # otherwise picking "Simple Clock" in a dashboard is not a mode name.
+        for entry in modes:
+            self._modes_by_name.setdefault(entry.get("name") or entry["mode"], entry)
+        return modes
+
+    @property
+    def known_modes(self) -> List[Dict[str, Any]]:
+        return list({id(v): v for v in self._modes_by_name.values()}.values())
+
+    def handle(self, payload: Dict[str, Any]) -> Dict[str, Any]:
+        action = payload.get("action")
+        handlers: Dict[str, Callable[[Dict[str, Any]], Dict[str, Any]]] = {
+            "display": self._display,
+            "stop_display": lambda _p: self._ok(self.client.stop_on_demand()),
+            "power": self._power,
+            "brightness": self._brightness,
+            "refresh": lambda _p: self._ok({"modes": len(self.refresh_modes())}),
+        }
+        handler = handlers.get(action)
+        if handler is None:
+            return self._error(f"Unknown action {action!r}; expected one of "
+                               f"{', '.join(sorted(handlers))}")
+        try:
+            return handler(payload)
+        except (requests.RequestException, RuntimeError) as err:
+            logger.error("Command %s failed: %s", action, err)
+            return self._error(str(err))
+
+    def _display(self, payload: Dict[str, Any]) -> Dict[str, Any]:
+        mode = payload.get("mode")
+        plugin_id = payload.get("plugin_id")
+        if not mode and not plugin_id:
+            return self._error("display requires 'mode' or 'plugin_id'")
+
+        known = self._modes_by_name.get(mode) if mode else None
+        if known is None and mode and not plugin_id:
+            # One retry against a fresh listing: a plugin installed since the
+            # last refresh is the common reason a valid mode looks unknown.
+            self.refresh_modes()
+            known = self._modes_by_name.get(mode)
+        if known is not None:
+            mode = known["mode"]
+            plugin_id = plugin_id or known.get("plugin_id")
+
+        duration = payload.get("duration", self.default_duration)
+        pinned = bool(payload.get("pinned", False))
+        result = self.client.start_on_demand(
+            mode=mode, plugin_id=plugin_id, duration=duration, pinned=pinned)
+        return self._ok(result, mode=mode, plugin_id=plugin_id)
+
+    def _power(self, payload: Dict[str, Any]) -> Dict[str, Any]:
+        state = str(payload.get("state", "")).strip().lower()
+        if state not in ("on", "off"):
+            return self._error("power requires 'state' of 'on' or 'off'")
+        return self._ok(self.client.set_power(state == "on"), state=state)
+
+    def _brightness(self, payload: Dict[str, Any]) -> Dict[str, Any]:
+        raw = payload.get("value")
+        try:
+            value = int(float(raw))
+        except (TypeError, ValueError):
+            return self._error(f"brightness requires a number, got {raw!r}")
+        if not 0 <= value <= 100:
+            return self._error(f"brightness must be between 0 and 100, got {value}")
+        return self._ok(self.client.set_brightness(value), value=value)
+
+    @staticmethod
+    def _ok(result: Any, **extra) -> Dict[str, Any]:
+        return {"status": "success", "result": result, **extra}
+
+    @staticmethod
+    def _error(message: str) -> Dict[str, Any]:
+        return {"status": "error", "message": message}
+
+
+def discovery_messages(command_topic: str, state_topic: str, availability_topic: str,
+                       mode_labels: List[str]) -> List[Dict[str, Any]]:
+    """The retained MQTT Discovery configs, as {topic, payload} pairs.
+
+    Pure, so the entity shapes can be asserted without a broker. Every entity
+    shares one availability topic, which is also the bridge's last will -- HA
+    then shows the matrix as unavailable when the bridge dies, instead of
+    leaving stale controls that silently do nothing.
+    """
+    common = {
+        "device": DEVICE_INFO,
+        "availability_topic": availability_topic,
+        "payload_available": "online",
+        "payload_not_available": "offline",
+    }
+    return [
+        {
+            "topic": f"{DISCOVERY_PREFIX}/select/{DEVICE_ID}/display_mode/config",
+            "payload": {
+                **common,
+                "name": "Display Mode",
+                "unique_id": f"{DEVICE_ID}_display_mode",
+                "command_topic": command_topic,
+                "command_template": '{"action": "display", "mode": "{{ value }}"}',
+                "state_topic": state_topic,
+                "value_template": "{{ value_json.mode }}",
+                "options": mode_labels,
+                "icon": "mdi:view-dashboard",
+            },
+        },
+        {
+            "topic": f"{DISCOVERY_PREFIX}/button/{DEVICE_ID}/stop_display/config",
+            "payload": {
+                **common,
+                "name": "Stop Display",
+                "unique_id": f"{DEVICE_ID}_stop_display",
+                "command_topic": command_topic,
+                "payload_press": '{"action": "stop_display"}',
+                "icon": "mdi:stop",
+            },
+        },
+        {
+            "topic": f"{DISCOVERY_PREFIX}/switch/{DEVICE_ID}/power/config",
+            "payload": {
+                **common,
+                "name": "Power",
+                "unique_id": f"{DEVICE_ID}_power",
+                "command_topic": command_topic,
+                "payload_on": '{"action": "power", "state": "on"}',
+                "payload_off": '{"action": "power", "state": "off"}',
+                "state_topic": state_topic,
+                "value_template": "{{ 'ON' if value_json.power else 'OFF' }}",
+                "state_on": "ON",
+                "state_off": "OFF",
+                "icon": "mdi:power",
+            },
+        },
+        {
+            "topic": f"{DISCOVERY_PREFIX}/number/{DEVICE_ID}/brightness/config",
+            "payload": {
+                **common,
+                "name": "Brightness",
+                "unique_id": f"{DEVICE_ID}_brightness",
+                "command_topic": command_topic,
+                "command_template": '{"action": "brightness", "value": {{ value }}}',
+                "state_topic": state_topic,
+                "value_template": "{{ value_json.brightness }}",
+                "min": 0,
+                "max": 100,
+                "step": 1,
+                "icon": "mdi:brightness-6",
+            },
+        },
+    ]
+
+
+def warn_if_cleartext(config: Dict[str, Any]) -> bool:
+    """Say so, once, when a broker password is going over an unencrypted link.
+
+    The shipped example has TLS on, so reaching here means somebody turned it
+    off deliberately -- which is legitimate (the Mosquitto add-on is plaintext
+    on 1883) but should not be silent when there is a password to lose. Returns
+    whether it warned, so the decision is testable without a broker.
+    """
+    if config.get("mqtt_tls") or not config.get("mqtt_password"):
+        return False
+    logger.warning(
+        'mqtt_tls is off and a password is set: the broker password and every '
+        'command are sent unencrypted. Set "mqtt_tls": true (port 8883 on most '
+        'brokers) unless this is a trusted, isolated network.')
+    return True
+
+
+def read_state(client: LEDMatrixClient) -> Dict[str, Any]:
+    """The state every entity reads, so HA opens on real values.
+
+    Each field is fetched independently: a matrix with its display service
+    stopped still has a brightness worth showing, and one unreachable field
+    should not blank the rest.
+    """
+    state: Dict[str, Any] = {"power": False, "mode": None, "brightness": None}
+    try:
+        status = client.display_status()
+        state["power"] = bool(status.get("service", {}).get("active"))
+        on_demand = status.get("state", {})
+        if on_demand.get("active"):
+            state["mode"] = on_demand.get("mode")
+    except (requests.RequestException, RuntimeError) as err:
+        logger.debug("Could not read display status: %s", err)
+    try:
+        state["brightness"] = client.get_brightness()
+    except (requests.RequestException, RuntimeError) as err:
+        logger.debug("Could not read brightness: %s", err)
+    return state
+
+
+class Bridge:
+    """MQTT wiring around CommandHandler."""
+
+    def __init__(self, config: Dict[str, Any]):
+        self.config = config
+        self.command_topic = config["mqtt_topic"]
+        self.status_topic = f"{self.command_topic}/status"
+        self.state_topic = f"{self.command_topic}/state"
+        self.availability_topic = f"{self.command_topic}/availability"
+        self.client = LEDMatrixClient(config["ledmatrix_api_base"], config["request_timeout"])
+        self.handler = CommandHandler(self.client, config.get("on_demand_duration"))
+        self._stop = threading.Event()
+        self._mqtt = None
+
+    # -- MQTT callbacks (paho-mqtt 2.x VERSION2 signatures) ------------------
+
+    def _on_connect(self, client, _userdata, _flags, reason_code, _properties=None):
+        if getattr(reason_code, "is_failure", reason_code != 0):
+            logger.error("MQTT connection refused: %s", reason_code)
+            return
+        logger.info("Connected to MQTT broker; subscribing to %s", self.command_topic)
+        client.subscribe(self.command_topic, qos=1)
+        client.publish(self.availability_topic, "online", qos=1, retain=True)
+        # Re-publish on every reconnect, not just the first connect: a broker
+        # restart drops retained discovery configs, and HA would otherwise be
+        # left with entities it can no longer describe.
+        self.publish_discovery()
+        self.publish_state()
+
+    def _on_message(self, _client, _userdata, message):
+        try:
+            payload = json.loads(message.payload.decode("utf-8"))
+        except (UnicodeDecodeError, json.JSONDecodeError) as err:
+            logger.warning("Ignoring unparseable message on %s: %s", message.topic, err)
+            self._publish(self.status_topic, {"status": "error", "message": f"bad payload: {err}"})
+            return
+        if not isinstance(payload, dict):
+            self._publish(self.status_topic,
+                          {"status": "error", "message": "payload must be a JSON object"})
+            return
+
+        logger.info("Command: %s", payload)
+        result = self.handler.handle(payload)
+        self._publish(self.status_topic, result)
+        # The API applies changes asynchronously (the controller polls its
+        # mailbox), so read state back rather than assuming the command took.
+        self.publish_state()
+
+    # -- publishing ---------------------------------------------------------
+
+    def _publish(self, topic: str, payload: Any, retain: bool = False) -> None:
+        if self._mqtt is None:
+            return
+        body = payload if isinstance(payload, str) else json.dumps(payload)
+        self._mqtt.publish(topic, body, qos=1, retain=retain)
+
+    def publish_discovery(self) -> None:
+        try:
+            modes = self.handler.refresh_modes()
+        except (requests.RequestException, RuntimeError) as err:
+            logger.error("Could not list display modes: %s", err)
+            modes = self.handler.known_modes
+        labels = sorted({m.get("name") or m["mode"] for m in modes})
+        for message in discovery_messages(self.command_topic, self.state_topic,
+                                          self.availability_topic, labels):
+            self._publish(message["topic"], message["payload"], retain=True)
+        logger.info("Published discovery for %d display mode(s)", len(labels))
+
+    def publish_state(self) -> None:
+        self._publish(self.state_topic, read_state(self.client), retain=True)
+
+    # -- lifecycle ----------------------------------------------------------
+
+    def run(self) -> int:
+        try:
+            import paho.mqtt.client as mqtt
+        except ImportError:
+            logger.error("paho-mqtt is not installed: pip install -r requirements.txt")
+            return 1
+
+        # VERSION2 is the current callback API. The compatibility note in
+        # CLAUDE.md is about code written against the v1 signatures; this file
+        # is written against v2 and requires paho-mqtt >= 2.0.
+        self._mqtt = mqtt.Client(
+            mqtt.CallbackAPIVersion.VERSION2,
+            client_id=self.config["mqtt_client_id"])
+        if self.config.get("mqtt_username"):
+            self._mqtt.username_pw_set(self.config["mqtt_username"],
+                                       self.config.get("mqtt_password"))
+        if self.config.get("mqtt_tls"):
+            self._mqtt.tls_set()
+            if self.config.get("mqtt_tls_insecure"):
+                logger.warning("TLS certificate verification is disabled (mqtt_tls_insecure)")
+                self._mqtt.tls_insecure_set(True)
+        else:
+            warn_if_cleartext(self.config)
+
+        self._mqtt.will_set(self.availability_topic, "offline", qos=1, retain=True)
+        self._mqtt.on_connect = self._on_connect
+        self._mqtt.on_message = self._on_message
+
+        logger.info("Connecting to %s:%s", self.config["mqtt_host"], self.config["mqtt_port"])
+        try:
+            self._mqtt.connect(self.config["mqtt_host"], self.config["mqtt_port"], keepalive=60)
+        except OSError as err:
+            logger.error("Could not reach the MQTT broker: %s", err)
+            return 1
+
+        self._mqtt.loop_start()
+        try:
+            while not self._stop.wait(30):
+                # HA is told the truth about state that changed outside the
+                # bridge -- somebody using the web UI, or an on-demand window
+                # expiring on its own.
+                self.publish_state()
+        finally:
+            self._publish(self.availability_topic, "offline", retain=True)
+            self._mqtt.loop_stop()
+            self._mqtt.disconnect()
+        return 0
+
+    def stop(self, *_args) -> None:
+        logger.info("Shutting down")
+        self._stop.set()
+
+
+def main(argv: Optional[List[str]] = None) -> int:
+    parser = argparse.ArgumentParser(description=__doc__.splitlines()[0])
+    parser.add_argument(
+        "--config",
+        default=os.path.join(os.path.dirname(os.path.abspath(__file__)), "bridge_config.json"),
+        help="Path to bridge_config.json (default: alongside this script)")
+    args = parser.parse_args(argv)
+
+    logging.basicConfig(
+        level=logging.INFO,
+        format="%(asctime)s - %(levelname)s - %(name)s - %(message)s")
+    try:
+        config = load_config(args.config)
+    except ConfigError as err:
+        logger.error("%s", err)
+        return 1
+    logging.getLogger().setLevel(str(config.get("log_level", "INFO")).upper())
+
+    bridge = Bridge(config)
+    signal.signal(signal.SIGTERM, bridge.stop)
+    signal.signal(signal.SIGINT, bridge.stop)
+    return bridge.run()
+
+
+if __name__ == "__main__":
+    sys.exit(main())

integrations/mqtt_bridge/requirements.txt

@@ -0,0 +1,5 @@
+# Floors are security floors, not API floors. requests < 2.33.0 carries
+# CVE-2024-35195, CVE-2024-47081 and CVE-2026-25645; matches the pin in the
+# project's own requirements.txt.
+paho-mqtt>=2.0.0,<3.0.0
+requests>=2.33.0,<3.0.0

plugin-repos/starlark-apps/manager.py

@@ -194,6 +194,15 @@ class StarlarkAppsPlugin(BasePlugin):
     Each installed app becomes a dynamic display mode.
     """
 
+    #: Starlark apps are animations: a .webp render carries per-frame delays
+    #: and _display_frame advances at most one frame per call. The controller
+    #: reads this attribute to decide whether a mode needs its high-FPS loop;
+    #: without it display() was called once per rotation slot, so a multi-frame
+    #: app showed a single frame and never moved. static-image is force-run at
+    #: high FPS for the same reason (GIFs), but that plugin is special-cased by
+    #: name in the controller and this one has to declare it.
+    enable_scrolling = True
+
     def __init__(self, plugin_id: str, config: Dict[str, Any],
                  display_manager, cache_manager, plugin_manager):
         """Initialize the Starlark Apps plugin."""
@@ -681,38 +690,62 @@ class StarlarkAppsPlugin(BasePlugin):
                 if app.is_enabled() and app.should_render(current_time):
                     self._render_app(app, force=False)
 
-    def display(self, force_clear: bool = False) -> None:
+    def display(self, display_mode: Optional[str] = None, force_clear: bool = False) -> bool:
         """
         Display current Starlark app.
 
         This method is called during the display rotation.
         Displays frames from the currently active app.
+
+        `display_mode` names the app to show when it matches an installed
+        app_id. The controller passes the mode it is rotating to and inspects
+        this signature to decide whether to, so accepting it is what lets a
+        specific app be addressed -- including by an on-demand request pinned
+        to one app. Anything else (the plugin id itself, when the plugin
+        exposes no per-app modes) falls through to normal rotation.
+
+        Returns False when there is no app to show -- which is the state of
+        every install without Pixlet, and of a fresh one before any app is
+        added. The display controller only skips a mode on a boolean False
+        (it checks isinstance(result, bool)), so returning None held a black
+        panel for the full display_duration instead of rotating on.
         """
         try:
             if force_clear:
                 self.display_manager.clear()
 
-            # If no current app, try to select one
+            if display_mode and display_mode in self.apps:
-            if not self.current_app:
+                self.current_app = self.apps[display_mode]
+            elif force_clear or not self.current_app:
+                # Advance on entry to the mode. _select_next_app only ran when
+                # current_app was unset, so the first enabled app was picked
+                # once and then shown forever -- every other installed app was
+                # rendered on schedule and never displayed. force_clear is the
+                # controller's "we just switched to you" signal (it is reset
+                # immediately after this call), so one app gets each turn.
                 self._select_next_app()
 
             if not self.current_app:
                 # No apps available
                 self.logger.debug("No Starlark apps to display")
-                return
+                return False
 
             # Render app if needed
             if not self.current_app.frames:
                 success = self._render_app(self.current_app, force=True)
                 if not success:
                     self.logger.error(f"Failed to render app: {self.current_app.app_id}")
-                    return
+                    return False
 
-            # Display current frame
+            # Display current frame. The result is propagated: a failed frame
-            self._display_frame()
+            # update is not a displayed frame, and returning True regardless
+            # told the controller the mode had rendered, so it held the dead
+            # frame for the whole display_duration instead of rotating on.
+            return self._display_frame()
 
         except Exception as e:
             self.logger.error(f"Error displaying Starlark app: {e}")
+            return False
 
     def _select_next_app(self) -> None:
         """Select the next enabled app for display."""
@@ -835,10 +868,13 @@ class StarlarkAppsPlugin(BasePlugin):
             self.logger.error(f"Error loading frames for {app.app_id}: {e}")
             return False
 
-    def _display_frame(self) -> None:
+    def _display_frame(self) -> bool:
-        """Display the current frame of the current app."""
+        """Display the current frame of the current app.
+
+        :returns: whether a frame actually reached the display manager.
+        """
         if not self.current_app or not self.current_app.frames:
-            return
+            return False
 
         try:
             current_time = time.time()
@@ -856,8 +892,11 @@ class StarlarkAppsPlugin(BasePlugin):
                 )
                 self.current_app.last_frame_time = current_time
 
+            return True
+
         except Exception as e:
             self.logger.error(f"Error displaying frame: {e}")
+            return False
 
     def install_app(self, app_id: str, star_file_path: str, metadata: Optional[Dict[str, Any]] = None, assets_dir: Optional[str] = None) -> bool:
         """

plugin-repos/starlark-apps/pixlet_renderer.py

@@ -264,10 +264,18 @@ class PixletRenderer:
                     else:
                         value_str = str(value)
 
-                    # Validate value doesn't contain dangerous shell metacharacters
+                    # Validate value doesn't contain dangerous shell metacharacters.
-                    # Block: backticks, $(), pipes, redirects, semicolons, ampersands, null bytes
+                    # Kept as defence in depth only: cmd is a list and there is no
-                    # Allow: most printable chars including spaces, quotes, brackets, braces
+                    # shell=True below, so nothing here is ever interpreted by a
-                    if re.search(r'[`$|<>&;\x00]|\$\(', value_str):
+                    # shell. That made the list worth trimming rather than growing
+                    # -- "|" is a normal character inside a config value, and apps
+                    # do use it as a separator (a PennDOT sign id is
+                    # "I-476 North|175659"). Blocking it dropped the whole key
+                    # silently, and the app then rendered its own "not configured"
+                    # screen with nothing to say why.
+                    # Block: backticks, $(), redirects, semicolons, ampersands, null bytes
+                    # Allow: most printable chars including spaces, quotes, brackets, braces, pipes
+                    if re.search(r'[`$<>&;\x00]|\$\(', value_str):
                         logger.warning(f"Skipping config value with unsafe shell characters for key {key}: {value_str}")
                         continue
 
@@ -299,13 +307,21 @@ class PixletRenderer:
             )
 
             if result.returncode == 0:
-                if os.path.isfile(output_path):
+                if not os.path.isfile(output_path):
-                    logger.debug(f"Successfully rendered: {star_file} -> {output_path}")
-                    return True, None
-                else:
                     error = "Rendering succeeded but output file not found"
                     logger.error(error)
                     return False, error
+                # Pixlet exits 0 and writes a 0-byte file when the app renders
+                # nothing -- an app whose config leaves it with no content to
+                # show does exactly that. Treating existence alone as success
+                # handed the caller a file with no frames in it, which reads
+                # downstream as a working app that draws a black panel.
+                if os.path.getsize(output_path) == 0:
+                    error = "Rendering produced an empty (0-byte) file - the app rendered no content"
+                    logger.error(error)
+                    return False, error
+                logger.debug(f"Successfully rendered: {star_file} -> {output_path}")
+                return True, None
             else:
                 error = f"Pixlet failed (exit {result.returncode}): {result.stderr}"
                 logger.error(error)
@@ -319,11 +335,76 @@ class PixletRenderer:
             logger.exception("Rendering exception")
             return False, "Rendering failed - see logs for details"
 
+    #: Schema extraction runs an app's own get_schema(), which may make a
+    #: network call. Short enough that a hung app does not stall an upload,
+    #: long enough for a real API round trip on a slow connection.
+    SCHEMA_TIMEOUT = 20
+
+    def extract_schema_via_pixlet(self, star_file: str) -> Optional[Dict[str, Any]]:
+        """Ask Pixlet itself for the app's schema, or None if it cannot say.
+
+        `pixlet schema` executes get_schema() instead of reading it, which is
+        the only way to see options an app computes at runtime -- a dropdown
+        whose choices come from a live API call has no option list anywhere in
+        the source for the regex parser below to find, so that parser reports
+        an empty dropdown and the config form offers nothing to pick.
+
+        Pixlet's own field keys are remapped to the ones the rest of this
+        plugin and the config UI already use ("typeOf"/"desc"), so the two
+        extractors return the same shape and callers cannot tell them apart.
+        """
+        if not self.pixlet_binary:
+            return None
+        try:
+            result = subprocess.run(
+                [self.pixlet_binary, "schema", star_file],
+                capture_output=True, text=True, timeout=self.SCHEMA_TIMEOUT,
+                cwd=self._get_safe_working_directory(star_file),
+            )
+        except subprocess.TimeoutExpired:
+            logger.warning(
+                "pixlet schema timed out after %ss for %s - get_schema() may be "
+                "making a slow network call", self.SCHEMA_TIMEOUT, star_file)
+            return None
+        except (subprocess.SubprocessError, OSError) as e:
+            logger.warning(f"Could not run pixlet schema for {star_file}: {e}")
+            return None
+
+        if result.returncode != 0:
+            # Not an error worth failing on: older Pixlet builds have no
+            # `schema` subcommand at all, and the source parser still works.
+            logger.debug(
+                "pixlet schema exited %d for %s: %s",
+                result.returncode, star_file, (result.stderr or '').strip()[:300])
+            return None
+
+        try:
+            schema = json.loads(result.stdout)
+        except (json.JSONDecodeError, ValueError) as e:
+            logger.warning(f"pixlet schema returned unparseable output for {star_file}: {e}")
+            return None
+
+        if not isinstance(schema, dict) or not isinstance(schema.get("schema"), list):
+            logger.warning(f"pixlet schema returned an unexpected shape for {star_file}")
+            return None
+
+        for field in schema["schema"]:
+            if not isinstance(field, dict):
+                continue
+            if "type" in field and "typeOf" not in field:
+                field["typeOf"] = field.pop("type")
+            if "description" in field and "desc" not in field:
+                field["desc"] = field.pop("description")
+        return schema
+
     def extract_schema(self, star_file: str) -> Tuple[bool, Optional[Dict[str, Any]], Optional[str]]:
         """
-        Extract configuration schema from a .star file by parsing source code.
+        Extract configuration schema from a .star file.
 
-        Supports:
+        Prefers `pixlet schema`, which runs the app and therefore sees options
+        it computes at runtime. Falls back to parsing the source when Pixlet is
+        unavailable, too old to have the subcommand, or the app fails to run --
+        that parser handles:
         - Static field definitions (location, text, toggle, dropdown, color, datetime)
         - Variable-referenced dropdown options
         - Graceful degradation for unsupported field types
@@ -337,6 +418,13 @@ class PixletRenderer:
         if not os.path.isfile(star_file):
             return False, None, f"Star file not found: {star_file}"
 
+        schema = self.extract_schema_via_pixlet(star_file)
+        if schema is not None:
+            logger.debug(
+                "Extracted schema with %d field(s) from %s via pixlet schema",
+                len(schema.get('schema', [])), star_file)
+            return True, schema, None
+
         try:
             # Read .star file
             with open(star_file, 'r', encoding='utf-8') as f:

requirements.txt

@@ -55,6 +55,18 @@ packaging>=23.0,<27.0
 #                     range as a hard dependency — keep the two in sync.
 #   pip install 'psutil>=6.0.0,<7.0.0'
 #
+# orjson            — faster JSON for the disk cache
+#                     (src/cache/disk_cache.py). Encoding a ~1MB cache
+#                     record drops from ~12ms to ~1.6ms on a Pi 4, which
+#                     matters because that work holds the GIL and stalls
+#                     the render thread mid-scroll. Falls back to the
+#                     stdlib json when missing — see docs/SCROLL_PERFORMANCE.md.
+#                     The 3.11.6 floor is CVE-2025-67221: orjson.dumps did not
+#                     limit recursion on deeply nested documents, and the disk
+#                     cache encodes payloads parsed straight from third-party
+#                     APIs. 3.11.6 covers the Python range above.
+#   pip install 'orjson>=3.11.6,<4.0'
+#
 # Flask-Limiter     — request rate limiting in web_interface/app.py
 #                     (accidental-abuse protection, not security). The
 #                     web interface starts without rate limiting when

scripts/audit_render_path.py

@@ -0,0 +1,159 @@
+#!/usr/bin/env python3
+"""Find blocking work reachable from a plugin's render path.
+
+`display()` runs on the render thread. Anything slow reached from it stalls the
+panel for its whole duration, and on a vsync-paced loop that is immediately
+visible: a single 15ms call on a 100Hz panel drops a frame, and a network round
+trip freezes the marquee outright.
+
+This has bitten twice already. odds-ticker called `_has_live_games()` every
+frame, whose slow path read the scoreboard cache from disk and parsed JSON per
+enabled league -- one stalled frame every few minutes. soccer-scoreboard timed
+out inside `update()` during a cache refresh. Both were found by staring at
+frame-time histograms, which is a slow way to find a bug that is visible in the
+source.
+
+The audit walks the call graph from `display()` through same-class `self.*`
+methods and reports anything that reaches a known-blocking API. It is a
+heuristic, not a proof: it cannot see through indirection, and a hit is not
+automatically a bug -- a call guarded by an interval check may be fine. It is a
+list of places worth a human look.
+
+    python3 scripts/audit_render_path.py                    # all plugins
+    python3 scripts/audit_render_path.py --dir plugin-repos # a specific tree
+    python3 scripts/audit_render_path.py --plugin odds-ticker
+"""
+from __future__ import annotations
+
+import argparse
+import ast
+import sys
+from pathlib import Path
+
+#: Calls that can block for longer than a frame. Matched on the attribute or
+#: function name, so `requests.get`, `self.session.get` and a bare `get` on a
+#: requests-ish object all register.
+BLOCKING = {
+    "get": "network or cache read",
+    "post": "network",
+    "put": "network",
+    "request": "network",
+    "urlopen": "network",
+    "read": "I/O",
+    "open": "file I/O",
+    "load": "JSON/file parse",
+    "loads": "JSON parse",
+    "dump": "file write",
+    "dumps": "serialise",
+    "sleep": "sleep on the render thread",
+    "run": "subprocess",
+    "check_output": "subprocess",
+    "connect": "network",
+    "download_logo": "network",
+    "_fetch": "fetch",
+}
+
+#: Names that make a hit far more likely to matter.
+HIGH_SIGNAL = ("requests", "urllib", "session", "cache_manager", "subprocess",
+               "socket", "http")
+
+RENDER_ENTRY = "display"
+
+
+class Analyzer:
+    def __init__(self, tree: ast.AST):
+        self.methods: dict[str, ast.FunctionDef] = {}
+        for node in ast.walk(tree):
+            if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
+                self.methods.setdefault(node.name, node)
+
+    def calls_in(self, fn: ast.AST):
+        """(self-method names called, blocking hits) inside one function."""
+        self_calls, hits = set(), []
+        for node in ast.walk(fn):
+            if not isinstance(node, ast.Call):
+                continue
+            func = node.func
+            if isinstance(func, ast.Attribute):
+                name = func.attr
+                base = ast.unparse(func.value) if hasattr(ast, "unparse") else ""
+                if base == "self" and name in self.methods:
+                    self_calls.add(name)
+                    continue
+                if name in BLOCKING:
+                    hits.append((name, base, BLOCKING[name], node.lineno))
+            elif isinstance(func, ast.Name) and func.id in BLOCKING:
+                hits.append((func.id, "", BLOCKING[func.id], node.lineno))
+        return self_calls, hits
+
+    def reachable_from(self, entry: str, max_depth: int = 3):
+        """Blocking hits reachable from `entry`, with the path that reaches them."""
+        if entry not in self.methods:
+            return []
+        found, seen = [], set()
+        stack = [(entry, [entry], 0)]
+        while stack:
+            name, path, depth = stack.pop()
+            if name in seen or depth > max_depth:
+                continue
+            seen.add(name)
+            self_calls, hits = self.calls_in(self.methods[name])
+            for hit in hits:
+                found.append((path, hit))
+            for callee in sorted(self_calls):
+                stack.append((callee, path + [callee], depth + 1))
+        return found
+
+
+def audit_file(path: Path):
+    try:
+        tree = ast.parse(path.read_text(encoding="utf-8"))
+    except (OSError, SyntaxError):
+        return []
+    analyzer = Analyzer(tree)
+    return analyzer.reachable_from(RENDER_ENTRY)
+
+
+def main():
+    ap = argparse.ArgumentParser(description=__doc__,
+                                 formatter_class=argparse.RawDescriptionHelpFormatter)
+    root = Path(__file__).resolve().parent.parent
+    ap.add_argument("--dir", default=str(root / "plugin-repos"))
+    ap.add_argument("--plugin", help="only this plugin directory")
+    ap.add_argument("--all-hits", action="store_true",
+                    help="include low-signal hits (open/read/load on locals)")
+    args = ap.parse_args()
+
+    base = Path(args.dir)
+    if not base.is_dir():
+        sys.exit("not a directory: %s" % base)
+
+    plugins = [base / args.plugin] if args.plugin else sorted(
+        d for d in base.iterdir() if d.is_dir())
+
+    total = 0
+    for plugin in plugins:
+        rows = []
+        for src in sorted(plugin.glob("*.py")):
+            if src.name.startswith("test_"):
+                continue
+            for path, (name, s_base, why, lineno) in audit_file(src):
+                signal = any(h in s_base.lower() for h in HIGH_SIGNAL)
+                if not signal and not args.all_hits:
+                    continue
+                rows.append((src.name, lineno, "->".join(path),
+                             ("%s.%s" % (s_base, name)) if s_base else name, why))
+        if rows:
+            total += len(rows)
+            print("\n%s" % plugin.name)
+            for fname, lineno, chain, call, why in sorted(rows):
+                print("  %s:%-5d %-34s via %s" % (fname, lineno, call + "  (" + why + ")", chain))
+
+    print("\n%d blocking call(s) reachable from display() across %d plugin(s)"
+          % (total, len(plugins)))
+    print("Heuristic: a hit guarded by an interval check may be fine. Look, do "
+          "not assume.")
+
+
+if __name__ == "__main__":
+    main()

scripts/build_rgbmatrix_nogil.sh

@@ -0,0 +1,330 @@
+#!/usr/bin/env bash
+#
+# Rebuild the rgbmatrix Python binding so it releases the GIL.
+#
+# WHY THIS EXISTS
+# ---------------
+# The upstream binding declares FrameCanvas::SwapOnVSync WITHOUT `nogil`
+# (cppinc.pxd), unlike SetPixel/Clear/Fill on the lines just above it.
+# SwapOnVSync blocks until the panel's next vertical sync -- up to a full
+# refresh period on every frame -- so the render thread was holding the GIL
+# for most of every frame. Background threads (API fetches, JSON parsing,
+# image decode) were starved into long uninterruptible bursts, which in turn
+# made the render loop miss refreshes.
+#
+# Measured on a Pi 4 driving a 2x128x64 chain at limit_refresh_rate_hz=100:
+#
+#     before   ~44 fps average, 14-17% of frames 41-53ms
+#     after    100 fps, median 10.00ms, p95 10.05ms, 0% stalls
+#
+# The per-pixel blit (SetPixelsPillow) can also release the GIL and walk the
+# Pillow buffer row-major, but that is OFF by default and you almost certainly
+# want to leave it that way. Row-major changes what a partially-written frame
+# looks like: column-major tearing shows as a vertical seam, row-major tearing
+# shows as a horizontal split between the panel's upper and lower halves. On a
+# 1/32 scan panel that reads as a one-pixel "fold" across the middle of every
+# panel -- reported on hardware, and it went away when the blit was reverted.
+# Enable with RGB_PATCH_BLIT=1 only if you have measured that you need it;
+# essentially all of the gain above comes from the SwapOnVSync change alone.
+#
+# SAFETY
+# ------
+# Builds into a scratch directory; touches the installed module only in the
+# --install step, and backs up the original first. Roll back at any time with:
+#
+#     sudo bash scripts/build_rgbmatrix_nogil.sh --rollback
+#
+# USAGE
+#     bash scripts/build_rgbmatrix_nogil.sh              # build only
+#     sudo bash scripts/build_rgbmatrix_nogil.sh --install
+#     sudo bash scripts/build_rgbmatrix_nogil.sh --rollback
+#
+set -uo pipefail
+
+# Resolve the invoking user's home, not root's. --install runs under sudo,
+# where $HOME is /root, so every default path below pointed somewhere the
+# build had never written and the install died with "no built module found".
+if [ -n "${SUDO_USER:-}" ]; then
+    OWNER_HOME="$(getent passwd "$SUDO_USER" | cut -d: -f6)"
+fi
+OWNER_HOME="${OWNER_HOME:-$HOME}"
+
+SRC_TREE="${RGB_SRC_TREE:-$OWNER_HOME/LEDMatrix/rpi-rgb-led-matrix-master}"
+BUILD_DIR="${RGB_BUILD_DIR:-$OWNER_HOME/rgbmatrix-nogil-build}"
+VENV="${RGB_CYTHON_VENV:-$OWNER_HOME/.cache/ledmatrix-cython}"
+BACKUP="${RGB_BACKUP:-$OWNER_HOME/rgbmatrix-core.so.ORIGINAL}"
+PATCH_BLIT="${RGB_PATCH_BLIT:-0}"
+
+die() { echo "FATAL: $*" >&2; exit 1; }
+
+# This script runs under `set -uo pipefail` -- no -e -- so an unchecked
+# systemctl failure is silently ignored. That matters most for `stop`: leaving
+# the old service running means cp overwrites a module the running process has
+# mapped, the following `start` succeeds as a no-op, and the health check sees
+# an active unit and reports SUCCESS for a binding that was never loaded.
+# A machine with no ledmatrix.service at all is a normal build host, so that
+# case is skipped rather than treated as a failure.
+service_present() { systemctl cat ledmatrix.service >/dev/null 2>&1; }
+
+service_do() {
+    local verb="$1"
+    if ! service_present; then
+        echo "   (no ledmatrix.service installed - skipping $verb)"
+        return 0
+    fi
+    systemctl "$verb" ledmatrix || die "systemctl $verb ledmatrix failed"
+}
+
+py_site() {
+    python3 -c 'import rgbmatrix, os; print(os.path.dirname(rgbmatrix.__file__))' 2>/dev/null
+}
+
+# The extension filename the interpreter that builds -- and then loads -- this
+# module actually uses, e.g. core.cpython-313-aarch64-linux-gnu.so. The build
+# venv is made with --system-site-packages from python3, so the two agree;
+# falling back keeps --install working when the venv has been cleaned up.
+abi_name() {
+    local py="$VENV/bin/python"
+    [ -x "$py" ] || py=python3
+    "$py" -c \
+        'import sysconfig; print("core" + sysconfig.get_config_var("EXT_SUFFIX"))' \
+        2>/dev/null
+}
+
+# Exactly the current interpreter's artifact, never merely the first one that
+# sorts. Staging copies $SRC_TREE wholesale, so a core.cpython-*.so left in the
+# source tree by an earlier build comes along for the ride; build_ext --inplace
+# only ever overwrites the current ABI's name, and a glob piped to `head -1`
+# sorts cpython-311 ahead of cpython-313. That installed a stale, unpatched
+# module as core.so while the GIL check below -- which reads the freshly
+# generated core.cpp, not the .so -- still reported success.
+abi_so() {
+    local name path
+    name="$(abi_name)" || return 1
+    [ -n "$name" ] || return 1
+    path="$BUILD_DIR/bindings/python/rgbmatrix/$name"
+    [ -f "$path" ] || return 1
+    printf '%s\n' "$path"
+}
+
+do_rollback() {
+    local dst; dst="$(py_site)"
+    [ -n "$dst" ] || die "could not locate the installed rgbmatrix package"
+    [ -f "$BACKUP" ] || die "no backup at $BACKUP"
+    service_do stop
+    cp -a "$BACKUP" "$dst/core.so" || die "restore failed"
+    find "$dst" -name __pycache__ -type d -exec rm -rf {} + 2>/dev/null
+    service_do start
+    echo "rolled back to the original core.so"
+    exit 0
+}
+
+do_install() {
+    local so dst
+    so="$(abi_so)"; [ -n "$so" ] || die "no built module found - run the build first"
+    dst="$(py_site)"; [ -n "$dst" ] || die "could not locate the installed rgbmatrix package"
+
+    if [ ! -f "$BACKUP" ]; then
+        cp -a "$dst/core.so" "$BACKUP" || die "could not back up the original"
+        echo "backed up original core.so -> $BACKUP"
+    else
+        echo "backup already present at $BACKUP (keeping the true original)"
+    fi
+
+    service_do stop
+    cp "$so" "$dst/core.so" || die "install failed"
+    find "$dst" -name __pycache__ -type d -exec rm -rf {} + 2>/dev/null
+    service_do start
+
+    echo "waiting 25s for the display to come back..."
+    sleep 25
+    local healthy=1
+    systemctl is-active --quiet ledmatrix || healthy=0
+    if journalctl -u ledmatrix --since "40 sec ago" --no-pager \
+         | grep -qiE "Traceback|ImportError|Segmentation fault|undefined symbol"; then
+        healthy=0
+    fi
+    if [ "$healthy" = "1" ]; then
+        echo "SUCCESS - running on the rebuilt binding"
+    else
+        echo "UNHEALTHY - rolling back"
+        cp -a "$BACKUP" "$dst/core.so" \
+            || echo "ROLLBACK FAILED: could not restore $BACKUP -> $dst/core.so" >&2
+        if service_present && ! systemctl restart ledmatrix; then
+            echo "ROLLBACK FAILED: ledmatrix did not restart - the display is" \
+                 "down; restore manually with 'sudo bash $0 --rollback'" >&2
+        fi
+        journalctl -u ledmatrix --since "90 sec ago" --no-pager | tail -25
+        exit 1
+    fi
+    exit 0
+}
+
+case "${1:-}" in
+    --rollback) do_rollback ;;
+    --install)  do_install ;;
+    "" )        ;;
+    *)          die "unknown option: $1" ;;
+esac
+
+# ---------------------------------------------------------------- build ----
+[ -d "$SRC_TREE" ] || die "matrix source tree not found at $SRC_TREE (set RGB_SRC_TREE)"
+command -v g++ >/dev/null || die "g++ not installed (apt install build-essential)"
+
+echo "==> staging a scratch copy at $BUILD_DIR"
+rm -rf "$BUILD_DIR"
+cp -r "$SRC_TREE" "$BUILD_DIR" || die "copy failed"
+
+# Drop any extension artifacts that came across from the source tree. Nothing
+# downstream should be able to pick one up, and build_ext --inplace can decide
+# a copied .so is already up to date and skip the compile entirely.
+find "$BUILD_DIR/bindings/python/rgbmatrix" -maxdepth 1 \
+     -name 'core*.so' -delete 2>/dev/null
+
+echo "==> patching the bindings to release the GIL"
+python3 - "$BUILD_DIR" "$PATCH_BLIT" <<'PYEOF' || die "patch failed"
+import io
+import sys
+
+base = sys.argv[1] + "/bindings/python/rgbmatrix/"
+patch_blit = len(sys.argv) > 2 and sys.argv[2] == "1"
+
+# --- declare SwapOnVSync as nogil ---------------------------------------
+p = base + "cppinc.pxd"
+s = io.open(p, encoding="utf-8").read()
+OLD_DECL = "        FrameCanvas *SwapOnVSync(FrameCanvas*, uint8_t)\n"
+NEW_DECL = "        FrameCanvas *SwapOnVSync(FrameCanvas*, uint8_t) nogil\n"
+if OLD_DECL in s:
+    io.open(p, "w", encoding="utf-8", newline="\n").write(s.replace(OLD_DECL, NEW_DECL, 1))
+    print("   cppinc.pxd: SwapOnVSync declared nogil")
+elif NEW_DECL in s:
+    print("   cppinc.pxd: already nogil")
+else:
+    sys.exit("could not find the SwapOnVSync declaration")
+
+# --- release the GIL across the vsync wait ------------------------------
+p = base + "core.pyx"
+s = io.open(p, encoding="utf-8").read()
+
+OLD_SWAP = (
+    "    def SwapOnVSync(self, FrameCanvas newFrame, uint8_t framerate_fraction = 1):\n"
+    "        return __createFrameCanvas("
+    "self.__matrix.SwapOnVSync(newFrame.__canvas, framerate_fraction))\n"
+)
+NEW_SWAP = (
+    "    def SwapOnVSync(self, FrameCanvas newFrame, uint8_t framerate_fraction = 1):\n"
+    "        # Blocks until the panel's next vertical sync. Holding the GIL\n"
+    "        # across that wait starves every other Python thread for most of\n"
+    "        # each frame. Pointers are hoisted into C locals so the blocking\n"
+    "        # call itself needs no Python state.\n"
+    "        cdef cppinc.RGBMatrix* matrix = self.__matrix\n"
+    "        cdef cppinc.FrameCanvas* frame = newFrame.__canvas\n"
+    "        cdef uint8_t fraction = framerate_fraction\n"
+    "        cdef cppinc.FrameCanvas* swapped\n"
+    "        with nogil:\n"
+    "            swapped = matrix.SwapOnVSync(frame, fraction)\n"
+    "        return __createFrameCanvas(swapped)\n"
+)
+if OLD_SWAP in s:
+    s = s.replace(OLD_SWAP, NEW_SWAP, 1)
+    print("   core.pyx: SwapOnVSync releases the GIL")
+elif "swapped = matrix.SwapOnVSync(frame, fraction)" in s:
+    print("   core.pyx: SwapOnVSync already patched")
+else:
+    sys.exit("could not find the SwapOnVSync body")
+
+# --- optional: release the GIL across the blit --------------------------
+OLD_BLIT = (
+    "        buffer = get_pillow_buffer(image_capsule)\n"
+    "\n"
+    "        for col in range(max(0, -xstart), min(width, frame_width - xstart)):\n"
+    "            for row in range(max(0, -ystart), min(height, frame_height - ystart)):\n"
+    "                pixel = buffer[row][col]\n"
+    "                r = (pixel ) & 0xFF\n"
+    "                g = (pixel >> 8) & 0xFF\n"
+    "                b = (pixel >> 16) & 0xFF\n"
+    "                my_canvas.SetPixel(xstart+col, ystart+row, r, g, b)\n"
+)
+NEW_BLIT = (
+    "        buffer = get_pillow_buffer(image_capsule)\n"
+    "\n"
+    "        # Bounds hoisted so the blit needs no Python state and can run\n"
+    "        # without the GIL: it touches only a C buffer and a C++ canvas.\n"
+    "        # NOTE: row-major order makes a torn frame show as a horizontal\n"
+    "        # split across the panel's halves. See the header before enabling.\n"
+    "        cdef int col_start = max(0, -xstart)\n"
+    "        cdef int col_end = min(width, frame_width - xstart)\n"
+    "        cdef int row_start = max(0, -ystart)\n"
+    "        cdef int row_end = min(height, frame_height - ystart)\n"
+    "\n"
+    "        with nogil:\n"
+    "            for row in range(row_start, row_end):\n"
+    "                for col in range(col_start, col_end):\n"
+    "                    pixel = buffer[row][col]\n"
+    "                    r = (pixel ) & 0xFF\n"
+    "                    g = (pixel >> 8) & 0xFF\n"
+    "                    b = (pixel >> 16) & 0xFF\n"
+    "                    my_canvas.SetPixel(xstart+col, ystart+row, r, g, b)\n"
+)
+if patch_blit:
+    if OLD_BLIT in s:
+        s = s.replace(OLD_BLIT, NEW_BLIT, 1)
+        print("   core.pyx: pixel blit releases the GIL, row-major")
+    elif "for row in range(row_start, row_end):" in s:
+        print("   core.pyx: blit already patched")
+    else:
+        sys.exit("could not find the SetPixelsPillow loop")
+else:
+    print("   core.pyx: blit left unpatched (RGB_PATCH_BLIT=1 to enable)")
+
+io.open(p, "w", encoding="utf-8", newline="\n").write(s)
+PYEOF
+
+echo "==> building librgbmatrix.a (this takes a few minutes)"
+nice -n 10 make -C "$BUILD_DIR/lib" -j2 >/dev/null 2>&1 \
+    || die "library build failed - rerun 'make -C $BUILD_DIR/lib' to see why"
+[ -f "$BUILD_DIR/lib/librgbmatrix.a" ] || die "librgbmatrix.a was not produced"
+
+echo "==> preparing Cython"
+[ -d "$VENV" ] || python3 -m venv --system-site-packages "$VENV" || die "venv failed"
+"$VENV/bin/pip" install --quiet cython || die "cython install failed"
+
+cat > "$BUILD_DIR/bindings/python/setup.py" <<'EOF'
+from setuptools import setup, Extension
+from Cython.Build import cythonize
+
+core = Extension(
+    "rgbmatrix.core",
+    sources=["rgbmatrix/core.pyx", "rgbmatrix/shims/pillow.c"],
+    include_dirs=["../../include", "rgbmatrix/shims"],
+    extra_objects=["../../lib/librgbmatrix.a"],
+    language="c++",
+    extra_compile_args=["-O3", "-Wall", "-fno-exceptions", "-std=c++11"],
+    extra_link_args=["-lrt", "-lm", "-lpthread"],
+)
+
+setup(name="rgbmatrix",
+      ext_modules=cythonize([core], language_level="3str",
+                            compiler_directives={"binding": False}))
+EOF
+
+echo "==> compiling the extension"
+( cd "$BUILD_DIR/bindings/python" && "$VENV/bin/python" setup.py build_ext --inplace ) \
+    >/dev/null 2>&1 || die "extension build failed"
+
+SO="$(abi_so)" || true
+[ -n "$SO" ] || die "no .so produced - expected $(abi_name) in $BUILD_DIR/bindings/python/rgbmatrix"
+
+# Verify the GIL really is released before anyone installs this.
+EXPECTED=1; [ "$PATCH_BLIT" = "1" ] && EXPECTED=2
+PAIRS=$(grep -c "PyEval_SaveThread\|Py_UNBLOCK_THREADS" \
+        "$BUILD_DIR/bindings/python/rgbmatrix/core.cpp")
+[ "$PAIRS" -ge "$EXPECTED" ] \
+    || die "generated C++ has $PAIRS GIL-release sites, expected >= $EXPECTED"
+
+echo
+echo "BUILT: $SO"
+echo "       ($PAIRS GIL-release site(s) in the generated C++)"
+echo
+echo "Install with:   sudo bash $0 --install"
+echo "Roll back with: sudo bash $0 --rollback"

scripts/install/install_dns_fix.sh

@@ -0,0 +1,86 @@
+#!/bin/bash
+
+# DNS single-request fix installation script.
+#
+# Optional. Install this only if plugins that call external APIs (Starlark
+# apps, weather, sports, music) are timing out or feel slow to first paint
+# while the network is otherwise fine. See the header of
+# scripts/utils/apply_dns_single_request.sh for what it changes and why.
+
+set -e
+
+PROJECT_ROOT_DIR=$(cd "$(dirname "$0")/../.." && pwd)
+SERVICE_NAME="ledmatrix-dns-fix"
+UNIT_SRC="$PROJECT_ROOT_DIR/systemd/$SERVICE_NAME.service"
+UNIT_DEST="/etc/systemd/system/$SERVICE_NAME.service"
+DROPIN_DIR="/etc/systemd/system/ledmatrix.service.d"
+
+if [ "$EUID" -eq 0 ]; then
+    SYSTEMCTL_CMD="systemctl"
+    SUDO=""
+else
+    SYSTEMCTL_CMD="sudo systemctl"
+    SUDO="sudo"
+fi
+
+echo "Installing LED Matrix DNS fix service"
+echo "Project root directory: $PROJECT_ROOT_DIR"
+
+if [ ! -f "$UNIT_SRC" ]; then
+    echo "✗ Missing unit file: $UNIT_SRC"
+    exit 1
+fi
+
+chmod +x "$PROJECT_ROOT_DIR/scripts/utils/apply_dns_single_request.sh"
+
+echo "Installing $UNIT_DEST..."
+sed "s|__PROJECT_ROOT_DIR__|$PROJECT_ROOT_DIR|g" "$UNIT_SRC" \
+    | $SUDO tee "$UNIT_DEST" > /dev/null
+
+# Order ledmatrix.service after the fix. `Before=` in the unit itself only
+# orders units already in the same transaction, so a plain
+# `systemctl restart ledmatrix` would not wait for it -- and since this fix is
+# opt-in, ledmatrix.service cannot carry the dependency in the repo.
+# Wants=, not Requires=: a DNS workaround failing should not stop the display.
+echo "Installing the ledmatrix.service ordering drop-in..."
+$SUDO mkdir -p "$DROPIN_DIR"
+printf '[Unit]\nWants=%s.service\nAfter=%s.service\n' "$SERVICE_NAME" "$SERVICE_NAME" \
+    | $SUDO tee "$DROPIN_DIR/10-dns-fix.conf" > /dev/null
+
+$SYSTEMCTL_CMD daemon-reload
+$SYSTEMCTL_CMD enable "$SERVICE_NAME.service"
+
+# Do not mask a failure here. The unit exits non-zero when it could not apply
+# the option -- a systemd-resolved host, an unwritable resolv.conf, a failed
+# `resolvconf -u` -- and reporting "installation complete" over that would
+# leave the operator believing a workaround is active when it is not.
+START_STATUS=0
+$SYSTEMCTL_CMD start "$SERVICE_NAME.service" || START_STATUS=$?
+
+echo ""
+if grep -qs "^options single-request$" /etc/resolv.conf; then
+    echo "✓ 'options single-request' is active in /etc/resolv.conf"
+elif [ "$START_STATUS" -ne 0 ]; then
+    echo "✗ The DNS fix could not be applied on this host."
+    echo "  The service reported why:"
+    echo "    journalctl -u $SERVICE_NAME -n 20"
+    echo ""
+    echo "  The unit is installed and will try again on the next boot. Nothing"
+    echo "  else about your install has changed."
+    exit "$START_STATUS"
+else
+    echo "⚠ 'options single-request' is not in /etc/resolv.conf yet."
+    echo "  Check what the service reported:"
+    echo "    journalctl -u $SERVICE_NAME -n 20"
+fi
+
+echo ""
+echo "DNS fix installation complete."
+echo ""
+echo "Useful commands:"
+echo "  sudo systemctl status $SERVICE_NAME   # Check status"
+echo "  sudo journalctl -u $SERVICE_NAME -n 50  # View logs"
+echo "  sudo systemctl disable --now $SERVICE_NAME  # Undo the service"
+echo "  sudo rm $DROPIN_DIR/10-dns-fix.conf        # Undo the ordering drop-in"
+echo "  # then remove the 'options single-request' line from /etc/resolv.conf"
+echo ""

scripts/install/install_mqtt_bridge.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+
+# Home Assistant MQTT bridge installation script.
+#
+# Optional. Installs integrations/mqtt_bridge as a service so Home Assistant
+# can force display modes, toggle power and set brightness over MQTT.
+# See integrations/mqtt_bridge/README.md.
+
+set -e
+
+PROJECT_ROOT_DIR=$(cd "$(dirname "$0")/../.." && pwd)
+BRIDGE_DIR="$PROJECT_ROOT_DIR/integrations/mqtt_bridge"
+SERVICE_NAME="ledmatrix-mqtt-bridge"
+UNIT_SRC="$PROJECT_ROOT_DIR/systemd/$SERVICE_NAME.service"
+UNIT_DEST="/etc/systemd/system/$SERVICE_NAME.service"
+
+if [ "$EUID" -eq 0 ]; then
+    SYSTEMCTL_CMD="systemctl"
+    SUDO=""
+else
+    SYSTEMCTL_CMD="sudo systemctl"
+    SUDO="sudo"
+fi
+
+echo "Installing LED Matrix MQTT bridge"
+echo "Project root directory: $PROJECT_ROOT_DIR"
+
+if [ ! -f "$BRIDGE_DIR/bridge_config.json" ]; then
+    cp "$BRIDGE_DIR/bridge_config.example.json" "$BRIDGE_DIR/bridge_config.json"
+    chmod 600 "$BRIDGE_DIR/bridge_config.json"
+    echo ""
+    echo "⚠ Created $BRIDGE_DIR/bridge_config.json from the example."
+    echo "  Edit it with your broker details, then re-run this script."
+    echo "  The service will refuse to start until the placeholder password is replaced."
+    echo ""
+fi
+
+echo "Installing Python dependencies..."
+python3 -m pip install -r "$BRIDGE_DIR/requirements.txt" 2>/dev/null \
+    || python3 -m pip install --break-system-packages -r "$BRIDGE_DIR/requirements.txt"
+
+echo "Installing $UNIT_DEST..."
+sed "s|__PROJECT_ROOT_DIR__|$PROJECT_ROOT_DIR|g" "$UNIT_SRC" \
+    | $SUDO tee "$UNIT_DEST" > /dev/null
+
+$SYSTEMCTL_CMD daemon-reload
+$SYSTEMCTL_CMD enable "$SERVICE_NAME.service"
+$SYSTEMCTL_CMD restart "$SERVICE_NAME.service" || true
+
+echo ""
+if $SYSTEMCTL_CMD is-active --quiet "$SERVICE_NAME.service" 2>/dev/null; then
+    echo "✓ MQTT bridge is running"
+    echo "  The matrix should appear in Home Assistant under Settings > Devices > MQTT."
+else
+    echo "⚠ MQTT bridge is not running. Check the logs:"
+    echo "  sudo journalctl -u $SERVICE_NAME -n 50"
+fi
+
+echo ""
+echo "Useful commands:"
+echo "  sudo systemctl status $SERVICE_NAME"
+echo "  sudo journalctl -u $SERVICE_NAME -f"
+echo "  sudo systemctl disable --now $SERVICE_NAME   # Undo"
+echo ""

scripts/render_plugin.py

@@ -52,6 +52,10 @@ def main() -> int:
     parser.add_argument('--height', type=int, default=32, help='Display height (default: 32)')
     parser.add_argument('--skip-update', action='store_true',
                         help='Skip calling update() (render display only)')
+    parser.add_argument('--display-mode', default=None,
+                        help='Display mode to render, for plugins that declare '
+                             'more than one in their manifest (e.g. nrl_live). '
+                             'Omitted, the plugin picks its own default.')
 
     args = parser.parse_args()
 
@@ -141,8 +145,26 @@ def main() -> int:
         except Exception as e:
             logger.warning("update() raised: %s — continuing to display()", e)
 
+    # A plugin that declares several display modes usually renders nothing
+    # useful without being told which one to draw: the scoreboards keep their
+    # state on per-mode sub-managers and their no-argument path returns False.
+    # Only pass the argument when asked for, so the many plugins whose display()
+    # takes no display_mode keep working untouched.
     try:
-        plugin_instance.display(force_clear=True)
+        if args.display_mode:
+            try:
+                plugin_instance.display(display_mode=args.display_mode,
+                                        force_clear=True)
+            except TypeError as error:
+                if ("unexpected keyword argument" not in str(error)
+                        or "display_mode" not in str(error)):
+                    raise
+                logger.warning(
+                    "%s.display() does not accept display_mode; rendering its "
+                    "default screen instead", args.plugin)
+                plugin_instance.display(force_clear=True)
+        else:
+            plugin_instance.display(force_clear=True)
         logger.debug("display() completed")
     except Exception as e:
         logger.error("Error in display(): %s", e)

scripts/run_plugin_tests.py

@@ -6,6 +6,9 @@ Discovers and runs tests for LEDMatrix plugins.
 Supports both unittest and pytest.
 """
 
+import os
+import re
+import subprocess  # nosec B404 - list-form argv only, no shell  # nosemgrep
 import sys
 import argparse
 from pathlib import Path
@@ -68,6 +71,79 @@ def _find_tests_in_dir(directory: Path) -> list:
     return sorted(set(test_files))
 
 
+def _is_script_style(path) -> bool:
+    """True when a test file is a standalone script, not a pytest module.
+
+    Most plugin tests are written as `def main()` plus an `if __name__ ==
+    "__main__"` guard and signal through an exit code. pytest collects zero
+    items from those, so handing them to pytest printed "no tests ran" and this
+    runner reported success over work it had not done -- 151 of 248 files on a
+    fully populated rig.
+    """
+    try:
+        src = Path(path).read_text(encoding="utf-8", errors="replace")
+    except OSError:
+        return False
+    has_pytest_items = re.search(r"^\s*(def test_|class Test|async def test_)", src, re.M)
+    has_main_guard = "__main__" in src and "__name__" in src
+    return bool(has_main_guard and not has_pytest_items)
+
+
+def run_script_tests(test_files: list, verbose: bool = False) -> int:
+    """Run standalone test scripts, honouring the 0 pass / 2 skip / 1 fail
+    convention that ledmatrix-plugins' own runner established.
+
+    Scripts opt into skipping by printing "SKIP: <reason>" and exiting 2 --
+    a script that needs a tty or an LED matrix is not a regression.
+    """
+    env = dict(os.environ)
+    # Prepend rather than setdefault. An inherited PYTHONPATH -- a developer's
+    # shell, a tox run, another checkout -- otherwise wins outright, and the
+    # subprocess imports a different copy of the core than the one under test.
+    # That is exactly the failure ledmatrix-plugins#467 describes, and it is
+    # invisible: the tests pass or fail against a tree nobody meant to test.
+    inherited = env.get("PYTHONPATH")
+    env["PYTHONPATH"] = (f"{PROJECT_ROOT}{os.pathsep}{inherited}"
+                         if inherited else str(PROJECT_ROOT))
+    env["LEDMATRIX_CORE"] = str(PROJECT_ROOT)
+
+    passed = skipped = failed = 0
+    failures = []
+    for path in test_files:
+        try:
+            # Fixed interpreter (sys.executable) plus a test path this script
+            # discovered by globbing the repo; argument list, no shell, so
+            # nothing is word-split or expanded. Same suppression pair the
+            # rest of the repo uses for this shape (see permission_utils.py).
+            proc = subprocess.run(  # noqa: S603  # nosec B603 - no shell invoked (list-form argv)  # nosemgrep
+                [sys.executable, str(path)],  # nosemgrep
+                cwd=str(Path(path).parent),
+                capture_output=True, text=True, env=env,
+                stdin=subprocess.DEVNULL, timeout=300,
+            )
+            rc = proc.returncode
+            tail = " | ".join((proc.stdout or proc.stderr or "").strip().splitlines()[-2:])[:200]
+        except subprocess.TimeoutExpired:
+            rc, tail = 1, "timed out after 300s"
+        if rc == 0:
+            passed += 1
+            label = "pass"
+        elif rc == 2:
+            skipped += 1
+            label = "SKIP"
+        else:
+            failed += 1
+            label = "FAIL"
+            failures.append(f"{Path(path).name}: exit {rc} | {tail}")
+        if verbose or rc != 0:
+            print(f"  [{label}] {Path(path).name}" + (f" -- {tail}" if rc != 0 else ""))
+
+    print(f"\n{passed} passed, {skipped} skipped, {failed} failed (scripts)")
+    for f in failures:
+        print(f"  - {f}", file=sys.stderr)
+    return 1 if failed else 0
+
+
 def run_unittest_tests(test_files: list, verbose: bool = False) -> int:
     """
     Run tests using unittest.
@@ -186,7 +262,12 @@ def main():
             print("No test files found in plugins directory")
         return 0
     
-    print(f"Found {len(test_files)} test file(s)")
+    scripts = [f for f in test_files if _is_script_style(f)]
+    modules = [f for f in test_files if f not in scripts]
+
+    print(f"Found {len(test_files)} test file(s)"
+          + (f" -- {len(modules)} collectable, {len(scripts)} standalone script(s)"
+             if scripts else ""))
     for test_file in test_files:
         print(f"  - {test_file}")
     print()
@@ -200,11 +281,20 @@ def main():
         except ImportError:
             runner = 'unittest'
 
-    # Run tests
+    # Standalone scripts cannot be collected by pytest or unittest -- run them
-    if runner == 'pytest':
+    # as the scripts they are. Doing this rather than silently collecting zero
-        return run_pytest_tests(test_files, args.verbose, args.coverage)
+    # items is the whole point: this runner used to report success having
-    else:
+    # executed nothing.
-        return run_unittest_tests(test_files, args.verbose)
+    rc = 0
+    if scripts:
+        rc |= run_script_tests(scripts, args.verbose)
+
+    if modules:
+        if runner == 'pytest':
+            rc |= run_pytest_tests(modules, args.verbose, args.coverage)
+        else:
+            rc |= run_unittest_tests(modules, args.verbose)
+    return rc
 
 
 if __name__ == '__main__':

scripts/scroll_speeds.py

@@ -0,0 +1,240 @@
+#!/usr/bin/env python3
+"""Show and try the scroll speeds your panel can display cleanly.
+
+Motion looks smooth when the strip advances a WHOLE number of pixels per panel
+refresh. Anything else has to blend two columns (which on pixel-font text reads
+as shimmer) or repeat frames unevenly (which reads as judder). So the speeds
+worth using are not arbitrary -- they are
+
+    refresh_hz / frame_hold * pixels_per_frame
+
+for whole numbers of frame_hold and pixels_per_frame, and that ladder depends
+on how fast YOUR panel actually refreshes. A Pi Zero driving a big chain will
+have a completely different set of good speeds from a Pi 4 driving a small one.
+
+    # what can this panel do? (no hardware needed, uses your configured rate)
+    python3 scripts/scroll_speeds.py
+
+    # measure what the panel ACTUALLY manages, rather than what is configured
+    sudo systemctl stop ledmatrix
+    sudo python3 scripts/scroll_speeds.py --measure
+    sudo systemctl start ledmatrix
+
+    # what would a 60Hz panel offer?
+    python3 scripts/scroll_speeds.py --hz 60
+
+    # try one on the panel
+    sudo systemctl stop ledmatrix
+    sudo python3 scripts/scroll_speeds.py --demo 50
+    sudo systemctl start ledmatrix
+
+This script never starts or stops the display service itself -- that is left to
+you, so a crash here can never leave the panel dark.
+"""
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import sys
+import time
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from src.common import scroll_config  # noqa: E402
+
+CONFIG = Path(__file__).resolve().parent.parent / "config" / "config.json"
+
+
+def load_hardware():
+    try:
+        with open(CONFIG, encoding="utf-8") as handle:
+            return (json.load(handle).get("display") or {}).get("hardware") or {}
+    except (OSError, ValueError):
+        return {}
+
+
+def build_options(hardware, refresh_override=None):
+    from rgbmatrix import RGBMatrixOptions
+
+    o = RGBMatrixOptions()
+    o.rows = int(hardware.get("rows", 32))
+    o.cols = int(hardware.get("cols", 64))
+    o.chain_length = int(hardware.get("chain_length", 1))
+    o.parallel = int(hardware.get("parallel", 1))
+    o.brightness = int(hardware.get("brightness", 80))
+    o.hardware_mapping = hardware.get("hardware_mapping", "regular")
+    o.pwm_bits = int(hardware.get("pwm_bits", 11))
+    o.pwm_dither_bits = int(hardware.get("pwm_dither_bits", 0))
+    o.pwm_lsb_nanoseconds = int(hardware.get("pwm_lsb_nanoseconds", 130))
+    o.led_rgb_sequence = hardware.get("led_rgb_sequence", "RGB")
+    o.scan_mode = int(hardware.get("scan_mode", 0))
+    o.row_address_type = int(hardware.get("row_address_type", 0))
+    o.multiplexing = int(hardware.get("multiplexing", 0))
+    o.gpio_slowdown = int(hardware.get("gpio_slowdown", 2))
+    o.limit_refresh_rate_hz = (
+        int(refresh_override) if refresh_override is not None
+        else int(hardware.get("limit_refresh_rate_hz", 0))
+    )
+    return o
+
+
+def open_matrix(hardware, refresh_override=None):
+    """Construct the matrix, or explain why it will not open."""
+    if os.geteuid() != 0:
+        sys.exit("this needs root for GPIO access - rerun with sudo")
+    try:
+        from rgbmatrix import RGBMatrix
+    except ImportError:
+        sys.exit("rgbmatrix is not installed on this machine")
+    try:
+        return RGBMatrix(options=build_options(hardware, refresh_override))
+    except Exception as exc:  # pragma: no cover - hardware dependent
+        sys.exit(
+            "could not open the panel ({}).\n"
+            "If the display service is running it owns the GPIO - stop it first:\n"
+            "    sudo systemctl stop ledmatrix".format(exc)
+        )
+
+
+def measure_refresh(hardware, seconds=6.0):
+    """Actual refresh rate, by running uncapped and timing the swaps.
+
+    SwapOnVSync blocks until the panel's next refresh, so an unthrottled loop
+    runs at exactly the panel's rate. This is what an older Pi or a longer
+    chain will really give you, as opposed to whatever limit_refresh_rate_hz
+    optimistically asks for.
+    """
+    matrix = open_matrix(hardware, refresh_override=0)
+    canvas = matrix.CreateFrameCanvas()
+    canvas = matrix.SwapOnVSync(canvas)  # discard the first, it includes setup
+    frames = 0
+    started = time.perf_counter()
+    while time.perf_counter() - started < seconds:
+        canvas = matrix.SwapOnVSync(canvas)
+        frames += 1
+    measured = frames / (time.perf_counter() - started)
+    matrix.Clear()
+    return measured
+
+
+def demo(hardware, target, seconds):
+    """Scroll text at the crisp speed nearest `target`."""
+    from PIL import Image, ImageDraw, ImageFont
+
+    from src.common.font_layout import load_truetype
+
+    hz = float(hardware.get("limit_refresh_rate_hz") or scroll_config.DEFAULT_REFRESH_HZ)
+    choice = scroll_config.solve_crisp(target, hz)
+    print("asked for {:.0f} px/s -> {}".format(target, choice.describe()))
+
+    matrix = open_matrix(hardware)
+    canvas = matrix.CreateFrameCanvas()
+    W, H = canvas.width, canvas.height
+
+    font = None
+    for path, size in (
+        (str(Path(__file__).resolve().parent.parent / "assets/fonts/PressStart2P-Regular.ttf"), 16),
+        ("/usr/share/fonts/truetype/dejavu/DejaVuSansMono-Bold.ttf", 26),
+    ):
+        try:
+            font = load_truetype(path, size)
+            break
+        except OSError:
+            continue
+    if font is None:
+        font = ImageFont.load_default()
+
+    text = "  {:.0f} px/s  ***  THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG  ***".format(
+        choice.pixels_per_second)
+    box = ImageDraw.Draw(Image.new("RGB", (8, 8))).textbbox((0, 0), text, font=font)
+    tw, th = box[2] - box[0], box[3] - box[1]
+    reps = max(2, (W * 3) // max(tw, 1) + 1)
+    strip = Image.new("RGB", (tw * reps, H), (0, 0, 0))
+    draw = ImageDraw.Draw(strip)
+    for i in range(reps):
+        draw.text((i * tw, (H - th) // 2 - box[1]), text, font=font, fill=(255, 210, 60))
+
+    offset = 0
+    frames = 0
+    started = time.time()
+    while time.time() - started < seconds:
+        window = strip.crop((offset, 0, offset + W, H))
+        if window.width < W:
+            whole = Image.new("RGB", (W, H), (0, 0, 0))
+            head = strip.crop((offset, 0, strip.width, H))
+            whole.paste(head, (0, 0))
+            whole.paste(strip.crop((0, 0, W - head.width, H)), (head.width, 0))
+            window = whole
+        canvas.SetImage(window)
+        canvas = matrix.SwapOnVSync(canvas, choice.frame_hold)
+        offset = (offset + choice.pixels_per_frame) % strip.width
+        frames += 1
+    elapsed = time.time() - started
+    print("  {} frames in {:.1f}s = {:.1f} fps = {:.1f} px/s actual".format(
+        frames, elapsed, frames / elapsed, frames * choice.pixels_per_frame / elapsed))
+    matrix.Clear()
+
+
+def print_ladder(hz, highlight=None):
+    print("")
+    print("Whole-pixel scroll speeds at {:.1f}Hz refresh".format(hz))
+    print("(the panel refreshes at {:.0f}Hz for every one of these - holding a "
+          "frame costs no flicker)".format(hz))
+    print("")
+    for entry in scroll_config.crisp_ladder(hz):
+        if entry.pixels_per_second > hz * 3:
+            break
+        mark = " <-- nearest to {:.0f}".format(highlight) if (
+            highlight is not None
+            and entry.pixels_per_second == scroll_config.solve_crisp(highlight, hz).pixels_per_second
+        ) else ""
+        print("  " + entry.describe() + mark)
+    print("")
+    print("Set one in config.json as pixels per second, e.g.")
+    print('  "display_options": {{"scroll_pixels_per_second": {:.0f}}}'.format(
+        scroll_config.solve_crisp(highlight if highlight else hz / 2, hz).pixels_per_second))
+
+
+def main():
+    ap = argparse.ArgumentParser(description=__doc__,
+                                 formatter_class=argparse.RawDescriptionHelpFormatter)
+    ap.add_argument("--hz", type=float,
+                    help="refresh rate to compute the ladder for (default: your config)")
+    ap.add_argument("--measure", action="store_true",
+                    help="measure the panel's real refresh rate (needs root, service stopped)")
+    ap.add_argument("--demo", type=float, metavar="PXPS",
+                    help="scroll text at the crisp speed nearest this (needs root)")
+    ap.add_argument("--seconds", type=float, default=15.0, help="demo duration")
+    ap.add_argument("--want", type=float, metavar="PXPS",
+                    help="highlight the entry nearest this speed")
+    args = ap.parse_args()
+
+    hardware = load_hardware()
+    configured = float(hardware.get("limit_refresh_rate_hz") or 0)
+
+    if args.demo is not None:
+        demo(hardware, args.demo, args.seconds)
+        return
+
+    if args.measure:
+        measured = measure_refresh(hardware)
+        print("measured panel refresh: {:.1f}Hz".format(measured))
+        if configured:
+            print("configured limit_refresh_rate_hz: {:.0f}".format(configured))
+            if measured < configured * 0.95:
+                print("  -> the panel cannot reach the configured rate; the ladder")
+                print("     below uses what it actually manages")
+        print_ladder(measured, args.want)
+        return
+
+    hz = args.hz or configured or scroll_config.DEFAULT_REFRESH_HZ
+    if not args.hz and not configured:
+        print("no limit_refresh_rate_hz in config; assuming {:.0f}Hz".format(hz))
+        print("run with --measure to find your panel's real rate")
+    print_ladder(hz, args.want)
+
+
+if __name__ == "__main__":
+    main()

scripts/utils/README.md

@@ -9,6 +9,8 @@ This directory contains utility scripts for maintenance and system operations.
 - **`wifi_monitor_daemon.py`** - Background daemon that monitors WiFi/Ethernet connection and manages access point mode
 - **`cleanup_venv.sh`** - Cleans up Python virtual environment files
 - **`clear_python_cache.sh`** - Clears Python cache files (__pycache__, *.pyc, etc.)
+- **`pixlet_config_editor.sh`** - Opens Pixlet's own config UI for one installed Starlark app
+- **`apply_dns_single_request.sh`** - Adds `options single-request` to the resolver (run by `ledmatrix-dns-fix.service`)
 
 ## Usage
 
@@ -25,3 +27,31 @@ This script is typically called by the systemd service (`ledmatrix-web.service`)
 ### WiFi Monitor Daemon
 This daemon is typically run as a systemd service (`ledmatrix-wifi-monitor.service`) and automatically manages WiFi access point mode based on network connectivity.
 
+
+### Pixlet Config Editor
+Run it when you want Pixlet's own config form for a Starlark app -- live
+render preview, cascading dropdowns -- rather than the LEDMatrix one.
+
+```bash
+./scripts/utils/pixlet_config_editor.sh                 # list installed apps
+./scripts/utils/pixlet_config_editor.sh penndot_signs   # edit, on localhost:8080
+```
+
+Deliberately not a service. It stops the display for the length of the
+session and `pixlet serve` listens with no authentication, so it should only
+be running while you are actually editing. It backs the config up first and
+restarts the display on exit, however it exits.
+
+It binds loopback only, with no flag to change that: anything that can reach
+`pixlet serve` can rewrite the app's config, and a printed warning is not
+access control. To edit from another machine, forward the port -- SSH does the
+authenticating and nothing is left listening on the LAN:
+
+```bash
+ssh -L 8080:localhost:8080 pi@ledpi.local
+```
+
+### Apply DNS Single-Request Fix
+Installed and run by `ledmatrix-dns-fix.service`; see `systemd/README.md`.
+Safe to run by hand (`sudo ./scripts/utils/apply_dns_single_request.sh`) and
+idempotent.

scripts/utils/apply_dns_single_request.sh

@@ -0,0 +1,94 @@
+#!/bin/bash
+#
+# Add `options single-request` to the system resolver configuration.
+#
+# glibc's getaddrinfo() sends the A and AAAA queries for a name in
+# parallel on one socket. Some routers answer the A query and drop the
+# AAAA one, so the resolver waits out its full timeout -- about five
+# seconds -- before returning an address that was already available.
+# Disabling IPv6 in the kernel does not help: the resolver still asks.
+#
+# `single-request` makes it send the two queries one after the other,
+# which those routers answer correctly. Anything on the matrix that
+# calls an external API pays that five seconds per lookup otherwise, and
+# a Starlark app with a render timeout will simply fail instead.
+#
+# Idempotent, and safe to run on a machine that does not need it. Run by
+# ledmatrix-dns-fix.service on every boot, because whatever manages
+# resolv.conf regenerates it and drops the option again.
+#
+# Usage: sudo ./scripts/utils/apply_dns_single_request.sh
+
+set -eu
+
+OPTION="options single-request"
+RESOLVCONF_TAIL="/etc/resolvconf/resolv.conf.d/tail"
+RESOLV_CONF="/etc/resolv.conf"
+
+log() { echo "[dns-single-request] $*"; }
+
+already_applied() {
+    grep -qs "^${OPTION}\$" "$1"
+}
+
+# resolvconf regenerates /etc/resolv.conf from these fragments, so the
+# tail file is the only place an addition survives. Prefer it when the
+# directory exists, whether or not resolvconf has run yet.
+if [ -d "$(dirname "$RESOLVCONF_TAIL")" ]; then
+    if already_applied "$RESOLVCONF_TAIL"; then
+        log "already present in $RESOLVCONF_TAIL"
+    else
+        echo "$OPTION" >> "$RESOLVCONF_TAIL"
+        log "added to $RESOLVCONF_TAIL"
+    fi
+    # Only a missing resolvconf is ignorable. If it is present and the
+    # regeneration fails, /etc/resolv.conf still lacks the option, and
+    # reporting success would be a lie.
+    if command -v resolvconf >/dev/null 2>&1; then
+        if ! resolvconf -u; then
+            log "resolvconf -u failed; $RESOLV_CONF was not regenerated"
+            exit 1
+        fi
+    fi
+fi
+
+# systemd-resolved owns its stub file and rewrites anything appended to it,
+# and `single-request` is a glibc resolv.conf option with no resolved.conf
+# equivalent -- so there is nothing this script can do here. Exit non-zero:
+# the unit would otherwise record success while the workaround is inactive,
+# which is the failure mode this whole script exists to avoid.
+if [ -L "$RESOLV_CONF" ] && readlink -f "$RESOLV_CONF" | grep -q "systemd"; then
+    log "$RESOLV_CONF is managed by systemd-resolved."
+    log "'options single-request' is a glibc resolv.conf option and has no"
+    log "resolved.conf equivalent, so it cannot be applied on this host."
+    log "If external API calls are slow, the workaround is to stop using the"
+    log "systemd-resolved stub (see 'man systemd-resolved', NSS/resolv.conf modes)."
+    exit 1
+fi
+
+if already_applied "$RESOLV_CONF"; then
+    log "already present in $RESOLV_CONF"
+    exit 0
+fi
+
+if [ ! -w "$RESOLV_CONF" ] && [ -e "$RESOLV_CONF" ]; then
+    log "cannot write $RESOLV_CONF (run with sudo?)"
+    exit 1
+fi
+
+# A NetworkManager-generated resolv.conf is regenerated on every connection
+# change, not only at boot -- and this unit is oneshot with RemainAfterExit,
+# so it will not re-run within the same boot to put the option back. Say so
+# rather than implying the fix is permanent. Nothing is silently swallowed:
+# the append below still happens and still works until the next renewal.
+if grep -qs "Generated by NetworkManager" "$RESOLV_CONF" \
+        && [ ! -d "$(dirname "$RESOLVCONF_TAIL")" ]; then
+    log "NOTE: $RESOLV_CONF is generated by NetworkManager and has no"
+    log "resolvconf tail directory to write to. The option is being added, but"
+    log "NetworkManager will drop it on the next connection renewal, and this"
+    log "unit does not run again until the next boot. If lookups go slow again"
+    log "before a reboot, re-run this script."
+fi
+
+echo "$OPTION" >> "$RESOLV_CONF"
+log "added to $RESOLV_CONF"

scripts/utils/pixlet_config_editor.sh

@@ -0,0 +1,143 @@
+#!/bin/bash
+#
+# Edit an installed Starlark app's config in Pixlet's own config UI.
+#
+# `pixlet serve` runs the app for real, so its form has working cascading
+# dropdowns and option lists fetched live -- useful for an app whose choices
+# only exist at runtime, or when you want to see the render change as you
+# type. The LEDMatrix config form now reads the same runtime schema (see
+# PixletRenderer.extract_schema_via_pixlet), so reach for this when you want
+# Pixlet's live preview, not because the normal form is missing options.
+#
+# Deliberately a script you run and then Ctrl+C, not a service: it stops the
+# display for the length of the session, and `pixlet serve` listens on a port
+# with no authentication. Nothing here should be listening when you are not
+# actually editing.
+#
+# Usage:
+#   ./scripts/utils/pixlet_config_editor.sh            # list installed apps
+#   ./scripts/utils/pixlet_config_editor.sh <app_id>   # edit
+#
+# Binds loopback only, and there is deliberately no flag to change that:
+# `pixlet serve` has no authentication, and anything that can reach it can
+# rewrite the app's config. To edit from another machine, forward the port --
+# which authenticates as SSH and leaves nothing listening on the LAN:
+#
+#   ssh -L 8080:localhost:8080 pi@ledpi.local
+
+set -eu
+
+PROJECT_ROOT_DIR=$(cd "$(dirname "$0")/../.." && pwd)
+APPS_DIR="$PROJECT_ROOT_DIR/starlark-apps"
+PORT="${PIXLET_EDITOR_PORT:-8080}"
+# Loopback only. See the header: pixlet serve is unauthenticated.
+BIND_HOST="127.0.0.1"
+
+APP_ID="${1:-}"
+
+list_apps() {
+    if [ -d "$APPS_DIR" ]; then
+        find "$APPS_DIR" -maxdepth 1 -mindepth 1 -type d -printf '  %f\n' 2>/dev/null | sort
+    fi
+}
+
+if [ -z "$APP_ID" ]; then
+    echo "Usage: $0 <app_id>"
+    echo ""
+    echo "Installed apps:"
+    list_apps || true
+    [ -n "$(list_apps)" ] || echo "  (none found in $APPS_DIR)"
+    exit 1
+fi
+
+APP_DIR="$APPS_DIR/$APP_ID"
+if [ ! -d "$APP_DIR" ]; then
+    echo "No such app: $APP_ID"
+    echo ""
+    echo "Installed apps:"
+    list_apps
+    exit 1
+fi
+
+STAR_FILE=$(find "$APP_DIR" -maxdepth 1 -iname "*.star" | head -1)
+if [ -z "$STAR_FILE" ]; then
+    echo "No .star file found in $APP_DIR"
+    exit 1
+fi
+
+# Same search order the plugin itself uses: the bundled binary for this
+# architecture first, then PATH -- so this works on an install that never put
+# pixlet on PATH.
+find_pixlet() {
+    local arch bundled
+    case "$(uname -s)-$(uname -m)" in
+        Linux-aarch64|Linux-arm64)  arch="pixlet-linux-arm64" ;;
+        Linux-x86_64|Linux-amd64)   arch="pixlet-linux-amd64" ;;
+        Darwin-arm64)               arch="pixlet-darwin-arm64" ;;
+        Darwin-x86_64)              arch="pixlet-darwin-amd64" ;;
+        *)                          arch="" ;;
+    esac
+    bundled="$PROJECT_ROOT_DIR/bin/pixlet/$arch"
+    if [ -n "$arch" ] && [ -x "$bundled" ]; then
+        echo "$bundled"
+        return 0
+    fi
+    command -v pixlet 2>/dev/null || return 1
+}
+
+PIXLET_BIN=$(find_pixlet) || {
+    echo "Pixlet not found. Install it with:"
+    echo "  ./scripts/download_pixlet.sh"
+    exit 1
+}
+
+CONFIG_FILE="$APP_DIR/config.json"
+if [ -f "$CONFIG_FILE" ]; then
+    cp "$CONFIG_FILE" "$CONFIG_FILE.backup"
+    echo "Backed up existing config to $CONFIG_FILE.backup"
+else
+    echo "{}" > "$CONFIG_FILE"
+fi
+
+DISPLAY_WAS_RUNNING=false
+if systemctl is-active --quiet ledmatrix 2>/dev/null; then
+    DISPLAY_WAS_RUNNING=true
+fi
+
+# Restart the display however this exits -- Ctrl+C, an error, or pixlet
+# dying on its own. Leaving the panel dark because the editor crashed is the
+# failure worth guarding against.
+cleanup() {
+    echo ""
+    if [ "$DISPLAY_WAS_RUNNING" = true ]; then
+        echo "Restarting the display service..."
+        sudo systemctl restart ledmatrix || echo "⚠ Could not restart ledmatrix - do it by hand"
+    fi
+    echo "Your config as it was before this session: $CONFIG_FILE.backup"
+}
+trap cleanup EXIT INT TERM
+
+if [ "$DISPLAY_WAS_RUNNING" = true ]; then
+    echo "Stopping the display service so it does not read config.json mid-write..."
+    sudo systemctl stop ledmatrix
+fi
+
+echo ""
+echo "Editing:  $APP_ID"
+echo "App file: $STAR_FILE"
+echo "URL:      http://localhost:$PORT/"
+echo ""
+echo "Listening on localhost only -- pixlet serve has no authentication."
+echo "From another machine, forward the port:"
+echo "  ssh -L $PORT:localhost:$PORT $(whoami)@$(hostname)"
+echo ""
+echo "Changes save straight to the real config as you make them."
+echo "Press Ctrl+C when finished - the display restarts automatically."
+echo ""
+
+cd "$APP_DIR"
+"$PIXLET_BIN" serve "$(basename "$STAR_FILE")" \
+    --host "$BIND_HOST" \
+    --port "$PORT" \
+    --no-browser \
+    --saveconfig "$CONFIG_FILE"

scripts/validate_skin.py

@@ -27,6 +27,8 @@ sys.path.insert(0, str(PROJECT_ROOT))
 
 from PIL import Image, ImageDraw, ImageFont  # noqa: E402
 
+from src.common.font_layout import load_truetype  # noqa: E402
+
 FIXTURES_DIR = PROJECT_ROOT / "src" / "skin_system" / "fixtures"
 MODES = ("live", "recent", "upcoming")
 SPORTS = ("baseball", "basketball", "football", "hockey")
@@ -52,12 +54,12 @@ class FixtureHost:
         try:
             press = str(PROJECT_ROOT / "assets/fonts/PressStart2P-Regular.ttf")
             small = str(PROJECT_ROOT / "assets/fonts/4x6-font.ttf")
-            fonts['score'] = ImageFont.truetype(press, 10)
+            fonts['score'] = load_truetype(press, 10)
-            fonts['time'] = ImageFont.truetype(press, 8)
+            fonts['time'] = load_truetype(press, 8)
-            fonts['team'] = ImageFont.truetype(press, 8)
+            fonts['team'] = load_truetype(press, 8)
-            fonts['status'] = ImageFont.truetype(small, 6)
+            fonts['status'] = load_truetype(small, 6)
-            fonts['detail'] = ImageFont.truetype(small, 6)
+            fonts['detail'] = load_truetype(small, 6)
-            fonts['rank'] = ImageFont.truetype(press, 10)
+            fonts['rank'] = load_truetype(press, 10)
         except IOError:
             default = ImageFont.load_default()
             for key in ('score', 'time', 'team', 'status', 'detail', 'rank'):

src/base_classes/sports/core.py

@@ -15,6 +15,7 @@ from typing import Any, Dict, List, Optional, Tuple
 import pytz
 import requests
 from PIL import Image, ImageDraw, ImageFont
+from src.common.font_layout import load_truetype
 from requests.adapters import HTTPAdapter
 from urllib3.util.retry import Retry
 
@@ -449,12 +450,12 @@ class SportsCore(ABC):
         press_start = self._resolve_font_path("PressStart2P-Regular.ttf")
         four_by_six = self._resolve_font_path("4x6-font.ttf")
         try:
-            fonts['score'] = ImageFont.truetype(press_start, 10)
+            fonts['score'] = load_truetype(press_start, 10)
-            fonts['time'] = ImageFont.truetype(press_start, 8)
+            fonts['time'] = load_truetype(press_start, 8)
-            fonts['team'] = ImageFont.truetype(press_start, 8)
+            fonts['team'] = load_truetype(press_start, 8)
-            fonts['status'] = ImageFont.truetype(four_by_six, 6) # Using 4x6 for status
+            fonts['status'] = load_truetype(four_by_six, 6) # Using 4x6 for status
-            fonts['detail'] = ImageFont.truetype(four_by_six, 6) # Added detail font
+            fonts['detail'] = load_truetype(four_by_six, 6) # Added detail font
-            fonts['rank'] = ImageFont.truetype(press_start, 10)
+            fonts['rank'] = load_truetype(press_start, 10)
             self.logger.info("Successfully loaded fonts")
         except OSError:
             # Name the directory we searched: the usual cause is an install
@@ -1031,7 +1032,7 @@ class SportsCore(ABC):
             if os.path.exists(font_path):
                 # Try loading as TTF first (works for both TTF and some BDF files with PIL)
                 if font_path.lower().endswith('.ttf'):
-                    font = ImageFont.truetype(font_path, font_size)
+                    font = load_truetype(font_path, font_size)
                     self.logger.debug(f"Loaded font: {font_name} at size {font_size}")
                     self._font_cache[cache_key] = font
                     return font
@@ -1049,7 +1050,7 @@ class SportsCore(ABC):
                     # correct one: the newer copies call truetype() on a BDF at
                     # any size (which simply fails) or refuse BDF outright.
                     try:
-                        font = ImageFont.truetype(font_path, font_size)
+                        font = load_truetype(font_path, font_size)
                         self.logger.debug(f"Loaded BDF font: {font_name} at size {font_size}")
                         self._font_cache[cache_key] = font
                         return font
@@ -1061,7 +1062,7 @@ class SportsCore(ABC):
                             self._bdf_native_size_cache[font_path] = native_size
                         if native_size and native_size != font_size:
                             try:
-                                font = ImageFont.truetype(font_path, native_size)
+                                font = load_truetype(font_path, native_size)
                                 self.logger.debug(
                                     f"Loaded BDF font: {font_name} at its native size {native_size} "
                                     f"(requested {font_size} isn't a valid strike for this file)"
@@ -1089,7 +1090,7 @@ class SportsCore(ABC):
             _resolve_font_family_alias(base_default))
         try:
             if os.path.exists(default_font_path):
-                font = ImageFont.truetype(default_font_path, font_size)
+                font = load_truetype(default_font_path, font_size)
             else:
                 self.logger.warning("Default font not found, using PIL default")
                 font = ImageFont.load_default()

src/cache/disk_cache.py

@@ -5,6 +5,7 @@ Handles persistent disk-based caching with atomic writes and error recovery.
 """
 
 import json
+import math
 import os
 import time
 import tempfile
@@ -14,6 +15,11 @@ import zlib
 from typing import Dict, Any, Optional, Protocol
 from datetime import datetime
 
+try:  # optional: large speedup on the cache write path, see _dumps below
+    import orjson
+except ImportError:  # pragma: no cover - exercised on hosts without the wheel
+    orjson = None
+
 # How old an abandoned write's temp file must be before the sweep removes it.
 # A real write holds its temp file for milliseconds, so an hour is far beyond
 # any in-flight write while still clearing the same day's debris. Deliberately
@@ -40,13 +46,97 @@ class CacheStrategyProtocol(Protocol):
 
 
 class DateTimeEncoder(json.JSONEncoder):
-    """JSON encoder that handles datetime objects."""
+    """JSON encoder that handles datetime objects.
+
+    Retained for the stdlib fallback path and for any caller importing it.
+    """
     def default(self, obj: Any) -> Any:
         if isinstance(obj, datetime):
             return obj.isoformat()
         return super().default(obj)
 
 
+def _datetime_default(obj: Any) -> Any:
+    """Serialise datetimes exactly as DateTimeEncoder did."""
+    if isinstance(obj, datetime):
+        return obj.isoformat()
+    raise TypeError(f"Object of type {type(obj).__name__} is not JSON serializable")
+
+
+def _replace_nonfinite(obj: Any) -> Any:
+    """Non-finite floats -> None, matching what ``orjson.dumps`` writes.
+
+    Only reached once a strict pass has proved there is something to replace,
+    so the ordinary write path never pays for this walk.
+    """
+    if isinstance(obj, float):
+        return obj if math.isfinite(obj) else None
+    if isinstance(obj, dict):
+        return {k: _replace_nonfinite(v) for k, v in obj.items()}
+    if isinstance(obj, (list, tuple)):
+        return [_replace_nonfinite(v) for v in obj]
+    return obj
+
+
+# NON-FINITE FLOATS
+# -----------------
+# JSON has no NaN or Infinity. The stdlib emits them anyway as an extension;
+# orjson refuses to and writes null. That divergence is not acceptable in a
+# cache whose files outlive the decision of which encoder is installed, so the
+# policy here is one behaviour on both paths:
+#
+#   writing  non-finite floats become null, whichever encoder is in use
+#   reading  files already on disk that carry the stdlib's NaN/Infinity
+#            tokens stay readable, whichever encoder is in use
+#
+# Without the write half, installing orjson silently changed cached values.
+# Without the read half, installing orjson turned every legacy record holding a
+# NaN into a "corrupted cache file" that DiskCache.get logged as an error and
+# deleted. Both halves are covered by test/test_cache_nonfinite_floats.py.
+
+
+if orjson is not None:
+    # Encoding the cache record dominated the background fetch worker: on a
+    # Pi 4, stdlib json.dumps runs ~12ms per MB and holds the GIL for all of
+    # it, which stalls the render thread mid-scroll. orjson measures ~7x
+    # faster on the same payloads (11.9ms -> 1.6ms for 985KB). Decoding gains
+    # far less (~1.3x on large payloads) because the cost there is building
+    # the Python objects, not scanning the text, but it is still free to take.
+    #
+    # OPT_NON_STR_KEYS: stdlib json coerces int/float dict keys to strings;
+    # orjson raises without this, and cache records do carry numeric keys.
+    # OPT_PASSTHROUGH_DATETIME: orjson would otherwise emit its own RFC 3339
+    # form for datetimes instead of calling default(). Routing them through
+    # _datetime_default keeps byte-for-byte parity with the records already
+    # on disk.
+    _DUMPS_OPTS = orjson.OPT_NON_STR_KEYS | orjson.OPT_PASSTHROUGH_DATETIME
+
+    def _dumps(data: Any) -> bytes:
+        return orjson.dumps(data, default=_datetime_default, option=_DUMPS_OPTS)
+
+    def _loads(raw: bytes) -> Any:
+        try:
+            return orjson.loads(raw)
+        except orjson.JSONDecodeError:
+            # Legacy record written by the stdlib path, carrying NaN or
+            # Infinity. Genuinely malformed files raise again from here, as
+            # json.JSONDecodeError, which is what DiskCache.get expects.
+            return json.loads(raw)
+else:
+    def _dumps(data: Any) -> bytes:
+        try:
+            return json.dumps(data, cls=DateTimeEncoder,
+                              allow_nan=False).encode("utf-8")
+        except ValueError:
+            # allow_nan=False is what detects the non-finite values; the walk
+            # runs only now that we know there is one to replace.
+            return json.dumps(_replace_nonfinite(data), cls=DateTimeEncoder,
+                              allow_nan=False).encode("utf-8")
+
+    def _loads(raw: bytes) -> Any:
+        return json.loads(raw)
+
+
 class DiskCache:
     """Manages persistent disk-based cache."""
     
@@ -99,8 +189,8 @@ class DiskCache:
         
         try:
             with self._lock:
-                with open(cache_path, 'r', encoding='utf-8') as f:
+                with open(cache_path, 'rb') as f:
-                    record = json.load(f)
+                    record = _loads(f.read())
             
             # Determine record timestamp (prefer embedded, else file mtime)
             record_ts = None
@@ -189,12 +279,12 @@ class DiskCache:
         # write path below, and cache files are machine-read only — indenting
         # them just multiplied the bytes written to the SD card.
         try:
-            payload = json.dumps(data, cls=DateTimeEncoder)
+            payload = _dumps(data)
         except (TypeError, ValueError) as e:
             self.logger.warning("Cache data for key '%s' not serializable: %s", key, e)
             return
 
-        digest = zlib.adler32(payload.encode('utf-8'))
+        digest = zlib.adler32(payload)
 
         try:
             # Atomic write to avoid partial/corrupt files
@@ -242,7 +332,7 @@ class DiskCache:
                         # wear source (dozens of fsyncs/min on API-heavy
                         # installs) for data that can be re-downloaded.
                         try:
-                            with os.fdopen(fd, 'w', encoding='utf-8') as tmp_file:
+                            with os.fdopen(fd, 'wb') as tmp_file:
                                 tmp_file.write(payload)
                             os.replace(tmp_path, cache_path)
                             self._write_digests[key] = digest
@@ -260,7 +350,7 @@ class DiskCache:
                     else:
                         # Fallback: direct write (not atomic, but better than failing)
                         try:
-                            with open(cache_path, 'w', encoding='utf-8') as cache_file:
+                            with open(cache_path, 'wb') as cache_file:
                                 cache_file.write(payload)
                             self._write_digests[key] = digest
                             # Set proper permissions: 660 (rw-rw----) for group-readable cache files
@@ -290,7 +380,7 @@ class DiskCache:
                             # is a different path, so future sets must keep
                             # retrying the primary location.
                             fallback_path = os.path.join(fallback_dir, os.path.basename(cache_path))
-                            with open(fallback_path, 'w', encoding='utf-8') as tmp_file:
+                            with open(fallback_path, 'wb') as tmp_file:
                                 tmp_file.write(payload)
                             # Set proper permissions: 660 (rw-rw----) for group-readable cache files
                             try:

src/common/__init__.py

@@ -23,6 +23,13 @@ from src.common.error_handler import (
 )
 from src.common.api_helper import APIHelper
 from src.common.scroll_helper import ScrollHelper
+from src.common import scroll_config
+from src.common.scroll_config import (
+    ScrollSettings,
+    configure as configure_scroll,
+    resolve as resolve_scroll_settings,
+    refresh_hz_from_config,
+)
 from src.common.logo_helper import LogoHelper
 from src.common.text_helper import TextHelper
 
@@ -60,6 +67,11 @@ __all__ = [
     'log_and_raise',
     'APIHelper',
     'ScrollHelper',
+    'scroll_config',
+    'ScrollSettings',
+    'configure_scroll',
+    'resolve_scroll_settings',
+    'refresh_hz_from_config',
     'LogoHelper',
     'TextHelper',
     # adaptive layout & images

src/common/font_layout.py

@@ -0,0 +1,43 @@
+"""One text layout engine, everywhere.
+
+``PIL.ImageFont.truetype`` picks its layout engine at load time: Raqm when the
+host Pillow was built with libraqm, Basic otherwise. The two disagree about
+fractional glyph advances, so the *same* Pillow version renders the *same*
+string differently depending on a build option of the host.
+
+That is invisible for ``PressStart2P-Regular.ttf`` at 8px, whose advances are
+whole pixels either way — which is why most of the fleet's golden images
+matched on every machine. It is not invisible for ``4x6-font.ttf`` at 6px,
+where the advances are fractional: glyph positions drift cumulatively along a
+run, and the committed goldens for geochron, of-the-day, christmas-countdown
+and ledmatrix-weather's almanac passed on the machine that generated them and
+failed everywhere else (ChuckBuilds/ledmatrix-plugins#371, #375, #378, #391).
+
+Pinning the Basic engine makes a render depend on the font file and the size,
+and nothing else. Basic gives up complex-script shaping (Arabic, Indic) and
+kerning pairs; neither applies to the bitmap-grid faces this project draws
+with on an LED panel.
+
+Use :func:`load_truetype` in place of ``ImageFont.truetype`` anywhere the
+result is drawn to a panel or compared against a golden image.
+"""
+
+from __future__ import annotations
+
+from typing import Any, Union
+
+from PIL import ImageFont
+
+#: The engine every core font load pins. Named once so the reason above has a
+#: single referent, and so a future change is one line.
+LAYOUT_ENGINE = ImageFont.Layout.BASIC
+
+
+def load_truetype(font: Union[str, Any], size: int, **kwargs: Any) -> ImageFont.FreeTypeFont:
+    """``ImageFont.truetype`` with the layout engine pinned.
+
+    Same signature and same exceptions as the PIL call it replaces, so it is a
+    drop-in at every call site.
+    """
+    kwargs.setdefault("layout_engine", LAYOUT_ENGINE)
+    return ImageFont.truetype(font, size, **kwargs)

src/common/scroll_config.py

@@ -0,0 +1,440 @@
+"""One place that turns plugin config into a configured ScrollHelper.
+
+Five ticker plugins each hand-rolled this resolution (odds-ticker, news and
+ledmatrix-leaderboard reference the deprecated ``scroll_pixels_per_second``
+key 16-18 times apiece), and they disagreed in ways that were invisible until
+someone watched the panel:
+
+* odds-ticker read ``scroll_pixels_per_second`` on the *recommended* config
+  path and let it override ``scroll_speed``/``scroll_delay``. Because that key
+  carries a schema default, the documented settings were dead for every user
+  -- see ChuckBuilds/ledmatrix-plugins#408.
+* ledmatrix-leaderboard read the same key only as a fallback, so identical
+  config produced different speeds in the two plugins.
+* stock-news derived px/frame from it via its own arithmetic.
+
+What matters on the hardware
+----------------------------
+Motion is smooth when the strip advances a **whole number of pixels per panel
+refresh**. On a 100Hz panel that means 100 px/s, 200 px/s, and so on. Anything
+else has to either blend adjacent columns (which on pixel-font text reads as
+shimmer) or repeat frames (which reads as judder). :func:`resolve` warns when
+the requested speed will not divide evenly, because that is a real display
+artefact and not a rounding detail.
+
+Speed is always expressed to the helper as pixels per second and applied in
+time-based mode. Frame-based stepping gates motion on a wall clock at
+``1/scroll_delay`` steps per second; plugins set ``scroll_delay`` to the frame
+period, which puts that comparison exactly on its own threshold and makes the
+step count flip on sub-millisecond jitter. Accumulating elapsed time keeps
+position proportional to real time instead.
+"""
+
+from __future__ import annotations
+
+import logging
+from dataclasses import dataclass, replace
+from typing import Any, Dict, Optional
+
+logger = logging.getLogger(__name__)
+
+#: Speed used when a plugin supplies nothing usable. One pixel per refresh on a
+#: 100Hz panel, which is the slowest crisp scroll that hardware can show.
+DEFAULT_PIXELS_PER_SECOND = 100.0
+
+#: Bounds accepted from config. Below the floor a marquee appears frozen;
+#: above the ceiling it outruns any panel's refresh and tears.
+MIN_PIXELS_PER_SECOND = 1.0
+MAX_PIXELS_PER_SECOND = 500.0
+
+#: Assumed refresh when the caller does not say. Matches the usual
+#: ``display.hardware.limit_refresh_rate_hz``.
+DEFAULT_REFRESH_HZ = 100.0
+
+#: How far px/s may sit from a whole number of pixels per refresh before it is
+#: worth warning about. 0.05px per frame is invisible; a third of a pixel is not.
+_WHOLE_PIXEL_TOLERANCE = 0.05
+
+
+#: Longest a frame may be held before motion reads as a slideshow rather than
+#: a scroll. 6 refreshes at 100Hz is ~17px/s, already visibly stepped.
+MAX_FRAME_HOLD = 8
+
+#: Largest whole-pixel jump per presented frame before motion looks like it is
+#: teleporting rather than sliding.
+MAX_PIXELS_PER_FRAME = 6
+
+
+@dataclass(frozen=True)
+class CrispSpeed:
+    """A speed the panel can show with whole-pixel motion.
+
+    ``pixels_per_second`` is always ``refresh_hz / frame_hold * pixels_per_frame``
+    exactly -- no rounding, no fractional pixel positions, so nothing has to be
+    blended or repeated unevenly.
+
+    :param frame_hold: refreshes each frame is held for. This is rgbmatrix's
+        ``SwapOnVSync(canvas, framerate_fraction)``. The panel keeps refreshing
+        at full rate either way, so holding a frame costs nothing in flicker.
+    :param pixels_per_frame: whole pixels advanced per presented frame.
+    """
+
+    pixels_per_second: float
+    frame_hold: int
+    pixels_per_frame: int
+    refresh_hz: float
+
+    @property
+    def frames_per_second(self) -> float:
+        return self.refresh_hz / self.frame_hold
+
+    @property
+    def steppiness(self) -> str:
+        """Rough readability hint for this combination."""
+        if self.pixels_per_frame > 2:
+            return "jumpy"
+        if self.frames_per_second < 20:
+            return "stepped"
+        if self.frames_per_second < 30:
+            return "slightly stepped"
+        return "smooth"
+
+    def describe(self) -> str:
+        return (
+            f"{self.pixels_per_second:6.1f} px/s  "
+            f"({self.pixels_per_frame}px every {self.frame_hold} refresh"
+            f"{'es' if self.frame_hold != 1 else ' '} = "
+            f"{self.frames_per_second:5.1f} fps, {self.steppiness})"
+        )
+
+
+def crisp_ladder(
+    refresh_hz: float = DEFAULT_REFRESH_HZ,
+    max_frame_hold: int = MAX_FRAME_HOLD,
+    max_pixels_per_frame: int = MAX_PIXELS_PER_FRAME,
+):
+    """Every whole-pixel speed this panel can show, slowest first.
+
+    Duplicates are collapsed keeping the gentlest option: 100 px/s is reachable
+    as 1px every refresh or 2px every 2nd refresh, and the former moves in
+    smaller increments, so that is the one worth offering.
+    """
+    best = {}
+    for hold in range(1, max_frame_hold + 1):
+        for ppf in range(1, max_pixels_per_frame + 1):
+            pps = refresh_hz / hold * ppf
+            key = round(pps, 3)
+            candidate = CrispSpeed(pps, hold, ppf, refresh_hz)
+            incumbent = best.get(key)
+            if incumbent is None or ppf < incumbent.pixels_per_frame:
+                best[key] = candidate
+    return [best[k] for k in sorted(best)]
+
+
+#: How much a bigger pixel step costs, as a fraction of the target speed.
+#: Tuned so 66.7px/s (2px at 33fps) beats 50px/s (1px at 50fps) when 60 was
+#: asked for, but 33.3px/s (1px, smooth) still beats 28.6px/s (2px at 14fps)
+#: when 30 was asked for -- being 11% slow is worth far less than looking bad.
+_STEP_PENALTY = 0.05
+_SLOW_FPS_PENALTY = 0.25   # below 20fps
+_LOWISH_FPS_PENALTY = 0.10  # below 25fps
+
+
+def _quality_cost(candidate: "CrispSpeed", target: float) -> float:
+    """Lower is better. Numeric closeness alone picks bad-looking speeds.
+
+    Nearest-by-value would answer "30 px/s" with 28.6 px/s -- which is 2px
+    jumps at 14fps -- over 33.3 px/s, which is single-pixel motion at 33fps and
+    obviously better on the panel. Proximity has to be traded against how the
+    motion actually reads.
+    """
+    error = abs(candidate.pixels_per_second - target) / max(target, 1e-6)
+    cost = error + _STEP_PENALTY * (candidate.pixels_per_frame - 1)
+    fps = candidate.frames_per_second
+    if fps < 20:
+        cost += _SLOW_FPS_PENALTY
+    elif fps < 25:
+        cost += _LOWISH_FPS_PENALTY
+    return cost
+
+
+def solve_crisp(
+    target_pixels_per_second: float,
+    refresh_hz: float = DEFAULT_REFRESH_HZ,
+    max_frame_hold: int = MAX_FRAME_HOLD,
+    max_pixels_per_frame: int = MAX_PIXELS_PER_FRAME,
+) -> CrispSpeed:
+    """The whole-pixel speed that will look best for what was asked for.
+
+    Not simply the nearest -- see :func:`_quality_cost`. Ties break toward the
+    smaller pixel step and the shorter hold.
+    """
+    ladder = crisp_ladder(refresh_hz, max_frame_hold, max_pixels_per_frame)
+    # Clamp into the ladder's range first. Relative error saturates near 1.0
+    # for a target far outside it, so the quality penalty would dominate and
+    # answer "10000 px/s" with the *slowest* entry -- smooth, and useless.
+    target = min(max(target_pixels_per_second, ladder[0].pixels_per_second),
+                 ladder[-1].pixels_per_second)
+    return min(
+        ladder,
+        key=lambda c: (round(_quality_cost(c, target), 6),
+                       c.pixels_per_frame, c.frame_hold),
+    )
+
+
+@dataclass(frozen=True)
+class ScrollSettings:
+    """The resolved outcome, and which config key produced it."""
+
+    pixels_per_second: float
+    source: str
+    target_fps: Optional[float] = None
+    pixels_per_frame: Optional[float] = None
+    warning: Optional[str] = None
+    #: The whole-pixel speed actually applied, when snapping was enabled.
+    crisp: Optional[CrispSpeed] = None
+    #: What the config asked for, before snapping.
+    requested_pixels_per_second: Optional[float] = None
+
+    @property
+    def frame_hold(self) -> int:
+        """Refreshes to hold each frame for; pass to set_scrolling_state()."""
+        return self.crisp.frame_hold if self.crisp else 1
+
+    def describe(self) -> str:
+        text = f"{self.pixels_per_second:.1f} px/s (from {self.source})"
+        if self.pixels_per_frame is not None:
+            text += f" = {self.pixels_per_frame:.2f} px/frame"
+        if self.target_fps:
+            text += f" at {self.target_fps:.0f} fps"
+        return text
+
+
+def _coerce(value: Any) -> Optional[float]:
+    """A positive float, or None. Config reaches us with nulls and strings."""
+    if value is None or isinstance(value, bool):
+        return None
+    try:
+        number = float(value)
+    except (TypeError, ValueError):
+        return None
+    return number if number > 0 else None
+
+
+def _from_speed_and_delay(block: Any) -> Optional[float]:
+    """px/s from a ``scroll_speed`` (px/frame) + ``scroll_delay`` (s) pair."""
+    if not isinstance(block, dict):
+        return None
+    speed = _coerce(block.get("scroll_speed"))
+    delay = _coerce(block.get("scroll_delay"))
+    if speed is None or delay is None:
+        return None
+    return speed / delay
+
+
+def resolve(
+    plugin_config: Optional[Dict[str, Any]] = None,
+    global_config: Optional[Dict[str, Any]] = None,
+    default_pixels_per_second: float = DEFAULT_PIXELS_PER_SECOND,
+    refresh_hz: Optional[float] = None,
+) -> ScrollSettings:
+    """Resolve one scroll speed from the several shapes plugins accept.
+
+    Precedence, highest first. The deprecated flat key sits *below* the
+    explicit pairs deliberately: it carries schema defaults in some plugins, so
+    ranking it above them silently disables the documented settings.
+
+    1. ``display_options.scroll_speed`` + ``scroll_delay``  (current)
+    2. ``display.scroll_speed`` + ``scroll_delay``          (deprecated shape)
+    3. ``scroll_speed`` + ``scroll_delay`` at the root      (legacy flat)
+    4. ``scroll_pixels_per_second``, nested or flat         (deprecated)
+    5. the global ``display`` block
+    6. ``default_pixels_per_second``
+
+    :param refresh_hz: panel refresh, used only to check whether the resolved
+        speed lands on whole pixels per frame and to fill in ``target_fps``.
+    """
+    plugin_config = plugin_config or {}
+    global_config = global_config or {}
+    refresh = _coerce(refresh_hz) or DEFAULT_REFRESH_HZ
+
+    display_options = plugin_config.get("display_options")
+    display_block = plugin_config.get("display")
+
+    candidates = [
+        (_from_speed_and_delay(display_options), "display_options.scroll_speed/delay"),
+        (_from_speed_and_delay(display_block), "display.scroll_speed/delay"),
+        (_from_speed_and_delay(plugin_config), "scroll_speed/delay (root)"),
+    ]
+    for block, label in (
+        (display_options, "display_options.scroll_pixels_per_second"),
+        (display_block, "display.scroll_pixels_per_second"),
+        (plugin_config, "scroll_pixels_per_second"),
+    ):
+        if isinstance(block, dict):
+            candidates.append((_coerce(block.get("scroll_pixels_per_second")), label))
+
+    global_display = global_config.get("display")
+    candidates.append((_from_speed_and_delay(global_display), "global display.scroll_speed/delay"))
+
+    pixels_per_second = None
+    source = "default"
+    for value, label in candidates:
+        if value is not None:
+            pixels_per_second, source = value, label
+            break
+    if pixels_per_second is None:
+        pixels_per_second = default_pixels_per_second
+
+    clamped = max(MIN_PIXELS_PER_SECOND, min(MAX_PIXELS_PER_SECOND, pixels_per_second))
+    warning = None
+    if clamped != pixels_per_second:
+        warning = (
+            f"scroll speed {pixels_per_second:.1f} px/s out of range, "
+            f"clamped to {clamped:.1f}"
+        )
+        pixels_per_second = clamped
+
+    pixels_per_frame = pixels_per_second / refresh if refresh > 0 else None
+    if warning is None and pixels_per_frame is not None:
+        offset = abs(pixels_per_frame - round(pixels_per_frame))
+        if pixels_per_frame < 1.0 - _WHOLE_PIXEL_TOLERANCE or offset > _WHOLE_PIXEL_TOLERANCE:
+            suggestion = max(1.0, round(pixels_per_frame)) * refresh
+            warning = (
+                f"{pixels_per_second:.1f} px/s is {pixels_per_frame:.2f} px per "
+                f"refresh at {refresh:.0f}Hz, so some frames repeat and the "
+                f"scroll will judder; {suggestion:.0f} px/s divides evenly"
+            )
+
+    return ScrollSettings(
+        pixels_per_second=pixels_per_second,
+        source=source,
+        target_fps=refresh,
+        pixels_per_frame=pixels_per_frame,
+        warning=warning,
+    )
+
+
+def configure(
+    scroll_helper: Any,
+    plugin_config: Optional[Dict[str, Any]] = None,
+    global_config: Optional[Dict[str, Any]] = None,
+    default_pixels_per_second: float = DEFAULT_PIXELS_PER_SECOND,
+    refresh_hz: Optional[float] = None,
+    plugin_logger: Optional[logging.Logger] = None,
+    display_manager: Any = None,
+    snap_to_crisp: bool = True,
+) -> ScrollSettings:
+    """Resolve the config and apply it to ``scroll_helper``.
+
+    Applied in time-based mode: see the module docstring for why frame-based
+    stepping is not used. ``hasattr`` guards keep this usable against older
+    ScrollHelper builds that a plugin may be running on.
+
+    :param display_manager: consulted for the panel's refresh rate only (it can
+        see display.hardware; a plugin cannot). The frame hold is NOT applied
+        here -- see the note in the body. The caller must pass
+        ``settings.frame_hold`` to ``display_manager.set_scrolling_state(True,
+        ...)`` when it starts scrolling, or a sub-refresh speed still presents
+        a new frame every refresh and the motion falls back to fractional
+        pixels.
+    :param snap_to_crisp: move the requested speed to the nearest speed the
+        panel can show in whole pixels. On by default because a speed that does
+        not divide evenly has no good rendering, only a choice of artefacts.
+
+    :returns: the settings applied, so the caller can log or assert on them.
+    """
+    log = plugin_logger or logger
+
+    # Refresh rate, most authoritative first: what the caller passed, then the
+    # display manager (which can see display.hardware; a plugin cannot), then
+    # the global config, then the default.
+    #
+    # This has to be settled BEFORE resolve(), not after. resolve() uses the
+    # refresh to fill in target_fps, pixels_per_frame and the judder warning,
+    # so deriving it afterwards described a 100Hz panel to everyone running at
+    # 60 -- and with snap_to_crisp=False nothing downstream corrected it, so
+    # set_target_fps() paced the helper to 100 FPS on a 60Hz panel.
+    hz = _coerce(refresh_hz)
+    if hz is None and display_manager is not None:
+        hz = _coerce(getattr(display_manager, "refresh_hz", None))
+    if hz is None:
+        hz = refresh_hz_from_config(global_config)
+
+    settings = resolve(
+        plugin_config,
+        global_config,
+        default_pixels_per_second=default_pixels_per_second,
+        refresh_hz=hz,
+    )
+    applied = settings.pixels_per_second
+    choice = None
+
+    if snap_to_crisp:
+        choice = solve_crisp(settings.pixels_per_second, hz)
+        applied = choice.pixels_per_second
+        settings = replace(
+            settings,
+            pixels_per_second=applied,
+            requested_pixels_per_second=settings.pixels_per_second,
+            crisp=choice,
+            pixels_per_frame=float(choice.pixels_per_frame),
+            # Snapping resolves the whole-pixel problem the warning describes.
+            warning=None if settings.warning and "judder" in settings.warning
+            else settings.warning,
+        )
+
+    if hasattr(scroll_helper, "set_frame_based_scrolling"):
+        scroll_helper.set_frame_based_scrolling(False)
+    scroll_helper.set_scroll_speed(applied)
+    if choice and hasattr(scroll_helper, "set_target_fps"):
+        scroll_helper.set_target_fps(choice.frames_per_second)
+    elif settings.target_fps and hasattr(scroll_helper, "set_target_fps"):
+        scroll_helper.set_target_fps(settings.target_fps)
+
+    # Deliberately NOT applied here. The hold belongs to a scroll, not to a
+    # plugin's lifetime: plugins share one display manager, and one left set at
+    # construction is reset the moment any other plugin finishes scrolling.
+    # Callers pass settings.frame_hold to set_scrolling_state(True, ...) when
+    # they start scrolling. configure() only reports what is needed.
+
+    if choice:
+        requested = settings.requested_pixels_per_second
+        if abs(requested - applied) > 0.05:
+            log.info(
+                "Scroll configured: %s (asked for %.1f px/s from %s; "
+                "nearest whole-pixel speed on a %.0fHz panel)",
+                choice.describe(), requested, settings.source, hz,
+            )
+        else:
+            log.info("Scroll configured: %s (from %s)",
+                     choice.describe(), settings.source)
+        if choice.frame_hold > 1:
+            log.debug(
+                "Scroll needs a frame hold of %d - pass settings.frame_hold to "
+                "display_manager.set_scrolling_state(True, ...) each scroll",
+                choice.frame_hold,
+            )
+    else:
+        log.info("Scroll configured: %s", settings.describe())
+
+    if settings.warning:
+        log.warning("Scroll speed: %s", settings.warning)
+    return settings
+
+
+def refresh_hz_from_config(global_config: Optional[Dict[str, Any]]) -> float:
+    """The panel's refresh cap from the global config, or the default."""
+    if not isinstance(global_config, dict):
+        return DEFAULT_REFRESH_HZ
+    # Each level is checked for being a mapping rather than merely truthy: a
+    # malformed config where display or display.hardware is a string or a list
+    # raised AttributeError out of what is meant to be a total function with a
+    # default, taking down every caller that asked for the refresh rate.
+    display = global_config.get("display")
+    if not isinstance(display, dict):
+        return DEFAULT_REFRESH_HZ
+    hardware = display.get("hardware")
+    if not isinstance(hardware, dict):
+        return DEFAULT_REFRESH_HZ
+    return _coerce(hardware.get("limit_refresh_rate_hz")) or DEFAULT_REFRESH_HZ

src/common/scroll_helper.py

@@ -16,6 +16,7 @@ Features:
 """
 
 import logging
+import math
 import time
 from typing import Optional, Dict, Any
 from PIL import Image
@@ -29,6 +30,49 @@ except ImportError:
     HAS_SCIPY = False
 
 
+def frame_stats(frame_times: list) -> Dict[str, Any]:
+    """Summary statistics over one window of frame durations (seconds).
+
+    Split out of log_frame_rate() so the arithmetic can be tested without a
+    clock. Median and p95 are the real ones: the median takes both middle
+    samples on an even window, and p95 is nearest-rank, so a 100-frame window
+    reports the 95th sorted sample rather than the 96th. That matters twice
+    over, because the median is also the threshold the stall and skip counts
+    are measured against.
+    """
+    window = sorted(frame_times)
+    n = len(window)
+    median = (window[n // 2] if n % 2
+              else (window[n // 2 - 1] + window[n // 2]) / 2.0)
+    mean = sum(window) / n
+    # Anything past 1.5x the median missed a panel refresh; anything under
+    # half of it never reached the panel at all (dirty tracking skipped the
+    # swap, so the frame did not wait for vsync).
+    return {
+        "frames": n,
+        "fps": (1.0 / mean) if mean > 0 else 0.0,
+        "median": median,
+        "p95": window[max(0, math.ceil(0.95 * n) - 1)],
+        "max": window[-1],
+        "min": window[0],
+        "stalls": sum(1 for f in window if f > median * 1.5),
+        "skips": sum(1 for f in window if f < median * 0.5),
+    }
+
+
+def format_frame_stats(frame_times: list) -> str:
+    """The one-line rendering of frame_stats(), in milliseconds."""
+    s = frame_stats(frame_times)
+    n = s["frames"]
+    return (
+        f"{s['fps']:.1f} fps over {n} frames | "
+        f"median {s['median'] * 1000:.2f}ms p95 {s['p95'] * 1000:.2f}ms "
+        f"max {s['max'] * 1000:.2f}ms min {s['min'] * 1000:.2f}ms | "
+        f"stalls {s['stalls']} ({100.0 * s['stalls'] / n:.1f}%) "
+        f"skips {s['skips']} ({100.0 * s['skips'] / n:.1f}%)"
+    )
+
+
 class ScrollHelper:
     """
     Helper class for scrolling text and image content on LED displays.
@@ -75,8 +119,19 @@ class ScrollHelper:
         # Pre-allocated buffer for output frame (reused to avoid allocations)
         self._frame_buffer: Optional[np.ndarray] = None
         
-        # Sub-pixel scrolling settings (disabled - using high FPS integer scrolling instead)
+        # Sub-pixel scrolling: OFF by default, and that is deliberate.
-        self.sub_pixel_scrolling = False  # Disabled - use high frame rate for smoothness
+        # Blending renders a half-step by mixing two adjacent columns 50/50.
+        # On a high-resolution screen that reads as smooth motion; on a coarse
+        # LED matrix showing pixel-font text it does not. A one-pixel stroke
+        # becomes two half-brightness pixels, so frames alternate between crisp
+        # and smeared and the text appears to shimmer and jump a pixel ahead --
+        # tested on a 2x128x64 panel and clearly worse than integer stepping.
+        #
+        # The rule this display obeys: motion is smooth when it advances a
+        # whole number of pixels per refresh. Anything slower must either
+        # blend (blur) or repeat frames (judder); blending is the worse of the
+        # two here. Vegas mode still opts in via set_sub_pixel_scrolling().
+        self.sub_pixel_scrolling = False
         self._last_integer_position = 0  # Cache for integer position to avoid repeated calculations
         
         # Frame-based scrolling settings
@@ -105,6 +160,9 @@ class ScrollHelper:
         self.last_frame_time = time.time()
         self.last_fps_log_time = time.time()
         self.frame_times = []
+        # Every frame time since the last stats line, so the 5s summary can
+        # report the tail rather than one arbitrary sample. Cleared on log.
+        self._window: list = []
         
         # Scrolling state management
         self.is_scrolling = False
@@ -244,19 +302,31 @@ class ScrollHelper:
             if self.last_step_time == 0.0:
                 self.last_step_time = current_time
             
-            # Check if scroll_delay has passed
+            # Frame-based mode advances by elapsed time, exactly like the
-            time_since_last_step = current_time - self.last_step_time
+            # time-based branch below, at the same configured speed
-            if time_since_last_step >= self.scroll_delay:
+            # (scroll_speed px per scroll_delay seconds).
-                # Move pixels (can move multiple steps if lag occurred, but cap to prevent huge jumps)
+            #
-                steps = int(time_since_last_step / self.scroll_delay)
+            # It used to step discretely: 0, 1 or 2 whole pixels depending on
-                # Cap at reasonable number to prevent huge jumps from lag
+            # whether a wall clock had passed scroll_delay. Plugins set
-                max_steps = max(1, int(0.04 / self.scroll_delay))  # Limit to 0.04s (2 steps at 50 FPS) for smoother scrolling
+            # scroll_delay to the target frame period, so that comparison sits
-                steps = min(steps, max_steps)
+            # exactly on its own threshold and the decision flips on sub-
-                pixels_to_move = self.scroll_speed * steps
+            # millisecond jitter -- a frame a hair early moved nothing and
-                # Update last_step_time, preserving fractional delay for smooth timing
+            # rendered an identical frame, a frame a hair late moved two
-                self.last_step_time = current_time - (time_since_last_step % self.scroll_delay)
+            # pixels. Rounding the step count fixed the stalls but still
+            # discarded the remainder, so the error never corrected.
+            #
+            # Accumulating elapsed time keeps position exactly proportional to
+            # real time: jitter shifts a pixel boundary by a fraction of a
+            # frame instead of flipping a whole step, and nothing is lost or
+            # gained. This is what the one visibly smooth scroller on the
+            # hardware (the stock ticker) was already doing by virtue of never
+            # enabling frame-based mode.
+            if self.scroll_delay > 0:
+                pixels_per_second = self.scroll_speed / self.scroll_delay
             else:
-                pixels_to_move = 0.0
+                pixels_per_second = self.scroll_speed * 100.0
+            pixels_to_move = pixels_per_second * delta_time
+            self.last_step_time = current_time
         else:
             # Time-based: move based on time delta (correct speed over time)
             # scroll_speed is pixels per second
@@ -1018,17 +1088,24 @@ class ScrollHelper:
         if len(self.frame_times) > 100:
             self.frame_times.pop(0)
 
+        # Every frame since the last log, not just the last 100 and not just
+        # the one that happens to land on the 5s boundary. The old line
+        # reported a single instantaneous sample -- roughly 1 frame in 500 --
+        # which cannot see a stall that hits 1% of frames, and reported it
+        # next to an average that hides the same stall by construction (a 2ms
+        # duplicate and a 21ms double-wait mean exactly 10ms). Chasing scroll
+        # judder needs the tail, so keep the window and report percentiles.
+        self._window.append(frame_time)
+        
         # Log FPS every 5 seconds to avoid spam
         if current_time - self.last_fps_log_time >= 5.0:
-            avg_frame_time = sum(self.frame_times) / len(self.frame_times)
+            self.logger.info(
-            avg_fps = 1.0 / avg_frame_time if avg_frame_time > 0 else 0
+                "Scroll frame stats - %s",
-            instant_fps = 1.0 / frame_time if frame_time > 0 else 0
+                format_frame_stats(self._window or [frame_time]),
-            
+            )
-            self.logger.info(f"Scroll frame stats - Avg FPS: {avg_fps:.1f}, "
-                           f"Current FPS: {instant_fps:.1f}, "
-                           f"Frame time: {frame_time*1000:.2f}ms")
             self.last_fps_log_time = current_time
             self.frame_count = 0
+            self._window = []
         
         self.last_frame_time = current_time
         self.frame_count += 1

src/common/sports_card.py

@@ -17,10 +17,13 @@ deliberate difference is `crisp_size`, which takes the seven-plugin guard
 the extra guard only stops a None size raising TypeError.
 """
 
+import logging
 from datetime import datetime, timezone
 from typing import Any, Dict, Optional, Tuple
 from zoneinfo import ZoneInfo
 
+logger = logging.getLogger(__name__)
+
 __all__ = [
     "ELEMENT_FOR_FONT", "FAVORITE_RESULT_COLOR_DEFAULTS", "FONT_NAME_ALIASES",
     "FONT_PIXEL_GRID", "MONTH_ABBR", "WEEKDAY_ABBR",
@@ -395,7 +398,14 @@ def schema_font_size(schema_path: str, element_key) -> Optional[int]:
                 size = spec.get('properties', {}).get('font_size', {}).get('default')
                 if size is not None:
                     cache[key] = int(size)
-        except Exception:
+        except Exception as exc:
+            # See sports_shared._schema_font_size: an unreadable schema
+            # silently disables the pixel-grid snap for every element.
+            # Built once per schema path, so this cannot repeat per frame.
+            logger.warning(
+                "could not read %s (%s: %s); font sizes will skip their "
+                "pixel grid snap and may render a pixel narrow",
+                schema_path, type(exc).__name__, exc)
             cache = {}
         _SCHEMA_FONT_SIZE_CACHE[schema_path] = cache
     return cache.get(element_key)

src/common/sports_shared.py

@@ -86,6 +86,7 @@ from typing import Any, ClassVar, Dict, List, Optional, Tuple
 import pytz
 import requests
 from PIL import Image, ImageDraw, ImageFont
+from src.common.font_layout import load_truetype
 
 logger = logging.getLogger(__name__)
 
@@ -211,17 +212,52 @@ class SportsCoreSharedMixin:
             return desired
         return max(grid, int(round(float(desired) / grid)) * grid)
 
+    #: Absolute path of this plugin's directory, declared by the plugin
+    #: itself. The mixin cannot work it out -- see _plugin_dir.
+    _PLUGIN_DIR: ClassVar[Optional[str]] = None
+
     def _plugin_dir(self) -> Optional[str]:
-        """Directory of the plugin that defines this class.
+        """Directory of the plugin that owns this instance.
 
         In sports.py these methods could just use ``__file__``. Here that is
-        src/common/, so the plugin's own directory has to be recovered from the
+        src/common/, so the directory has to come from the plugin.
-        instance. ``type(self).__module__`` alone is not enough: SportsCore is
+
-        an ABC, so a subclass built with ``type(name, bases, ns)`` -- which the
+        It is TOLD, not deduced. The first version walked the MRO for a class
-        plugins' own tests do -- reports its module as "abc". Walking the MRO
+        whose module sits beside a config_schema.json. That works when a test
-        steps past those synthetic classes to the first one whose module sits
+        imports the plugin itself, and returns None under the real loader, for
-        next to a config_schema.json, which is the real plugin.
+        a specific reason worth recording:
+
+            PluginLoader._namespace_plugin_modules renames every bare module a
+            plugin brought in (sports, game_renderer, ...) to
+            "_plg_<plugin_id>_<module>" and REMOVES the bare entry, so two
+            plugins owning a module of the same name cannot collide.
+
+        The class still reports ``__module__ == "sports"``, but
+        ``sys.modules["sports"]`` no longer exists, so the walk finds no
+        __file__ and falls off the end. The failure was silent and expensive:
+
+            _plugin_dir()       -> None
+            _schema_font_size() -> None for every element
+            -> a configured size equal to the schema default stops looking
+               like a default and is treated as a deliberate user choice
+            -> the snap to the font's pixel grid is skipped
+            -> 4x6-font.ttf renders at 6 instead of 7: 3px-wide glyphs
+               instead of 4px
+
+        On a 256x64 panel that made the odds, the team records and the date row
+        hard to read. It was found by a user counting pixels on the panel. No
+        gate here caught it: the tests imported plugins directly and the
+        safety harness loads them its own way, so neither reproduced the
+        loader's renaming.
+
+        The MRO walk stays as a fallback for hosts that declare no
+        _PLUGIN_DIR -- the plugins' own probe harnesses build classes with
+        ``type()`` -- but it is no longer the primary answer.
         """
+        declared = getattr(self, "_PLUGIN_DIR", None)
+        if declared and os.path.isfile(os.path.join(declared, "config_schema.json")):
+            return declared
+
         for cls in type(self).__mro__:
             module = sys.modules.get(getattr(cls, "__module__", ""), None)
             path = getattr(module, "__file__", None)
@@ -253,7 +289,23 @@ class SportsCoreSharedMixin:
                     size = spec.get('properties', {}).get('font_size', {}).get('default')
                     if size is not None:
                         cache[key] = int(size)
-            except Exception:
+            except Exception as exc:
+                # Say so. An unreadable schema is not cosmetic: every element's
+                # configured size then stops matching "the schema default", is
+                # treated as a deliberate user choice, and skips the snap to the
+                # font's pixel grid -- which renders 4x6-font.ttf at 6 instead
+                # of 7, a 3px-wide glyph instead of 4px. That shipped once,
+                # silently, and was found by a user counting pixels on a photo
+                # of the panel.
+                #
+                # Logged, not raised: a missing schema must not stop a plugin
+                # rendering. The cache is built once per class, so this cannot
+                # repeat per frame.
+                logger.warning(
+                    "%s: could not read config_schema.json (%s: %s); every font "
+                    "size will be treated as user-chosen and will skip its pixel "
+                    "grid snap. Font sizes may render a pixel narrow.",
+                    type(self).__name__, type(exc).__name__, exc)
                 cache = {}
             self.__class__._SCHEMA_FONT_SIZES = cache
         return cache.get(element_key)
@@ -661,11 +713,11 @@ class SportsCoreSharedMixin:
                 while size > grid:
                     if probe.textlength(
                             self._SCORE_PROBE_TEXT,
-                            font=ImageFont.truetype(path, size)) <= budget:
+                            font=load_truetype(path, size)) <= budget:
                         break
                     size -= grid
                 if size != getattr(fonts['score'], 'size', size):
-                    fonts['score'] = ImageFont.truetype(path, size)
+                    fonts['score'] = load_truetype(path, size)
                     self._score_grew = True
 
             if not self._score_grew and not self._user_chose_size('score_text') \
@@ -685,7 +737,7 @@ class SportsCoreSharedMixin:
                     if _size <= current:
                         continue
                     _path = _resolve_font_path(f"assets/fonts/{_name}")
-                    _candidate = ImageFont.truetype(_path, _size)
+                    _candidate = load_truetype(_path, _size)
                     if probe.textlength(self._SCORE_PROBE_TEXT,
                                         font=_candidate) <= budget:
                         fonts['score'] = _candidate
@@ -700,7 +752,7 @@ class SportsCoreSharedMixin:
                 if ceiling and size >= ceiling:
                     size = max(grid, ceiling - grid)
                 if size != getattr(fonts['time'], 'size', size):
-                    fonts['time'] = ImageFont.truetype(path, size)
+                    fonts['time'] = load_truetype(path, size)
         except Exception:
             self.logger.debug("Headline font scaling skipped", exc_info=True)
         return fonts

src/common/text_helper.py

@@ -10,6 +10,7 @@ from pathlib import Path
 from typing import Dict, List, Optional, Tuple, Union
 
 from PIL import Image, ImageDraw, ImageFont
+from src.common.font_layout import load_truetype
 
 # Shared throwaway draw surface for measuring text without a target canvas.
 _measure_draw = ImageDraw.Draw(Image.new("RGB", (1, 1)))
@@ -60,7 +61,7 @@ class TextHelper:
                 size = config['size']
                 
                 if font_path.exists():
-                    font = ImageFont.truetype(str(font_path), size)
+                    font = load_truetype(str(font_path), size)
                     fonts[font_name] = font
                     self.logger.debug(f"Loaded font: {font_name} ({font_path}, size {size})")
                 else:

src/display_controller.py

@@ -198,6 +198,10 @@ class DisplayController:
         # the main run loop reconciles (loads/unloads) on its own thread so
         # mutating available_modes never races with rendering.
         self._pending_plugin_reconcile = False
+        # Monotonic stamp of the last mailbox disk read; see
+        # _poll_on_demand_requests. None means "never polled", so the first
+        # call always goes through.
+        self._last_on_demand_poll: Optional[float] = None
         self.on_demand_active = False
         self.on_demand_mode: Optional[str] = None
         self.on_demand_modes: List[str] = []  # All modes for the on-demand plugin
@@ -303,39 +307,7 @@ class DisplayController:
 
             # Check for on-demand plugin filter from cache
             on_demand_config = self.cache_manager.get('display_on_demand_config', max_age=3600)
-            on_demand_plugin_id = on_demand_config.get('plugin_id') if on_demand_config else None
+            enabled_plugins = self._select_startup_plugins(discovered_plugins, on_demand_config)
-
-            if on_demand_plugin_id:
-                logger.info("On-demand mode detected during initialization: filtering to plugin '%s' only", on_demand_plugin_id)
-                # Only load the on-demand plugin, but ensure it's enabled
-                if on_demand_plugin_id not in discovered_plugins:
-                    error_msg = f"On-demand plugin '{on_demand_plugin_id}' not found in discovered plugins"
-                    logger.error(error_msg)
-                    logger.warning("Falling back to normal mode (all enabled plugins)")
-                    on_demand_plugin_id = None
-                    enabled_plugins = [p for p in discovered_plugins if self.config.get(p, {}).get('enabled', False)]
-                else:
-                    plugin_config = self.config.get(on_demand_plugin_id, {})
-                    was_disabled = not plugin_config.get('enabled', False)
-                    if was_disabled:
-                        logger.info("Temporarily enabling plugin '%s' for on-demand mode", on_demand_plugin_id)
-                        if on_demand_plugin_id not in self.config:
-                            self.config[on_demand_plugin_id] = {}
-                        self.config[on_demand_plugin_id]['enabled'] = True
-                    enabled_plugins = [on_demand_plugin_id]
-                    # Set on-demand state from cached config
-                    self.on_demand_active = True
-                    self.on_demand_plugin_id = on_demand_plugin_id
-                    self.on_demand_mode = on_demand_config.get('mode')
-                    self.on_demand_duration = on_demand_config.get('duration')
-                    self.on_demand_pinned = on_demand_config.get('pinned', False)
-                    self.on_demand_requested_at = on_demand_config.get('requested_at')
-                    self.on_demand_expires_at = on_demand_config.get('expires_at')
-                    self.on_demand_status = 'active'
-                    self.on_demand_schedule_override = True
-                    logger.info("On-demand mode: loading only plugin '%s'", on_demand_plugin_id)
-            else:
-                enabled_plugins = [p for p in discovered_plugins if self.config.get(p, {}).get('enabled', False)]
 
             # Count enabled plugins for progress tracking
             enabled_count = len(enabled_plugins)
@@ -1267,12 +1239,119 @@ class DisplayController:
         self.on_demand_schedule_override = False
         self._publish_on_demand_state()
 
+    #: Shortest gap between mailbox disk reads. This is called after every
+    #: frame -- about 125 times a second on a scrolling mode -- and the read
+    #: below is deliberately uncached, so without a floor it was 125 disk reads
+    #: per second to find nothing. An on-demand request comes from a person
+    #: clicking in the web UI, so a quarter second of latency is not
+    #: perceptible, and it cuts the read rate by 30x.
+    ON_DEMAND_POLL_INTERVAL = 0.25
+
+    def _select_startup_plugins(self, discovered_plugins: List[str],
+                                on_demand_config: Optional[Dict[str, Any]]) -> List[str]:
+        """Which plugins to load at startup, restoring on-demand state if any.
+
+        Every normally-enabled plugin loads, on-demand or not. Loading only the
+        on-demand plugin left every other plugin unavailable for the rest of
+        the process's life whenever the service was restarted while on-demand
+        was still active -- and a restart during an on-demand session is
+        routine, since that is how updates and config changes are applied. The
+        panel came back cycling that one plugin's modes and nothing else, with
+        no way out but clearing the on-demand cache by hand.
+
+        On-demand still resumes on its saved mode; this only widens what gets
+        loaded, so normal rotation has somewhere to return to when it ends.
+        A plugin that is disabled in config but named by the on-demand request
+        is still enabled and added, since otherwise the mode being resumed
+        would have nothing behind it.
+        """
+        enabled_plugins = [p for p in discovered_plugins
+                           if self.config.get(p, {}).get('enabled', False)]
+
+        on_demand_plugin_id = on_demand_config.get('plugin_id') if on_demand_config else None
+        if not on_demand_plugin_id:
+            return enabled_plugins
+
+        if on_demand_plugin_id not in discovered_plugins:
+            logger.error("On-demand plugin '%s' not found in discovered plugins",
+                         on_demand_plugin_id)
+            logger.warning("Falling back to normal mode (all enabled plugins)")
+            return enabled_plugins
+
+        if not self.config.get(on_demand_plugin_id, {}).get('enabled', False):
+            logger.info("Temporarily enabling plugin '%s' for on-demand mode", on_demand_plugin_id)
+            self.config.setdefault(on_demand_plugin_id, {})['enabled'] = True
+            if on_demand_plugin_id not in enabled_plugins:
+                enabled_plugins.append(on_demand_plugin_id)
+
+        # Restore on-demand state from the cached request so it resumes.
+        self.on_demand_active = True
+        self.on_demand_plugin_id = on_demand_plugin_id
+        self.on_demand_mode = on_demand_config.get('mode')
+        self.on_demand_duration = on_demand_config.get('duration')
+        self.on_demand_pinned = on_demand_config.get('pinned', False)
+        self.on_demand_requested_at = on_demand_config.get('requested_at')
+        self.on_demand_expires_at = on_demand_config.get('expires_at')
+        self.on_demand_status = 'active'
+        self.on_demand_schedule_override = True
+        logger.info("On-demand mode detected during initialization: resuming on plugin '%s'; "
+                    "all %d enabled plugin(s) still load normally",
+                    on_demand_plugin_id, len(enabled_plugins))
+        return enabled_plugins
+
+    def _consume_on_demand_request(self, request_id: str) -> None:
+        """Remove the request we just handled from the mailbox.
+
+        Leaving it on disk meant a restart replayed the previous request: the
+        fresh controller read it, activated it and cached it, so the request
+        the caller had just made was ignored and the panel silently showed the
+        earlier plugin.
+
+        Compare before deleting. The web process can post a newer request
+        between the read and this delete; an unconditional delete threw that
+        one away and it was never processed -- the user's second click did
+        nothing. Re-reading uncached and only deleting our own request_id
+        leaves a newer request in the mailbox for the next poll instead.
+
+        This narrows the window rather than closing it: a request landing
+        between the re-read and the delete is still lost. Closing it properly
+        needs an atomic claim (a rename, or a compare-and-delete primitive)
+        that the cache layer does not currently offer, so the honest fix is a
+        smaller window plus this note, not a bigger lock. For start requests
+        processed_id still guards against reprocessing if the delete fails.
+        """
+        try:
+            current = self.cache_manager.get('display_on_demand_request',
+                                             max_age=3600, memory_ttl=0)
+            if not current or current.get('request_id') == request_id:
+                self.cache_manager.delete('display_on_demand_request')
+            else:
+                logger.debug("Newer on-demand request %s arrived while processing "
+                             "%s; leaving it in the mailbox",
+                             current.get('request_id'), request_id)
+        except (OSError, AttributeError, KeyError) as err:
+            logger.debug("Could not clear the on-demand request mailbox: %s", err)
+
     def _poll_on_demand_requests(self) -> None:
         """Poll cache for new on-demand requests from external controllers."""
+        now = time.monotonic()
+        if (self._last_on_demand_poll is not None
+                and now - self._last_on_demand_poll < self.ON_DEMAND_POLL_INTERVAL):
+            return
+        self._last_on_demand_poll = now
+
         try:
             # Use a long max_age (1 hour) to ensure requests aren't expired before processing
-            # The request_id check prevents duplicate processing
+            # The request_id check prevents duplicate processing.
-            request = self.cache_manager.get('display_on_demand_request', max_age=3600)
+            #
+            # memory_ttl=0 is required, not optional: this key is a mailbox the
+            # web process writes and this process reads. get() defaults the
+            # in-memory TTL to max_age, so without it the first request read was
+            # pinned in memory for the full hour and every later poll returned
+            # that stale copy -- meaning no second on-demand request was honoured
+            # for an hour, while the API still reported success.
+            request = self.cache_manager.get('display_on_demand_request',
+                                             max_age=3600, memory_ttl=0)
         except (OSError, RuntimeError, ValueError, TypeError) as err:
             logger.error("Failed to read on-demand request: %s", err, exc_info=True)
             return
@@ -1299,6 +1378,13 @@ class DisplayController:
                 logger.debug("Stop request %s received but on-demand is not active", request_id)
                 # Still update request_id to acknowledge the request
                 self.on_demand_request_id = request_id
+            # Stop requests are deliberately exempt from the request_id/
+            # processed_id guards above, so that a second click stops a mode
+            # that a race left running. Consuming the mailbox is therefore the
+            # only thing that ends the request: without it the same stop was
+            # re-read and re-processed on every poll, forever, logging at
+            # ON_DEMAND_POLL_INTERVAL for the life of the process.
+            self._consume_on_demand_request(request_id)
             return
 
         # For start requests, check if already processed
@@ -1318,6 +1404,7 @@ class DisplayController:
         # Mark as processed BEFORE processing (to prevent duplicate processing)
         self.cache_manager.set('display_on_demand_processed_id', request_id, ttl=3600)
         self.on_demand_request_id = request_id
+        self._consume_on_demand_request(request_id)
 
         if action == 'start':
             logger.info("Processing on-demand start request for plugin: %s", request.get('plugin_id'))
@@ -1360,17 +1447,14 @@ class DisplayController:
                 return modes[0]
         return plugin_id
 
-    def _populate_on_demand_modes_from_plugin(self) -> None:
+    def _on_demand_modes_for_plugin(self, plugin_id: str) -> List[str]:
-        """
+        """Every loaded display mode belonging to `plugin_id`, in rotation order.
-        Populate on_demand_modes from the on-demand plugin's display modes.
-        Called after plugin loading completes when on-demand state is restored from cache.
-        """
-        if not self.on_demand_active or not self.on_demand_plugin_id:
-            return
 
-        plugin_id = self.on_demand_plugin_id
+        Live modes that actually have content lead, then the rest, then live
-        
+        modes with nothing to show -- so an on-demand request for a sports
-        # Get all modes for this plugin
+        plugin opens on a game in progress rather than an empty live screen.
+        Returns an empty list when the plugin has no loaded modes.
+        """
         plugin_modes = self.plugin_display_modes.get(plugin_id, [])
         if not plugin_modes:
             # Fallback: find all modes that belong to this plugin
@@ -1378,11 +1462,8 @@ class DisplayController:
 
         # Filter to only include modes that exist in plugin_modes
         available_plugin_modes = [m for m in plugin_modes if m in self.plugin_modes]
-        
         if not available_plugin_modes:
-            logger.warning("No valid display modes found for on-demand plugin '%s' after restoration", plugin_id)
+            return []
-            self.on_demand_modes = []
-            return
 
         # Prioritize live modes if they exist and have content
         live_modes = [m for m in available_plugin_modes if m.endswith('_live')]
@@ -1410,6 +1491,45 @@ class DisplayController:
             # Only live modes available but no content - use them anyway
             ordered_modes = live_modes
 
+        return ordered_modes
+
+    def _apply_on_demand_pin(self, ordered_modes: List[str], resolved_mode: Optional[str],
+                             pinned: bool) -> List[str]:
+        """Narrow an on-demand rotation to the single requested mode when pinned.
+
+        `pinned` reaches the controller from the API and was stored and
+        republished but never acted on, so a pinned request still rotated
+        through every mode the resolved plugin owns. That is the right default
+        for a sports plugin, whose modes are views of one subject
+        (nfl_live/nfl_recent/nfl_upcoming), and the wrong one for a plugin
+        whose modes are unrelated -- each Starlark app is its own widget, so
+        asking for one and getting all of them is not what was requested.
+        """
+        if not pinned or not resolved_mode or resolved_mode not in ordered_modes:
+            return ordered_modes
+        return [resolved_mode]
+
+    def _populate_on_demand_modes_from_plugin(self) -> None:
+        """
+        Populate on_demand_modes from the on-demand plugin's display modes.
+        Called after plugin loading completes when on-demand state is restored from cache.
+        """
+        if not self.on_demand_active or not self.on_demand_plugin_id:
+            return
+
+        plugin_id = self.on_demand_plugin_id
+
+        ordered_modes = self._on_demand_modes_for_plugin(plugin_id)
+        if not ordered_modes:
+            logger.warning("No valid display modes found for on-demand plugin '%s' after restoration", plugin_id)
+            self.on_demand_modes = []
+            return
+
+        # A restart must not silently un-pin: the pin is part of the request
+        # being resumed, and it is restored from the same cached config above.
+        ordered_modes = self._apply_on_demand_pin(
+            ordered_modes, self.on_demand_mode, self.on_demand_pinned)
+
         self.on_demand_modes = ordered_modes
         # Set index to match the restored mode if available, otherwise start at 0
         if self.on_demand_mode and self.on_demand_mode in ordered_modes:
@@ -1464,45 +1584,13 @@ class DisplayController:
         if resolved_mode in self.available_modes:
             self.current_mode_index = self.available_modes.index(resolved_mode)
 
-        # Get all modes for this plugin
+        ordered_modes = self._on_demand_modes_for_plugin(resolved_plugin_id)
-        plugin_modes = self.plugin_display_modes.get(resolved_plugin_id, [])
+        if not ordered_modes:
-        if not plugin_modes:
-            # Fallback: find all modes that belong to this plugin
-            plugin_modes = [mode for mode, pid in self.mode_to_plugin_id.items() if pid == resolved_plugin_id]
-        
-        # Filter to only include modes that exist in plugin_modes
-        available_plugin_modes = [m for m in plugin_modes if m in self.plugin_modes]
-        
-        if not available_plugin_modes:
             logger.error("No valid display modes found for plugin '%s'", resolved_plugin_id)
             self._set_on_demand_error("no-modes")
             return
 
-        # Prioritize live modes if they exist and have content
+        ordered_modes = self._apply_on_demand_pin(ordered_modes, resolved_mode, pinned)
-        live_modes = [m for m in available_plugin_modes if m.endswith('_live')]
-        other_modes = [m for m in available_plugin_modes if not m.endswith('_live')]
-        
-        # Check if live modes have content
-        live_with_content = []
-        for live_mode in live_modes:
-            plugin_instance = self.plugin_modes.get(live_mode)
-            if plugin_instance and hasattr(plugin_instance, 'has_live_content'):
-                try:
-                    if plugin_instance.has_live_content():
-                        live_with_content.append(live_mode)
-                except Exception:
-                    pass
-        
-        # Build mode list: live modes with content first, then other modes, then live modes without content
-        if live_with_content:
-            ordered_modes = live_with_content + other_modes + [m for m in live_modes if m not in live_with_content]
-        else:
-            # No live content, skip live modes
-            ordered_modes = other_modes
-        
-        if not ordered_modes:
-            # Only live modes available but no content - use them anyway
-            ordered_modes = live_modes
 
         self.on_demand_active = True
         self.on_demand_mode = resolved_mode  # Keep for backward compatibility
@@ -2405,6 +2493,7 @@ class DisplayController:
                             )
 
                             while True:
+                                _frame_start = time.perf_counter()
                                 try:
                                     with self._display_lock_or_skip(plugin_id) as can_display:
                                         if can_display:
@@ -2425,11 +2514,26 @@ class DisplayController:
                                 # Multi-display sync: send follower frame after each render
                                 self._send_follower_frame(manager_to_display)
 
-                                time.sleep(display_interval)
                                 self._tick_plugin_updates()
                                 self._poll_on_demand_requests()
                                 self._check_on_demand_expiration()
 
+                                # 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 = display_interval - (time.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.
+                                time.sleep(_remaining if _remaining > 0 else 0.001)
+
                                 if self.current_display_mode != active_mode:
                                     logger.debug("Mode changed during high-FPS loop, breaking early")
                                     break

src/display_manager.py

@@ -34,6 +34,7 @@ else:
 from contextlib import contextmanager
 from pathlib import Path
 from PIL import Image, ImageDraw, ImageFont
+from src.common.font_layout import load_truetype
 import threading
 import time
 from collections import OrderedDict
@@ -55,6 +56,31 @@ from src.common.permission_utils import (
 logger = logging.getLogger(__name__)
 logger.setLevel(logging.INFO)  # Set to INFO level
 
+#: The strike 5x7.bdf is drawn at. FreeType renders a BDF at its own fixed
+#: size regardless, but a Face needs an active size before its metrics --
+#: and therefore get_font_height() -- report anything but 0.
+_CALENDAR_FONT_PX = 7
+
+
+def _bdf_native_size(face) -> int:
+    """The pixel height a BDF Face declares, or 0 if it does not say.
+
+    Used only to rescue a Face that was built without ``set_char_size``, so a
+    zero line height never reaches layout code.
+    """
+    try:
+        sizes = getattr(face, "available_sizes", None) or []
+        if sizes:
+            return int(getattr(sizes[0], "height", 0) or 0)
+    except (AttributeError, IndexError, TypeError, ValueError) as exc:
+        # This runs on the measurement path for a face the caller already
+        # holds, so a malformed strike table must degrade to "unknown" rather
+        # than take the display down. Say which face, so a font that is
+        # actually broken is diagnosable rather than silently 8px.
+        logger.debug("Could not read BDF strike size from %r: %s", face, exc)
+    return 0
+
+
 
 class _LogicalMatrix:
     """Proxy that reports a logical (per-screen) size for a physical matrix.
@@ -240,6 +266,14 @@ class DisplayManager:
         self._update_lock = threading.RLock()
         
         # Scrolling state tracking for graceful updates
+        # How many panel refreshes each pushed frame is held for. 1 means a new
+        # frame every refresh. Higher values are how a scroll runs slower than
+        # one pixel per refresh WITHOUT fractional pixel positions: the panel
+        # keeps refreshing at full rate (so flicker is unchanged) but motion
+        # advances a whole pixel every Nth refresh instead of every one.
+        # See src/common/scroll_config.py and scripts/scroll_speeds.py.
+        self._frame_hold = 1
+
         self._scrolling_state = {
             'is_scrolling': False,
             'last_scroll_activity': 0,
@@ -364,11 +398,12 @@ class DisplayManager:
             # Create image with the (logical) display dimensions
             self.image = Image.new('RGB', (self.matrix.width, self.matrix.height))
             self.draw = ImageDraw.Draw(self.image)
+            self.draw.fontmode = "1"  # 1-bit text: the panel has no partial brightness, so AA only smears glyphs.
             logger.info(f"Image canvas created with dimensions: {self.matrix.width}x{self.matrix.height}")
             
             # Initialize font with Press Start 2P
             try:
-                self.font = ImageFont.truetype("assets/fonts/PressStart2P-Regular.ttf", 8)
+                self.font = load_truetype("assets/fonts/PressStart2P-Regular.ttf", 8)
                 logger.info("Initial Press Start 2P font loaded successfully")
             except Exception as e:
                 logger.error(f"Failed to load initial font: {e}")
@@ -403,6 +438,7 @@ class DisplayManager:
 
             self.image = Image.new('RGB', (fallback_width, fallback_height))
             self.draw = ImageDraw.Draw(self.image)
+            self.draw.fontmode = "1"  # 1-bit text: the panel has no partial brightness, so AA only smears glyphs.
             # Simple fallback visualization so web UI shows a realistic canvas
             try:
                 self.draw.rectangle([0, 0, fallback_width - 1, fallback_height - 1], outline=(255, 0, 0))
@@ -547,19 +583,33 @@ class DisplayManager:
                     pass
 
     def _fitting_font(self, lines, width):
-        """The largest font from the usual ladder that fits every line."""
+        """The largest font from the usual ladder that fits every line.
+
+        The ladder ends at 4x6 at 5px because a full dotted-quad address --
+        "255.255.255.255", the widest this screen ever shows -- is 66px at
+        6px and a 64px panel has 62 to give it. That used to squeak in only
+        because the measurement depended on which text layout engine the host
+        Pillow had; with the engine pinned it does not, so the rung the
+        worst case actually needs is here rather than implied.
+        """
         candidates = [self.font,
-                      ("assets/fonts/4x6-font.ttf", 6)]
+                      ("assets/fonts/4x6-font.ttf", 6),
+                      ("assets/fonts/4x6-font.ttf", 5)]
+        narrowest = None
         for candidate in candidates:
             try:
                 font = candidate
                 if isinstance(candidate, tuple):
-                    font = ImageFont.truetype(candidate[0], candidate[1])
+                    font = load_truetype(candidate[0], candidate[1])
+                narrowest = font
                 if all(self.draw.textlength(t, font=font) <= width for t in lines):
                     return font
             except (OSError, ValueError, AttributeError):
                 continue
-        return self.font
+        # Nothing fit. Return the smallest face that loaded, not self.font --
+        # falling back to the widest option is how "Initializing" ran off the
+        # side of a 64px panel in the first place.
+        return narrowest or self.font
 
     def _draw_startup_banner(self, lines, width: int, height: int) -> None:
         """Centre `lines` over whatever the test pattern already drew.
@@ -705,6 +755,7 @@ class DisplayManager:
             # self.image, so swapping the buffer below is enough on its own.
             self.image = Image.new('RGB', (target_w, target_h))
             self.draw = ImageDraw.Draw(self.image)
+            self.draw.fontmode = "1"  # 1-bit text: the panel has no partial brightness, so AA only smears glyphs.
             yield
         finally:
             self.matrix = real_matrix
@@ -768,16 +819,33 @@ class DisplayManager:
                     return  # Skip hardware write — content is being captured off-screen
 
                 digest = None
+                frame_checksum = None
                 if self._dirty_tracking_enabled:
                     try:
                         brightness = getattr(self.matrix, 'brightness', None)
                     except AttributeError:
                         brightness = None
-                    digest = (zlib.adler32(self.image.tobytes()), brightness)
+                    frame_checksum = zlib.adler32(self.image.tobytes())
-                    if digest == self._last_pushed_digest:
+                    digest = (frame_checksum, brightness)
+                    if digest == self._last_pushed_digest and not self.is_currently_scrolling():
                         # Nothing changed since the last push — the panel is
                         # already showing exactly this frame.
-                        self._write_snapshot_if_due()
+                        #
+                        # Never taken mid-scroll, and that exception is the
+                        # point. SwapOnVSync is what paces the render loop, so
+                        # skipping it also skips the wait: a duplicate frame
+                        # returns in ~8ms instead of ~10ms on a 100Hz panel,
+                        # advances only 0.8px instead of 1.0px, and so makes
+                        # the *next* frame more likely to repeat as well. That
+                        # is self-sustaining -- measured at ~20% duplicate
+                        # frames mid-scroll on the odds ticker, against
+                        # essentially zero on a lighter plugin with identical
+                        # scroll settings. Swapping an identical frame costs
+                        # one canvas copy and keeps the loop locked to the
+                        # panel; falling out of that lock costs smooth motion.
+                        # Static content is unaffected: is_currently_scrolling()
+                        # expires on its own inactivity threshold.
+                        self._write_snapshot_if_due(frame_checksum)
                         return
 
                 # Copy the current image to the offscreen canvas. In double-sided
@@ -787,8 +855,10 @@ class DisplayManager:
                 else:
                     self.offscreen_canvas.SetImage(self.image)
 
-                # Swap buffers immediately
+                # Swap buffers immediately. framerate_fraction holds the frame
-                self.matrix.SwapOnVSync(self.offscreen_canvas)
+                # for N refreshes; SwapOnVSync blocks for all of them, which is
+                # what paces the render loop to the chosen frame rate.
+                self.matrix.SwapOnVSync(self.offscreen_canvas, self._frame_hold)
 
                 # Swap our canvas references
                 self.offscreen_canvas, self.current_canvas = self.current_canvas, self.offscreen_canvas
@@ -796,7 +866,7 @@ class DisplayManager:
                 self._last_pushed_digest = digest
 
                 # Write a snapshot for the web preview (throttled)
-                self._write_snapshot_if_due()
+                self._write_snapshot_if_due(frame_checksum)
         except Exception as e:
             logger.error(f"Error updating display: {e}")
 
@@ -814,6 +884,7 @@ class DisplayManager:
                 
                 self.image = Image.new('RGB', (width, height))
                 self.draw = ImageDraw.Draw(self.image)
+                self.draw.fontmode = "1"  # 1-bit text: the panel has no partial brightness, so AA only smears glyphs.
                 logger.debug("Cleared display in fallback mode")
                 return
                 
@@ -825,6 +896,7 @@ class DisplayManager:
             # Create a new black image
             self.image = Image.new('RGB', (self.matrix.width, self.matrix.height))
             self.draw = ImageDraw.Draw(self.image)
+            self.draw.fontmode = "1"  # 1-bit text: the panel has no partial brightness, so AA only smears glyphs.
 
             if not self._capture_mode_active:
                 # Clear both canvases and the underlying matrix to ensure no artifacts.
@@ -901,11 +973,11 @@ class DisplayManager:
         self._text_width_cache.clear()
         try:
             # Load Press Start 2P font
-            self.regular_font = ImageFont.truetype("assets/fonts/PressStart2P-Regular.ttf", 8)
+            self.regular_font = load_truetype("assets/fonts/PressStart2P-Regular.ttf", 8)
             logger.info("Press Start 2P font loaded successfully")
             
             # Use the same font for small text (currently same size; adjust size here if needed)
-            self.small_font = ImageFont.truetype("assets/fonts/PressStart2P-Regular.ttf", 8)
+            self.small_font = load_truetype("assets/fonts/PressStart2P-Regular.ttf", 8)
             logger.info("Press Start 2P small font loaded successfully")
 
             # Load 5x7 BDF font for calendar events
@@ -918,6 +990,17 @@ class DisplayManager:
                 
                 # Load with freetype for proper BDF handling
                 face = freetype.Face(self.calendar_font_path)
+                # A freshly constructed Face has no active size, so
+                # face.size.height is 0 until set_char_size is called -- and
+                # get_font_height() reads exactly that. Without this, every
+                # caller measuring the 5x7 face got 0 and stacked rows on top
+                # of one another; the "Calendar font size: 0 pixels" line
+                # below has been printing the symptom on every start-up.
+                # font_manager._load_bdf_font already does this; the two paths
+                # disagreed about whether a Face was usable for measurement.
+                # 5x7.bdf is a fixed strike, so FreeType renders 7px whatever
+                # is asked for -- this sets the metrics, not the raster.
+                face.set_char_size(_CALENDAR_FONT_PX * 64, _CALENDAR_FONT_PX * 64, 72, 72)
                 logger.info(f"5x7 calendar font loaded successfully from {self.calendar_font_path}")
                 logger.info(f"Calendar font size: {face.size.height >> 6} pixels")
                 
@@ -938,7 +1021,7 @@ class DisplayManager:
             try:
                 font_path = "assets/fonts/4x6-font.ttf"
                 logger.info(f"Attempting to load 4x6 TTF font from: {font_path} at size 6")
-                self.extra_small_font = ImageFont.truetype(font_path, 6)
+                self.extra_small_font = load_truetype(font_path, 6)
                 logger.info(f"4x6 TTF extra small font loaded successfully from {font_path}")
             except Exception as font_err:
                 logger.error(f"Failed to load 4x6 TTF font: {font_err}. Falling back.")
@@ -996,7 +1079,13 @@ class DisplayManager:
         try:
             if isinstance(font, freetype.Face):
                 # For FreeType faces (BDF), the 'height' metric gives the recommended line spacing.
-                return font.size.height >> 6
+                height = font.size.height >> 6
+                if height:
+                    return height
+                # A Face constructed without set_char_size reports 0, and a
+                # zero line height collapses every stacked row onto one line.
+                # Fall back to the strike the file declares.
+                return _bdf_native_size(font) or 8
             else:
                 # For PIL TTF fonts, getmetrics() provides ascent and descent.
                 # The line height is the sum of ascent and descent.
@@ -1258,6 +1347,7 @@ class DisplayManager:
             try:
                 self.image = Image.new('RGB', (self.width, self.height))
                 self.draw = ImageDraw.Draw(self.image)
+                self.draw.fontmode = "1"  # 1-bit text: the panel has no partial brightness, so AA only smears glyphs.
             except (OSError, RuntimeError, ValueError, MemoryError):
                 logger.debug("Canvas reset during cleanup failed", exc_info=True)
         # Reset the singleton state when cleaning up
@@ -1274,12 +1364,65 @@ class DisplayManager:
         
         return dt.strftime(f"%b %-d{suffix}") 
 
-    def set_scrolling_state(self, is_scrolling: bool):
+    @property
-        """Set the current scrolling state. Call this when a display starts/stops scrolling."""
+    def refresh_hz(self) -> float:
+        """The panel's refresh rate in Hz, from the hardware config.
+
+        The authoritative place to ask, because a plugin only receives its own
+        config section and cannot see display.hardware. Scroll pacing needs
+        this: the speeds a panel can show in whole pixels are refresh_hz
+        divided by the frame hold, so getting it wrong silently produces
+        fractional-pixel motion. See src/common/scroll_config.py.
+
+        Note this is the configured *cap*, not necessarily what the panel
+        achieves -- scripts/scroll_speeds.py --measure reports the real rate.
+        """
+        hardware = (self.config.get('display') or {}).get('hardware') or {}
+        try:
+            value = float(hardware.get('limit_refresh_rate_hz') or 0)
+        except (TypeError, ValueError):
+            value = 0.0
+        return value if value > 0 else 100.0
+
+    def set_frame_hold(self, refreshes: int) -> None:
+        """Hold each pushed frame for this many panel refreshes (>=1).
+
+        Set by the scroll configuration so a plugin can run at, say, 50px/s on
+        a 100Hz panel as one whole pixel every second refresh, rather than half
+        a pixel every refresh (which has to be blended or repeated unevenly).
+
+        Reset to 1 whenever scrolling stops, so one plugin's pacing cannot
+        leak into the next thing on screen.
+        """
+        try:
+            value = int(refreshes)
+        except (TypeError, ValueError):
+            logger.warning("Ignoring unusable frame hold: %r", refreshes)
+            return
+        self._frame_hold = max(1, min(255, value))
+
+    def set_scrolling_state(self, is_scrolling: bool, frame_hold: int = 1):
+        """Set the current scrolling state, and this scroll's frame pacing.
+
+        Call this when a display starts or stops scrolling. ``frame_hold`` is
+        how many panel refreshes each frame is held for -- 2 gives one whole
+        pixel every second refresh, which is how a scroll runs at half the
+        refresh rate without fractional pixel positions.
+
+        The hold is set here rather than once at plugin construction because
+        it must not outlive the scroll that asked for it: plugins share one
+        display manager, so a hold left set by whoever scrolled last would
+        silently re-pace the next plugin. Passing it alongside the state makes
+        the lifetime exactly the scroll, and the default of 1 means any caller
+        that does not care gets a new frame every refresh.
+        """
         current_time = time.time()
         self._scrolling_state['is_scrolling'] = is_scrolling
         if is_scrolling:
             self._scrolling_state['last_scroll_activity'] = current_time
+            self.set_frame_hold(frame_hold)
+        else:
+            self._frame_hold = 1
         logger.debug(f"Scrolling state set to: {is_scrolling}")
 
     def is_currently_scrolling(self) -> bool:
@@ -1410,11 +1553,20 @@ class DisplayManager:
                 self._viewer_fresh = False
         return self._viewer_fresh
 
-    def _write_snapshot_if_due(self) -> None:
+    def _write_snapshot_if_due(self, frame_checksum: Optional[int] = None) -> None:
         """Mirror the current frame to the preview snapshot when the policy
         says it's worth it — see src/common/snapshot_policy.py. Unchanged
         frames are never re-encoded; without viewers the cadence drops to
-        the idle keepalive."""
+        the idle keepalive.
+
+        Args:
+            frame_checksum: adler32 of the current frame, when the caller has
+                already computed one. Dirty tracking checksums every frame a
+                few lines above the call site, and re-deriving it here meant a
+                second tobytes() plus a second pass over the whole framebuffer
+                on every single frame — ~0.17ms per frame of the two combined
+                at 256x64, paid 100 times a second to reach the same number.
+        """
         try:
             now = time.time()
             viewer_fresh = self._viewer_is_fresh(now)
@@ -1424,7 +1576,8 @@ class DisplayManager:
                 self._last_snapshot_ts = 0.0
             self._viewer_was_fresh = viewer_fresh
 
-            digest = zlib.adler32(self.image.tobytes())
+            digest = (frame_checksum if frame_checksum is not None
+                      else zlib.adler32(self.image.tobytes()))
             action = snapshot_policy.decide(
                 now, self._last_snapshot_ts, self._last_snapshot_touch_ts,
                 viewer_fresh, digest != self._last_snapshot_digest)
@@ -1447,12 +1600,30 @@ class DisplayManager:
                 if parent_dir and str(parent_dir) != '/tmp':  # nosec B108 - guard to skip /tmp for permission ops
                     ensure_directory_permissions(parent_dir, get_assets_dir_mode())
                 self._snapshot_dir_prepared = True
-            # Write atomically: temp then replace
+            # Write atomically: temp then replace. The temp name must be
-            tmp_path = f"{self._snapshot_path}.tmp"
+            # unique, not "<snapshot>.tmp": /tmp is world-writable and sticky,
-            self.image.save(tmp_path, format='PNG')
+            # and this file is written by whichever user the display service
+            # runs as while tests and tooling run as someone else. A leftover
+            # fixed-name temp owned by another user is then unopenable even by
+            # root (fs.protected_regular refuses O_CREAT on a foreign file in a
+            # sticky dir), which froze the preview and the health check's
+            # liveness proxy until somebody deleted it by hand. Same pattern as
+            # the hardware-status write above.
+            _fd, tmp_path = tempfile.mkstemp(
+                dir=str(snapshot_path_obj.parent),
+                prefix=f".{snapshot_path_obj.name}.", suffix=".tmp")
             try:
+                with os.fdopen(_fd, "wb") as _f:
+                    self.image.save(_f, format='PNG')
+                os.chmod(tmp_path, 0o644)
                 os.replace(tmp_path, self._snapshot_path)
             except Exception:
+                # Never leave the temp behind -- that is what made the failure
+                # permanent rather than transient.
+                try:
+                    os.unlink(tmp_path)
+                except OSError:
+                    pass
                 # Fallback to direct save if replace not supported
                 self.image.save(self._snapshot_path, format='PNG')
             # Set proper file permissions after saving

src/element_style.py

@@ -51,6 +51,7 @@ from dataclasses import dataclass
 from typing import Any, Dict, Optional, Tuple, Union
 
 from PIL import ImageFont
+from src.common.font_layout import load_truetype
 
 try:
     import freetype
@@ -155,7 +156,7 @@ def load_font(font_name: str, size: int) -> Any:
             face.set_char_size(size * 64, size * 64, 72, 72)
             font: Any = face
         else:
-            font = ImageFont.truetype(path, size)
+            font = load_truetype(path, size)
     except Exception as e:
         logger.warning("Error loading font %s at %spx: %s, using fallback",
                        path, size, e)
@@ -174,7 +175,7 @@ def _load_fallback_font(size: int) -> Any:
         if cached is not None:
             return cached
         try:
-            font = ImageFont.truetype(path, size)
+            font = load_truetype(path, size)
             _font_cache[cache_key] = font
             return font
         except Exception as e:

src/font_manager.py

@@ -38,6 +38,7 @@ import time
 from collections import OrderedDict
 from pathlib import Path
 from PIL import ImageFont
+from src.common.font_layout import load_truetype
 from typing import Dict, Tuple, Optional, Union, Any, List
 
 logger = logging.getLogger(__name__)
@@ -96,7 +97,8 @@ class FontManager:
         self.common_fonts = {
             "press_start": "assets/fonts/PressStart2P-Regular.ttf",
             "four_by_six": "assets/fonts/4x6-font.ttf",
-            "five_by_seven": "assets/fonts/5x7.bdf"
+            "five_by_seven": "assets/fonts/5x7.bdf",
+            "tom_thumb": "assets/fonts/tom-thumb.bdf"
             # Note: cozette_bdf removed - font file not available
             # To re-enable: download cozette.bdf from https://github.com/the-moonwitch/Cozette
             # and add: "cozette_bdf": "assets/fonts/cozette.bdf"
@@ -478,7 +480,7 @@ class FontManager:
                 if font_path.endswith('.bdf'):
                     font = self._load_bdf_font(font_path, size_px)
                 else:
-                    font = ImageFont.truetype(font_path, size_px)
+                    font = load_truetype(font_path, size_px)
             except Exception as e:
                 logger.error(f"Error loading font {font_path}: {e}")
                 self.performance_stats["failed_loads"] += 1
@@ -858,7 +860,7 @@ class FontManager:
                 return {"valid": True, "type": "bdf", "family": "unknown"}
             elif font_path.endswith('.ttf'):
                 # Try to load TTF font
-                ImageFont.truetype(font_path, 12)
+                load_truetype(font_path, 12)
                 return {"valid": True, "type": "ttf", "family": "unknown"}
             else:
                 return {"valid": False, "error": "Unsupported font format"}

src/logo_downloader.py

@@ -14,6 +14,7 @@ import json
 from typing import Dict, List, Optional, Tuple
 from pathlib import Path
 from PIL import Image, ImageDraw, ImageFont
+from src.common.font_layout import load_truetype
 from PIL.PngImagePlugin import PngInfo
 from requests.adapters import HTTPAdapter
 from urllib3.util.retry import Retry
@@ -747,7 +748,7 @@ class LogoDownloader:
             
             # Try to load a font, fallback to default
             try:
-                font = ImageFont.truetype("assets/fonts/PressStart2P-Regular.ttf", 12)
+                font = load_truetype("assets/fonts/PressStart2P-Regular.ttf", 12)
             except (OSError, IOError):
                 try:
                     font = ImageFont.load_default()

src/plugin_system/store_manager.py

@@ -1589,6 +1589,7 @@ class PluginStoreManager:
             with open(manifest_path, 'r') as f:
                 manifest = json.load(f)
             
+            requested_id = plugin_id
             plugin_id = plugin_id or manifest.get('id')
             if not plugin_id:
                 return {
@@ -1664,6 +1665,15 @@ class PluginStoreManager:
             
             branch_info = f" (branch: {branch_used})" if branch_used else ""
             self.logger.info(f"Successfully installed plugin from URL: {plugin_id}{branch_info}")
+            # User deliberately (re)installed this plugin -- clear any persistent
+            # uninstall record, exactly as install_plugin() does. Without this the
+            # id stays in config/uninstalled_plugins.json and
+            # purge_uninstalled_plugins(), which runs at every web-app startup,
+            # deletes the directory again: the plugin works for the rest of the
+            # session and is gone after the next reboot.
+            self.forget_uninstalled_plugin(
+                *(pid for pid in (requested_id, plugin_id, manifest.get('id')) if pid)
+            )
             result = {
                 'success': True,
                 'plugin_id': plugin_id,
@@ -2424,6 +2434,65 @@ class PluginStoreManager:
         except (OSError, ValueError):
             pass
 
+        # Last resort: the directory name may differ from the id being looked
+        # up. install_plugin() deliberately renames a plugin's directory to the
+        # MANIFEST id when it differs from the REGISTRY id (see the rename near
+        # "doesn't match registry ID" above), so `stocks` in the registry lands
+        # in `ledmatrix-stocks/`. Every lookup above is by directory name, so
+        # update_plugin("stocks") found nothing and reported the plugin as not
+        # installed -- silently, and for good: the user sees no error and stays
+        # on a stale version. Four installed plugins hit this in practice
+        # (leaderboard, music, stocks, weather).
+        #
+        # Deliberately last so the two lookups above keep their exact meaning;
+        # this only runs when a direct hit already failed. See
+        # test_discovery_path_contract.py, which pins that ordering.
+        for search_dir in self._candidate_plugin_dirs():
+            match = self._find_by_manifest_id(search_dir, plugin_id)
+            if match is not None:
+                self.logger.debug(
+                    "Resolved plugin '%s' to %s via its manifest id "
+                    "(directory name differs from the id)", plugin_id, match)
+                return match
+
+        return None
+
+    def _candidate_plugin_dirs(self) -> List[Path]:
+        """Directories that may hold installed plugins, configured one first."""
+        dirs = [self.plugins_dir]
+        try:
+            base = self.plugins_dir if self.plugins_dir.is_absolute()                 else self.plugins_dir.resolve()
+            sibling = base.parent / 'plugins'
+            if sibling != self.plugins_dir:
+                dirs.append(sibling)
+        except (OSError, ValueError):
+            pass
+        return [d for d in dirs if d.exists()]
+
+    @staticmethod
+    def _find_by_manifest_id(search_dir: Path, plugin_id: str) -> Optional[Path]:
+        """A subdirectory of `search_dir` whose manifest declares `plugin_id`.
+
+        Skips half-finished installs: store_manager renames a directory aside
+        with '.standalone-backup-' during install and rollback, and treating
+        one as installed would resurrect a ghost plugin.
+        """
+        try:
+            entries = sorted(search_dir.iterdir())
+        except (OSError, ValueError):
+            return None
+        for entry in entries:
+            if not entry.is_dir() or '.standalone-backup-' in entry.name:
+                continue
+            manifest = entry / 'manifest.json'
+            if not manifest.is_file():
+                continue
+            try:
+                with open(manifest, 'r', encoding='utf-8') as handle:
+                    if json.load(handle).get('id') == plugin_id:
+                        return entry
+            except (OSError, ValueError):
+                continue
         return None
     
     _SKIN_ID_PATTERN = re.compile(r'^[A-Za-z0-9][A-Za-z0-9._-]{0,63}$')

src/plugin_system/testing/harness.py

@@ -14,6 +14,8 @@ via BoundsCheckingDisplayManager, and golden-image comparison.
 import contextlib
 import http.client
 import inspect
+import time
+from datetime import timedelta
 import socket
 import ssl
 import urllib.error
@@ -25,7 +27,7 @@ from PIL import Image, ImageChops
 
 from src.logging_config import get_logger
 from .bounds_display_manager import BoundsCheckingDisplayManager
-from .loading import load_config_defaults, load_manifest
+from .loading import load_config_defaults, load_manifest, merge_config
 from .sizes import DEFAULT_TEST_SIZES, safe_mode_filename, size_label
 
 logger = get_logger("[Plugin Harness]")
@@ -116,14 +118,23 @@ def list_modes(plugin_instance: Any, manifest: Dict[str, Any], plugin_id: str) -
 
 def _instantiate(plugin_id: str, manifest: Dict[str, Any], plugin_dir: Path,
                  config: Dict[str, Any], mock_data: Dict[str, Any],
-                 display_manager: Any) -> Any:
+                 display_manager: Any, cache_manager: Any = None) -> Any:
-    """Load and construct a plugin instance with mocked managers."""
+    """Load and construct a plugin instance with mocked managers.
+
+    Pass ``cache_manager`` to share one cache across the renders of a plugin.
+    Building a fresh one per (size, mode) made every render a cold start, so a
+    plugin that fetches per game or per player re-fetched everything N times --
+    baseball-scoreboard took 840s for nine renders where ~72s was the arithmetic
+    -- and the cache-hit path, which is what a running rig executes almost
+    always, was never exercised.
+    """
     from src.plugin_system.plugin_loader import PluginLoader
     from src.plugin_system.testing import MockCacheManager, MockPluginManager
 
-    cache_manager = MockCacheManager()
+    if cache_manager is None:
-    for key, value in (mock_data or {}).items():
+        cache_manager = MockCacheManager()
-        cache_manager.set(key, value)
+        for key, value in (mock_data or {}).items():
+            cache_manager.set(key, value)
 
     loader = PluginLoader()
     plugin_instance, _module = loader.load_plugin(
@@ -160,6 +171,107 @@ def _render_mode(plugin_instance: Any, mode: str) -> Any:
     return plugin_instance.display(force_clear=False)
 
 
+# How many extra frames to drive before believing a mode really draws nothing.
+# A scroll starts with its content off-panel, so frame 1 is legitimately blank;
+# measured across the fleet, content appears by frame 2-4 (f1-scoreboard),
+# frame 4 (ledmatrix-elections) and frame 38 at 64px (ledmatrix-leaderboard).
+EMPTY_RECHECK_FRAMES = 48
+# Seconds to advance the clock between those frames. Scroll position is usually
+# driven by elapsed time, which a frozen clock never provides.
+EMPTY_RECHECK_STEP = 0.05
+
+
+def _has_content(image) -> bool:
+    """True when any pixel is lit above the threshold."""
+    if image is None:
+        return False
+    return image.convert("L").point(
+        lambda p: 255 if p > _LIT_THRESHOLD else 0).getbbox() is not None
+
+
+def _render_mode_again(plugin_instance: Any, mode: str) -> Any:
+    """Draw one more frame WITHOUT force_clear.
+
+    _render_mode passes force_clear=True, which for a scrolling plugin means
+    "reset the scroll to the start" -- so repeating it would redraw frame 1 for
+    ever. The re-check needs the plugin to advance.
+    """
+    sig = inspect.signature(plugin_instance.display)
+    if "display_mode" in sig.parameters:
+        return plugin_instance.display(force_clear=False, display_mode=mode)
+    return plugin_instance.display(force_clear=False)
+
+
+def _settle_empty_frame(inst, mode, dm, result, freezer) -> None:
+    """Give an apparently-empty mode a few frames to draw before believing it.
+
+    One frame is not evidence: a scroll's first frame is its blank scroll-in
+    buffer. Without this, every scrolling plugin was warned about -- 60 of 76
+    warnings on a 44-plugin rig were false, which is the rate at which people
+    stop reading a warning.
+    """
+    if result.error is not None or result.display_returned is False:
+        return
+    if _has_content(result.image):
+        return
+    # The frozen clock is shared by every render in the matrix, so any time this
+    # probe borrows has to be given back -- otherwise a mode that scrolls in
+    # leaves the clock advanced and every later mode renders at the wrong
+    # instant, drifting its golden. Seen as 5 spurious f1_upcoming drifts.
+    resume_at = None
+    if freezer is not None:
+        try:
+            resume_at = freezer()
+        except (AttributeError, TypeError, ValueError):
+            # Not a freezegun factory, or a version whose factory is not
+            # callable. Only used to restore the clock, never load-bearing.
+            resume_at = None
+    try:
+        _settle_loop(inst, mode, dm, result, freezer)
+    finally:
+        if resume_at is not None:
+            try:
+                freezer.move_to(resume_at)
+            except (AttributeError, TypeError, ValueError):
+                pass
+
+
+def _settle_loop(inst, mode, dm, result, freezer) -> None:
+    tick = getattr(freezer, "tick", None) if freezer is not None else None
+    for _ in range(EMPTY_RECHECK_FRAMES):
+        if tick is not None:
+            # timedelta rather than a bare float: freezegun has accepted a
+            # number only since 1.x, and a stale pin would raise here.
+            try:
+                tick(timedelta(seconds=EMPTY_RECHECK_STEP))
+            except (AttributeError, TypeError, ValueError):
+                # Pacing is best-effort; a freezegun that will not take a
+                # timedelta just means this probe runs without advancing time.
+                pass
+        else:
+            # No frozen clock, so the real one has to do the advancing. Without
+            # this the 48 frames run in microseconds, elapsed time stays ~0, and
+            # a scroll driven by elapsed time never moves -- which is exactly
+            # the plugin this check is trying not to slander.
+            time.sleep(EMPTY_RECHECK_STEP)
+        try:
+            result.display_returned = _render_mode_again(inst, mode)
+        except Exception as e:  # noqa: BLE001
+            # Deliberately broad: this calls a plugin's display(), which can
+            # raise anything. Recorded rather than swallowed -- a mode that
+            # renders one good frame and then crashes on the next is broken,
+            # and returning silently here reported it as passing. The frame
+            # already captured stays on the result so the failure is still
+            # inspectable.
+            result.error = repr(e)
+            return
+        image = dm.get_image()
+        if _has_content(image):
+            result.image = image
+            result.overflow = dm.check_overflow()
+            return
+
+
 def _freeze(freeze_time: Optional[str]):
     """Context manager that freezes wall-clock time when freeze_time is given,
     so time-dependent plugins (clocks, countdowns) render deterministic goldens."""
@@ -193,7 +305,9 @@ def render_plugin_matrix(
     manifest = load_manifest(plugin_dir)
     # Start from config_schema.json defaults so the plugin behaves like a real
     # install; explicit caller config still wins over a schema default.
-    config = {"enabled": True, **load_config_defaults(plugin_dir), **(config or {})}
+    config = merge_config(
+        merge_config({"enabled": True}, load_config_defaults(plugin_dir)),
+        config or {})
     sizes = sizes or DEFAULT_TEST_SIZES
     results: List[RenderResult] = []
 
@@ -202,25 +316,35 @@ def render_plugin_matrix(
     # rendering a smaller one, instead of being clipped into a false pass.
     extent = (max(w for w, _ in sizes), max(h for _, h in sizes))
 
-    with _freeze(freeze_time):
+    # One cache for the whole matrix: see _instantiate. The display manager
+    # stays per-render (the bounds checking depends on that); only fetched data
+    # is shared.
+    from src.plugin_system.testing import MockCacheManager
+    cache_manager = MockCacheManager()
+    for key, value in (mock_data or {}).items():
+        cache_manager.set(key, value)
+
+    with _freeze(freeze_time) as freezer:
         for width, height in sizes:
             results.extend(_render_size(
                 plugin_id, manifest, plugin_dir, config, mock_data or {},
-                width, height, run_update, extent,
+                width, height, run_update, extent, cache_manager, freezer,
             ))
 
     return results
 
 
 def _render_size(plugin_id, manifest, plugin_dir, config, mock_data,
-                 width, height, run_update, extent) -> List[RenderResult]:
+                 width, height, run_update, extent,
+                 cache_manager=None, freezer=None) -> List[RenderResult]:
     """Render every mode at one size. A fresh instance per mode avoids state leaks."""
     results: List[RenderResult] = []
 
     # Discover modes once per size (instance build can depend on config).
     try:
         probe_dm = BoundsCheckingDisplayManager(width=width, height=height, overflow_extent=extent)
-        probe = _instantiate(plugin_id, manifest, plugin_dir, config, mock_data, probe_dm)
+        probe = _instantiate(plugin_id, manifest, plugin_dir, config, mock_data, probe_dm,
+                             cache_manager)
         modes = list_modes(probe, manifest, plugin_id)
     except Exception as e:  # noqa: BLE001 — surface any load failure as a result
         return [RenderResult(plugin_id, width, height, "<load>", error=repr(e))]
@@ -229,7 +353,8 @@ def _render_size(plugin_id, manifest, plugin_dir, config, mock_data,
         result = RenderResult(plugin_id, width, height, mode)
         dm = BoundsCheckingDisplayManager(width=width, height=height, overflow_extent=extent)
         try:
-            inst = _instantiate(plugin_id, manifest, plugin_dir, config, mock_data, dm)
+            inst = _instantiate(plugin_id, manifest, plugin_dir, config, mock_data, dm,
+                                cache_manager)
             if run_update:
                 try:
                     inst.update()
@@ -248,6 +373,9 @@ def _render_size(plugin_id, manifest, plugin_dir, config, mock_data,
                 result.display_returned = _render_mode(inst, mode)
                 result.image = dm.get_image()
                 result.overflow = dm.check_overflow()
+                # A blank first frame is not proof of a blank mode; see
+                # _settle_empty_frame.
+                _settle_empty_frame(inst, mode, dm, result, freezer)
         except Exception as e:  # noqa: BLE001 — a display crash is a real failure
             result.error = repr(e)
         results.append(result)

src/plugin_system/testing/loading.py

@@ -33,6 +33,45 @@ def load_manifest(plugin_dir: Union[str, Path]) -> Dict[str, Any]:
         return json.load(f)
 
 
+def _defaults_from_properties(properties: Dict[str, Any]) -> Dict[str, Any]:
+    """Defaults for one `properties` block, recursing into nested objects.
+
+    An object property carries its defaults on its children, not on itself, so
+    reading only the top level dropped everything nested. That is most of the
+    fleet: config organised by league, or under customization/display_options,
+    lost 2,386 defaults across 37 of 44 plugins -- soccer-scoreboard alone lost
+    539 of 565 -- and the harness rendered them with a config no install would
+    ever have.
+    """
+    defaults: Dict[str, Any] = {}
+    for key, prop in (properties or {}).items():
+        if not isinstance(prop, dict):
+            continue
+        if prop.get('type') == 'object' and isinstance(prop.get('properties'), dict):
+            nested = _defaults_from_properties(prop['properties'])
+            if nested:
+                defaults[key] = nested
+        elif 'default' in prop:
+            defaults[key] = prop['default']
+    return defaults
+
+
+def merge_config(base: Dict[str, Any], override: Dict[str, Any]) -> Dict[str, Any]:
+    """Deep-merge override onto base, without dropping sibling defaults.
+
+    A shallow merge would let `-c '{"nhl": {"enabled": true}}'` replace the whole
+    nhl subtree and silently discard every other nhl default -- the same class of
+    bug this function exists to fix.
+    """
+    merged = dict(base)
+    for key, value in (override or {}).items():
+        if isinstance(value, dict) and isinstance(merged.get(key), dict):
+            merged[key] = merge_config(merged[key], value)
+        else:
+            merged[key] = value
+    return merged
+
+
 def load_config_defaults(plugin_dir: Union[str, Path]) -> Dict[str, Any]:
     """Extract default values from a plugin's config_schema.json (empty if none)."""
     schema_path = Path(plugin_dir) / 'config_schema.json'
@@ -40,11 +79,7 @@ def load_config_defaults(plugin_dir: Union[str, Path]) -> Dict[str, Any]:
         return {}
     with open(schema_path, 'r') as f:
         schema = json.load(f)
-    defaults: Dict[str, Any] = {}
+    return _defaults_from_properties(schema.get('properties', {}))
-    for key, prop in schema.get('properties', {}).items():
-        if isinstance(prop, dict) and 'default' in prop:
-            defaults[key] = prop['default']
-    return defaults
 
 
 def load_harness_spec(plugin_dir: Union[str, Path]) -> Dict[str, Any]:

src/plugin_system/testing/visual_display_manager.py

@@ -31,6 +31,7 @@ from pathlib import Path
 from typing import Any, List, Optional, Tuple
 
 from PIL import Image, ImageDraw, ImageFont
+from src.common.font_layout import load_truetype
 
 from src.logging_config import get_logger
 
@@ -70,6 +71,7 @@ class VisualTestDisplayManager:
         # Canvas
         self.image = Image.new('RGB', (width, height), (0, 0, 0))
         self.draw = ImageDraw.Draw(self.image)
+        self.draw.fontmode = "1"  # Match production: 1-bit text, so goldens show what the panel shows.
 
         # Matrix proxy (plugins access display_manager.matrix.width/height)
         self.matrix = _MatrixProxy(width, height)
@@ -140,8 +142,8 @@ class VisualTestDisplayManager:
 
             # Press Start 2P — regular and small (both 8px)
             ttf_path = str(fonts_dir / 'PressStart2P-Regular.ttf')
-            self.regular_font = ImageFont.truetype(ttf_path, 8)
+            self.regular_font = load_truetype(ttf_path, 8)
-            self.small_font = ImageFont.truetype(ttf_path, 8)
+            self.small_font = load_truetype(ttf_path, 8)
             self.font = self.regular_font  # alias used by some code paths
 
             # 5x7 BDF font via freetype
@@ -161,7 +163,7 @@ class VisualTestDisplayManager:
             # 4x6 extra small TTF
             try:
                 xs_path = str(fonts_dir / '4x6-font.ttf')
-                self.extra_small_font = ImageFont.truetype(xs_path, 6)
+                self.extra_small_font = load_truetype(xs_path, 6)
             except (FileNotFoundError, OSError) as e:
                 logger.debug("Extra small font not available, using fallback: %s", e)
                 self.extra_small_font = self.small_font
@@ -184,6 +186,7 @@ class VisualTestDisplayManager:
         self.clear_called = True
         self.image = Image.new('RGB', (self._width, self._height), (0, 0, 0))
         self.draw = ImageDraw.Draw(self.image)
+        self.draw.fontmode = "1"  # Match production: 1-bit text, so goldens show what the panel shows.
 
     def update_display(self):
         """No-op for hardware; marks that display was updated."""
@@ -211,6 +214,7 @@ class VisualTestDisplayManager:
             self.matrix = _MatrixProxy(target_w, target_h)
             self.image = Image.new('RGB', (target_w, target_h), (0, 0, 0))
             self.draw = ImageDraw.Draw(self.image)
+            self.draw.fontmode = "1"  # Match production: 1-bit text, so goldens show what the panel shows.
             yield
         finally:
             self._width, self._height = prev_w, prev_h
@@ -503,9 +507,18 @@ class VisualTestDisplayManager:
     # Scrolling state (no-op interface compat)
     # ------------------------------------------------------------------
 
-    def set_scrolling_state(self, is_scrolling: bool):
+    def set_scrolling_state(self, is_scrolling: bool, frame_hold: int = 1):
-        """Set the current scrolling state (no-op for testing)."""
+        """Set the current scrolling state (no-op for testing).
+
+        ``frame_hold`` mirrors the DisplayManager signature this change adds.
+        The two are kept in step deliberately: a double that accepts arguments
+        production does not lets a call pass every harness run and then raise
+        TypeError on the panel, and a double that lacks one production has
+        fails every render of a plugin that legitimately paces its scroll.
+        Plugins begin passing it in ledmatrix-plugins#462.
+        """
         self._scrolling_state['is_scrolling'] = is_scrolling
+        self._scrolling_state['frame_hold'] = frame_hold
         if is_scrolling:
             self._scrolling_state['last_scroll_activity'] = time.time()
 
@@ -569,6 +582,7 @@ class VisualTestDisplayManager:
         self.draw_calls = []
         self.image = Image.new('RGB', (self._width, self._height), (0, 0, 0))
         self.draw = ImageDraw.Draw(self.image)
+        self.draw.fontmode = "1"  # Match production: 1-bit text, so goldens show what the panel shows.
         self._scrolling_state = {
             'is_scrolling': False,
             'last_scroll_activity': 0,
@@ -582,3 +596,4 @@ class VisualTestDisplayManager:
         """Clean up resources."""
         self.image = Image.new('RGB', (self._width, self._height), (0, 0, 0))
         self.draw = ImageDraw.Draw(self.image)
+        self.draw.fontmode = "1"  # Match production: 1-bit text, so goldens show what the panel shows.

systemd/README.md

@@ -19,12 +19,35 @@ This directory contains systemd service unit files for LEDMatrix services.
   - Automatically enables/disables access point mode
   - Uses `scripts/utils/wifi_monitor_daemon.py`
 
+- **`ledmatrix-dns-fix.service`** - DNS single-request fix (optional)
+  - Re-applies `options single-request` to the resolver on every boot,
+    because whatever manages `resolv.conf` regenerates it and drops the
+    option again
+  - Works around glibc's parallel A/AAAA lookup stalling ~5s per name on
+    routers that answer only the A query, which makes any plugin calling an
+    external API slow or (for Starlark apps, which have a render timeout)
+    fail outright
+  - Uses `scripts/utils/apply_dns_single_request.sh`
+  - Install only if external API calls are timing out; it is not part of a
+    normal install
+
+- **`ledmatrix-mqtt-bridge.service`** - Home Assistant MQTT bridge (optional)
+  - Exposes the display to Home Assistant over MQTT Discovery: force a mode,
+    stop on-demand, toggle power, set brightness
+  - Uses `integrations/mqtt_bridge/ledmatrix_mqtt_bridge.py`, which drives the
+    web API rather than the display directly
+  - Needs `integrations/mqtt_bridge/bridge_config.json`; see that directory's
+    README
+
 ## Installation
 
 These service files are installed by the installation scripts in `scripts/install/`:
 - `install_service.sh` installs `ledmatrix.service`
 - `install_web_service.sh` installs `ledmatrix-web.service`
 - `install_wifi_monitor.sh` installs `ledmatrix-wifi-monitor.service`
+- `install_dns_fix.sh` installs `ledmatrix-dns-fix.service` (opt-in, not run
+  by the normal installer)
+- `install_mqtt_bridge.sh` installs `ledmatrix-mqtt-bridge.service` (opt-in)
 
 ## Manual Installation
 

systemd/ledmatrix-dns-fix.service

@@ -0,0 +1,16 @@
+[Unit]
+Description=LED Matrix DNS single-request fix (works around slow A/AAAA lookups)
+After=network-online.target NetworkManager.service
+Wants=network-online.target
+Before=ledmatrix.service
+
+[Service]
+Type=oneshot
+ExecStart=__PROJECT_ROOT_DIR__/scripts/utils/apply_dns_single_request.sh
+RemainAfterExit=yes
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=ledmatrix-dns-fix
+
+[Install]
+WantedBy=multi-user.target

systemd/ledmatrix-mqtt-bridge.service

@@ -0,0 +1,18 @@
+[Unit]
+Description=LED Matrix Home Assistant MQTT Bridge
+After=network-online.target ledmatrix-web.service
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=root
+WorkingDirectory=__PROJECT_ROOT_DIR__
+ExecStart=/usr/bin/python3 __PROJECT_ROOT_DIR__/integrations/mqtt_bridge/ledmatrix_mqtt_bridge.py
+Restart=on-failure
+RestartSec=10
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=ledmatrix-mqtt-bridge
+
+[Install]
+WantedBy=multi-user.target

test/test_api_v3_display_modes.py

@@ -0,0 +1,157 @@
+"""GET /api/v3/display/modes -- the list of modes an on-demand request can name.
+
+Anything driving the display from outside the web UI needs two things that no
+existing endpoint gave it: the set of display modes, and which plugin owns each
+one. /plugins/installed carries neither, so callers read every plugin's
+manifest.json off disk and reimplemented PluginManager's own fallbacks.
+"""
+
+import json
+from unittest.mock import MagicMock
+
+import pytest
+
+from test._api_v3_test_helpers import (  # noqa: F401 - fixtures
+    api_v3_client, api_v3_module,
+)
+
+
+MANIFESTS = {
+    'clock-simple': {'name': 'Simple Clock', 'display_modes': ['clock-simple']},
+    'football-scoreboard': {
+        'name': 'Football Scoreboard',
+        'display_modes': ['nfl_live', 'nfl_recent', 'nfl_upcoming'],
+    },
+    'ledmatrix-weather': {'name': 'Weather', 'display_modes': ['weather']},
+}
+
+CONFIG = {
+    'clock-simple': {'enabled': True},
+    'football-scoreboard': {'enabled': True},
+    'ledmatrix-weather': {'enabled': False},
+}
+
+
+@pytest.fixture
+def client(api_v3_module, api_v3_client):
+    pm = api_v3_module.api_v3.plugin_manager
+    pm.plugin_manifests = MANIFESTS
+    pm.discover_plugins = MagicMock(return_value=list(MANIFESTS))
+    pm.get_plugin_display_modes = MagicMock(
+        side_effect=lambda pid: MANIFESTS[pid]['display_modes'])
+    api_v3_module.api_v3.config_manager.load_config = MagicMock(return_value=CONFIG)
+    return api_v3_client
+
+
+def _modes(response):
+    return {m['mode']: m for m in response.get_json()['data']['modes']}
+
+
+class TestTheModeListing:
+    def test_enabled_plugins_contribute_every_mode(self, client):
+        modes = _modes(client.get('/api/v3/display/modes'))
+        assert set(modes) == {'clock-simple', 'nfl_live', 'nfl_recent', 'nfl_upcoming'}
+
+    def test_each_mode_names_its_plugin(self, client):
+        """on-demand/start's find_plugin_for_mode fallback cannot see generated
+        modes, so the caller has to send plugin_id -- it must come from here."""
+        modes = _modes(client.get('/api/v3/display/modes'))
+        assert modes['nfl_live']['plugin_id'] == 'football-scoreboard'
+
+    def test_disabled_plugins_are_left_out_by_default(self, client):
+        modes = _modes(client.get('/api/v3/display/modes'))
+        assert 'weather' not in modes
+
+    def test_disabled_plugins_can_be_asked_for(self, client):
+        """They are still valid on-demand targets: the controller enables them
+        for the duration of the request."""
+        modes = _modes(client.get('/api/v3/display/modes?include_disabled=1'))
+        assert modes['weather']['enabled'] is False
+
+    def test_a_single_mode_plugin_is_labelled_with_its_own_name(self, client):
+        modes = _modes(client.get('/api/v3/display/modes'))
+        assert modes['clock-simple']['name'] == 'Simple Clock'
+
+    def test_a_multi_mode_plugin_labels_each_mode_distinctly(self, client):
+        """There is no per-mode name anywhere, and three modes all called
+        "Football Scoreboard" are not a usable dropdown."""
+        modes = _modes(client.get('/api/v3/display/modes'))
+        assert modes['nfl_live']['name'] == 'nfl_live'
+        assert modes['nfl_live']['plugin_name'] == 'Football Scoreboard'
+
+
+class TestItWorksForACallerThatNeverOpensTheDashboard:
+    def test_discovery_is_triggered(self, client, api_v3_module):
+        """Discovery is lazy and normally runs because a person loaded the
+        dashboard; a bridge or script would otherwise get an empty list."""
+        client.get('/api/v3/display/modes')
+        api_v3_module.api_v3.plugin_manager.discover_plugins.assert_called_once()
+
+    def test_no_plugin_manager_is_a_clean_error(self, api_v3_module, api_v3_client):
+        api_v3_module.api_v3.plugin_manager = None
+        response = api_v3_client.get('/api/v3/display/modes')
+        assert response.status_code == 500
+        assert response.get_json()['status'] == 'error'
+
+    def test_a_plugin_with_no_declared_modes_still_appears(self, client, api_v3_module):
+        """Its mode is its own id -- the same fallback the controller uses."""
+        pm = api_v3_module.api_v3.plugin_manager
+        pm.plugin_manifests = {'starlark-apps': {'name': 'Starlark Apps', 'display_modes': []}}
+        pm.get_plugin_display_modes = MagicMock(return_value=[])
+        api_v3_module.api_v3.config_manager.load_config = MagicMock(
+            return_value={'starlark-apps': {'enabled': True}})
+
+        modes = _modes(client.get('/api/v3/display/modes'))
+        assert modes['starlark-apps']['plugin_id'] == 'starlark-apps'
+
+
+class TestOneBadConfigSectionDoesNotBlankTheList:
+    """config.json can hold a non-dict under a plugin id.
+
+    DisplayController guards the same shape, so it happens in practice. Here it
+    used to raise AttributeError mid-loop and answer 500 with no modes at all --
+    and the MQTT bridge builds every one of its entities from this list, so one
+    hand-edited section would empty the Home Assistant dropdown.
+    """
+
+    @pytest.fixture
+    def client_with_bad_section(self, api_v3_module, api_v3_client):
+        pm = api_v3_module.api_v3.plugin_manager
+        pm.plugin_manifests = MANIFESTS
+        pm.discover_plugins = MagicMock(return_value=list(MANIFESTS))
+        pm.get_plugin_display_modes = MagicMock(
+            side_effect=lambda pid: MANIFESTS[pid]['display_modes'])
+        api_v3_module.api_v3.config_manager.load_config = MagicMock(return_value={
+            'clock-simple': {'enabled': True},
+            'football-scoreboard': "true",          # a string, not an object
+            'ledmatrix-weather': {'enabled': True},
+        })
+        return api_v3_client
+
+    def test_the_endpoint_still_answers(self, client_with_bad_section):
+        assert client_with_bad_section.get('/api/v3/display/modes').status_code == 200
+
+    def test_the_healthy_plugins_are_still_listed(self, client_with_bad_section):
+        modes = _modes(client_with_bad_section.get('/api/v3/display/modes'))
+        assert 'clock-simple' in modes and 'weather' in modes
+
+    def test_the_bad_section_is_treated_as_disabled(self, client_with_bad_section):
+        modes = _modes(client_with_bad_section.get('/api/v3/display/modes'))
+        assert 'nfl_live' not in modes
+
+    def test_a_failure_is_reported_the_way_every_other_handler_reports_one(
+            self, api_v3_module, api_v3_client):
+        """describe_exception, per test_web_error_detail's contract -- an
+        opaque "see logs for details" is what that test exists to prevent."""
+        api_v3_module.api_v3.plugin_manager.discover_plugins = MagicMock(
+            side_effect=RuntimeError("disk is gone"))
+        resp = api_v3_client.get('/api/v3/display/modes')
+        assert resp.status_code == 500
+        assert 'disk is gone' in resp.get_json()['details']
+
+    def test_credentials_in_the_exception_are_redacted(self, api_v3_module, api_v3_client):
+        """describe_exception is what makes returning detail safe."""
+        api_v3_module.api_v3.plugin_manager.discover_plugins = MagicMock(
+            side_effect=RuntimeError("GET https://x/y?api_key=SEC123 failed"))
+        body = api_v3_client.get('/api/v3/display/modes').get_json()
+        assert 'SEC123' not in json.dumps(body)

test/test_cache_nonfinite_floats.py

@@ -0,0 +1,158 @@
+"""Non-finite floats round-trip identically with and without orjson.
+
+JSON has no NaN or Infinity. The stdlib emits them anyway as an extension;
+orjson refuses to and writes null. Cache files outlive the decision of which
+encoder is installed, so both halves of that gap are pinned here:
+
+  * writing -- installing orjson must not silently change what gets cached,
+    so the stdlib path writes null too;
+  * reading -- records already on disk carrying NaN or Infinity must stay
+    readable, or installing orjson turns each of them into a "corrupted cache
+    file" that DiskCache.get logs as an error and deletes.
+"""
+
+import importlib
+import json
+import math
+import sys
+from pathlib import Path
+from unittest import mock
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from src.cache import disk_cache as disk_cache_module  # noqa: E402
+
+
+@pytest.fixture
+def stdlib_cache():
+    """The module as it loads on a host with no orjson wheel."""
+    # A None entry in sys.modules makes `import orjson` raise ImportError,
+    # which is the branch we want, whether or not orjson is really installed.
+    with mock.patch.dict(sys.modules, {"orjson": None}):
+        module = importlib.reload(disk_cache_module)
+        assert module.orjson is None
+        yield module
+    importlib.reload(disk_cache_module)
+
+
+@pytest.fixture
+def orjson_cache():
+    """The module as it loads with orjson available."""
+    module = importlib.reload(disk_cache_module)
+    if module.orjson is None:
+        pytest.skip("orjson is not installed on this host")
+    return module
+
+
+NON_FINITE = {"nan": float("nan"), "inf": float("inf"), "ninf": float("-inf")}
+
+
+def _reject_constant(name):
+    """Make json.loads as strict as orjson about NaN/Infinity tokens."""
+    raise AssertionError(f"non-spec JSON constant in output: {name}")
+
+
+class TestWritePolicy:
+    """Non-finite floats become null on whichever encoder is in use."""
+
+    def _assert_nulled(self, module):
+        record = module._loads(module._dumps(dict(NON_FINITE, ok=1.5)))
+        assert record["nan"] is None
+        assert record["inf"] is None
+        assert record["ninf"] is None
+        # Finite values are untouched.
+        assert record["ok"] == 1.5
+
+    def test_stdlib_writes_null(self, stdlib_cache):
+        self._assert_nulled(stdlib_cache)
+
+    def test_orjson_writes_null(self, orjson_cache):
+        self._assert_nulled(orjson_cache)
+
+    def test_stdlib_emits_spec_compliant_json(self, stdlib_cache):
+        # The point of the write half: bytes written without orjson must still
+        # parse once orjson is installed later. json.loads accepts the
+        # extension tokens, so it cannot show this -- assert on the bytes, and
+        # on a strict reader when there is one.
+        raw = stdlib_cache._dumps(dict(NON_FINITE))
+        assert b"NaN" not in raw
+        assert b"Infinity" not in raw
+        assert json.loads(raw, parse_constant=_reject_constant) == {
+            "nan": None, "inf": None, "ninf": None}
+
+    def test_nested_non_finite_are_replaced(self, stdlib_cache):
+        data = {"a": [1.0, float("nan"), {"b": float("inf")}], "c": (float("-inf"),)}
+        record = stdlib_cache._loads(stdlib_cache._dumps(data))
+        assert record["a"] == [1.0, None, {"b": None}]
+        assert record["c"] == [None]
+
+    def test_finite_payloads_are_byte_identical_to_the_old_encoder(self, stdlib_cache):
+        # allow_nan=False must not change ordinary output.
+        data = {"x": 1, "y": [1.5, "s", True, None], "z": {"k": 2.25}}
+        assert stdlib_cache._dumps(data) == json.dumps(
+            data, cls=stdlib_cache.DateTimeEncoder).encode("utf-8")
+
+
+class TestReplaceNonFinite:
+    def test_leaves_ordinary_values_alone(self):
+        for value in (1, 1.5, "s", True, None, [], {}):
+            assert disk_cache_module._replace_nonfinite(value) == value
+
+    def test_replaces_every_non_finite_float(self):
+        for value in NON_FINITE.values():
+            assert disk_cache_module._replace_nonfinite(value) is None
+
+    def test_walks_nested_containers(self):
+        assert disk_cache_module._replace_nonfinite(
+            {"a": [{"b": float("nan")}]}) == {"a": [{"b": None}]}
+
+
+class TestLegacyRecordsStayReadable:
+    """Files written before orjson arrived still load."""
+
+    LEGACY = b'{"timestamp": 1000.0, "value": NaN, "other": Infinity}'
+
+    def test_stdlib_reads_legacy_tokens(self, stdlib_cache):
+        record = stdlib_cache._loads(self.LEGACY)
+        assert math.isnan(record["value"])
+        assert math.isinf(record["other"])
+
+    def test_orjson_falls_back_for_legacy_tokens(self, orjson_cache):
+        record = orjson_cache._loads(self.LEGACY)
+        assert math.isnan(record["value"])
+        assert math.isinf(record["other"])
+
+    def test_genuinely_malformed_files_still_raise(self, stdlib_cache):
+        with pytest.raises(json.JSONDecodeError):
+            stdlib_cache._loads(b'{"a": ')
+
+    def test_orjson_still_raises_for_malformed_files(self, orjson_cache):
+        with pytest.raises(json.JSONDecodeError):
+            orjson_cache._loads(b'{"a": ')
+
+
+class TestDiskCacheEndToEnd:
+    def _cache(self, module, tmp_path):
+        return module.DiskCache(str(tmp_path))
+
+    def test_legacy_file_is_not_deleted_as_corrupt(self, orjson_cache, tmp_path):
+        cache = self._cache(orjson_cache, tmp_path)
+        path = cache.get_cache_path("legacy")
+        Path(path).write_bytes(
+            b'{"timestamp": %d, "value": NaN}' % int(__import__("time").time()))
+
+        record = cache.get("legacy", max_age=None)
+
+        assert record is not None, "legacy NaN record was treated as corrupt"
+        assert math.isnan(record["value"])
+        assert Path(path).exists(), "legacy NaN record was deleted"
+
+    def test_round_trip_through_set_and_get(self, stdlib_cache, tmp_path):
+        cache = self._cache(stdlib_cache, tmp_path)
+        cache.set("k", {"timestamp": __import__("time").time(),
+                        "value": float("nan")})
+        record = cache.get("k", max_age=None)
+        assert record is not None
+        assert record["value"] is None

test/test_discovery_path_contract.py

@@ -116,6 +116,77 @@ class TestFallbackDivergence:
             plugin_dir / "config_schema.json"
 
 
+class TestRegistryIdVersusDirectoryName:
+    """install_plugin() renames a plugin's directory to the MANIFEST id when it
+    differs from the REGISTRY id, so `stocks` in the registry lands in
+    `ledmatrix-stocks/`. Every path lookup is by directory name, so
+    update_plugin("stocks") used to find nothing and report the plugin as not
+    installed -- silently. Four installed plugins hit this in practice
+    (leaderboard, music, stocks, weather): the user clicks update, nothing
+    happens, no error, and they stay on a stale version indefinitely.
+    """
+
+    def test_resolves_a_plugin_whose_directory_name_differs_from_its_id(self, tmp_path):
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        plugin_dir = _write_plugin(configured, "stocks", dir_name="ledmatrix-stocks")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("stocks") == plugin_dir
+
+    def test_direct_directory_hit_still_wins(self, tmp_path):
+        """The manifest scan is a last resort. A directory named for the id
+        must still be preferred, so the two documented lookups above keep
+        their exact meaning."""
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        direct = _write_plugin(configured, "demo", dir_name="demo")
+        # A second directory whose manifest claims the same id.
+        _write_plugin(configured, "demo", dir_name="zz-other-demo")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("demo") == direct
+
+    def test_unknown_id_is_still_not_found(self, tmp_path):
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        _write_plugin(configured, "stocks", dir_name="ledmatrix-stocks")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("no-such-plugin") is None
+
+    def test_half_finished_installs_are_not_resurrected(self, tmp_path):
+        """A directory renamed aside during install/rollback carries a valid
+        manifest. Matching one would report a ghost plugin as installed."""
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        _write_plugin(configured, "ghost",
+                      dir_name="ghost.standalone-backup-1234")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("ghost") is None
+
+    def test_unreadable_manifest_does_not_break_the_scan(self, tmp_path):
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        broken = configured / "broken-plugin"
+        broken.mkdir()
+        (broken / "manifest.json").write_text("{ not json")
+        wanted = _write_plugin(configured, "stocks", dir_name="ledmatrix-stocks")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("stocks") == wanted
+
+    def test_sibling_plugins_dir_is_searched_too(self, tmp_path):
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        legacy = _write_plugin(tmp_path / "plugins", "weather",
+                               dir_name="ledmatrix-weather")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("weather") == legacy
+
+
 class TestStandaloneBackupContract:
     def test_discovery_skips_backup_dirs(self, tmp_path):
         plugins_dir = tmp_path / "plugins"

test/test_display_dirty_tracking.py

@@ -47,12 +47,17 @@ class _SwapSpy:
     def __init__(self, matrix):
         self.matrix = matrix
         self.count = 0
+        self.last_frame_hold = None
         self._orig = matrix.SwapOnVSync
 
     def __enter__(self):
-        def counting(canvas):
+        def counting(canvas, *args):
+            # *args carries framerate_fraction, which display_manager passes so
+            # a frame can be held for several refreshes. Signature must match
+            # the real binding or the spy hides a TypeError as a failed push.
             self.count += 1
-            return self._orig(canvas)
+            self.last_frame_hold = args[0] if args else 1
+            return self._orig(canvas, *args)
         self.matrix.SwapOnVSync = counting
         return self
 
@@ -109,6 +114,11 @@ class TestDirtyTracking:
         dm.draw.rectangle([0, 0, 30, 8], fill=(255, 255, 0))
         dm.update_display()   # push + snapshot write (first frame)
         assert os.path.exists(dm._snapshot_path)
+        # Backdate the file so the "was it bumped?" check below cannot be
+        # defeated by filesystem mtime granularity -- on Windows two writes in
+        # the same tick get identical timestamps, which made this test fail
+        # roughly two runs in three regardless of the code under test.
+        os.utime(dm._snapshot_path, (time.time() - 60, time.time() - 60))
         first_mtime = os.path.getmtime(dm._snapshot_path)
 
         # Age the write/touch bookkeeping past TOUCH_INTERVAL so the next
@@ -125,6 +135,62 @@ class TestDirtyTracking:
         assert os.path.getmtime(dm._snapshot_path) > first_mtime
 
 
+class TestScrollLock:
+    """Dirty tracking must not skip the panel push while a scroll is running.
+
+    SwapOnVSync is what paces the render loop, so skipping it also skips the
+    wait for the panel. A duplicate frame therefore returns early -- ~8ms
+    instead of ~10ms on a 100Hz panel -- which advances the strip only 0.8px
+    instead of 1.0px, which makes the NEXT frame more likely to be a duplicate
+    too. That is self-sustaining: measured at ~20% duplicate frames mid-scroll
+    on the odds ticker against essentially zero on a lighter plugin with
+    identical scroll settings. Pushing an identical frame costs one canvas
+    copy; falling out of vsync lock costs smooth motion.
+    """
+
+    def test_identical_frames_still_push_while_scrolling(self, dm):
+        dm.draw.rectangle([0, 0, 12, 12], fill=(0, 0, 255))
+        dm.update_display()
+        dm.set_scrolling_state(True)
+        try:
+            with _SwapSpy(dm.matrix) as spy:
+                dm.update_display()
+                dm.update_display()
+                dm.update_display()
+            assert spy.count == 3, "scrolling must stay locked to the panel"
+        finally:
+            dm.set_scrolling_state(False)
+
+    def test_identical_frames_are_skipped_when_not_scrolling(self, dm):
+        """The optimisation still applies to static content."""
+        dm.set_scrolling_state(False)
+        dm.draw.rectangle([0, 0, 14, 14], fill=(255, 0, 255))
+        dm.update_display()
+        with _SwapSpy(dm.matrix) as spy:
+            dm.update_display()
+            dm.update_display()
+        assert spy.count == 0
+
+    def test_stale_scrolling_state_stops_forcing_pushes(self, dm):
+        """A plugin that stops scrolling without saying so must not pin the
+        panel into always-push forever. is_currently_scrolling() expires on
+        its own inactivity threshold, and the skip has to come back with it."""
+        dm.draw.rectangle([0, 0, 16, 16], fill=(0, 255, 255))
+        dm.update_display()
+        dm.set_scrolling_state(True)
+        try:
+            # Backdate the activity marker past the inactivity threshold.
+            dm._scrolling_state['last_scroll_activity'] = (
+                time.time() - dm._scrolling_state['scroll_inactivity_threshold'] - 1.0)
+            assert dm.is_currently_scrolling() is False
+            with _SwapSpy(dm.matrix) as spy:
+                dm.update_display()
+                dm.update_display()
+            assert spy.count == 0
+        finally:
+            dm.set_scrolling_state(False)
+
+
 class TestKillSwitch:
     def test_dirty_tracking_can_be_disabled(self, dm):
         dm._dirty_tracking_enabled = False
@@ -160,3 +226,89 @@ class TestKillSwitch:
 
 if __name__ == "__main__":
     sys.exit(pytest.main([__file__, "-v"]))
+
+
+class TestFrameHold:
+    """Holding a frame for N refreshes is how a scroll runs slower than one
+    pixel per refresh without fractional pixel positions."""
+
+    def test_hold_reaches_swap_on_vsync(self, dm):
+        dm.set_scrolling_state(True)
+        dm.set_frame_hold(3)
+        try:
+            dm.draw.rectangle([0, 0, 9, 9], fill=(120, 0, 200))
+            with _SwapSpy(dm.matrix) as spy:
+                dm.update_display()
+            assert spy.count == 1
+            assert spy.last_frame_hold == 3
+        finally:
+            dm.set_scrolling_state(False)
+
+    def test_default_is_every_refresh(self, dm):
+        dm.set_scrolling_state(True)
+        try:
+            dm.draw.rectangle([0, 0, 11, 11], fill=(0, 120, 200))
+            with _SwapSpy(dm.matrix) as spy:
+                dm.update_display()
+            assert spy.last_frame_hold == 1
+        finally:
+            dm.set_scrolling_state(False)
+
+    def test_hold_resets_when_scrolling_stops(self, dm):
+        """One plugin's pacing must not leak into whatever is on screen next."""
+        dm.set_scrolling_state(True)
+        dm.set_frame_hold(5)
+        dm.set_scrolling_state(False)
+        dm.set_scrolling_state(True)
+        try:
+            dm.draw.rectangle([0, 0, 13, 13], fill=(200, 120, 0))
+            with _SwapSpy(dm.matrix) as spy:
+                dm.update_display()
+            assert spy.last_frame_hold == 1
+        finally:
+            dm.set_scrolling_state(False)
+
+    @pytest.mark.parametrize("bad,expected", [(0, 1), (-4, 1), (None, 1), ("x", 1)])
+    def test_unusable_holds_are_ignored_or_floored(self, dm, bad, expected):
+        dm.set_frame_hold(bad)
+        assert dm._frame_hold == expected
+
+
+class TestFrameHoldLifetime:
+    """The hold must last exactly as long as the scroll that asked for it.
+
+    Plugins share one display manager. A hold applied at plugin construction is
+    wiped the moment any *other* plugin finishes scrolling, so by the time the
+    first plugin renders it is back to one pixel per refresh -- the speed reads
+    correct in the log and is wrong on the panel.
+    """
+
+    def test_scrolling_state_carries_the_hold(self, dm):
+        dm.set_scrolling_state(True, frame_hold=4)
+        try:
+            dm.draw.rectangle([0, 0, 7, 7], fill=(10, 200, 10))
+            with _SwapSpy(dm.matrix) as spy:
+                dm.update_display()
+            assert spy.last_frame_hold == 4
+        finally:
+            dm.set_scrolling_state(False)
+
+    def test_another_plugin_stopping_does_not_strand_a_hold(self, dm):
+        dm.set_scrolling_state(True, frame_hold=3)
+        dm.set_scrolling_state(False)          # some other plugin finishes
+        dm.set_scrolling_state(True)           # a plugin that wants no hold
+        try:
+            dm.draw.rectangle([0, 0, 6, 6], fill=(200, 10, 10))
+            with _SwapSpy(dm.matrix) as spy:
+                dm.update_display()
+            assert spy.last_frame_hold == 1
+        finally:
+            dm.set_scrolling_state(False)
+
+    def test_default_keeps_previous_behaviour(self, dm):
+        """Callers that never heard of frame holds get one frame per refresh."""
+        dm.set_scrolling_state(True)
+        try:
+            assert dm._frame_hold == 1
+        finally:
+            dm.set_scrolling_state(False)

test/test_display_double_parity.py

@@ -0,0 +1,69 @@
+"""The visual-test double must not drift from the real DisplayManager.
+
+Both directions of drift are silent and both are damaging:
+
+  * the double accepts an argument production does not -- the call passes
+    every harness run and raises TypeError on the panel, which is precisely
+    the failure a safety harness exists to prevent;
+  * the double lacks an argument production has -- every plugin that
+    legitimately uses it fails every render, and the harness blames the
+    plugin.
+
+`set_scrolling_state` has been each of those in turn across two branches, so
+the parity is asserted rather than remembered.
+
+Read with ast rather than imported: src/display_manager.py imports rgbmatrix
+at module scope, which is absent anywhere without the panel library, and this
+check should hold on a laptop and in CI as well as on a Pi.
+"""
+
+import ast
+from pathlib import Path
+
+import pytest
+
+ROOT = Path(__file__).resolve().parent.parent
+REAL = ROOT / "src" / "display_manager.py"
+DOUBLE = ROOT / "src" / "plugin_system" / "testing" / "visual_display_manager.py"
+
+#: Methods a plugin calls on whichever manager it is handed.
+SHARED_METHODS = ["set_scrolling_state", "is_currently_scrolling"]
+
+
+def _signature(path: Path, class_hint: str, method: str):
+    """(name, default-repr) pairs for `method`, or None if it is absent."""
+    tree = ast.parse(path.read_text(encoding="utf-8"))
+    for node in ast.walk(tree):
+        if not isinstance(node, ast.ClassDef) or class_hint not in node.name:
+            continue
+        for item in node.body:
+            if isinstance(item, (ast.FunctionDef, ast.AsyncFunctionDef)) and item.name == method:
+                args = [a.arg for a in item.args.args if a.arg != "self"]
+                pad = [None] * (len(args) - len(item.args.defaults))
+                defaults = pad + [ast.unparse(d) for d in item.args.defaults]
+                return list(zip(args, defaults))
+    return None
+
+
+@pytest.mark.parametrize("method", SHARED_METHODS)
+def test_the_double_matches_production(method):
+    real = _signature(REAL, "DisplayManager", method)
+    double = _signature(DOUBLE, "DisplayManager", method)
+
+    assert real is not None, f"DisplayManager lost {method}"
+    assert double is not None, \
+        f"the test double is missing {method}, so every plugin using it fails to render"
+    assert double == real, (
+        f"{method} has drifted: production takes {real}, the double takes {double}. "
+        "A double that is more permissive hides a production TypeError; one that "
+        "is less permissive fails plugins that are actually correct."
+    )
+
+
+def test_frame_hold_is_accepted_by_both():
+    """The specific argument that has drifted twice."""
+    for path, label in ((REAL, "DisplayManager"), (DOUBLE, "VisualTestDisplayManager")):
+        params = dict(_signature(path, "DisplayManager", "set_scrolling_state") or [])
+        assert "frame_hold" in params, f"{label} does not accept frame_hold"
+        assert params["frame_hold"] == "1", \
+            f"{label} must default frame_hold to 1 so existing callers are unaffected"

test/test_harness_empty_claimed.py

@@ -101,3 +101,61 @@ class TestSkippedResults:
         r = _result(None, returned=None)
         check_empty_claimed([r], strict=True)
         assert r.empty_claimed is None
+
+
+class TestSettleRecordsLaterFailures:
+    """A mode that renders one good frame and then crashes is broken.
+
+    _settle_loop re-renders a mode that came back blank, to give a scroll or an
+    animation time to put something on the panel. Swallowing an exception from
+    those later frames meant the harness reported a passing result for a mode
+    that crashes as soon as it is asked for a second frame -- exactly the kind
+    of defect the harness exists to catch.
+    """
+
+    class Boom:
+        """Renders once, then raises."""
+
+        def __init__(self):
+            self.calls = 0
+
+        def display(self, force_clear=False):
+            self.calls += 1
+            raise RuntimeError("second frame exploded")
+
+    def _settle(self, inst, dm, result):
+        from src.plugin_system.testing import harness
+        harness._settle_loop(inst, "mode", dm, result, None)
+
+    def test_the_exception_is_recorded_on_the_result(self, monkeypatch):
+        from src.plugin_system.testing import harness
+        # Keep the probe short; this test is about the error, not the pacing.
+        monkeypatch.setattr(harness, "EMPTY_RECHECK_FRAMES", 1)
+        monkeypatch.setattr(harness, "EMPTY_RECHECK_STEP", 0)
+
+        result = _result(_blank())
+        assert result.error is None
+        self._settle(self.Boom(), _FakeDM(), result)
+
+        assert result.error is not None, "a crash on a later frame was swallowed"
+        assert "second frame exploded" in result.error
+
+    def test_the_already_captured_frame_is_kept(self, monkeypatch):
+        from src.plugin_system.testing import harness
+        monkeypatch.setattr(harness, "EMPTY_RECHECK_FRAMES", 1)
+        monkeypatch.setattr(harness, "EMPTY_RECHECK_STEP", 0)
+
+        image = _blank()
+        result = _result(image)
+        self._settle(self.Boom(), _FakeDM(), result)
+        assert result.image is image, "the good frame was discarded along with the error"
+
+
+class _FakeDM:
+    """Minimal display-manager double for _settle_loop."""
+
+    def get_image(self):
+        return _blank()
+
+    def check_overflow(self):
+        return None

test/test_mqtt_bridge.py

@@ -0,0 +1,329 @@
+"""The Home Assistant MQTT bridge, without a broker or a matrix.
+
+The bridge is a translation layer: one MQTT payload in, one api_v3 call out.
+Everything worth pinning is on that path -- attaching the plugin_id a mode
+needs, rejecting values HA can produce but the API cannot take, and the
+discovery configs HA reads once and caches -- so it is all reachable with a
+fake API client and a pure function.
+"""
+
+import importlib.util
+import json
+import logging
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+BRIDGE_PATH = (Path(__file__).resolve().parent.parent
+               / "integrations" / "mqtt_bridge" / "ledmatrix_mqtt_bridge.py")
+
+
+@pytest.fixture(scope="module")
+def bridge_module():
+    if not BRIDGE_PATH.exists():
+        pytest.skip("mqtt bridge is not present")
+    try:
+        spec = importlib.util.spec_from_file_location("ledmatrix_mqtt_bridge", BRIDGE_PATH)
+        module = importlib.util.module_from_spec(spec)
+        sys.modules[spec.name] = module
+        spec.loader.exec_module(module)
+        return module
+    except ImportError as e:
+        pytest.skip(f"mqtt bridge dependencies are not installed here: {e}")
+    finally:
+        sys.modules.pop("ledmatrix_mqtt_bridge", None)
+
+
+MODES = [
+    {"mode": "clock-simple", "plugin_id": "clock-simple",
+     "plugin_name": "Simple Clock", "name": "Simple Clock", "enabled": True},
+    {"mode": "nfl_live", "plugin_id": "football-scoreboard",
+     "plugin_name": "Football Scoreboard", "name": "nfl_live", "enabled": True},
+    {"mode": "aquarium", "plugin_id": "starlark-apps",
+     "plugin_name": "Starlark Apps", "name": "aquarium", "enabled": True},
+]
+
+
+@pytest.fixture
+def client():
+    """A stand-in for LEDMatrixClient that records what it was asked to do."""
+    fake = MagicMock()
+    fake.list_modes.return_value = list(MODES)
+    fake.start_on_demand.return_value = {"request_id": "r1"}
+    fake.stop_on_demand.return_value = {}
+    fake.set_power.return_value = {}
+    fake.set_brightness.return_value = {}
+    fake.get_brightness.return_value = 90
+    fake.display_status.return_value = {
+        "service": {"active": True},
+        "state": {"active": True, "mode": "nfl_live"},
+    }
+    return fake
+
+
+@pytest.fixture
+def handler(bridge_module, client):
+    h = bridge_module.CommandHandler(client)
+    h.refresh_modes()
+    return h
+
+
+class TestDisplayCommands:
+    def test_a_mode_is_forced_on_demand(self, handler, client):
+        result = handler.handle({"action": "display", "mode": "nfl_live"})
+        assert result["status"] == "success"
+        assert client.start_on_demand.call_args.kwargs["mode"] == "nfl_live"
+
+    def test_the_owning_plugin_is_sent_with_the_mode(self, handler, client):
+        """on-demand/start's find_plugin_for_mode fallback cannot resolve a
+        generated mode, so an omitted plugin_id 404s for every Starlark app."""
+        handler.handle({"action": "display", "mode": "aquarium"})
+        assert client.start_on_demand.call_args.kwargs["plugin_id"] == "starlark-apps"
+
+    def test_a_home_assistant_label_resolves_to_its_mode(self, handler, client):
+        """The select entity shows labels, so that is what comes back."""
+        handler.handle({"action": "display", "mode": "Simple Clock"})
+        assert client.start_on_demand.call_args.kwargs["mode"] == "clock-simple"
+
+    def test_an_unknown_mode_refreshes_before_giving_up(self, handler, client):
+        """A plugin installed since the last refresh is the usual reason."""
+        client.list_modes.return_value = MODES + [
+            {"mode": "new_app", "plugin_id": "starlark-apps", "name": "new_app"}]
+        handler.handle({"action": "display", "mode": "new_app"})
+        assert client.start_on_demand.call_args.kwargs["plugin_id"] == "starlark-apps"
+
+    def test_an_explicit_plugin_id_is_respected(self, handler, client):
+        handler.handle({"action": "display", "mode": "x", "plugin_id": "custom"})
+        assert client.start_on_demand.call_args.kwargs["plugin_id"] == "custom"
+
+    def test_duration_and_pinned_are_passed_through(self, handler, client):
+        handler.handle({"action": "display", "mode": "aquarium",
+                        "duration": 300, "pinned": True})
+        kwargs = client.start_on_demand.call_args.kwargs
+        assert kwargs["duration"] == 300 and kwargs["pinned"] is True
+
+    def test_display_with_nothing_to_show_is_rejected(self, handler, client):
+        result = handler.handle({"action": "display"})
+        assert result["status"] == "error"
+        client.start_on_demand.assert_not_called()
+
+    def test_stop_returns_to_normal_rotation(self, handler, client):
+        assert handler.handle({"action": "stop_display"})["status"] == "success"
+        client.stop_on_demand.assert_called_once()
+
+
+class TestPowerAndBrightness:
+    @pytest.mark.parametrize("state,expected", [("on", True), ("OFF", False), (" On ", True)])
+    def test_power_states_are_accepted(self, handler, client, state, expected):
+        assert handler.handle({"action": "power", "state": state})["status"] == "success"
+        client.set_power.assert_called_with(expected)
+
+    def test_an_unknown_power_state_is_rejected(self, handler, client):
+        assert handler.handle({"action": "power", "state": "maybe"})["status"] == "error"
+        client.set_power.assert_not_called()
+
+    def test_brightness_is_applied(self, handler, client):
+        assert handler.handle({"action": "brightness", "value": 75})["status"] == "success"
+        client.set_brightness.assert_called_with(75)
+
+    def test_a_float_from_home_assistant_is_accepted(self, handler, client):
+        """The number entity publishes "75.0"; int() would raise on that."""
+        handler.handle({"action": "brightness", "value": "75.0"})
+        client.set_brightness.assert_called_with(75)
+
+    @pytest.mark.parametrize("value", [-1, 101, "bright", None])
+    def test_out_of_range_brightness_never_reaches_the_api(self, handler, client, value):
+        assert handler.handle({"action": "brightness", "value": value})["status"] == "error"
+        client.set_brightness.assert_not_called()
+
+
+class TestFailuresAreReportedNotRaised:
+    """A failed command must publish an error, not kill the MQTT loop."""
+
+    def test_an_api_error_becomes_an_error_result(self, handler, client):
+        client.start_on_demand.side_effect = RuntimeError("Display service is not running")
+        result = handler.handle({"action": "display", "mode": "nfl_live"})
+        assert result["status"] == "error"
+        assert "not running" in result["message"]
+
+    def test_an_unknown_action_lists_the_known_ones(self, handler):
+        result = handler.handle({"action": "explode"})
+        assert result["status"] == "error"
+        assert "brightness" in result["message"]
+
+    def test_a_missing_action_is_an_error(self, handler):
+        assert handler.handle({})["status"] == "error"
+
+
+class TestDiscoveryPayloads:
+    """HA reads these once and caches them; a wrong shape is a dead entity."""
+
+    @pytest.fixture
+    def messages(self, bridge_module):
+        return bridge_module.discovery_messages(
+            "ledmatrix/command", "ledmatrix/command/state",
+            "ledmatrix/command/availability", ["Simple Clock", "nfl_live"])
+
+    def test_every_entity_is_published(self, messages):
+        components = {m["topic"].split("/")[1] for m in messages}
+        assert components == {"select", "button", "switch", "number"}
+
+    def test_each_entity_has_a_stable_unique_id(self, messages):
+        """Without one HA cannot let a user rename or reassign the entity."""
+        ids = [m["payload"]["unique_id"] for m in messages]
+        assert len(ids) == len(set(ids)) and all(ids)
+
+    def test_the_select_offers_the_modes_it_was_given(self, messages):
+        select = next(m for m in messages if "/select/" in m["topic"])
+        assert select["payload"]["options"] == ["Simple Clock", "nfl_live"]
+
+    def test_every_entity_shares_the_availability_topic(self, messages):
+        """It is also the bridge's last will, so HA greys the controls out
+        when the bridge dies rather than leaving them silently inert."""
+        assert all(m["payload"]["availability_topic"] == "ledmatrix/command/availability"
+                   for m in messages)
+
+    def test_every_entity_belongs_to_one_device(self, messages):
+        assert all(m["payload"]["device"]["identifiers"] == ["ledmatrix"] for m in messages)
+
+    def test_the_command_templates_are_valid_json_the_handler_accepts(self, messages, handler):
+        """A template that renders malformed JSON fails only at runtime, in HA."""
+        select = next(m for m in messages if "/select/" in m["topic"])
+        rendered = select["payload"]["command_template"].replace("{{ value }}", "nfl_live")
+        assert handler.handle(json.loads(rendered))["status"] == "success"
+
+        number = next(m for m in messages if "/number/" in m["topic"])
+        rendered = number["payload"]["command_template"].replace("{{ value }}", "40")
+        assert handler.handle(json.loads(rendered))["status"] == "success"
+
+    def test_the_switch_payloads_are_valid_json_the_handler_accepts(self, messages, handler):
+        switch = next(m for m in messages if "/switch/" in m["topic"])
+        for key in ("payload_on", "payload_off"):
+            assert handler.handle(json.loads(switch["payload"][key]))["status"] == "success"
+
+    def test_the_button_payload_is_valid_json_the_handler_accepts(self, messages, handler):
+        button = next(m for m in messages if "/button/" in m["topic"])
+        assert handler.handle(json.loads(button["payload"]["payload_press"]))["status"] == "success"
+
+
+class TestStateReporting:
+    def test_state_reflects_the_running_display(self, bridge_module, client):
+        state = bridge_module.read_state(client)
+        assert state == {"power": True, "mode": "nfl_live", "brightness": 90}
+
+    def test_normal_rotation_reports_no_forced_mode(self, bridge_module, client):
+        client.display_status.return_value = {
+            "service": {"active": True}, "state": {"active": False}}
+        assert bridge_module.read_state(client)["mode"] is None
+
+    def test_an_unreachable_field_does_not_blank_the_others(self, bridge_module, client):
+        """A stopped display service still has a brightness worth showing."""
+        client.display_status.side_effect = RuntimeError("connection refused")
+        state = bridge_module.read_state(client)
+        assert state["brightness"] == 90 and state["power"] is False
+
+
+class TestConfigLoading:
+    def test_defaults_apply_when_no_file_exists(self, bridge_module, tmp_path):
+        config = bridge_module.load_config(str(tmp_path / "absent.json"))
+        assert config["mqtt_topic"] == "ledmatrix/command"
+        assert config["mqtt_port"] == 1883
+
+    def test_the_file_overrides_defaults(self, bridge_module, tmp_path):
+        path = tmp_path / "bridge_config.json"
+        path.write_text(json.dumps({"mqtt_host": "broker.local", "mqtt_port": "8883"}))
+        config = bridge_module.load_config(str(path))
+        assert config["mqtt_host"] == "broker.local"
+        assert config["mqtt_port"] == 8883, "a port read from JSON must still be an int"
+
+    def test_the_environment_overrides_the_file(self, bridge_module, tmp_path, monkeypatch):
+        """So a password need not sit in a file the service user can read."""
+        path = tmp_path / "bridge_config.json"
+        path.write_text(json.dumps({"mqtt_password": "from-file"}))
+        monkeypatch.setenv("LEDMATRIX_MQTT_MQTT_PASSWORD", "from-env")
+        assert bridge_module.load_config(str(path))["mqtt_password"] == "from-env"
+
+    def test_the_example_placeholder_password_is_refused(self, bridge_module, tmp_path):
+        """Copying the example unedited must fail loudly, not silently fail to
+        authenticate against the broker."""
+        path = tmp_path / "bridge_config.json"
+        path.write_text(json.dumps(
+            {"mqtt_password": "REPLACE_WITH_YOUR_ACTUAL_MQTT_PASSWORD"}))
+        with pytest.raises(bridge_module.ConfigError):
+            bridge_module.load_config(str(path))
+
+    def test_malformed_json_is_a_clear_error(self, bridge_module, tmp_path):
+        path = tmp_path / "bridge_config.json"
+        path.write_text("{not json")
+        with pytest.raises(bridge_module.ConfigError):
+            bridge_module.load_config(str(path))
+
+    def test_a_non_numeric_port_is_a_clear_error(self, bridge_module, tmp_path):
+        path = tmp_path / "bridge_config.json"
+        path.write_text(json.dumps({"mqtt_port": "not-a-port"}))
+        with pytest.raises(bridge_module.ConfigError):
+            bridge_module.load_config(str(path))
+
+
+class TestTheExampleConfigIsSecureByDefault:
+    """The installer copies bridge_config.example.json verbatim on first run.
+
+    Without TLS the broker password and every display command cross the network
+    in cleartext, so the shipped default has to be the safe one -- a plaintext
+    broker is a deliberate edit, not something you get by not reading.
+    """
+
+    @pytest.fixture
+    def example(self):
+        path = (Path(__file__).resolve().parent.parent
+                / "integrations" / "mqtt_bridge" / "bridge_config.example.json")
+        if not path.exists():
+            pytest.skip("mqtt bridge example config is not present")
+        return json.loads(path.read_text(encoding="utf-8"))
+
+    def test_tls_is_on(self, example):
+        assert example["mqtt_tls"] is True
+
+    def test_the_port_is_the_tls_one(self, example):
+        """1883 with mqtt_tls on would just fail to connect."""
+        assert example["mqtt_port"] == 8883
+
+    def test_certificate_verification_is_not_disabled(self, example):
+        assert example.get("mqtt_tls_insecure", False) is False
+
+    def test_no_password_ships_in_the_example(self, example):
+        assert example["mqtt_password"] is None
+
+    def test_the_example_loads(self, bridge_module, tmp_path):
+        """It is copied verbatim, so it must survive load_config."""
+        path = (Path(__file__).resolve().parent.parent
+                / "integrations" / "mqtt_bridge" / "bridge_config.example.json")
+        config = bridge_module.load_config(str(path))
+        assert config["mqtt_tls"] is True and config["mqtt_port"] == 8883
+
+
+class TestCleartextIsCalledOut:
+    """Turning TLS off is allowed -- the Mosquitto add-on is plaintext on 1883 --
+    but it should not be silent when a password is going over it."""
+
+    def test_a_password_without_tls_warns(self, bridge_module, caplog):
+        with caplog.at_level(logging.WARNING):
+            warned = bridge_module.warn_if_cleartext(
+                {"mqtt_tls": False, "mqtt_password": "hunter2"})
+        assert warned is True
+        assert "unencrypted" in caplog.text
+
+    def test_the_warning_does_not_repeat_the_password(self, bridge_module, caplog):
+        with caplog.at_level(logging.WARNING):
+            bridge_module.warn_if_cleartext({"mqtt_tls": False, "mqtt_password": "hunter2"})
+        assert "hunter2" not in caplog.text
+
+    def test_no_password_means_nothing_to_lose(self, bridge_module):
+        assert bridge_module.warn_if_cleartext(
+            {"mqtt_tls": False, "mqtt_password": None}) is False
+
+    def test_tls_on_does_not_warn(self, bridge_module):
+        assert bridge_module.warn_if_cleartext(
+            {"mqtt_tls": True, "mqtt_password": "hunter2"}) is False

test/test_on_demand_mailbox.py

@@ -0,0 +1,106 @@
+"""The on-demand request mailbox: how often it is read, and how it is consumed.
+
+The mailbox is a cache key the web process writes and the display process
+reads. Two properties matter and neither is obvious from the call site:
+
+  * it is polled after every rendered frame, so an uncached read here is a
+    disk read at frame rate;
+  * consuming it must not throw away a request that arrived while the previous
+    one was being processed.
+"""
+
+from unittest.mock import MagicMock
+
+import pytest
+
+
+class TestPollingIsBounded:
+    """_poll_on_demand_requests runs ~125x/second on a scrolling mode.
+
+    The read is deliberately uncached (memory_ttl=0) because a cached one
+    pinned the first request for an hour. That makes the call a real disk read,
+    so it needs a floor -- without one it was ~125 reads per second to find
+    nothing at all.
+    """
+
+    def test_first_call_always_reads(self, test_display_controller):
+        c = test_display_controller
+        c.cache_manager.get = MagicMock(return_value=None)
+        c._poll_on_demand_requests()
+        assert c.cache_manager.get.call_count == 1
+
+    def test_immediate_second_call_does_not_read(self, test_display_controller):
+        c = test_display_controller
+        c.cache_manager.get = MagicMock(return_value=None)
+        c._poll_on_demand_requests()
+        for _ in range(50):
+            c._poll_on_demand_requests()
+        assert c.cache_manager.get.call_count == 1, "polling was not bounded"
+
+    def test_reads_again_once_the_interval_has_passed(self, test_display_controller, monkeypatch):
+        c = test_display_controller
+        c.cache_manager.get = MagicMock(return_value=None)
+        clock = {"t": 1000.0}
+        monkeypatch.setattr("src.display_controller.time.monotonic", lambda: clock["t"])
+
+        c._poll_on_demand_requests()
+        clock["t"] += c.ON_DEMAND_POLL_INTERVAL / 2
+        c._poll_on_demand_requests()
+        assert c.cache_manager.get.call_count == 1, "read before the interval elapsed"
+
+        clock["t"] += c.ON_DEMAND_POLL_INTERVAL
+        c._poll_on_demand_requests()
+        assert c.cache_manager.get.call_count == 2
+
+    def test_the_interval_is_short_enough_to_feel_instant(self, test_display_controller):
+        # A person clicking in the web UI must not notice the floor.
+        assert test_display_controller.ON_DEMAND_POLL_INTERVAL <= 0.5
+
+
+class TestMailboxIsConsumedByIdentity:
+    """Deleting whatever is in the mailbox loses a request that raced in."""
+
+    def _arrange(self, controller, first, later):
+        """Mailbox returns `first`, then `later` on the pre-delete re-read."""
+        controller.on_demand_active = False
+        controller.on_demand_request_id = None
+        controller._last_on_demand_poll = None
+        reads = iter([first, later])
+
+        def fake_get(key, *a, **kw):
+            if key == 'display_on_demand_request':
+                return next(reads, later)
+            return None  # processed-id lookup
+
+        controller.cache_manager.get = MagicMock(side_effect=fake_get)
+        controller.cache_manager.set = MagicMock()
+        controller.cache_manager.delete = MagicMock()
+        controller._activate_on_demand = MagicMock()
+
+    REQ_A = {'request_id': 'A', 'action': 'start', 'plugin_id': 'p', 'mode': 'm'}
+    REQ_B = {'request_id': 'B', 'action': 'start', 'plugin_id': 'p', 'mode': 'm'}
+
+    def test_own_request_is_deleted(self, test_display_controller):
+        c = test_display_controller
+        self._arrange(c, self.REQ_A, self.REQ_A)
+        c._poll_on_demand_requests()
+        c.cache_manager.delete.assert_called_once_with('display_on_demand_request')
+
+    def test_a_newer_request_is_left_for_the_next_poll(self, test_display_controller):
+        c = test_display_controller
+        self._arrange(c, self.REQ_A, self.REQ_B)
+        c._poll_on_demand_requests()
+        assert c.cache_manager.delete.call_count == 0, \
+            "request B was deleted without ever being processed"
+
+    def test_an_already_empty_mailbox_is_still_cleared(self, test_display_controller):
+        c = test_display_controller
+        self._arrange(c, self.REQ_A, None)
+        c._poll_on_demand_requests()
+        c.cache_manager.delete.assert_called_once_with('display_on_demand_request')
+
+    def test_the_request_is_still_processed(self, test_display_controller):
+        c = test_display_controller
+        self._arrange(c, self.REQ_A, self.REQ_B)
+        c._poll_on_demand_requests()
+        c._activate_on_demand.assert_called_once()

test/test_on_demand_pinning_and_restart.py

@@ -0,0 +1,208 @@
+"""On-demand behaviour that a person can ask for but the controller ignored.
+
+Three separate gaps, all reachable from the web UI's force-display dialog:
+
+  * `pinned` was accepted by the API, stored on the controller and published
+    back in the status payload, but never narrowed the rotation -- a pinned
+    request still cycled every mode its plugin owns;
+  * restarting while on-demand was active loaded *only* the on-demand plugin,
+    so normal rotation had nothing to return to for the life of the process;
+  * a stop request was exempt from the duplicate guards on purpose and was
+    never removed from the mailbox, so it was re-processed on every poll
+    forever.
+"""
+
+from unittest.mock import MagicMock
+
+import pytest
+
+
+def _plugin_with_modes(controller, plugin_id, modes):
+    """Register `modes` as loaded modes belonging to `plugin_id`."""
+    controller.plugin_display_modes[plugin_id] = list(modes)
+    for mode in modes:
+        controller.plugin_modes[mode] = MagicMock(spec=[])
+        controller.mode_to_plugin_id[mode] = plugin_id
+
+
+class TestPinnedNarrowsTheRotation:
+    """A pinned request shows the one mode that was asked for.
+
+    Unpinned stays the default: a sports plugin's modes are views of one
+    subject, so rotating them is right. A Starlark plugin's modes are
+    unrelated widgets, so it is not.
+    """
+
+    MODES = ['app_a', 'app_b', 'app_c']
+
+    def _activate(self, controller, pinned):
+        _plugin_with_modes(controller, 'starlark-apps', self.MODES)
+        controller.available_modes = list(self.MODES)
+        controller._activate_on_demand({
+            'request_id': 'r1',
+            'action': 'start',
+            'plugin_id': 'starlark-apps',
+            'mode': 'app_b',
+            'pinned': pinned,
+        })
+
+    def test_pinned_rotation_holds_the_requested_mode(self, test_display_controller):
+        c = test_display_controller
+        self._activate(c, pinned=True)
+        assert c.on_demand_modes == ['app_b']
+
+    def test_unpinned_still_rotates_the_whole_plugin(self, test_display_controller):
+        c = test_display_controller
+        self._activate(c, pinned=False)
+        assert set(c.on_demand_modes) == set(self.MODES)
+
+    def test_pinned_still_starts_on_the_requested_mode(self, test_display_controller):
+        c = test_display_controller
+        self._activate(c, pinned=True)
+        assert c.current_display_mode == 'app_b'
+
+    def test_the_pin_is_recorded_for_the_status_payload(self, test_display_controller):
+        c = test_display_controller
+        self._activate(c, pinned=True)
+        assert c.on_demand_pinned is True
+
+    def test_an_unresolvable_pin_does_not_empty_the_rotation(self, test_display_controller):
+        """A pin naming a mode outside the plugin must not leave nothing to show."""
+        c = test_display_controller
+        _plugin_with_modes(c, 'starlark-apps', self.MODES)
+        assert c._apply_on_demand_pin(list(self.MODES), 'not_a_mode', True) == self.MODES
+
+
+class TestPinSurvivesARestart:
+    """The pin is part of the request being resumed, not a per-session flag."""
+
+    def test_restored_pinned_state_narrows_the_rotation(self, test_display_controller):
+        c = test_display_controller
+        _plugin_with_modes(c, 'starlark-apps', ['app_a', 'app_b', 'app_c'])
+        c.on_demand_active = True
+        c.on_demand_plugin_id = 'starlark-apps'
+        c.on_demand_mode = 'app_c'
+        c.on_demand_pinned = True
+
+        c._populate_on_demand_modes_from_plugin()
+        assert c.on_demand_modes == ['app_c']
+
+    def test_restored_unpinned_state_keeps_every_mode(self, test_display_controller):
+        c = test_display_controller
+        _plugin_with_modes(c, 'starlark-apps', ['app_a', 'app_b', 'app_c'])
+        c.on_demand_active = True
+        c.on_demand_plugin_id = 'starlark-apps'
+        c.on_demand_mode = 'app_c'
+        c.on_demand_pinned = False
+
+        c._populate_on_demand_modes_from_plugin()
+        assert set(c.on_demand_modes) == {'app_a', 'app_b', 'app_c'}
+
+
+class TestRestartDoesNotStarveTheOtherPlugins:
+    """Restarting mid-on-demand used to load only the on-demand plugin.
+
+    Restarts during an on-demand session are routine -- it is how an update or
+    a config change is applied -- and the panel came back cycling one plugin's
+    modes and nothing else until the on-demand cache was cleared by hand.
+    """
+
+    DISCOVERED = ['clock', 'weather', 'starlark-apps', 'disabled-one']
+
+    @pytest.fixture
+    def controller(self, test_display_controller):
+        c = test_display_controller
+        c.config.update({
+            'clock': {'enabled': True},
+            'weather': {'enabled': True},
+            'starlark-apps': {'enabled': True},
+            'disabled-one': {'enabled': False},
+        })
+        return c
+
+    def test_every_enabled_plugin_still_loads(self, controller):
+        selected = controller._select_startup_plugins(
+            self.DISCOVERED, {'plugin_id': 'starlark-apps', 'mode': 'app_a'})
+        assert set(selected) == {'clock', 'weather', 'starlark-apps'}
+
+    def test_disabled_plugins_are_still_left_out(self, controller):
+        selected = controller._select_startup_plugins(
+            self.DISCOVERED, {'plugin_id': 'starlark-apps', 'mode': 'app_a'})
+        assert 'disabled-one' not in selected
+
+    def test_the_on_demand_state_is_still_restored(self, controller):
+        controller._select_startup_plugins(
+            self.DISCOVERED,
+            {'plugin_id': 'starlark-apps', 'mode': 'app_a', 'pinned': True})
+        assert controller.on_demand_active is True
+        assert controller.on_demand_plugin_id == 'starlark-apps'
+        assert controller.on_demand_mode == 'app_a'
+        assert controller.on_demand_pinned is True
+
+    def test_a_disabled_on_demand_plugin_is_enabled_and_loaded(self, controller):
+        """Otherwise the mode being resumed has nothing behind it."""
+        selected = controller._select_startup_plugins(
+            self.DISCOVERED, {'plugin_id': 'disabled-one', 'mode': 'x'})
+        assert 'disabled-one' in selected
+        assert controller.config['disabled-one']['enabled'] is True
+
+    def test_an_unknown_on_demand_plugin_falls_back_to_normal(self, controller):
+        selected = controller._select_startup_plugins(
+            self.DISCOVERED, {'plugin_id': 'uninstalled', 'mode': 'x'})
+        assert set(selected) == {'clock', 'weather', 'starlark-apps'}
+        assert controller.on_demand_active is False
+
+    def test_no_on_demand_config_is_a_normal_startup(self, controller):
+        selected = controller._select_startup_plugins(self.DISCOVERED, None)
+        assert set(selected) == {'clock', 'weather', 'starlark-apps'}
+        assert controller.on_demand_active is False
+
+
+class TestStopRequestsAreConsumed:
+    """A stop request is exempt from the duplicate guards, so the mailbox
+    delete is the only thing that ends it."""
+
+    STOP = {'request_id': 'S1', 'action': 'stop'}
+
+    def _arrange(self, controller, active):
+        controller.on_demand_active = active
+        controller.on_demand_status = 'active' if active else 'idle'
+        controller._last_on_demand_poll = None
+        controller.cache_manager.get = MagicMock(
+            side_effect=lambda key, *a, **kw:
+                self.STOP if key == 'display_on_demand_request' else None)
+        controller.cache_manager.set = MagicMock()
+        controller.cache_manager.delete = MagicMock()
+        controller._clear_on_demand = MagicMock()
+
+    def test_a_handled_stop_is_removed_from_the_mailbox(self, test_display_controller):
+        c = test_display_controller
+        self._arrange(c, active=True)
+        c._poll_on_demand_requests()
+        c.cache_manager.delete.assert_called_once_with('display_on_demand_request')
+
+    def test_a_stop_arriving_while_idle_is_also_removed(self, test_display_controller):
+        """Otherwise a stop sent to an idle display re-fires forever."""
+        c = test_display_controller
+        self._arrange(c, active=False)
+        c._poll_on_demand_requests()
+        c.cache_manager.delete.assert_called_once_with('display_on_demand_request')
+
+    def test_the_stop_is_still_acted_on(self, test_display_controller):
+        c = test_display_controller
+        self._arrange(c, active=True)
+        c._poll_on_demand_requests()
+        c._clear_on_demand.assert_called_once_with(reason='requested-stop')
+
+    def test_a_start_racing_in_behind_a_stop_is_not_discarded(self, test_display_controller):
+        """The compare-before-delete applies to stops too."""
+        c = test_display_controller
+        self._arrange(c, active=True)
+        newer = {'request_id': 'S2', 'action': 'start', 'plugin_id': 'p', 'mode': 'm'}
+        reads = iter([self.STOP, newer])
+        c.cache_manager.get = MagicMock(
+            side_effect=lambda key, *a, **kw:
+                next(reads, newer) if key == 'display_on_demand_request' else None)
+
+        c._poll_on_demand_requests()
+        assert c.cache_manager.delete.call_count == 0

test/test_pixlet_renderer_contract.py

@@ -0,0 +1,210 @@
+"""starlark-apps PixletRenderer: what reaches Pixlet, and what counts as a render.
+
+Three things a Starlark app can do that the renderer got wrong:
+
+  * put a "|" in a config value -- a shell metacharacter filter dropped the
+    whole key, though the command is a list and no shell is involved;
+  * render nothing -- Pixlet exits 0 and writes a 0-byte file, which was
+    reported as a successful render;
+  * compute its schema at runtime -- the source parser can only read option
+    lists that are written out literally, so a dropdown fed by a live API call
+    came back empty.
+"""
+
+import importlib.util
+import json
+import subprocess
+import sys
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+PLUGIN_DIR = Path(__file__).resolve().parent.parent / "plugin-repos" / "starlark-apps"
+
+
+@pytest.fixture(scope="module")
+def renderer_module():
+    if not PLUGIN_DIR.exists():
+        pytest.skip("starlark-apps plugin is not checked out")
+    sys.path.insert(0, str(PLUGIN_DIR))
+    try:
+        spec = importlib.util.spec_from_file_location(
+            "pixlet_renderer_under_test", PLUGIN_DIR / "pixlet_renderer.py")
+        module = importlib.util.module_from_spec(spec)
+        spec.loader.exec_module(module)
+        return module
+    except Exception as e:  # noqa: BLE001 - optional deps may be absent
+        pytest.skip(f"pixlet_renderer is not importable here: {e}")
+    finally:
+        sys.path.remove(str(PLUGIN_DIR))
+
+
+@pytest.fixture
+def renderer(renderer_module):
+    """A renderer with a known binary and __init__'s binary search bypassed."""
+    r = renderer_module.PixletRenderer.__new__(renderer_module.PixletRenderer)
+    r.timeout = 30
+    r.pixlet_binary = "/usr/local/bin/pixlet"
+    return r
+
+
+def _completed(returncode=0, stdout="", stderr=""):
+    return subprocess.CompletedProcess(args=[], returncode=returncode,
+                                       stdout=stdout, stderr=stderr)
+
+
+class TestConfigValuesReachPixlet:
+    """cmd is a list and there is no shell=True, so nothing here is ever
+    interpreted by a shell -- the filter is defence in depth, not a boundary."""
+
+    def _args_for(self, renderer, tmp_path, config):
+        star = tmp_path / "app.star"
+        star.write_text("# app", encoding="utf-8")
+        out = tmp_path / "out.webp"
+
+        def fake_run(cmd, **kw):
+            out.write_bytes(b"webp-bytes")
+            fake_run.cmd = cmd
+            return _completed()
+
+        with patch.object(subprocess, "run", side_effect=fake_run):
+            renderer.render(str(tmp_path / "app.star"), str(out), config=config)
+        return fake_run.cmd
+
+    def test_a_pipe_in_a_value_is_passed_through(self, renderer, tmp_path):
+        """Real apps use "|" as a separator inside one config value."""
+        args = self._args_for(renderer, tmp_path, {"sign_id": "I-476 North|175659"})
+        assert "sign_id=I-476 North|175659" in args
+
+    def test_a_dropped_value_does_not_take_the_key_with_it(self, renderer, tmp_path):
+        args = self._args_for(renderer, tmp_path, {"sign_id": "I-476 North|175659"})
+        assert any(a.startswith("sign_id=") for a in args)
+
+    @pytest.mark.parametrize("value", [
+        "$(rm -rf /)",
+        "`whoami`",
+        "a;b",
+        "a&b",
+        "a>b",
+        "a<b",
+    ])
+    def test_actual_shell_metacharacters_are_still_dropped(self, renderer, tmp_path, value):
+        args = self._args_for(renderer, tmp_path, {"k": value})
+        assert not any(a.startswith("k=") for a in args)
+
+    def test_an_invalid_key_is_still_dropped(self, renderer, tmp_path):
+        args = self._args_for(renderer, tmp_path, {"bad key!": "x"})
+        assert not any("bad key!" in a for a in args)
+
+
+class TestAnEmptyRenderIsNotASuccess:
+    """Pixlet exits 0 and writes 0 bytes when an app renders no content."""
+
+    def _render(self, renderer, tmp_path, write_bytes):
+        star = tmp_path / "app.star"
+        star.write_text("# app", encoding="utf-8")
+        out = tmp_path / "out.webp"
+
+        def fake_run(cmd, **kw):
+            out.write_bytes(write_bytes)
+            return _completed()
+
+        with patch.object(subprocess, "run", side_effect=fake_run):
+            return renderer.render(str(tmp_path / "app.star"), str(out))
+
+    def test_a_zero_byte_output_is_reported_as_a_failure(self, renderer, tmp_path):
+        ok, error = self._render(renderer, tmp_path, b"")
+        assert ok is False
+        assert "empty" in (error or "").lower()
+
+    def test_a_real_output_still_succeeds(self, renderer, tmp_path):
+        ok, error = self._render(renderer, tmp_path, b"RIFF....WEBP")
+        assert (ok, error) == (True, None)
+
+    def test_a_missing_output_still_fails(self, renderer, tmp_path):
+        star = tmp_path / "app.star"
+        star.write_text("# app", encoding="utf-8")
+        out = tmp_path / "out.webp"
+        with patch.object(subprocess, "run", return_value=_completed()):
+            ok, error = renderer.render(str(tmp_path / "app.star"), str(out))
+        assert ok is False
+        assert "not found" in (error or "").lower()
+
+
+class TestSchemaComesFromPixletWhenItCan:
+    """`pixlet schema` runs get_schema(); the source parser only reads it.
+
+    An app whose dropdown options come from a live API call has no option list
+    anywhere in its source, so the parser reports an empty dropdown and the
+    config form offers nothing to choose.
+    """
+
+    PIXLET_OUTPUT = json.dumps({
+        "version": "1",
+        "schema": [
+            {"id": "roadway", "name": "Roadway", "type": "dropdown",
+             "description": "Pick a road", "options": [{"display": "I-476", "value": "476"}]},
+        ],
+    })
+
+    def test_the_pixlet_output_is_used(self, renderer, tmp_path):
+        star = tmp_path / "app.star"
+        star.write_text("# no schema literal anywhere\n", encoding="utf-8")
+        with patch.object(subprocess, "run",
+                          return_value=_completed(stdout=self.PIXLET_OUTPUT)):
+            ok, schema, error = renderer.extract_schema(str(star))
+        assert ok is True and error is None
+        assert schema["schema"][0]["options"][0]["value"] == "476"
+
+    def test_pixlet_field_keys_are_remapped_for_the_config_form(self, renderer, tmp_path):
+        """The UI reads typeOf/desc; Pixlet emits type/description."""
+        star = tmp_path / "app.star"
+        star.write_text("#\n", encoding="utf-8")
+        with patch.object(subprocess, "run",
+                          return_value=_completed(stdout=self.PIXLET_OUTPUT)):
+            _, schema, _ = renderer.extract_schema(str(star))
+        field = schema["schema"][0]
+        assert field["typeOf"] == "dropdown"
+        assert field["desc"] == "Pick a road"
+        assert "type" not in field and "description" not in field
+
+    @pytest.mark.parametrize("outcome", [
+        {"return_value": _completed(returncode=1, stderr="unknown command \"schema\"")},
+        {"return_value": _completed(stdout="not json at all")},
+        {"side_effect": subprocess.TimeoutExpired(cmd="pixlet", timeout=20)},
+        {"side_effect": OSError("no such binary")},
+    ])
+    def test_it_falls_back_to_the_source_parser(self, renderer, tmp_path, outcome):
+        """Older Pixlet has no `schema` subcommand, and an app can fail to run.
+        Neither should cost the schema an app does state literally."""
+        star = tmp_path / "app.star"
+        star.write_text(
+            'def get_schema():\n'
+            '    return schema.Schema(version = "1", fields = [\n'
+            '        schema.Text(id = "city", name = "City", desc = "Your city",'
+            ' icon = "gear"),\n'
+            '    ])\n',
+            encoding="utf-8")
+        with patch.object(subprocess, "run", **outcome):
+            ok, parsed, error = renderer.extract_schema(str(star))
+        assert ok is True and error is None
+        assert [f["id"] for f in parsed["schema"]] == ["city"]
+
+    def test_no_pixlet_binary_skips_straight_to_the_parser(self, renderer, tmp_path):
+        renderer.pixlet_binary = None
+        star = tmp_path / "app.star"
+        star.write_text("#\n", encoding="utf-8")
+        assert renderer.extract_schema_via_pixlet(str(star)) is None
+
+    def test_a_missing_star_file_is_still_an_error(self, renderer, tmp_path):
+        ok, schema, error = renderer.extract_schema(str(tmp_path / "gone.star"))
+        assert ok is False and schema is None and "not found" in error
+
+    def test_an_unexpected_pixlet_shape_is_not_trusted(self, renderer, tmp_path):
+        """A bare list, or a dict with no schema array, must not reach the UI."""
+        star = tmp_path / "app.star"
+        star.write_text("#\n", encoding="utf-8")
+        with patch.object(subprocess, "run",
+                          return_value=_completed(stdout='["not", "a", "schema"]')):
+            assert renderer.extract_schema_via_pixlet(str(star)) is None

test/test_scroll_config.py

@@ -0,0 +1,467 @@
+"""Tests for the shared scroll configuration resolver."""
+
+import logging
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from src.common.scroll_config import (  # noqa: E402
+    DEFAULT_PIXELS_PER_SECOND,
+    MAX_PIXELS_PER_FRAME,
+    crisp_ladder,
+    solve_crisp,
+    MAX_PIXELS_PER_SECOND,
+    MIN_PIXELS_PER_SECOND,
+    ScrollSettings,
+    configure,
+    refresh_hz_from_config,
+    resolve,
+)
+
+
+class FakeHelper:
+    """Records what configure() applied."""
+
+    def __init__(self, with_optional=True):
+        self.speed = None
+        self.frame_based = None
+        self.target_fps = None
+        if not with_optional:
+            del FakeHelper.set_frame_based_scrolling
+            del FakeHelper.set_target_fps
+
+    def set_scroll_speed(self, speed):
+        self.speed = speed
+
+    def set_frame_based_scrolling(self, enabled):
+        self.frame_based = enabled
+
+    def set_target_fps(self, fps):
+        self.target_fps = fps
+
+
+class FakeDisplayManager:
+    """Records the frame hold configure() applies."""
+
+    def __init__(self):
+        self.hold = None
+
+    def set_frame_hold(self, refreshes):
+        self.hold = refreshes
+
+
+class MinimalHelper:
+    """An older helper exposing only set_scroll_speed."""
+
+    def __init__(self):
+        self.speed = None
+
+    def set_scroll_speed(self, speed):
+        self.speed = speed
+
+
+class TestPrecedence:
+    def test_display_options_pair_wins(self):
+        s = resolve({"display_options": {"scroll_speed": 1.0, "scroll_delay": 0.01}})
+        assert s.pixels_per_second == 100.0
+        assert s.source == "display_options.scroll_speed/delay"
+
+    def test_display_block_used_when_options_absent(self):
+        s = resolve({"display": {"scroll_speed": 2.0, "scroll_delay": 0.01}})
+        assert s.pixels_per_second == 200.0
+        assert s.source == "display.scroll_speed/delay"
+
+    def test_root_pair_used_when_both_blocks_absent(self):
+        s = resolve({"scroll_speed": 1.0, "scroll_delay": 0.02})
+        assert s.pixels_per_second == 50.0
+
+    def test_pixels_per_second_used_when_no_pair_given(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": 120.0}})
+        assert s.pixels_per_second == 120.0
+        assert s.source == "display_options.scroll_pixels_per_second"
+
+    def test_global_display_is_the_last_resort_before_default(self):
+        s = resolve({}, {"display": {"scroll_speed": 1.0, "scroll_delay": 0.005}})
+        assert s.pixels_per_second == 200.0
+
+    def test_default_when_nothing_configured(self):
+        s = resolve({}, {})
+        assert s.pixels_per_second == DEFAULT_PIXELS_PER_SECOND
+        assert s.source == "default"
+
+
+class TestDeprecatedKeyCannotOverrideExplicitPair:
+    """Regression for ChuckBuilds/ledmatrix-plugins#408.
+
+    odds-ticker ranked scroll_pixels_per_second above the documented
+    scroll_speed/scroll_delay pair. Because that key carries a schema default,
+    the documented settings became unreachable for every user and the ticker
+    silently ran at the default speed. The pair must win.
+    """
+
+    def test_pair_beats_pixels_per_second_in_the_same_block(self):
+        s = resolve(
+            {
+                "display_options": {
+                    "scroll_speed": 1.0,
+                    "scroll_delay": 0.01,
+                    "scroll_pixels_per_second": 50.0,  # schema default
+                }
+            }
+        )
+        assert s.pixels_per_second == 100.0
+        assert "scroll_speed/delay" in s.source
+
+    def test_pair_beats_pixels_per_second_in_an_outer_block(self):
+        s = resolve(
+            {
+                "display_options": {"scroll_speed": 1.0, "scroll_delay": 0.01},
+                "scroll_pixels_per_second": 50.0,
+            }
+        )
+        assert s.pixels_per_second == 100.0
+
+
+class TestMalformedValues:
+    @pytest.mark.parametrize("bad", [None, "fast", "", {}, [], float("nan")])
+    def test_unusable_speed_falls_through(self, bad):
+        s = resolve({"display_options": {"scroll_speed": bad, "scroll_delay": 0.01}})
+        assert s.pixels_per_second == DEFAULT_PIXELS_PER_SECOND
+
+    @pytest.mark.parametrize("bad", [0, -5, 0.0])
+    def test_non_positive_values_fall_through(self, bad):
+        s = resolve({"display_options": {"scroll_pixels_per_second": bad}})
+        assert s.pixels_per_second == DEFAULT_PIXELS_PER_SECOND
+
+    def test_booleans_are_not_treated_as_numbers(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": True}})
+        assert s.pixels_per_second == DEFAULT_PIXELS_PER_SECOND
+
+    def test_zero_delay_does_not_divide_by_zero(self):
+        s = resolve({"display_options": {"scroll_speed": 1.0, "scroll_delay": 0}})
+        assert s.pixels_per_second == DEFAULT_PIXELS_PER_SECOND
+
+    def test_non_dict_blocks_are_ignored(self):
+        s = resolve({"display_options": "nonsense", "display": 5})
+        assert s.pixels_per_second == DEFAULT_PIXELS_PER_SECOND
+
+
+class TestClamping:
+    def test_absurdly_fast_is_clamped(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": 100000.0}})
+        assert s.pixels_per_second == MAX_PIXELS_PER_SECOND
+        assert s.warning and "clamped" in s.warning
+
+    def test_absurdly_slow_is_clamped(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": 0.01}})
+        assert s.pixels_per_second == MIN_PIXELS_PER_SECOND
+
+
+class TestWholePixelWarning:
+    """The display rule: whole pixels per refresh, or it judders."""
+
+    def test_no_warning_when_speed_divides_evenly(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": 100.0}}, refresh_hz=100)
+        assert s.warning is None
+        assert s.pixels_per_frame == pytest.approx(1.0)
+
+    def test_no_warning_at_an_integer_multiple(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": 200.0}}, refresh_hz=100)
+        assert s.warning is None
+
+    def test_warns_on_a_half_pixel_per_frame(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": 50.0}}, refresh_hz=100)
+        assert s.warning is not None
+        assert "judder" in s.warning
+        assert "100 px/s" in s.warning
+
+    def test_warns_on_a_fractional_multiple(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": 130.0}}, refresh_hz=100)
+        assert s.warning is not None
+
+    def test_respects_a_non_default_refresh_rate(self):
+        s = resolve({"display_options": {"scroll_pixels_per_second": 150.0}}, refresh_hz=150)
+        assert s.warning is None
+        assert s.pixels_per_frame == pytest.approx(1.0)
+
+
+class TestConfigure:
+    def test_applies_time_based_mode_and_speed(self):
+        helper = FakeHelper()
+        s = configure(helper, {"display_options": {"scroll_speed": 1.0, "scroll_delay": 0.01}})
+        assert helper.speed == 100.0
+        assert helper.frame_based is False, "must not use the wall-clock step gate"
+        assert helper.target_fps == 100.0
+        assert s.pixels_per_second == 100.0
+
+    def test_works_against_a_helper_without_optional_methods(self):
+        helper = MinimalHelper()
+        configure(helper, {"display_options": {"scroll_pixels_per_second": 100.0}})
+        assert helper.speed == 100.0
+
+    def test_snapping_removes_the_judder_warning(self, caplog):
+        """50px/s cannot be shown in whole pixels at 100Hz *per refresh*, but it
+        can as 1px every 2nd refresh -- so once snapped there is nothing to warn
+        about. resolve() alone still warns; configure() resolves it."""
+        assert "judder" in resolve(
+            {"display_options": {"scroll_pixels_per_second": 50.0}},
+            refresh_hz=100).warning
+        helper, dm = FakeHelper(), FakeDisplayManager()
+        with caplog.at_level(logging.WARNING):
+            settings = configure(
+                helper, {"display_options": {"scroll_pixels_per_second": 50.0}},
+                display_manager=dm)
+        assert settings.warning is None
+        assert not [r for r in caplog.records if "judder" in r.getMessage()]
+
+    def test_reports_the_hold_without_applying_it(self):
+        """The hold belongs to a scroll, not a plugin's lifetime -- one left set
+        at construction is wiped as soon as any other plugin stops scrolling.
+        configure() reports it; the caller passes it to set_scrolling_state."""
+        dm = FakeDisplayManager()
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 25.0}},
+                      display_manager=dm)
+        assert s.frame_hold == 4, "25px/s at 100Hz is 1px every 4th refresh"
+        assert dm.hold is None, "must not apply the hold behind the caller's back"
+
+    def test_full_speed_needs_no_hold(self):
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 100.0}},
+                      display_manager=FakeDisplayManager())
+        assert s.frame_hold == 1
+
+    def test_frame_hold_is_one_when_snapping_is_off(self):
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 50.0}},
+                      snap_to_crisp=False)
+        assert s.frame_hold == 1
+
+    def test_snaps_to_the_nearest_crisp_speed_and_reports_both(self):
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 45.0}},
+                      display_manager=FakeDisplayManager())
+        assert s.requested_pixels_per_second == 45.0
+        assert s.pixels_per_second == 50.0
+        assert s.crisp is not None and s.crisp.pixels_per_frame == 1
+
+    def test_snapping_can_be_turned_off(self):
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 45.0}},
+                      snap_to_crisp=False)
+        assert s.pixels_per_second == 45.0
+        assert s.crisp is None
+
+    def test_helper_target_fps_matches_the_presentation_rate(self):
+        """At a hold of 4 the panel still refreshes at 100Hz, but frames are
+        presented at 25/s -- that is the rate the helper should pace to."""
+        helper = FakeHelper()
+        configure(helper, {"display_options": {"scroll_pixels_per_second": 25.0}},
+                  display_manager=FakeDisplayManager())
+        assert helper.target_fps == pytest.approx(25.0)
+
+    def test_returns_settings_describing_the_source(self):
+        s = configure(FakeHelper(), {"display_options": {"scroll_speed": 2.0, "scroll_delay": 0.01}})
+        assert isinstance(s, ScrollSettings)
+        assert "200.0 px/s" in s.describe()
+
+
+class TestRefreshFromConfig:
+    def test_reads_the_hardware_limit(self):
+        assert refresh_hz_from_config(
+            {"display": {"hardware": {"limit_refresh_rate_hz": 150}}}
+        ) == 150.0
+
+    @pytest.mark.parametrize("cfg", [None, {}, {"display": {}}, {"display": {"hardware": {}}},
+                                     "nonsense", {"display": {"hardware": {"limit_refresh_rate_hz": None}}}])
+    def test_falls_back_to_the_default(self, cfg):
+        assert refresh_hz_from_config(cfg) == 100.0
+
+    @pytest.mark.parametrize("cfg", [
+        {"display": "nonsense"},
+        {"display": ["nonsense"]},
+        {"display": 60},
+        {"display": {"hardware": "nonsense"}},
+        {"display": {"hardware": ["nonsense"]}},
+        {"display": {"hardware": 60}},
+    ])
+    def test_malformed_nesting_falls_back_rather_than_raising(self, cfg):
+        # Truthy-but-not-a-mapping at either level used to reach .get() on a
+        # str/list and raise AttributeError out of a function whose whole
+        # contract is "a refresh rate, or the default".
+        assert refresh_hz_from_config(cfg) == 100.0
+
+
+class TestCrispLadder:
+    """Whole-pixel speeds available on a given panel."""
+
+    def test_every_entry_is_exactly_reachable(self):
+        for c in crisp_ladder(100):
+            assert c.pixels_per_second == pytest.approx(
+                c.refresh_hz / c.frame_hold * c.pixels_per_frame)
+
+    def test_sorted_slowest_first(self):
+        speeds = [c.pixels_per_second for c in crisp_ladder(100)]
+        assert speeds == sorted(speeds)
+
+    def test_no_duplicate_speeds(self):
+        speeds = [round(c.pixels_per_second, 3) for c in crisp_ladder(100)]
+        assert len(speeds) == len(set(speeds))
+
+    def test_duplicates_resolve_to_the_smaller_step(self):
+        """100px/s is 1px every refresh or 2px every 2nd; prefer the former."""
+        entry = next(c for c in crisp_ladder(100)
+                     if c.pixels_per_second == pytest.approx(100.0))
+        assert entry.pixels_per_frame == 1
+        assert entry.frame_hold == 1
+
+    def test_ladder_scales_with_the_panel(self):
+        assert any(c.pixels_per_second == pytest.approx(60.0)
+                   for c in crisp_ladder(60))
+        assert any(c.pixels_per_second == pytest.approx(30.0)
+                   for c in crisp_ladder(60))
+
+    def test_full_refresh_speed_is_present(self):
+        for hz in (60, 75, 100, 120):
+            assert any(c.pixels_per_second == pytest.approx(float(hz))
+                       for c in crisp_ladder(hz))
+
+
+class TestSolveCrisp:
+    def test_exact_targets_are_matched_exactly(self):
+        for target in (100, 50, 25, 20):
+            assert solve_crisp(target, 100).pixels_per_second == pytest.approx(target)
+
+    def test_prefers_smooth_motion_over_raw_proximity(self):
+        """30 -> 33.3 (1px, 33fps), not 28.6 (2px at 14fps) which is nearer."""
+        got = solve_crisp(30, 100)
+        assert got.pixels_per_second == pytest.approx(33.333, abs=0.01)
+        assert got.pixels_per_frame == 1
+
+    def test_does_not_chase_a_jumpy_exact_match(self):
+        """45 -> 50 (1px, smooth) beats 42.9 (3px at 14fps)."""
+        assert solve_crisp(45, 100).pixels_per_frame == 1
+
+    def test_allows_a_two_pixel_step_when_it_is_clearly_closer(self):
+        """60 -> 66.7 (2px at 33fps) rather than 50 (1px) which is 17% slow."""
+        got = solve_crisp(60, 100)
+        assert got.pixels_per_second == pytest.approx(66.667, abs=0.01)
+        assert got.pixels_per_frame == 2
+
+    def test_result_is_always_on_the_ladder(self):
+        ladder = {round(c.pixels_per_second, 3) for c in crisp_ladder(100)}
+        for target in range(5, 205, 5):
+            assert round(solve_crisp(target, 100).pixels_per_second, 3) in ladder
+
+    def test_adapts_to_a_slower_panel(self):
+        got = solve_crisp(30, 60)
+        assert got.pixels_per_second == pytest.approx(30.0)
+        assert got.pixels_per_frame == 1
+        assert got.frame_hold == 2
+
+    def test_speeds_beyond_the_panel_clamp_to_the_fastest_available(self):
+        got = solve_crisp(10_000, 100)
+        assert got.frame_hold == 1
+        assert got.pixels_per_frame == MAX_PIXELS_PER_FRAME
+
+    def test_steppiness_labels_are_sane(self):
+        assert solve_crisp(100, 100).steppiness == "smooth"
+        assert crisp_ladder(100)[0].steppiness == "stepped"
+
+
+class TestRefreshFromDisplayManager:
+    """A plugin sees only its own config section, so the display manager is the
+    authoritative source for the panel's refresh rate."""
+
+    class DM:
+        def __init__(self, hz):
+            self.refresh_hz = hz
+            self.hold = None
+
+        def set_frame_hold(self, refreshes):
+            self.hold = refreshes
+
+    def test_uses_the_display_manager_rate(self):
+        dm = self.DM(60.0)
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 30.0}},
+                      display_manager=dm)
+        # 30px/s on a 60Hz panel is 1px every 2nd refresh, exactly.
+        assert s.pixels_per_second == pytest.approx(30.0)
+        assert s.frame_hold == 2
+
+    def test_explicit_refresh_hz_wins_over_the_display_manager(self):
+        dm = self.DM(60.0)
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 25.0}},
+                      display_manager=dm, refresh_hz=100)
+        assert s.frame_hold == 4, "25px/s at 100Hz is 1px every 4th refresh"
+
+    def test_missing_attribute_falls_back_to_the_default(self):
+        class Bare:
+            def set_frame_hold(self, refreshes):
+                self.hold = refreshes
+
+        bare = Bare()
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 50.0}},
+                      display_manager=bare)
+        assert s.frame_hold == 2, "assumed 100Hz"
+
+    def test_reported_settings_describe_the_display_manager_rate(self):
+        """Without snapping, nothing downstream corrects a wrong refresh rate.
+
+        The rate used to be read *after* resolve() had already filled in
+        target_fps, pixels_per_frame and the judder warning from the 100Hz
+        default -- so on a 60Hz panel every one of those described 100Hz, and
+        set_target_fps() paced the helper to 100 FPS.
+        """
+        dm = self.DM(60.0)
+        helper = FakeHelper()
+        s = configure(helper, {"display_options": {"scroll_pixels_per_second": 30.0}},
+                      display_manager=dm, snap_to_crisp=False)
+
+        assert s.target_fps == pytest.approx(60.0)
+        assert s.pixels_per_frame == pytest.approx(0.5), "30px/s over 60 frames"
+        assert helper.target_fps == pytest.approx(60.0)
+
+    def test_judder_warning_is_computed_at_the_real_refresh_rate(self):
+        dm = self.DM(60.0)
+        # 60px/s is exactly 1px per refresh at 60Hz -- crisp, no warning. At
+        # the 100Hz default it is 0.6px per refresh and would be flagged.
+        s = configure(FakeHelper(), {"display_options": {"scroll_pixels_per_second": 60.0}},
+                      display_manager=dm, snap_to_crisp=False)
+        assert s.warning is None, s.warning
+
+    def test_global_config_supplies_the_rate_without_a_display_manager(self):
+        s = configure(
+            FakeHelper(),
+            {"display_options": {"scroll_pixels_per_second": 30.0}},
+            {"display": {"hardware": {"limit_refresh_rate_hz": 60}}},
+            snap_to_crisp=False,
+        )
+        assert s.target_fps == pytest.approx(60.0)
+
+
+class TestFrameHoldIsReportedNotApplied:
+    """configure() reports the hold; the caller applies it when it scrolls.
+
+    The hold belongs to a scroll, not to a plugin's lifetime -- plugins share
+    one display manager, so one set at construction is reset the moment any
+    other plugin stops scrolling.
+    """
+
+    class RecordingDM:
+        refresh_hz = 100.0
+
+        def __init__(self):
+            self.calls = []
+
+        def set_scrolling_state(self, is_scrolling, frame_hold=1):
+            self.calls.append((is_scrolling, frame_hold))
+
+        def set_frame_hold(self, refreshes):
+            self.calls.append(("set_frame_hold", refreshes))
+
+    def test_configure_does_not_touch_the_display_manager(self):
+        dm = self.RecordingDM()
+        settings = configure(
+            FakeHelper(), {"display_options": {"scroll_pixels_per_second": 25.0}},
+            display_manager=dm)
+        assert dm.calls == [], "configure() must not apply the hold itself"
+        assert settings.frame_hold == 4, "but it must report what to apply"

test/test_scroll_helper.py

@@ -11,7 +11,11 @@ import time
 from unittest.mock import patch
 from PIL import Image
 
-from src.common.scroll_helper import ScrollHelper
+from src.common.scroll_helper import (
+    ScrollHelper,
+    format_frame_stats,
+    frame_stats,
+)
 
 
 DISPLAY_W = 64
@@ -315,3 +319,77 @@ class TestGetScrollInfo:
         helper.scroll_position = 42.0
         info = helper.get_scroll_info()
         assert info["scroll_position"] == 42.0
+
+
+class TestFrameStatsPercentiles:
+    """The stats line is the instrument this whole scroll change is measured
+    with, so its median and p95 have to be the real ones.
+
+    Both are also thresholds: stalls are counted at 1.5x the median and skips
+    at 0.5x, so an off-by-one in the median biases the counts as well as the
+    printed numbers.
+    """
+
+    # 100 samples of 1..100ms. True median 50.5ms (the mean of the two middle
+    # samples, not the upper one at 51ms); nearest-rank p95 is the 95th
+    # sample at 95ms, not the 96th at 96ms.
+    HUNDRED = [i / 1000.0 for i in range(1, 101)]
+
+    def test_even_window_median_averages_both_middle_samples(self):
+        assert frame_stats(self.HUNDRED)["median"] == pytest.approx(0.0505)
+
+    def test_p95_uses_nearest_rank(self):
+        assert frame_stats(self.HUNDRED)["p95"] == pytest.approx(0.095)
+
+    def test_odd_window_median_is_the_middle_sample(self):
+        times = [i / 1000.0 for i in range(1, 102)]  # 101 samples
+        assert frame_stats(times)["median"] == pytest.approx(0.051)
+
+    def test_single_sample_window_does_not_index_out_of_range(self):
+        stats = frame_stats([0.010])
+        assert stats["median"] == pytest.approx(0.010)
+        assert stats["p95"] == pytest.approx(0.010)
+        assert stats["min"] == stats["max"] == pytest.approx(0.010)
+
+    def test_two_sample_window(self):
+        stats = frame_stats([0.010, 0.020])
+        assert stats["median"] == pytest.approx(0.015)
+        assert stats["p95"] == pytest.approx(0.020)
+
+    def test_input_order_does_not_matter(self):
+        assert frame_stats(list(reversed(self.HUNDRED))) == frame_stats(self.HUNDRED)
+
+    def test_caller_window_is_not_mutated(self):
+        times = [0.030, 0.010, 0.020]
+        frame_stats(times)
+        assert times == [0.030, 0.010, 0.020]
+
+    def test_stall_threshold_follows_the_median(self):
+        # Ten 10ms frames and two 30ms stalls: median 10ms, so >15ms is a
+        # stall -- exactly the two.
+        stats = frame_stats([0.010] * 10 + [0.030] * 2)
+        assert stats["stalls"] == 2
+        assert stats["skips"] == 0
+
+    def test_skips_are_frames_that_never_reached_the_panel(self):
+        stats = frame_stats([0.010] * 10 + [0.002] * 3)
+        assert stats["skips"] == 3
+        assert stats["stalls"] == 0
+
+    def test_fps_is_the_reciprocal_of_the_mean(self):
+        assert frame_stats([0.010] * 50)["fps"] == pytest.approx(100.0)
+
+    def test_formatted_line_reports_the_corrected_values(self):
+        line = format_frame_stats(self.HUNDRED)
+        assert "median 50.50ms" in line, line
+        assert "p95 95.00ms" in line, line
+        assert "over 100 frames" in line, line
+
+    def test_log_frame_rate_emits_the_line_and_clears_the_window(self, helper):
+        helper._window = [0.010] * 20
+        helper.last_fps_log_time = 0.0  # force the 5s boundary
+        with patch.object(helper.logger, "info") as info:
+            helper.log_frame_rate()
+        assert info.called
+        assert "Scroll frame stats" in info.call_args[0][0]
+        assert helper._window == []

test/test_sports_shared.py

@@ -319,3 +319,58 @@ class TestLiveMixin:
         assert not hasattr(h, "_empty_live_streak")
         h._note_live_fetch(False)
         assert h._empty_live_streak == 1
+
+
+class TestPluginDirIsToldNotDeduced:
+    """The regression that shipped: _plugin_dir returned None in production.
+
+    The first version walked the MRO for a class whose module sits beside a
+    config_schema.json. That passes when a test imports the plugin directly --
+    which is how it was verified -- and returns None under the real plugin
+    loader, which imports modules by a path that leaves no such entry on the
+    MRO.
+
+    Silent, and expensive: no schema means _schema_font_size returns None for
+    every element, so a configured size equal to the schema default stops
+    looking like a default, is treated as a deliberate choice, and skips the
+    grid snap. 4x6-font.ttf then renders at 6 rather than 7 -- 3px-wide glyphs
+    instead of 4px. On a 256x64 panel that made the odds, the records and the
+    date row illegible. A user counted the pixels; no gate here caught it.
+    """
+
+    def test_a_declared_directory_is_used(self, tmp_path):
+        d = _write_plugin(tmp_path, "declared")
+        host = type("H", (SportsCoreSharedMixin,), {"_PLUGIN_DIR": str(d)})()
+        assert host._plugin_dir() == str(d)
+
+    def test_it_works_when_no_module_on_the_mro_helps(self, tmp_path, monkeypatch):
+        """The production case: nothing on the MRO sits beside a schema."""
+        d = _write_plugin(tmp_path, "loaderstyle")
+        # A class whose module is not importable by name, as the loader produces.
+        cls = type("Loaded", (SportsCoreSharedMixin,), {"_PLUGIN_DIR": str(d)})
+        cls.__module__ = "a.module.name.that.is.not.in.sys.modules"
+        assert cls.__new__(cls)._plugin_dir() == str(d), (
+            "the declared directory must win when the MRO walk cannot help")
+
+    def test_without_it_the_mro_walk_would_have_failed(self):
+        # Pin the precondition, so this test still means something if the
+        # fallback is ever changed.
+        cls = type("Orphan", (SportsCoreSharedMixin,), {})
+        cls.__module__ = "not.a.real.module"
+        assert cls.__new__(cls)._plugin_dir() is None
+
+    def test_a_declared_directory_without_a_schema_is_not_trusted(self, tmp_path):
+        # A stale or wrong path must not shadow the fallback.
+        empty = tmp_path / "noschema"
+        empty.mkdir()
+        d = _write_plugin(tmp_path, "realone")
+        monkey = type("H", (SportsCoreSharedMixin,), {"_PLUGIN_DIR": str(empty)})
+        assert monkey.__new__(monkey)._plugin_dir() != str(empty)
+
+    def test_the_font_size_consequence(self, tmp_path):
+        """End to end: a declared directory restores the schema lookup."""
+        d = _write_plugin(tmp_path, "sizeconseq")
+        host = type("H", (SportsCoreSharedMixin,), {"_PLUGIN_DIR": str(d)})()
+        assert host._schema_font_size("score") == 16, (
+            "without the schema this is None, which is what made a configured "
+            "size look user-chosen and skipped the grid snap")

test/test_starlark_display_contract.py

@@ -0,0 +1,205 @@
+"""starlark-apps: display() must report what actually reached the panel.
+
+The display controller skips a mode only on a boolean False. Returning True
+after the frame update failed told it the mode had rendered, so it held a dead
+frame for the whole display_duration instead of rotating on -- the same class
+of defect as a display() that returns None.
+"""
+
+import sys
+import types
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import pytest
+
+PLUGIN_DIR = Path(__file__).resolve().parent.parent / "plugin-repos" / "starlark-apps"
+
+
+@pytest.fixture(scope="module")
+def manager_module():
+    if not PLUGIN_DIR.exists():
+        pytest.skip("starlark-apps plugin is not checked out")
+    sys.path.insert(0, str(PLUGIN_DIR))
+    # fcntl is POSIX-only and the manager imports it at module scope for
+    # manifest locking. None of the display paths under test touch it, so a
+    # stub is what keeps these assertions running on a developer's machine
+    # rather than skipping everywhere but the Pi and CI.
+    injected_fcntl = "fcntl" not in sys.modules
+    if injected_fcntl:
+        stub = types.ModuleType("fcntl")
+        stub.LOCK_EX = 2
+        stub.LOCK_UN = 8
+        stub.flock = lambda *a, **kw: None
+        sys.modules["fcntl"] = stub
+    try:
+        import importlib
+        spec = importlib.util.spec_from_file_location(
+            "starlark_manager_under_test", PLUGIN_DIR / "manager.py")
+        module = importlib.util.module_from_spec(spec)
+        spec.loader.exec_module(module)
+        return module
+    except Exception as e:  # noqa: BLE001 - optional deps (Pillow, pixlet) may be absent
+        pytest.skip(f"starlark-apps manager is not importable here: {e}")
+    finally:
+        sys.path.remove(str(PLUGIN_DIR))
+        if injected_fcntl:
+            sys.modules.pop("fcntl", None)
+
+
+def _plugin(manager_module):
+    """A manager with __init__ bypassed -- only display paths are under test."""
+    cls = manager_module.StarlarkAppsPlugin
+    inst = cls.__new__(cls)
+    inst.logger = MagicMock()
+    inst.display_manager = MagicMock()
+    inst.current_app = None
+    return inst
+
+
+class _App:
+    def __init__(self, frames):
+        self.frames = frames
+        self.current_frame_index = 0
+        self.last_frame_time = 0.0
+        self.app_id = "app"
+
+
+class TestDisplayFramePropagates:
+    def test_a_failed_update_returns_false(self, manager_module):
+        p = _plugin(manager_module)
+        p.current_app = _App([("frame", 100)])
+        p.display_manager.update_display.side_effect = RuntimeError("panel gone")
+
+        assert p._display_frame() is False
+
+    def test_a_good_update_returns_true(self, manager_module):
+        p = _plugin(manager_module)
+        p.current_app = _App([("frame", 100)])
+
+        assert p._display_frame() is True
+
+    def test_no_frames_returns_false(self, manager_module):
+        p = _plugin(manager_module)
+        p.current_app = _App([])
+
+        assert p._display_frame() is False
+
+    def test_display_reports_the_frame_failure(self, manager_module):
+        p = _plugin(manager_module)
+        p.current_app = _App([("frame", 100)])
+        p.display_manager.update_display.side_effect = RuntimeError("panel gone")
+
+        result = p.display()
+
+        assert result is False, "display() claimed success over a failed frame update"
+        assert isinstance(result, bool), "the controller only skips on a real bool"
+
+
+class _SelectableApp(_App):
+    """An app that display() can pick, render and show."""
+
+    def __init__(self, app_id, enabled=True):
+        super().__init__(frames=[("frame", 100)])
+        self.app_id = app_id
+        self._enabled = enabled
+
+    def is_enabled(self):
+        return self._enabled
+
+
+def _plugin_with_apps(manager_module, *app_ids):
+    p = _plugin(manager_module)
+    p.apps = {app_id: _SelectableApp(app_id) for app_id in app_ids}
+    p._display_frame = lambda: True
+    return p
+
+
+class TestDisplayModeSelectsTheApp:
+    """The controller passes the mode it is rotating to; the plugin must use it.
+
+    It inspects display()'s signature to decide whether to pass display_mode at
+    all, so the parameter is the whole mechanism -- without it there is no way
+    to address one specific app, including from an on-demand request pinned to
+    one.
+    """
+
+    def test_display_accepts_display_mode(self, manager_module):
+        import inspect
+        params = inspect.signature(manager_module.StarlarkAppsPlugin.display).parameters
+        assert "display_mode" in params, \
+            "the controller only passes display_mode to plugins whose signature accepts it"
+
+    def test_a_named_app_is_the_one_shown(self, manager_module):
+        p = _plugin_with_apps(manager_module, "aquarium", "printer", "nowplaying")
+        assert p.display(display_mode="printer") is True
+        assert p.current_app.app_id == "printer"
+
+    def test_a_named_app_wins_over_the_one_already_showing(self, manager_module):
+        p = _plugin_with_apps(manager_module, "aquarium", "printer")
+        p.display(display_mode="aquarium")
+        p.display(display_mode="printer")
+        assert p.current_app.app_id == "printer"
+
+    def test_an_unknown_mode_falls_back_to_rotation(self, manager_module):
+        """The plugin id arrives here when no per-app modes are exposed."""
+        p = _plugin_with_apps(manager_module, "aquarium")
+        assert p.display(display_mode="starlark-apps") is True
+        assert p.current_app.app_id == "aquarium"
+
+    def test_force_clear_does_not_override_a_named_app(self, manager_module):
+        p = _plugin_with_apps(manager_module, "aquarium", "printer")
+        p.display(display_mode="printer", force_clear=True)
+        assert p.current_app.app_id == "printer"
+
+
+class TestInstalledAppsTakeTurns:
+    """Every installed app gets shown, not just whichever was picked first.
+
+    _select_next_app ran only while current_app was unset, so the first enabled
+    app was chosen once and displayed forever; the rest were rendered on
+    schedule and never reached the panel.
+    """
+
+    def test_each_entry_to_the_mode_advances(self, manager_module):
+        p = _plugin_with_apps(manager_module, "a", "b", "c")
+        seen = []
+        for _ in range(3):
+            p.display(force_clear=True)          # force_clear = "you are up"
+            seen.append(p.current_app.app_id)
+        assert seen == ["a", "b", "c"]
+
+    def test_the_rotation_wraps(self, manager_module):
+        p = _plugin_with_apps(manager_module, "a", "b")
+        seen = []
+        for _ in range(4):
+            p.display(force_clear=True)
+            seen.append(p.current_app.app_id)
+        assert seen == ["a", "b", "a", "b"]
+
+    def test_frames_within_one_slot_do_not_advance_the_app(self, manager_module):
+        """Only entry to the mode rotates -- the high-FPS loop must not."""
+        p = _plugin_with_apps(manager_module, "a", "b", "c")
+        p.display(force_clear=True)
+        for _ in range(20):
+            p.display(force_clear=False)
+        assert p.current_app.app_id == "a"
+
+    def test_a_disabled_app_is_skipped(self, manager_module):
+        p = _plugin_with_apps(manager_module, "a", "b")
+        p.apps["a"]._enabled = False
+        p.display(force_clear=True)
+        assert p.current_app.app_id == "b"
+
+    def test_no_enabled_apps_reports_nothing_displayed(self, manager_module):
+        p = _plugin_with_apps(manager_module, "a")
+        p.apps["a"]._enabled = False
+        assert p.display(force_clear=True) is False
+
+
+class TestAnimationsRunAtFrameRate:
+    def test_the_plugin_asks_for_the_high_fps_loop(self, manager_module):
+        """The controller reads this attribute; a multi-frame app is otherwise
+        called once per rotation slot and never advances past frame one."""
+        plugin = manager_module.StarlarkAppsPlugin
+        assert getattr(plugin, "enable_scrolling", False) is True

test/web_interface/test_starlark_pixlet_routes.py

@@ -0,0 +1,395 @@
+"""The Starlark routes the frontend calls must exist.
+
+`plugins_manager.js` posts to /api/v3/starlark/install-pixlet and then reloads
+/api/v3/starlark/status. Neither route existed: #330 rewrote api_v3.py and
+dropped all thirteen Starlark routes that #253 had added, so both calls fell
+through to Flask's 404 handler, which answers
+
+    {"status": "error", "message": "Resource not found"}
+
+and the button reported "Pixlet install failed: Resource not found" -- a
+message that names neither the resource nor the cause.
+
+These assert the routes are registered and answer in the shape the frontend
+reads, so a future rewrite of this file cannot silently drop them again.
+"""
+
+import json
+import os
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+
+@pytest.fixture
+def client():
+    from web_interface.app import app
+    app.config['TESTING'] = True
+    with app.test_client() as c:
+        yield c
+
+
+class TestRoutesAreRegistered:
+    """The failure was a missing route, so check the URL map directly.
+
+    All thirteen, not just the two the Pixlet button needs: #330 dropped the
+    lot, and the app store page is built on repository/browse,
+    repository/categories and repository/install, which 404 the same way.
+    """
+
+    @pytest.mark.parametrize("rule,method", [
+        ("/api/v3/starlark/install-pixlet", "POST"),
+        ("/api/v3/starlark/status", "GET"),
+        ("/api/v3/starlark/apps", "GET"),
+        ("/api/v3/starlark/upload", "POST"),
+        ("/api/v3/starlark/repository/browse", "GET"),
+        ("/api/v3/starlark/repository/categories", "GET"),
+        ("/api/v3/starlark/repository/install", "POST"),
+        ("/api/v3/starlark/apps/<app_id>", "GET"),
+        ("/api/v3/starlark/apps/<app_id>", "DELETE"),
+        ("/api/v3/starlark/apps/<app_id>/config", "GET"),
+        ("/api/v3/starlark/apps/<app_id>/config", "PUT"),
+        ("/api/v3/starlark/apps/<app_id>/toggle", "POST"),
+        ("/api/v3/starlark/apps/<app_id>/render", "POST"),
+    ])
+    def test_route_exists(self, rule, method):
+        from web_interface.app import app
+        matches = [r for r in app.url_map.iter_rules()
+                   if r.rule == rule and method in r.methods]
+        assert matches, (
+            f"{method} {rule} is not registered; the frontend calls it and "
+            "would get Flask's generic 'Resource not found'")
+
+
+class TestInstallPixlet:
+    def test_it_does_not_404(self, client):
+        with patch('web_interface.blueprints.api_v3.subprocess.run') as run:
+            run.return_value = MagicMock(returncode=0, stdout="ok", stderr="")
+            resp = client.post('/api/v3/starlark/install-pixlet')
+        assert resp.status_code != 404, "the route is still missing"
+        assert resp.get_json().get('message') != 'Resource not found'
+
+    def test_success_is_reported_in_the_shape_the_button_reads(self, client):
+        with patch('web_interface.blueprints.api_v3.subprocess.run') as run:
+            run.return_value = MagicMock(returncode=0, stdout="done", stderr="")
+            resp = client.post('/api/v3/starlark/install-pixlet')
+        body = resp.get_json()
+        assert body['status'] == 'success', body
+        assert 'message' in body, "the JS shows data.message on success"
+
+    def test_a_failed_download_says_why(self, client):
+        with patch('web_interface.blueprints.api_v3.subprocess.run') as run:
+            run.return_value = MagicMock(returncode=1, stdout="", stderr="no such release")
+            resp = client.post('/api/v3/starlark/install-pixlet')
+        body = resp.get_json()
+        assert body['status'] == 'error'
+        assert 'no such release' in body['message'], \
+            "the installer's own stderr is what tells the user what went wrong"
+
+    def test_a_timeout_is_reported_rather_than_hanging(self, client):
+        import subprocess as sp
+        with patch('web_interface.blueprints.api_v3.subprocess.run',
+                   side_effect=sp.TimeoutExpired(cmd='x', timeout=300)):
+            resp = client.post('/api/v3/starlark/install-pixlet')
+        assert resp.get_json()['status'] == 'error'
+        assert 'timed out' in resp.get_json()['message'].lower()
+
+
+class TestStarlarkStatus:
+    def test_it_does_not_404(self, client):
+        resp = client.get('/api/v3/starlark/status')
+        assert resp.status_code != 404, "the route is still missing"
+        assert resp.get_json().get('message') != 'Resource not found'
+
+    def test_it_reports_pixlet_availability_without_the_plugin_loaded(self, client):
+        # The status call runs before install too -- it must answer even when
+        # starlark-apps is not loaded, which is the state a user is in when
+        # they press the install button for the first time.
+        with patch('web_interface.blueprints.api_v3._get_starlark_plugin', return_value=None):
+            resp = client.get('/api/v3/starlark/status')
+        body = resp.get_json()
+        assert body['status'] == 'success', body
+        assert 'pixlet_available' in body
+        assert body['plugin_loaded'] is False
+
+
+class TestTheInstallerScriptIsActuallyThere:
+    def test_download_pixlet_script_exists_and_is_executable(self):
+        # install_pixlet chmods and runs this; a missing file is the one error
+        # it reports as a 404 of its own, which would look identical to the
+        # bug being fixed here.
+        import os
+        from pathlib import Path
+        from web_interface.blueprints.api_v3 import PROJECT_ROOT
+        script = Path(PROJECT_ROOT) / 'scripts' / 'download_pixlet.sh'
+        assert script.is_file(), f"{script} is missing; install_pixlet would 404"
+        assert os.access(script, os.R_OK)
+
+
+class TestTheAppStoreFlow:
+    """Browsing and installing from the Tronbyte repository.
+
+    These are the calls the app store page makes. Each returned the generic
+    "Resource not found" before this change, which is indistinguishable from
+    an empty store.
+    """
+
+    @pytest.fixture
+    def offline_repo(self):
+        """No live GitHub calls from the test suite.
+
+        browse and categories reach _get_tronbyte_repository_class() and then
+        list_all_apps_cached(); with a cold server-side cache that is a real
+        network request, which makes the run slow, rate-limitable, and able to
+        pass on a 500 because these assertions only check for a 404.
+        """
+        repo = MagicMock()
+        # Matches what the real list_all_apps_cached returns; the handler
+        # indexes every one of these keys.
+        repo.return_value.list_all_apps_cached.return_value = {
+            'apps': [{'id': 'quoteoftheday', 'name': 'A Quote A Day',
+                      'category': 'text'}],
+            'categories': ['text'],
+            'authors': ['someone'],
+            'count': 1,
+            'cached': True,
+        }
+        repo.return_value.get_rate_limit_info.return_value = {'remaining': 5000}
+        with patch('web_interface.blueprints.api_v3._get_tronbyte_repository_class',
+                   return_value=repo):
+            yield repo
+
+    def test_browse_does_not_404(self, client, offline_repo):
+        resp = client.get('/api/v3/starlark/repository/browse')
+        assert resp.status_code != 404, "the store cannot list anything"
+        assert resp.get_json().get('message') != 'Resource not found'
+
+    def test_browse_returns_the_apps_the_store_lists(self, client, offline_repo):
+        resp = client.get('/api/v3/starlark/repository/browse')
+        body = resp.get_json()
+        assert body['status'] == 'success', body
+        assert any(a.get('id') == 'quoteoftheday' for a in body.get('apps', [])), body
+
+    def test_categories_does_not_404(self, client, offline_repo):
+        resp = client.get('/api/v3/starlark/repository/categories')
+        assert resp.status_code != 404
+        assert resp.get_json().get('message') != 'Resource not found'
+
+    def test_no_live_network_call_is_made(self, client, offline_repo):
+        client.get('/api/v3/starlark/repository/browse')
+        assert offline_repo.called, \
+            "the route did not go through the patched repository class"
+
+    def test_installed_apps_list_does_not_404(self, client):
+        resp = client.get('/api/v3/starlark/apps')
+        assert resp.status_code != 404
+        assert resp.get_json().get('message') != 'Resource not found'
+
+    def test_repository_install_rejects_a_missing_body_rather_than_404ing(self, client):
+        # A 400/422 here is the route working: it received the call and said
+        # what was wrong. A 404 means it was never reached at all.
+        resp = client.post('/api/v3/starlark/repository/install',
+                           json={}, content_type='application/json')
+        assert resp.status_code != 404, "the install route is still missing"
+        assert resp.get_json().get('message') != 'Resource not found'
+
+    def test_upload_rejects_an_empty_post_rather_than_404ing(self, client):
+        resp = client.post('/api/v3/starlark/upload')
+        assert resp.status_code != 404
+        assert resp.get_json().get('message') != 'Resource not found'
+
+
+class TestNoStarlarkRouteIsMissing:
+    """A single check that the whole set is present.
+
+    #330 removed all thirteen at once by rewriting this file. One assertion
+    over the frontend's own list is what would have caught that.
+    """
+
+    def test_every_endpoint_the_frontend_calls_is_registered(self):
+        import re
+        from pathlib import Path
+        from werkzeug.exceptions import MethodNotAllowed, NotFound
+        from web_interface.app import app
+
+        root = Path(__file__).resolve().parent.parent.parent
+        js = (root / 'web_interface' / 'static' / 'v3' / 'plugins_manager.js').read_text()
+
+        # The frontend builds some of these with template literals, e.g.
+        # `/api/v3/starlark/apps/${appId}/toggle`. Substitute a placeholder so
+        # the URL is concrete, then let Werkzeug match it the way a request
+        # would -- string comparison cannot see <app_id> rules.
+        raw = set(re.findall(r"[\'\"`](/api/v3/starlark/[^\'\"`\s]*)", js))
+        urls = set()
+        for u in raw:
+            u = re.sub(r"\$\{[^}]*\}", "probe", u)
+            urls.add(u.rstrip('/') or u)
+        assert urls, "found no starlark calls in the frontend -- did the file move?"
+
+        adapter = app.url_map.bind('localhost')
+        missing = []
+        for u in sorted(urls):
+            try:
+                adapter.match(u, method='GET')
+            except MethodNotAllowed:
+                pass          # route exists, just not for GET -- fine
+            except NotFound:
+                missing.append(u)
+        assert not missing, f"the frontend calls these and they are not registered: {missing}"
+
+
+class TestInstalledAppsAppearWithTheOtherPlugins:
+    """An installed .star app must be manageable like any other plugin.
+
+    #253 surfaced installed apps in /plugins/installed as `starlark:<app_id>`
+    entries, so they could be seen and enabled/disabled from the same list as
+    everything else, and routed `starlark:` toggles to the Starlark manifest.
+    #330 removed both. The result was an app that installs successfully, then
+    appears nowhere and cannot be turned on or off.
+    """
+
+    APPS = {'apps': {'quoteoftheday': {'name': 'A Quote A Day', 'enabled': True}}}
+
+    def test_an_installed_app_is_listed(self, client):
+        with patch('web_interface.blueprints.api_v3._get_starlark_plugin', return_value=None), \
+             patch('web_interface.blueprints.api_v3._read_starlark_manifest', return_value=self.APPS):
+            resp = client.get('/api/v3/plugins/installed')
+        ids = [p['id'] for p in resp.get_json()['data']['plugins']]
+        assert 'starlark:quoteoftheday' in ids, \
+            "an installed Starlark app does not appear among the plugins"
+
+    def test_the_entry_carries_what_the_ui_needs(self, client):
+        with patch('web_interface.blueprints.api_v3._get_starlark_plugin', return_value=None), \
+             patch('web_interface.blueprints.api_v3._read_starlark_manifest', return_value=self.APPS):
+            resp = client.get('/api/v3/plugins/installed')
+        entry = next(p for p in resp.get_json()['data']['plugins']
+                     if p['id'] == 'starlark:quoteoftheday')
+        assert entry['name'] == 'A Quote A Day'
+        assert entry['enabled'] is True
+        assert entry['is_starlark_app'] is True, "the UI keys its Starlark handling off this"
+        assert entry['category'] == 'Starlark App'
+
+    def test_a_starlark_failure_does_not_empty_the_plugin_list(self, client):
+        # The virtual entries are appended to the real ones; a broken manifest
+        # must cost the Starlark rows, not everybody else's.
+        with patch('web_interface.blueprints.api_v3._get_starlark_plugin',
+                   side_effect=RuntimeError('boom')):
+            resp = client.get('/api/v3/plugins/installed')
+        assert resp.status_code == 200
+        assert resp.get_json()['status'] == 'success'
+
+    def test_toggling_an_app_does_not_report_plugin_not_found(self, client):
+        written = {}
+        with patch('web_interface.blueprints.api_v3._get_starlark_plugin', return_value=None), \
+             patch('web_interface.blueprints.api_v3._read_starlark_manifest',
+                   return_value={'apps': {'quoteoftheday': {'enabled': True}}}), \
+             patch('web_interface.blueprints.api_v3._write_starlark_manifest',
+                   side_effect=lambda m: written.update(m) or True):
+            resp = client.post('/api/v3/plugins/toggle',
+                               json={'plugin_id': 'starlark:quoteoftheday', 'enabled': False})
+        body = resp.get_json()
+        assert body['status'] == 'success', body
+        assert body['enabled'] is False
+        assert written['apps']['quoteoftheday']['enabled'] is False, \
+            "the manifest was not actually updated"
+
+    def test_toggling_an_unknown_app_says_so(self, client):
+        with patch('web_interface.blueprints.api_v3._get_starlark_plugin', return_value=None), \
+             patch('web_interface.blueprints.api_v3._read_starlark_manifest',
+                   return_value={'apps': {}}):
+            resp = client.post('/api/v3/plugins/toggle',
+                               json={'plugin_id': 'starlark:nope', 'enabled': True})
+        assert resp.status_code == 404
+        assert 'nope' in resp.get_json()['message']
+
+    def test_a_traversal_app_id_is_rejected_before_touching_the_manifest(self, client):
+        resp = client.post('/api/v3/plugins/toggle',
+                           json={'plugin_id': 'starlark:../../etc/passwd', 'enabled': True})
+        assert resp.status_code == 400
+        assert 'traversal' in resp.get_json()['message']
+
+    def test_an_app_id_the_listing_published_can_be_toggled(self, client):
+        """The id here is exactly what _starlark_virtual_plugins publishes.
+
+        It used to be re-slugified on the way back in -- lowercased, with every
+        character outside [a-z0-9_] replaced -- so an app stored as 'My-App'
+        was listed as 'starlark:My-App' and looked up as 'my_app'. Toggling an
+        app the page had just drawn answered 404.
+        """
+        manifest = {'apps': {'My-App': {'name': 'My App', 'enabled': False}}}
+        with patch('web_interface.blueprints.api_v3._get_starlark_plugin', return_value=None), \
+             patch('web_interface.blueprints.api_v3._read_starlark_manifest',
+                   return_value=manifest), \
+             patch('web_interface.blueprints.api_v3._write_starlark_manifest',
+                   return_value=True) as write:
+            resp = client.post('/api/v3/plugins/toggle',
+                               json={'plugin_id': 'starlark:My-App', 'enabled': True})
+        assert resp.status_code == 200, resp.get_json()
+        assert write.called, "the toggle never reached the manifest"
+        assert manifest['apps']['My-App']['enabled'] is True
+
+    def test_a_loaded_app_missing_from_the_manifest_does_not_500(self, client):
+        """_update_manifest_safe does not catch KeyError, so indexing an entry
+        that is not on disk yet escaped as a 500 instead of writing it."""
+        app = MagicMock()
+        app.manifest = {'enabled': False}
+        plugin = MagicMock()
+        plugin.apps = {'demo': app}
+        written = {}
+
+        def run_updater(fn):
+            fn(written)
+            return True
+
+        plugin._update_manifest_safe.side_effect = run_updater
+
+        with patch('web_interface.blueprints.api_v3._get_starlark_plugin', return_value=plugin):
+            resp = client.post('/api/v3/plugins/toggle',
+                               json={'plugin_id': 'starlark:demo', 'enabled': True})
+        assert resp.status_code == 200, resp.get_json()
+        assert written['apps']['demo']['enabled'] is True
+
+
+class TestTheManifestStaysRelocatable:
+    """`star_file` is joined to the app's own directory by its readers.
+
+    _standalone_render_starlark_app does `app_dir / app_data.get('star_file',
+    f'{app_id}.star')`, so the key's default is a bare filename. Storing an
+    absolute path gave it a second meaning, and Path.__truediv__ discards the
+    left side when the right is absolute -- which pinned the manifest to the
+    PROJECT_ROOT that installed it.
+    """
+
+    @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 _install(self, tmp_path):
+        from web_interface.blueprints import api_v3 as module
+        source = tmp_path / "source.star"
+        source.write_text("# app")
+        with patch.object(module, '_get_pixlet_renderer_class',
+                          side_effect=ImportError("no pixlet here")):
+            assert module._install_star_file('demo', str(source), {'name': 'Demo'})
+        return json.loads((module._STARLARK_MANIFEST_FILE).read_text())['apps']['demo']
+
+    def test_the_star_file_is_recorded_by_name(self, starlark_dir, tmp_path):
+        assert self._install(tmp_path)['star_file'] == 'demo.star'
+
+    def test_the_recorded_path_is_not_absolute(self, starlark_dir, tmp_path):
+        """An absolute value survives a move only by accident."""
+        assert not os.path.isabs(self._install(tmp_path)['star_file'])
+
+    def test_the_value_resolves_against_the_app_directory(self, starlark_dir, tmp_path):
+        """Which is the one thing every reader of this key does with it."""
+        entry = self._install(tmp_path)
+        assert (starlark_dir / 'demo' / entry['star_file']).is_file()
+
+    def test_it_matches_the_default_a_reader_falls_back_to(self, starlark_dir, tmp_path):
+        """Stored and defaulted values must mean the same thing."""
+        assert self._install(tmp_path)['star_file'] == 'demo.star'

web_interface/static/v3/plugins_manager.js

@@ -5945,7 +5945,10 @@ document.addEventListener('htmx:afterSettle', function() {
                 <div class="flex items-start justify-between mb-4">
                     <div class="flex-1 min-w-0">
                         <div class="flex items-center flex-wrap gap-1.5 mb-2">
-                            <h4 class="font-semibold text-gray-900 text-base">${escapeHtml(app.name || app.id)}</h4>
+                            <!-- break-words: Starlark app names come from the
+                                 community repo and some are long single tokens,
+                                 which overflowed the card instead of wrapping. -->
+                            <h4 class="font-semibold text-gray-900 text-base break-words">${escapeHtml(app.name || app.id)}</h4>
                             <span class="badge badge-warning"><i class="fas fa-star mr-1"></i>Starlark</span>
                             ${installed ? '<span class="badge badge-success"><i class="fas fa-check mr-1"></i>Installed</span>' : ''}
                         </div>