refactor(server): extract the settings routes into routers/settings.py (R3)

GET/POST /api/settings, /api/settings/reset, and the two-phase atomic
export/import bundle (/api/settings/export|import) move to lib/routers/settings.py
with their exclusive helpers (the relpath allowlist validator, the atomic writer,
the library-DB snapshot + sqlite integrity gate, the config-type validator, the
bundle schema). Bodies verbatim except @app->@router and the seam reads:
meta_db->appstate.meta_db, CONFIG_DIR->appstate.config_dir,
_running_version->appstate.running_version(), and _default_settings->
appstate.default_settings (the canonical defaults builder stays in server.py —
the scan + artist-links code share it — and is injected as a new seam callable).

server.py: 5,539 -> 4,478 (-1,061).

Verified: pyflakes clean (bar the pre-existing File/safe_join/tuning_name/ET);
route table IDENTICAL (143); full pytest 2397 passed (154 settings cases incl the
export→import round-trip + library-DB snapshot/restore + relpath-allowlist SSRF/
traversal guards, retargeted onto the settings module). eslint 0.

BEHAVIORAL — needs an on-device settings export→import round-trip sign-off before
merge (do not merge on green CI alone).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -123,3 +123,28 @@ jobs:
               sys.exit(1)
           print(f"Validated {len(manifests)} manifest(s) — OK")
           EOF
+
+  lint:
+    # Maintainer/CI-only size + module-hygiene gate (constitution Principle I:
+    # dev tooling, never on the serve/Docker path — same category as
+    # scripts/build-tailwind.sh). max-lines WARNS (the 1,500-line size ratchet;
+    # non-blocking), while import-x/no-unresolved + no-cycle HARD-ERROR on the
+    # ES-module graphs the refactor produces. Exemptions: docs/size-exemptions.md.
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        # npm ci runs third-party postinstall scripts; don't leave the token in
+        # git config for them (this job never pushes).
+        with:
+          persist-credentials: false
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: ESLint (size norm + module hygiene)
+        run: npm run lint

.github/workflows/nightly.yml

@@ -6,7 +6,7 @@ name: Nightly
 # builds from release/** come from rc.yml instead.
 on:
   schedule:
-    - cron: '0 2 * * *'
+    - cron: '0 23 * * *'
   workflow_dispatch:
 
 permissions:

.specify/memory/constitution.md

@@ -48,11 +48,30 @@ output is committed, so Docker / desktop / end users never build. New
 features extend `app.js` and the existing globals (`window.playSong`,
 `window.showScreen`, `window.createHighway`, `window.feedBack`).
 
+Native ES modules are a first-class, build-free extension mechanism.
+Because `<script type="module">` and `import` are browser features — not
+a bundler — a large source file MAY be split into an `import`-ed module
+graph of plain source files, with **no build step and no framework**. A
+plugin opts in with `"scriptType": "module"` in `plugin.json`: its
+`screen.js` becomes a one-line `import './src/main.js'`, and the host
+serves the `src/` subtree from the sandboxed `/api/plugins/<id>/src/…`
+route and injects the entry as `<script type="module">`. The classic
+global-scope `screen.js` path remains fully supported; both coexist, and
+module scripts are still source-served — the no-bundler, no-transpiler,
+build-free-at-serve rule is unchanged. Core's own `static/` tree may
+migrate to the same module-graph shape (`static/js/…`) over time under
+this rule.
+
 **Non-negotiable rules**
 
 - Do not introduce a frontend framework, JSX, or a JS build pipeline in
   core. Plugins MAY ship their own bundled assets but core MUST remain
   source-served.
+- ES-module plugins remain source-served: no bundler or transpiler, and
+  their own asset URLs (worklets, WASM, images) resolve via
+  `import.meta.url` — never `document.currentScript`, which is `null`
+  inside a module. `scriptType:"module"` and the optional `minHost`
+  version floor are the only new `plugin.json` keys the module path adds.
 - Because the core Tailwind stylesheet is prebuilt, it contains only the
   classes present in core source at build time. Core's committed
   `static/tailwind.min.css` MUST stay in sync with source — CI enforces
@@ -214,6 +233,15 @@ no `..`, no absolute paths).
   runs first). Plugins MUST tolerate dependent globals being absent
   at load time and check at runtime
   (`typeof window.X === 'function'`).
+- **Module load contract**: a `scriptType:"module"` plugin is injected
+  as `<script type="module">`, whose load event fires only after its
+  whole static-import graph fetches and evaluates — so the loader's
+  completion-by-`onload` guarantee (and the `playSong` wrapper-chain
+  order above) is preserved exactly. The host loads `screen.js` once per
+  version and `showScreen` re-injects nothing, so a plugin's per-visit
+  re-initialization comes from its `screen:changed` handler, not from
+  screen.js re-running; ES-module plugins inherit this unchanged (module
+  top-level code does not re-execute on same-version re-mount).
 
 ## Development Workflow
 
@@ -256,4 +284,4 @@ no `..`, no absolute paths).
   higher-numbered principle's escape hatch is to live in a plugin
   with its own bundled assets.
 
-**Version**: 1.1.0 | **Ratified**: 2026-05-09 | **Last Amended**: 2026-06-01
+**Version**: 1.2.0 | **Ratified**: 2026-05-09 | **Last Amended**: 2026-07-08

CHANGELOG.md

@@ -7,7 +7,113 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- **The packaged desktop app could not start (`ModuleNotFoundError: No module named
+  'appstate'`).** feedback-desktop's `scripts/bundle-slopsmith.sh` copies a *hardcoded
+  list* of core files into the app bundle — `server.py`, `VERSION`, `lib/`, `data/`,
+  `static/`, `plugins/__init__.py`. The root-level `appstate.py` and `routers/` added in
+  R3 shipped correctly in Docker and passed every test, and were then silently dropped
+  from the packaged app, which died at startup. Both now live under **`lib/`** — the one
+  core directory the Dockerfile (`COPY lib/`), `docker-compose.yml`, and the desktop
+  bundler (`cp -r lib`) all copy wholesale, and that all three put on `sys.path` (on
+  Windows via the embeddable-Python `._pth`, where `PYTHONPATH` is ignored). This needs no
+  change in feedback-desktop and no new release to take effect. Placing them there is also
+  correct under Principle V: with the injection seam, `appstate.py` constructs nothing and
+  does no import-time IO, and a route module only builds an `APIRouter`. The
+  `Dockerfile` / `.dockerignore` / `docker-compose.yml` entries added for the root layout
+  are reverted. New `tests/test_packaging.py` walks `server.py`'s module-level imports and
+  fails if any first-party module resolves outside a directory the packagers copy, so the
+  next root-level module can't ship broken.
+
 ### Added
+- **Perf harness now measures 2D-highway frame time (R3c gate).** `scripts/perf-baseline.mjs` gains a `--song` mode that reports per-frame draw-cost p50/p95/p99 (draw-tagged via `highway.addDrawHook`), the metric that gates the `highway.js` split. Maintainer/CI-only; baseline recorded in `docs/perf-baseline.md`.
+- **`routers/` — extracting `server.py`'s route layer, cheapest-first (R3).** Each PR moves a cohesive route group into a `fastapi.APIRouter` under `lib/routers/`, mounted with `app.include_router(...)` at its original site (FastAPI matches in registration order; the full route table stays byte-identical). Bodies are verbatim — only the decorator receiver (`@app` → `@router`) and singleton reads (`meta_db` → `appstate.meta_db`, resolved at call time) change. So far: `audio_effects` (5), `artist_aliases` (5), `loops` (3), `playlists` (12 + covers), `ws_highway` (the 902-line highway chart WebSocket), `chart` (split/unsplit/work/fileinfo — unblocked by the DLC-path substrate), `library_extras`, `wanted`, `shop`, `progression`, `profile`, `stats` (the `/api/stats/{path}` catch-all stays registered last so it can't shadow `/recent` `/best` `/top`), `version` (`/api/version`; VERSION-file lookup adjusted for the router subdir depth), `art` (the `/api/song/{f}/art*` serve/cover-search/candidates/upload/url + `/api/art/{f}/override` routes; the shared `_song_pack_art_exists`/`_art_override_paths`/`_art_safe_name` helpers stay in `server.py` for the song/delete routes and are reached through the `appstate` seam, the CAA/release transport as `enrichment.X`), and `settings` (`GET`/`POST /api/settings`, `/reset`, and the two-phase atomic export/import bundle `/api/settings/export|import`; the shared `_default_settings` builder stays in `server.py` and is reached through the `appstate` seam), and `diagnostics` (`/api/diagnostics/export|preview|hardware`; the plugins-root lookup adjusted for the router subdir depth, `_running_version` reached through the `appstate` seam, pure payload-cap helpers re-exported for the `server._diag_*` tests), and `tunings` (`/api/tunings`; the pure `config.json` reader moved to `lib/appconfig.py`, the tuning-provider registry read through the `appstate` seam so plugin-contributed tunings still merge). The DLC library-path resolution (`_get_dlc_dir`, pure `_resolve_dlc_path`) moved to `lib/dlc_paths.py`, reading paths through the seam; `config_dir`/`dlc_dir`/`dlc_dir_env` now ride the `appstate` seam (env-derived, so the pop-and-reimport fixtures reconfigure it for free), and the shared request-field sanitizer `_clean_str` moved to `lib/reqfields.py`. The next cut is picked by a dependency-closure scan that ranks groups by how many `monkeypatch.setattr(server, …)` targets they'd drag along.
+- **`routers/` — the first extracted route module (R3).** The five audio-effects mapping
+  endpoints move out of `server.py` into `lib/routers/audio_effects.py` as a
+  `fastapi.APIRouter`, mounted with `app.include_router(...)` **at the point in the file
+  where they used to be defined** — FastAPI matches routes in registration order, so the
+  mount site preserves it. Verified: the full 143-route table (paths, methods, *and*
+  order) is byte-for-byte identical to `main`. Bodies are verbatim; the only edits are
+  the decorator receiver (`@app.get` → `@router.get`) and the singleton read
+  (`audio_effect_mappings` → `appstate.audio_effect_mappings`, a module attribute
+  resolved at call time). This proves the seam from #833 under a real consumer, including
+  the second slot. The `_demo_mode_guard` middleware still blocks all four moved write
+  routes with 403, and `Query(...)` validation still 422s — both checked against a running
+  server. `server.py`: **9,445 → 9,386 lines**.
+- **`lib/enrichment.py` — the metadata-enrichment subsystem leaves `server.py` (R3, move-only).** MusicBrainz / Cover-Art-Archive / AcoustID transport, the match-scorer glue, and the background enrichment worker (~930 lines, 61 defs) move out as one cohesive unit. Bodies are verbatim; the only changes are seam reads — `meta_db`/`config_dir`/`sloppak_cache_dir`/`art_cache_dir` and the two shared art helpers (`song_pack_art_exists`, `art_override_paths`, which stay in `server.py` for the art/delete routes) are reached through `appstate` at call time, and the User-Agent VERSION lookup is corrected for the module's new depth. `server.py` drives the worker through the module (`import enrichment`; the routes + scan lifecycle call `enrichment.X`); tests that faked the network on `server` now patch the same names on `enrichment` (module attribute resolved at call time, so one `setattr` reaches both the routes and the worker's internal callers). Acyclic — `enrichment` imports no `server`. Route table byte-identical; full suite green. `server.py`: 6,917 → 5,988.
+- **`appstate.py` — the router seam (R3).** Route modules moving out of `server.py`
+  need `meta_db` and friends but must not `import server`, or the import graph goes
+  circular the moment `server` imports them back. So `server.py` keeps *constructing*
+  its singletons and now **injects** them once — `appstate.configure(meta_db=…,
+  audio_effect_mappings=…)` — and a router reads them back as module attributes at call
+  time (`import appstate; appstate.meta_db.…`). This is the Python analogue of the
+  frontend refactor's injected `configureX({…})` seams and of the plugin
+  `setup(app, context)` contract: dependencies flow one way, `server → routers →
+  appstate`. Two properties are load-bearing and pinned by `tests/test_appstate.py`:
+  (1) `import appstate` constructs nothing and touches no disk, so the ~49 test fixtures
+  that `sys.modules.pop("server")` + re-import (to rebuild `meta_db` under a patched
+  `CONFIG_DIR`) keep working untouched — a singleton *owned* by `appstate` would survive
+  that pop and go stale; (2) reads must be late-bound (`appstate.meta_db`, never
+  `from appstate import meta_db`), since a `from` import freezes the binding and defeats
+  both a later `configure()` and `monkeypatch.setattr` — the same read-only-binding trap
+  as ES `import`. `configure()` rejects an unknown slot rather than silently creating a
+  global nothing reads, and the suite asserts `server` actually calls it (a seam whose
+  wiring can no-op undetected is worse than no seam). Lives at `lib/appstate.py`.
+
+### Changed
+- **`AudioEffectsMappingDB` moved out of `server.py` into `lib/audio_effects_db.py`
+  (R3, move-only).** The core-owned song/tone → provider routing index follows
+  `MetadataDB` out of the host file, byte-identical apart from the same constructor
+  seam (`__init__` takes `config_dir`; `audio_effect_mappings = AudioEffectsMappingDB(CONFIG_DIR)`),
+  so the module does no IO at import. The singleton stays in `server.py`; no route,
+  no test and no `monkeypatch.setattr(server, …)` target moves. `server.py`:
+  **9,705 → 9,433 lines**.
+- **`MetadataDB` moved out of `server.py` into `lib/metadata_db.py` (R3, move-only).**
+  The library metadata cache — the `MetadataDB` class (4,018 lines) plus the query
+  helpers it owns (keyset paging cursors, the tuning grouping key, smart-arrangement
+  naming, tag normalisation, the startup DB-restore swap) — now lives in its own flat
+  `lib/` module. `server.py` drops from **14,037 → 9,705 lines** and keeps the
+  `meta_db` singleton, so `server.meta_db` and `server.app` resolve exactly as before
+  and every route is untouched. The only non-verbatim change is the seam that lets the
+  class leave `server.py`: `MetadataDB.__init__` now takes `config_dir` explicitly
+  (`meta_db = MetadataDB(CONFIG_DIR)`) instead of reading the module-level `CONFIG_DIR`,
+  which also means `lib/metadata_db.py` performs no IO at import (Principle V). Logging
+  still goes through the `feedBack.server` logger, so existing log filters and `caplog`
+  assertions resolve to the same logger object. `tests/test_settings_export_library_db.py`
+  now imports `_apply_pending_db_restore` from `metadata_db` (the test moved with its
+  subject); no other test changed. Every moved block is byte-identical to its
+  `server.py` original.
+
+### Added
+- **Plugins can ship an ES-module `src/` tree (module-migration rails, R0).** The host gains three things so a plugin can move off a single global-scope `screen.js` IIFE onto native ES modules with **no build step**: (1) a new sandboxed `GET /api/plugins/{id}/src/{path}` route that serves a plugin's `src/` source subtree, containment-checked by the same `safe_join` guard as `assets/` (traversal/absolute/NUL → 404); (2) the live-edit cache contract — `Cache-Control: no-cache` + a weak mtime/size `ETag` + `If-None-Match`→`304` — applied to `src/`, `screen.js`, and `assets/` (previously `screen.js` sent no cache headers and `assets/` emitted an ETag but never revalidated), so an edited module reloads on refresh while unchanged ones `304`; and (3) `scriptType`/`minHost` passthrough from `plugin.json` to `/api/plugins`, with the loader injecting a plugin that declares `"scriptType":"module"` as `<script type="module">` (its screen.js becomes `import './src/main.js'`). A `<script type=module>` fires its load event only after its whole static-import graph evaluates, preserving the loader's completion-by-`onload` + `_loadingPluginId` contract. Classic plugins are unaffected; `minHost` is passthrough-only for now (enforcement deferred). Tests: `tests/test_plugin_src_route.py` (serve/media-type/traversal/304/no-stale-304/screen.js+assets conditional), `tests/js/plugin_loader_script_type.test.js` (guarded module injection).
+- **Module-migration governance & rails (R0).** Constitution amended to **v1.2.0**: Principle II now names native ES modules as a first-class, *build-free* extension mechanism (the `scriptType:"module"` load path, both plugins and — over time — core's `static/js/`), keeping the no-bundler/no-transpiler/source-served rule intact; Operating Constraints gains a "Module load contract" clause (a `<script type=module>` load event awaits the whole static-import graph, so completion-by-`onload` is preserved; per-visit re-init comes from the `screen:changed` event, not screen.js re-execution). Mirrored into `CLAUDE.md`. New `docs/plugin-modules.md` (the migration playbook — layering, import-time purity, `import.meta.url` assets, the ETag live-edit loop) and `docs/size-exemptions.md` (the signed 1,500-line size-norm register; Byron signs core/bundled rows, Christian the authored virtuoso row). Adds a **maintainer/CI-only** ESLint gate (`eslint.config.js` + a `lint` CI job): `max-lines` warns at 1,500 as a non-blocking ratchet (ceilings for exempt files mirror the register), and `import-x/no-unresolved` + `import-x/no-cycle` hard-error on ES-module graphs — dormant until module code lands, never on the serve/Docker path.
+- **Perf-baseline harness (R0).** `scripts/perf-baseline.mjs` (maintainer-only, Playwright-driven) captures server p50/p95/p99 latency, cold boot-to-interactive, JS-heap after an idle soak, and the injected plugin-script shape (how many are `type=module`), so every refactor phase can be checked for "screen-entry and frame-time no worse." Methodology + the R0 baseline live in `docs/perf-baseline.md`; playback frame-time and chart-loaded screen-entry rows need a seeded library and are re-taken per environment.
+- **Sort and filter the library by your personal difficulty rating — now visible at a glance, not just in the edit drawer.** `song_user_meta.user_difficulty` (the 1–5 planning rating, settable manually or seeded by a plugin like the community `difficulty_tagger`) already existed but was only readable by opening a song's per-song details drawer. The library API gains `sort=difficulty` / `sort=difficulty-desc` — a correlated subquery over `song_user_meta`, following the same unrated-rows-sort-to-the-bottom-in-both-directions pattern as the existing `mastery` sort — and library cards now show the rating as a `◆N` badge (v2 grid/tree views and the v3 grid alike), next to the tuning and lyrics badges. The classic tree view's `query_artists` batch-attaches `user_difficulty` the same way `query_page` already did for the grid, so the badge actually renders there too instead of staying dark. Tests: `tests/test_library_filters.py::test_difficulty_sort_pushes_unrated_to_bottom`, `tests/test_library_filters.py::test_tree_view_songs_carry_user_difficulty`.
+- **`lib/midi_import.py`: `convert_midi_tempo_map` — MIDI imports can finally carry
+  their bars.** The keys/drums note converters always computed a tempo-aware
+  tick→seconds map internally (to bake note times to absolute seconds) and then threw
+  it away — and never read `time_signature` meta at all — so every MIDI import landed
+  with no measures and an implied 4/4 regardless of what the file said. The new helper
+  extracts the whole grid: `tempos` (`{time, bpm}`), `time_signatures` (`{time,
+  ts:[num,den]}`, the song-timeline sidecar shape), and a full `beats` grid on the
+  editor's row shape (numbered downbeats with a `den` hint, `-1` interior beats,
+  eighth-note rows in 6/8 etc.). Event scope mirrors the existing tick map — SMF
+  type 0/1 merge meta across tracks, type 2 reads only the chosen track (independent
+  timelines must never share a grid); mid-bar signature events apply at the next bar
+  boundary; times are computed from absolute ticks through the cumulative tempo table
+  and rounded once at emit, so rounding error never accumulates with song length.
+  Consumed by the editor's upcoming multitrack MIDI import (tempo-seed dialog). Tests:
+  `tests/test_midi_tempo_map.py`.
+
+### Fixed
+- **Tuner: opening the player screen no longer throws `NotFoundError` and aborts the player render (feedBack#800).** `injectPlayerButton()` anchored the injected Tuner button with `controls.querySelector('button:last-child')`, which — unlike a `:scope`-scoped query — can match a **nested** button that is not a direct child of `#player-controls`. `controls.insertBefore(btn, nestedButton)` then throws `NotFoundError` (the reference node must be a direct child), and because the injection runs from the tuner's `screen:changed` → player handler, the throw propagated out of the player-screen transition and stalled its render (surfaced by a headless render of a notation arrangement; the v3 path was already safe via the plugin-control slot, only the classic path had the bad anchor). The anchor is now `:scope > button:last-of-type` (a direct child only) with a `parentNode === controls` guard before `insertBefore`, falling back to `appendChild`. `plugins/tuner` → 1.3.4. Tests: `tests/plugins/tuner/js/inject_player_button.test.js` (nested-last-button repro, direct-child insert, no-button append, idempotency, v3 slot path).
+- **Auto-sync: DTW step constraint — riff-based songs no longer produce garbage sync points.** `librosa.sequence.dtw`'s default step pattern allows unbounded horizontal/vertical path runs, and on music with long self-similar chroma stretches (riff-driven stoner/doom, drone sections) the flat cost surface let the warping path collapse — minutes of score mapped onto a single audio frame, so the per-bar warp imported charts wildly out of sync while reporting success (observed on a real 138 BPM tab: effective displayed tempo 159 BPM, three sync points sharing one audio timestamp). `_dtw_align` now uses the standard music-sync slope-constrained step pattern (`[[1,1],[1,2],[2,1]]`, local tempo ratio bounded to 0.5x–2x), which makes the degenerate path impossible, with a fallback to unconstrained steps when the global length ratio makes the constrained pattern infeasible (e.g. a tab aligned against a full-concert video). Validated on the failing song: coarse points track the recording 1:1, refined downbeats land on onset peaks at 3.3x background energy.
+
+### Added
+- **3D Keys Highway: key layout modes, lane-color opacity & octave lines.** A new **Highway layout** settings section rebuilds how sharps/flats and lanes draw on the 3D piano highway. **Sharps & flats layout** (`keys3d_bg_sharpMode`) picks between **floating** (the original raised-sharp look), **flat** (one plane, zero-overlap piano-shaped tiled lanes with the naturals evened out), and **realistic** (one plane, bars sized like the physical keys) — default **realistic**; the geometry lives in pure, unit-tested `laneSpanFlat()`/`laneSpanReal()` helpers. **Lane color opacity** (`keys3d_bg_laneOpacity`, 0–1, default 0) fades the pitch-class lane tint from full vivid color down to a dark floor with guide lines only at the key-block boundaries (E→F and each octave); the lane strips, per-lane separators and block lines crossfade with the value. **Octave separators** (`keys3d_bg_octaveGaps`, default on) and **Octave line contrast** (`keys3d_bg_octaveContrast`, 0–1) control the B→C octave divider, which auto-shifts from a dark to a bright layer as lane opacity fades. Settings re-read on init and apply on the next chart build. `plugins/keys_highway_3d` → 0.2.0. Tests: `plugins/keys_highway_3d/tests/fx_settings.test.js` (new defaults, sharp-mode setting, lane-geometry tiling/evening for flat, uniform/overlap for realistic, and an active-range boundary case where a white key's edge stays untrimmed when its neighboring sharp falls outside the active range).
+- **Unmapped-percussion capture now records velocities alongside times.** Both drum converters' opt-in `out_unmapped` reporting (`lib/midi_import.py` `convert_drum_track_from_midi`, `lib/gp2rs.py` `convert_drum_track_to_drumtab`) gain an index-aligned `velocities` list next to `times`, carrying each dropped note's real dynamics (MIDI velocity verbatim; GP velocity with the same 1–127 gate as mapped hits, falling back to the 100 import default). This lets a hand-mapping UI (the editor's unmapped-notes dialog) restore mapped notes at their source dynamics instead of flattening everything to `v:100`. The GP path's chronological sort now reorders times and velocities in lockstep so multi-voice measures can't silently reassign dynamics. Additive — callers that ignore the new key are unaffected. Tests: `tests/test_midi_import_drums.py`, `tests/test_gp2rs_drums.py`.
+- **Handedness (left-handed) is now a first-class choice in the instrument selector — and surfaced during onboarding.** Left-handed players could already mirror the highway, but only via a buried Settings toggle they had to find *after* setup — so a lefty hit the tour, the tuner and calibration all right-handed first. The v3 instrument badge popover now has a **Handedness: Right / Left** row alongside Instrument / Strings / Tuning (all player-orientation choices), writing the same `lefty` preference (`highway.setLefty` when a live highway exists, else the `lefty` localStorage key it reads on init; the Settings checkbox stays in sync). The first-run tour's "Choose your instrument" step — which runs **before** the tuner/audio-calibration steps — now calls it out so lefties flip it up front. Frontend-only, additive: `static/v3/badges.js`, `static/v3/onboarding-tour.js`. Tests: `tests/js/badges_handedness.test.js`.
+- **"Colorblind (deuteranope)" highway string-color preset.** Adds a one-click preset to the shared "Highway String Colors" picker, sitting next to the existing Okabe–Ito "Colorblind-friendly" preset — contributed by a deuteranopic player who found the Okabe–Ito set still hard to separate. It retunes the six main strings (red / yellow-green / blue / orange / teal / deep-purple) and keeps that set's 7/8-string colors, and applies to **both** the 2D and 3D highways via the shared picker. Frontend-only, additive: `static/app.js` (`HWC_PRESETS`).
 - **`lib/gp_autosync.py`: piecewise time-warp helpers + a working `refine_sync()`.** `auto_sync()` has always computed per-bar sync points (DTW), but consumers could only apply the scalar bar-1 `audio_offset`, so any tempo difference between the recording and the tab's authored tempo accumulated audibly over the song. New librosa-free helpers expose the full mapping: `bar_start_times(gp_path)` (per-bar score times on the same axis as the sync points — GPIF bar-resolution map for `.gp`/`.gpx`, per-tick integration for GP3/4/5), `build_warp_anchors(points, bar_starts)` (strictly-monotonic `(score, audio)` anchor pairs), `warp_time(t, anchors)` (piecewise-linear map with edge-slope extrapolation for count-ins/tails), `warp_song_times(song, warp)` (retimes a `lib.song.Song` in place: notes + sustains, chords, beats, sections, anchors, handshapes, per-phrase difficulty levels, tone changes, tempo overrides), and `gp_has_expandable_repeats(gp_path)` (detects GP3/4/5 repeat/volta/direction markup whose playback expansion the as-written sync points cannot map — callers fall back to offset-only sync). Also implements `refine_sync()`, which the editor plugin's refine-sync endpoint has imported since the snapshot but which never existed in core (the Refine button 500'd): it densifies the coarse DTW points to every Nth bar and re-times each with a local onset phase sweep (sweep radius clamped under half a beat so periodic material can't lock a full beat off; short scoring grid + median residual snap). Synthetic click-track validation: ~13ms mean / ~40ms max error from ±180ms coarse input across 117–123 BPM recordings of a 120 BPM tab. Tests: `tests/test_gp_autosync_warp.py`.
 - **Playlist shuffle.** The v3 playlist detail page gains a crossing-arrows shuffle toggle next to Play all / Play album. When on, `playQueue.start` Fisher-Yates-shuffles the queue once at start (on a copy — the stored playlist order is untouched), swapping any per-slot album arrangements in lockstep so each slot keeps its pinned arrangement. The preference is global and persists in `localStorage` (`v3PlaylistShuffle`). Tests: `tests/js/play_queue_shuffle.test.js`.
 
@@ -15,6 +121,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **Player frame-time hotspots removed (trace-backed) + weak-hardware hardening.** A Chrome performance trace of a 3D-highway session surfaced two core per-frame layout-thrash sources, now fixed: the highway's visibility check read `canvas.offsetParent` every rAF frame (forces style/layout recalc — now sampled every 10th frame with a cached value, force-refreshed on init/canvas-replace/resize/override-clear), and the v3 player chrome loop called `matches(':hover')` per frame and unconditionally rewrote the Up-Next pill's `textContent`/bar width at 6 Hz (now hover-tracked via mouseenter/mouseleave, DOM writes only on value change, progress bar moved from `width` to compositor-only `scaleX`). The 3D highway pre-warms shader programs (`ren.compile`) and deterministic label textures at init — and chart-dependent chord/section label textures on first draw — so first-appearance shader-compile/texture-upload frame spikes move into the load spinner. For weaker hardware: the per-frame renderer bundle is now a single reused object instead of a fresh ~35-field allocation per frame (object identity is stable and meaningless; array fields still swap reference on chart changes), custom viz get `bundle.lowerBoundT`/`bundle.lowerBoundTime` binary-search helpers for visible-window culling, the default 2D highway's beat lines no longer scan every beat in the song per frame, and the 3D highway stops reading `localStorage` per frame (1 Hz poll) and caches its lyrics text-measurement layout per displayed line instead of re-measuring every syllable every frame. A second, throttled-CPU trace pass additionally removed: shader-program re-resolution churn from label texture swaps (`material.needsUpdate` is now only set on a null↔texture transition — swapping between two cached label textures never changes the compiled program), the 3D highway's per-frame `getBoundingClientRect` layout read in its canvas-size self-check (now every 10th frame, still immediate on backing-store change), and the core 60 Hz HUD clock rewriting `textContent` on every tick (now write-on-change, ~1/s). The dominant residual — steady `getParameters` shader-program re-resolution (~4% of throttled main thread) — turned out to be Three r158+'s transparent-DoubleSide two-pass rendering, which sets `material.needsUpdate` twice per object per frame; all 18 of the 3D highway's transparent DoubleSide materials are flat unlit quads (labels, rails, chord frames, lanes), so they now declare `forceSinglePass: true`, eliminating the recompile churn and halving those objects' draw calls.
 
 ### Fixed
+- **`playback.loop-api` bridge no longer fires dozens of times per second.** Every `window.feedBack.getLoop()` call recorded a full bridge hit — compat-shim bookkeeping, a `playback:bridge-hit` event, and a diagnostics snapshot rebuild + stringify — so a plugin polling loop state from a HUD tick (note_detect at ~30 Hz) flooded the capability inspector and burned main-thread time even with no song playing. `_recordPlaybackBridge` now throttles per bridge/surface (5 s window): bridge hits are a "surface still in use" signal, not a call counter. The manual A/B loop buttons (`setLoopEnd`) also now emit the same `loop-set` transport event as `setLoop()`, so plugins can react to loop changes via `playback:loop-set` / `playback:loop-cleared` events instead of polling `getLoop()`.
+- **3D Highway: recover from a WebGL context loss instead of crashing on alt-tab.** Switching the active window / alt-tabbing away from the app (most often on Windows) can trigger a GPU context reset; the 3D highway's WebGL renderer had **no `webglcontextlost` handler**, so a lost context was left to escalate into a render-process crash — matching the intermittent "randomly crashes when I change windows" desktop reports. The renderer now binds `webglcontextlost`/`webglcontextrestored` on its own WebGL canvas (`ren.domElement`): the loss is `preventDefault()`'d so the browser keeps the context restorable, `draw()` bails while the context is down so no GL work runs on a dead context, and on restore the viewport is re-applied and rendering resumes (Three re-uploads scene resources on the next frame). Listeners are torn down with the renderer. `plugins/highway_3d` → 3.31.3. Tests: `tests/js/highway_3d_context_loss.test.js`. (The sibling `keys_highway_3d` / `drum_highway_3d` renderers share the same gap — tracked as a follow-up in their repos.)
 - **Guitar Pro 6 (`.gpx`) import no longer fails on every real file.** The GPX BCFS container reader (`lib/gp2rs_gpx.py`) rejected any file whose final sector wasn't a full `0x1000` block — but a real `.gpx`'s BCFZ-declared decompressed size isn't sector-aligned, so the last (small) container file always lands in a partial trailing sector. The bounds check *raised* `GPX BCFS sector pointer out of range (malformed file)` instead of clamping the tail read, so `_load_gpif` threw before `score.gpif` could be extracted and **no GP6 file could be imported into the song editor** (both real test files failed identically — this wasn't file-specific). GP7/GP8 `.gp` files were unaffected — they take the ZIP path, not BCFS, which is why prior GP-import work didn't surface it. The reader now **clamps the final sector read to the buffer end** (the per-file size field trims the padding anyway), matching canonical GPX readers (alphaTab / PyGuitarPro); a sector whose *start* is past the end still raises, preserving the malformed-file guard. Verified against two real GP6 files — both now unpack to valid GPIF with all tracks. Tests: `tests/test_gp2rs_gpx.py` (partial-final-sector round-trip, multi-file container, sector-aligned baseline, and the preserved out-of-range guard).
 - **v3 Songs grid: fixed the scroll stutter that "skips every so many scrolls," up or down.** The virtualized grid rebuilt its **entire** visible window (`grid.innerHTML = …` + a full `wireCards` pass) every time it slid by one row, so each row-boundary crossing was a heavy synchronous frame that stalled the main thread and buffered held-arrow key-repeats into a visible lurch (a tester's "super fast for a second then slowed down") at fixed scroll offsets — in **both directions and regardless of whether the page was already loaded** (the cost was DOM teardown, not fetching, which is why scrolling back up over cached songs hitched too). `renderWindow()` now **reconciles the window in place**: it reuses the card nodes that stay on-screen and builds only the row that enters/leaves (~6 nodes per slide instead of ~60), keyed by absolute index with a real-vs-skeleton + select-mode signature so hole-fills (after a page fetch) and select-mode toggles still rebuild exactly the nodes that changed. `wireCards`'s `data-wired` guard then wires only the freshly-built nodes, so per-slide listener churn drops with it. Follow-up to the stage-2 virtualized grid (got-feedback/feedBack#636 item 3). Frontend-only: `static/v3/songs.js`. Tests: `tests/js/v3_songs_window_recycle.test.js` (window stays `[start,end)` contiguous + in-window node identity reused across a down-then-up scroll; select-mode toggle and rail-seek jump rebuild correctly).
 - **Starter content seeds again (and now ships The Adicts' "Ode to Joy").** `_BUILTIN_STARTER_SOURCES` still listed `beethoven-ode_to_joy.feedpak` after that pack was deleted, and never wired up its replacement `the_adicts-ode-to-joy_vst_cover.feedpak` that landed on disk. The listed-but-missing file made the all-present gate never fire, so **no** starter songs seeded on first run. Synced the manifest to what's on disk (Für Elise, Star Spangled Banner, The Adicts' Ode to Joy). Tests: `tests/test_builtin_starter_seed.py` (the present/unlisted guards were red on `main`).

CLAUDE.md

@@ -117,6 +117,8 @@ Notes:
 
 **Frontend scripts** — `screen.js` runs in the global scope via a `<script>` tag. It can access `window.playSong`, `window.showScreen`, `window.createHighway`, the `<audio>` element, and the `window.feedBack` event emitter.
 
+**ES-module plugins (`scriptType:"module"`)** — a plugin may instead ship a native ES-module graph with **no build step**: set `"scriptType": "module"` in `plugin.json`, make `screen.js` a one-line `import './src/main.js'`, and put the module tree under `src/` (served by the sandboxed `/api/plugins/<id>/src/{path}` route). The host injects it as `<script type="module">`, whose `onload` fires only after the whole static-import graph evaluates — so the loader's completion-by-`onload` + `_loadingPluginId` + `playSong` wrapper-chain ordering all hold. Resolve your own asset URLs (worklets, WASM) with `import.meta.url` — `document.currentScript` is `null` in a module. Module top-level code does **not** re-run when the user re-enters the screen at the same version (the host loads screen.js once and `showScreen` re-injects nothing), so keep per-visit re-init in a `screen:changed` handler, exactly as classic plugins do. Classic global-scope `screen.js` remains fully supported. See `docs/plugin-modules.md`.
+
 **The playSong wrapper chain** — Plugins commonly wrap `window.playSong` to hook into song playback. Plugins load alphabetically, so the last-loaded (alphabetically later) wrapper runs first, while the alphabetically first plugin runs closest to the original. Be aware that `await` calls in inner wrappers yield to the event loop — WebSocket messages can arrive before outer wrappers finish setup.
 
 ## Plugin Best Practices

docs/perf-baseline.md

@@ -0,0 +1,92 @@
+# Perf baseline — module-migration refactor
+
+The refactor promises "measured runtime wins, no hand-waved perf claims" and
+"screen-entry and frame-time no worse." This is the baseline to hold it to.
+Rerun the harness after every phase (R0 → R3c) and compare.
+
+## Running it
+
+```
+# 1. start core against a library with real charts (see caveat below)
+CONFIG_DIR=… DLC_DIR=/path/to/songs PYTHONPATH=lib \
+  python3 -m uvicorn server:app --host 127.0.0.1 --port 8000
+
+# 2. capture (maintainer/CI-only; uses the committed Playwright chromium)
+node scripts/perf-baseline.mjs --base http://127.0.0.1:8000 --n 60 --soak 30
+```
+
+The script prints a markdown block; paste it under "Results" below with the date
+and the commit it was taken at.
+
+## What it measures
+
+- **Server latency** — p50/p95/p99 over N requests for `/api/version`,
+  `/api/plugins`, `/api/library`, `/api/library/artists`.
+- **Cold boot → interactive** — full page load to `networkidle`.
+- **JS heap** — `performance.memory.usedJSHeapSize` after load and after an idle
+  soak (a leak signal across a session).
+- **Plugin-script shape** — how many plugin `<script>`s the loader injected (a
+  "the app booted with its plugins" sanity signal).
+
+**Not yet captured — needs a seeded library with charts** (fill in when run
+against a real environment): playback **frame-time p95** on the 2D and 3D
+highway, and **screen-entry** (plugin inject → interactive) for
+editor / notedetect / highway_3d with a chart loaded. These are the
+perf-sensitive numbers that gate the `highway.js` split (R3c); the harness has
+the hooks, they just need real songs in `DLC_DIR`.
+
+## Results
+
+### R3c pre-lift baseline — 2026-07-10 (2D highway draw cost)
+
+The gate for the `highway.js` split. Captured on a seeded library (the 33 MB
+Arcturus feedpak) with the new `--song` mode, which measures **per-frame draw
+cost** — rAF callbacks are tagged via `highway.addDrawHook`, so only frames the
+highway actually painted count (the other ~half are cheap no-op loops that would
+otherwise mask a regression). Any `highway.js` change must re-run this on the
+same machine and stay within noise of these numbers.
+
+```bash
+node scripts/perf-baseline.mjs --base http://127.0.0.1:8300 \
+    --song "Arcturus - The Sham Mirrors - Kinetic.feedpak"
+```
+
+| run | draw frames | p50 | p95 | p99 | max |
+|---|---|---|---|---|---|
+| 1 | 53/106 | 2.2 | 3.2 | 3.6 | 3.6 |
+| 2 | 50/100 | 2.2 | 2.9 | 3.2 | 3.2 |
+| 3 | 53/106 | 2.1 | 2.7 | 3.5 | 3.5 |
+
+**p50 ≈ 2.2 ms · p95 spread 2.7–3.2 ms** (3 runs × 10 s playback, headless
+chromium on the dev box). The `H`-container lift changes each closure-slot read
+to a `H.<slot>` property load; this is the number that proves it doesn't cost the
+hot loop.
+
+### R0 baseline — 2026-07-08 (branch `feat/r0-plugin-module-rails`)
+
+> ⚠️ A quick capture (`--n 50 --soak 8`) against an **empty** library (no charts
+> in `DLC_DIR`), so the `/api/library*` and boot numbers are floor values —
+> re-take on a seeded environment with the recommended `--n 60 --soak 30` for the
+> real R0 baseline before comparing R1+ against it. Recorded here to prove the
+> harness and lock the methodology.
+
+Server latency (ms), n=50:
+
+| Endpoint | status | p50 | p95 | p99 |
+|---|---|---|---|---|
+| `/api/version` | 200 | 0.9 | 1.8 | 22.3 |
+| `/api/plugins` | 200 | 1.6 | 2.1 | 3.4 |
+| `/api/library?limit=60` | 200 | 1.4 | 1.7 | 2.9 |
+| `/api/library/artists` | 200 | 1.3 | 1.8 | 2.7 |
+
+Client:
+
+| Metric | Value |
+|---|---|
+| Cold boot → networkidle | 1268 ms |
+| JS heap after load | 10.1 MB |
+| JS heap after idle soak | 10.1 MB (no idle growth) |
+| Plugin scripts injected | 12 |
+
+No plugin has migrated yet, so all 12 are classic. When the R1 pilot (stems)
+lands, cold-boot / heap should not regress.

docs/plugin-modules.md

@@ -0,0 +1,103 @@
+# Plugin ES-module migration playbook
+
+How to move a plugin off a single global-scope `screen.js` IIFE onto a native
+ES-module graph — **no build step, no framework, no bundler**. This is the
+mechanism the monolith-killing refactor uses; the host rails for it shipped in
+R0 (see `.specify/memory/constitution.md` Principle II + the "Module load
+contract" in Operating Constraints).
+
+## The shape
+
+```
+my-plugin/
+  plugin.json      +  "scriptType": "module"        ← opt in
+  screen.js           import './src/main.js';        ← the entire file
+  src/
+    state.js          (0) module state + accessors
+    util/…            (1) pure helpers — real-import testable
+    …/…               (2..4) model → render/audio/io → input
+    globals.js        (5) THE ONLY file that writes window.*
+    main.js           (5) boot: wire modules, register screen:changed
+  assets/…            worklets / WASM / images (unchanged, served as today)
+```
+
+`screen.js` becomes a one-line static `import`. The host injects it as
+`<script type="module">`, whose load event fires **only after the whole
+static-import graph fetches and evaluates** — so the loader's
+completion-by-`onload` + `_loadingPluginId` window + `playSong` wrapper-chain
+order are all preserved. (A classic IIFE that fired a fire-and-forget
+`import()` would break that contract — don't do that; use `scriptType:"module"`.)
+
+## Non-negotiable rules
+
+1. **Source-served, no build.** Modules are plain source files fetched from
+   `/api/plugins/<id>/src/<path>`. No bundler, transpiler, or TypeScript.
+2. **Layering points downward** — `state → util → commands/model →
+   render/audio/io → input → globals/main`. A lint check (`import-x/no-cycle`)
+   enforces acyclicity; extract bottom-up so each move only imports
+   already-extracted layers.
+3. **`globals.js` is the only writer of `window.*`.** The deliberate global
+   surface shrinks to one auditable file; everything else is module-scoped.
+4. **Import-time purity.** `node --test` runs a module's top-level code on
+   import, so a module you want to unit-test must be side-effect-free at import:
+   no `document` / `window` / `localStorage` at module top level — lift init
+   into an exported `init()` called by `main.js`. (Constitution Principle V's
+   "no implicit IO at import time", applied to the frontend.) Tests are `.mjs`
+   and use real `import`, retiring the regex/`extractFunction` harness.
+5. **Assets resolve via `import.meta.url`.** `document.currentScript` is `null`
+   inside a module. `assets/` lives at the plugin root, so a `src/` module must
+   climb out of `src/`: from `src/main.js`, `new URL('../assets/x.js',
+   import.meta.url)` (deeper modules need more `../`). Simpler and
+   depth-independent: the absolute route `/api/plugins/<id>/assets/x.js`.
+   Worklets run in a *separate* module graph (`AudioWorkletGlobalScope`) and
+   cannot share modules with `src/`.
+6. **Re-init comes from `screen:changed`, not re-execution.** The host loads
+   `screen.js` once per version and `showScreen` re-injects nothing, so module
+   top-level code does **not** re-run when the user re-enters the screen at the
+   same version. Keep per-visit setup/teardown in a `window.feedBack.on(
+   'screen:changed', …)` handler — exactly as classic plugins (tuner,
+   minigames) already do. Do not rely on the IIFE re-running.
+7. **Inline `onclick=` keeps working** during migration via `globals.js` (which
+   keeps every referenced symbol on `window`); retire inline handlers to
+   module-side `addEventListener` opportunistically, never as a blocking step.
+
+## The live-edit loop
+
+The host serves `screen.js`, `src/**`, and `assets/**` with
+`Cache-Control: no-cache` + a weak `ETag` and honors `If-None-Match` → `304`.
+So: edit a `src/` file → **refresh the browser** → the edited module returns
+`200` and reloads while every unchanged module `304`s. There is no hot-reload;
+the loop is edit → refresh → see change, exactly as before. The `?v=<version>`
+query on `screen.js` is the legacy version buster; it does **not** propagate
+into the `src/` graph and does not need to — ETag/mtime is the correctness
+authority for the whole graph.
+
+## Host-version floor (`minHost`)
+
+A migrated plugin *requires* a host new enough to serve `src/` and inject
+`type=module`. Declare the floor with `"minHost": "X.Y.Z"` in `plugin.json`.
+(R0 plumbs the field through `/api/plugins`; enforcement — refuse-with-message
+on an older host — is deferred, so bundled plugins are unaffected. Community
+plugins should state the floor and not migrate below it.)
+
+## Migration mechanics
+
+- **Move-only PRs.** One slice extracts one module: cut code, add
+  imports/exports, update `globals.js` — zero behavior change. Behavior fixes
+  are separate PRs. (Init-lifts for import purity are the one non-pure move —
+  budget them.)
+- **Bottom-up, layer by layer.** Within a layer, independent modules are
+  independent PRs (a DAG, not a chain); use a git worktree per branch.
+- Tests move with their subject and convert to real `.mjs` imports in the same
+  PR (assertions unchanged).
+- Size norm: no source file over **1,500 lines**; legitimate exceptions
+  (hot renderers, etc.) go in the signed register at `docs/size-exemptions.md`.
+
+## Verifying a migration
+
+`node --test <plugin>/tests/*.mjs`; load the plugin on the `:8000` testbed and
+confirm it boots (`<script type=module>` in DevTools, the `src/` graph in
+Network); edit a `src/` file → refresh → change visible (`200` on the edited
+file, `304` on the rest); leave and re-enter the screen at the same version →
+it re-inits via `screen:changed`. The R1 pilots (stems, then studio) certify
+this end-to-end before the flagship repos migrate.

docs/size-exemptions.md

@@ -0,0 +1,66 @@
+# Size-exemption register
+
+The working norm (constitution Principle II; enforced by the `max-lines` lint
+gate) is **no source file over 1,500 lines**. A few files are allowed to exceed
+it because splitting them would do more harm than good — hot per-frame
+renderers, C++, offline generators, cohesive registries. This register is the
+list of those exceptions: each row is a **deliberate, signed** decision with a
+ceiling, a rationale, and a review trigger. Without it, "no file over 1,500
+without a *signed* exemption" is unenforceable.
+
+**Rules**
+- One row per file: a ceiling, a rationale, a signer, a review trigger.
+- The `max-lines` per-file ceilings in `eslint.config.js` mirror this table —
+  keep them in sync (this register is canonical).
+- Files with a scheduled split **plan** are *not* exempt — they live in
+  "Planned, not exempt" at the bottom so nothing falls between the two states.
+- **Signers** (decided 2026-07-08): **Byron** signs core + bundled rows;
+  **Christian** signs the authored-plugin row (virtuoso, its own repo/track).
+
+## Permanent exemptions (structural rationale)
+
+| Repo / file | Lines (7-07) | Ceiling | Rationale | Signer | Review |
+|---|---|---|---|---|---|
+| core `static/highway.js` → residual `renderer-2d.js` (post-split) | ~2,400–2,900 est. | **3,000** | 60 fps hot path; no module boundary inside the per-frame loop | Byron | after the highway.js split |
+| core `plugins/highway_3d/` → residual renderer | sized at split; likely **>3,000** | set at split, flagged now | same hot-path rule; the draw core can't be cut without behavior risk | Byron | after the highway_3d split |
+| core `static/capabilities.js` | 1,538 | 1,600 | cohesive registry + `window.feedBack` bus, 38 lines over; a split spends credibility for nothing | Byron | R4 |
+| tutorials `builtin/reading-the-highway/generate.py` | 1,818 | 2,000 | offline content generator, never imported at runtime, deps not in runtime requirements | Byron | if a 3rd builtin pack appears |
+| desktop `src/audio/NodeAddon.cpp` | 3,542 | as-is | C++, outside the ESM/routes playbooks; under active use-after-free crash work — do not churn | Byron | after crash-class work settles |
+| desktop `src/audio/AudioEngine.cpp` | 2,977 | as-is | same | Byron | same |
+| desktop `src/vst-host/main.cpp` | 1,928 | as-is | same | Byron | same |
+| virtuoso `screen.js` (authored, own track) | 25,741 | as-is until its own split | authored plugin on a separate roadmap; migrates on its own schedule | Christian | virtuoso split kickoff |
+
+## Split-when-touched (no scheduled train; row retires when split)
+
+| Repo / file | Lines | Ceiling | Rationale | Signer | Review |
+|---|---|---|---|---|---|
+| core `lib/gp2rs_gpx.py` | 2,540 | as-is | import converter, off the serve-path hot loop | Byron | when next touched |
+| core `lib/gp2rs.py` | 2,055 | as-is | same | Byron | when next touched |
+| core `lib/song.py` | 1,689 | as-is | data models + wire format; cohesive | Byron | when next touched |
+| core `lib/gp_autosync.py` | 1,572 | as-is | under active dev (#787/#791) — don't collide | Byron | after in-flight work lands |
+| core `plugins/capability_inspector/screen.js` | 1,752 | as-is | bundled diagnostics plugin, low churn | Byron | when next touched |
+| core `plugins/folder_library/screen.js` | 1,672 | as-is | bundled plugin, low churn | Byron | when next touched |
+
+## Temporary rows (cleared by a scheduled PR)
+
+| Repo / file | Lines | Cleared by |
+|---|---|---|
+| core `plugins/__init__.py` | ~2,470 (grew under R0) | the `plugins/_routes.py` + `plugins/_registry.py` split (rides the server.py router work) |
+
+## Watch list (under the norm — no row needed, re-census each phase)
+
+`musicxml-import/mxml2notation.py` (1,456) · core `static/capabilities/audio-effects.js`
+(1,436) · `studio routes.py` (1,399) · `update-manager screen.js` (1,492 — zero headroom).
+
+## Planned, NOT exempt (owned by split plans — listed so nothing falls between states)
+
+core `static/app.js` (11,852) · `static/highway.js` (4,168, whole file) · `server.py`
+(4,478 — was 14,037; ratcheted by the R3 `MetadataDB` + `AudioEffectsMappingDB`
+extractions and seventeen `routers/` modules (album-art in `lib/routers/art.py`, the settings + export/import bundle in `lib/routers/settings.py`); the ~930-line metadata-enrichment subsystem — MB/CAA/AcoustID transport, matcher, background worker — now lives in `lib/enrichment.py`) ·
+`lib/metadata_db.py` (4,373 — new in R3; the `MetadataDB` class alone is 4,018 lines
+and is a monolith in its own right, to be split per-table once the router train
+lands) · `static/v3/songs.js` (4,134) · `static/capabilities/audio-session.js`
+(2,974) · `plugins/highway_3d/screen.js` (15,656) · `plugins/keys_highway_3d/screen.js`
+(3,780) · `plugins/drum_highway_3d/screen.js` (3,597) — and every monolith with a PR
+train in the refactor plan. Test files (e.g. `tests/test_plugins.py`) are out of scope
+by policy — the norm governs source files.

eslint.config.js

@@ -0,0 +1,66 @@
+// Flat ESLint config — MAINTAINER / CI ONLY. Never runs on the serve or Docker
+// path (constitution Principle I: dev-only tooling is exempt, same category as
+// scripts/build-tailwind.sh). It enforces the module-migration guardrails:
+//
+//   * max-lines — the 1,500-line size norm, as a WARNING ratchet. Legacy
+//     monoliths warn (the "this is over the norm, split it" signal) and shrink
+//     as the refactor lands; warnings do not fail CI. Genuinely-large files are
+//     exempted below, mirroring the signed register in docs/size-exemptions.md.
+//   * import-x/no-unresolved + no-cycle — module hygiene, scoped to the real
+//     ES-module graphs the refactor produces (a plugin's src/ tree, .mjs
+//     tests). no-unresolved (a HARD error) catches broken import paths;
+//     no-cycle enforces the downward-only layering rule. Core's classic scripts
+//     have no import graph, so both are dormant today and become live gates the
+//     moment module code appears — validated against the first real module
+//     plugin (R1 pilot).
+
+const importX = require('eslint-plugin-import-x');
+
+// Per-file size ceilings — a mirror of docs/size-exemptions.md (canonical).
+// Keep in sync; each entry corresponds to a signed row in the register.
+const SIZE_EXEMPTIONS = [
+    { files: ['**/static/capabilities.js'], max: 1600 },
+    { files: ['**/plugins/capability_inspector/screen.js'], max: 100000 },
+    { files: ['**/plugins/folder_library/screen.js'], max: 100000 },
+];
+
+const sizeRule = (max) => ['warn', { max, skipBlankLines: false, skipComments: false }];
+
+module.exports = [
+    {
+        ignores: [
+            'node_modules/**',
+            'static/vendor/**',
+            'plugins/**/assets/vendor/**',
+            '**/*.min.js',
+            'static/tailwind.min.css',
+        ],
+    },
+    // Size norm across all first-party JS. Classic scripts are parsed as
+    // scripts (no import/export); module files get their own block below.
+    {
+        files: ['**/*.js', '**/*.cjs'],
+        languageOptions: { ecmaVersion: 'latest', sourceType: 'script' },
+        rules: { 'max-lines': sizeRule(1500) },
+    },
+    // ES-module graphs (a plugin's src/ tree, .mjs tests): module parsing + the
+    // acyclic-imports hard gate + the size norm. A migrated bundled plugin's
+    // entry `import './src/main.js'` screen.js must parse as a module — add its
+    // glob here in that plugin's migration PR (classic screen.js stays a script).
+    {
+        files: ['**/src/**/*.js', '**/*.mjs'],
+        languageOptions: { ecmaVersion: 'latest', sourceType: 'module' },
+        plugins: { 'import-x': importX },
+        // v4 flat-config resolver (resolver-next + createNodeResolver). Without
+        // it the import rules silently skip imports they can't resolve.
+        settings: { 'import-x/resolver-next': [importX.createNodeResolver()] },
+        rules: {
+            'max-lines': sizeRule(1500),
+            'import-x/no-unresolved': 'error',
+            'import-x/no-cycle': 'error',
+        },
+    },
+    // Signed size exemptions (docs/size-exemptions.md) — raise the ceiling so
+    // registered files don't warn below it.
+    ...SIZE_EXEMPTIONS.map(({ files, max }) => ({ files, rules: { 'max-lines': sizeRule(max) } })),
+];

lib/appconfig.py

@@ -0,0 +1,28 @@
+"""Reading the app's config.json — the one shared, pure helper (R3).
+
+Extracted verbatim from server.py so route modules that need a config value
+(reference pitch, server_config, …) can read it without reaching back into the
+host file. server.py re-imports it, so its ~11 call sites and any
+`server._load_config` test reference keep resolving unchanged.
+"""
+
+import json
+
+
+def _load_config(config_file):
+    """Read and parse config.json. Returns the parsed dict, or None if
+    the file is missing, unreadable, invalid JSON, or parses to a
+    non-dict (e.g. the file contains `[]` or `42`). Callers treat None
+    as "fall back to defaults". Shared between GET and POST so both
+    handle bad files the same way."""
+    if not config_file.exists():
+        return None
+    try:
+        # Explicit UTF-8: save_settings()/import write config.json as
+        # UTF-8 bytes, so the read must not depend on the platform's
+        # default text encoding (cp1252 on Windows would mojibake or
+        # UnicodeDecodeError on a non-ASCII DLC path).
+        parsed = json.loads(config_file.read_text(encoding="utf-8"))
+    except Exception:
+        return None
+    return parsed if isinstance(parsed, dict) else None

lib/appstate.py

@@ -0,0 +1,127 @@
+"""Shared application state — the seam that lets route modules reach core
+singletons without importing ``server``.
+
+``server.py`` is the host: it owns the FastAPI ``app``, constructs the DB
+singletons, and runs the lifecycle. As routes move out into ``routers/`` (R3),
+those modules need ``meta_db`` and friends — but they must not ``import
+server``, or the import graph goes circular the moment ``server`` imports them
+back.
+
+So ``server`` **injects** its singletons here once, at the point it builds them::
+
+    # server.py
+    meta_db = MetadataDB(CONFIG_DIR)
+    appstate.configure(meta_db=meta_db, ...)
+
+and a router reads them back as **module attributes, at call time**::
+
+    # routers/artists.py
+    import appstate
+
+    @router.get("/api/artist/{name}/page")
+    def artist_page(name):
+        return appstate.meta_db.artist_page(name)
+
+This is the Python analogue of the injected `configureX({...})` seams the
+frontend refactor uses (stems' ``configureStreaming``, studio's
+``configureAudioGraph``, the editor's ``src/host.js``), and of the plugin
+``setup(app, context)`` contract in Principle III: dependencies flow one way,
+``server -> routers -> appstate``, and nothing imports back up.
+
+Two properties this shape buys, both load-bearing:
+
+* **``import appstate`` performs no IO and constructs nothing.** ``server``
+  still owns construction, so the ~49 test fixtures that do
+  ``sys.modules.pop("server")`` + re-import (to rebuild ``meta_db`` under a
+  patched ``CONFIG_DIR``) keep working untouched — a singleton *owned* here
+  would survive that pop and go stale.
+* **Reads are late-bound.** Routers must use ``appstate.meta_db``, never
+  ``from appstate import meta_db`` — a ``from`` import freezes the binding at
+  its current value, so a later ``configure()`` (or a
+  ``monkeypatch.setattr(appstate, "meta_db", fake)``) would not reach the
+  router. This is the same read-only-binding trap as ES ``import``.
+
+Defaults are ``None`` on purpose: they are inert but *type-honest*, so a router
+that runs before ``configure()`` fails loudly on ``NoneType`` instead of
+quietly operating on a stand-in.
+
+Slots are added here only when a router actually needs one — this is a seam,
+not a grab-bag for everything in ``server.py``.
+
+**Why this lives in ``lib/`` and not the repo root.** Because it constructs
+nothing and does no import-time IO, it satisfies Principle V's rule for ``lib/``
+modules — and ``lib/`` is the only core directory every packaging path already
+copies: the Dockerfile (``COPY lib/``), ``docker-compose.yml``, and
+feedback-desktop's ``bundle-slopsmith.sh`` (``cp -r lib``). All three also put
+both the bundle root and ``lib/`` on ``sys.path``. A root-level module ships in
+Docker but is silently dropped from the packaged desktop app, whose bundler
+copies a hardcoded file list — that regression is what moved this file here.
+"""
+
+# The singletons routers may read. Every name here must also be a `_SLOTS` key.
+meta_db = None
+audio_effect_mappings = None
+# The tuning-provider registry instance (built-ins + plugin-contributed). A
+# stable object mutated in place via register()/unregister() — injected here by
+# reference so routers read the same registry plugins populate.
+tuning_providers = None
+
+# Config paths. server.py derives these from the environment (fresh on every
+# import, so the ~49 pop-and-reimport fixtures keep working) and injects them
+# here. Routers read them as `appstate.config_dir` etc. — a module attribute at
+# call time. NOTE: config_dir/dlc_dir are env-derived, so a `setenv`+reimport
+# test reconfigures them for free; STATIC_DIR/SLOPPAK_CACHE_DIR are patched via
+# `setattr(server, …)` in a few tests, so those slots (when added) need their
+# tests retargeted to appstate in the same PR.
+config_dir = None
+dlc_dir = None          # the DLC_DIR env value as a Path (Path("") if unset)
+dlc_dir_env = None      # the raw DLC_DIR env string, "" if unset — distinguishes
+                        # "unset" from Path("")→"." (see dlc_paths._get_dlc_dir)
+# Cache/asset dirs. static_dir + sloppak_cache_dir are patched via
+# `setattr(server, …)` in a few tests, so a router reading them here needs those
+# setattr sites retargeted to `setattr(appstate, …)` in the same PR (ws_highway
+# retargets the 3 test_highway_ws_* SLOPPAK sites). config_dir-derived dirs are
+# reconfigured for free on a setenv+reimport.
+static_dir = None
+sloppak_cache_dir = None
+audio_cache_dir = None
+
+# Injected callables (not values): server owns the impl + its state, routers call
+# through the seam. get_progression_content wraps a lazy content cache that stays
+# in server.py (its `setattr(server, "_progression_content")` test is untouched).
+get_progression_content = None
+builtin_diagnostic_filename = None
+running_version = None
+# Art helpers that stay in server.py (shared with the art/delete routes) but are
+# also called by the enrichment worker in lib/enrichment.py — injected as
+# callables to keep enrichment acyclic. art_cache_dir is server's ART_CACHE_DIR.
+art_cache_dir = None
+song_pack_art_exists = None
+art_override_paths = None
+art_safe_name = None
+# The canonical settings-defaults builder — stays in server.py (shared with the
+# scan/artist-links code) but the settings router calls it through the seam.
+default_settings = None
+
+_SLOTS = frozenset({
+    "meta_db", "audio_effect_mappings", "tuning_providers",
+    "config_dir", "dlc_dir", "dlc_dir_env",
+    "static_dir", "sloppak_cache_dir", "audio_cache_dir",
+    "get_progression_content", "builtin_diagnostic_filename",
+    "running_version",
+    "art_cache_dir", "song_pack_art_exists", "art_override_paths", "art_safe_name",
+    "default_settings",
+})
+
+
+def configure(**kwargs) -> None:
+    """Publish `server`'s singletons into this module. Called once per
+    `server` import (and again on re-import), so it must be idempotent."""
+    unknown = set(kwargs) - _SLOTS
+    if unknown:
+        raise TypeError(
+            f"appstate.configure() got unknown slot(s): {sorted(unknown)}. "
+            f"Known slots: {sorted(_SLOTS)}. Add the name to _SLOTS if a router "
+            f"genuinely needs it."
+        )
+    globals().update(kwargs)

lib/audio_effects_db.py

@@ -0,0 +1,287 @@
+"""Core-owned song/tone -> audio-effect-provider mapping index.
+
+Extracted verbatim from ``server.py`` (R3). ``server.py`` still owns the
+``audio_effect_mappings`` singleton; this module only supplies the class, so
+nothing here touches config paths at import time — the caller passes
+``config_dir`` in.
+"""
+
+import json
+import sqlite3
+import threading
+from pathlib import Path
+
+
+class AudioEffectsMappingDB:
+    """Core-owned public song/tone -> provider mapping index.
+
+    Providers own the preset/chain rows addressed by provider_ref. Core owns
+    the cross-provider routing index and the active mapping per song/tone.
+    """
+
+    def __init__(self, config_dir: Path):
+        config_dir.mkdir(parents=True, exist_ok=True)
+        self.db_path = str(config_dir / "audio_effects.db")
+        self.conn = sqlite3.connect(self.db_path, check_same_thread=False)
+        self.conn.execute("PRAGMA journal_mode=WAL")
+        self.conn.execute("PRAGMA foreign_keys=ON")
+        self.conn.execute("""
+            CREATE TABLE IF NOT EXISTS audio_effect_mappings (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                song_key TEXT NOT NULL,
+                filename TEXT NOT NULL DEFAULT '',
+                tone_key TEXT NOT NULL,
+                provider_id TEXT NOT NULL,
+                provider_ref TEXT NOT NULL,
+                label TEXT NOT NULL DEFAULT '',
+                source TEXT NOT NULL DEFAULT 'manual',
+                metadata_json TEXT NOT NULL DEFAULT '{}',
+                created_at TEXT NOT NULL DEFAULT (datetime('now')),
+                updated_at TEXT NOT NULL DEFAULT (datetime('now')),
+                UNIQUE(song_key, tone_key, provider_id)
+            )
+        """)
+        self.conn.execute("""
+            CREATE TABLE IF NOT EXISTS audio_effect_active_mappings (
+                song_key TEXT NOT NULL,
+                tone_key TEXT NOT NULL,
+                mapping_id INTEGER NOT NULL,
+                updated_at TEXT NOT NULL DEFAULT (datetime('now')),
+                PRIMARY KEY (song_key, tone_key),
+                FOREIGN KEY (mapping_id) REFERENCES audio_effect_mappings(id) ON DELETE CASCADE
+            )
+        """)
+        self.conn.execute(
+            "CREATE INDEX IF NOT EXISTS idx_audio_effect_mappings_provider "
+            "ON audio_effect_mappings(provider_id)"
+        )
+        self.conn.execute(
+            "CREATE INDEX IF NOT EXISTS idx_audio_effect_mappings_filename "
+            "ON audio_effect_mappings(filename)"
+        )
+        self.conn.commit()
+        self._lock = threading.Lock()
+
+    @staticmethod
+    def _text(value, *, field: str, limit: int, allow_empty: bool = False) -> str:
+        if value is None:
+            text = ""
+        elif not isinstance(value, str):
+            raise ValueError(f"{field} must be a string")
+        else:
+            text = value.strip()
+        if not text and not allow_empty:
+            raise ValueError(f"{field} is required")
+        if len(text) > limit:
+            raise ValueError(f"{field} is too long")
+        return text
+
+    @staticmethod
+    def _mapping_id(value) -> int | None:
+        # Bind only values SQLite can store as an INTEGER; an out-of-range id is a
+        # clean miss (404), not a 500 at bind time.
+        if isinstance(value, int) and not isinstance(value, bool) and -(2 ** 63) <= value < 2 ** 63:
+            return value
+        return None
+
+    @staticmethod
+    def _field(data: dict, *keys):
+        # Select the first present snake/camel alias by key, not by truthiness, so a
+        # falsey non-string value (false/0) still reaches _text() and is rejected
+        # instead of being silently swallowed by an `or` chain.
+        for key in keys:
+            if key in data:
+                return data[key]
+        return None
+
+    @staticmethod
+    def _metadata(value) -> str:
+        if value is None:
+            return "{}"
+        if not isinstance(value, dict):
+            raise ValueError("metadata must be an object")
+        encoded = json.dumps(value, ensure_ascii=True, sort_keys=True)
+        if len(encoded) > 8192:
+            raise ValueError("metadata is too large")
+        return encoded
+
+    @staticmethod
+    def _row(row) -> dict | None:
+        if row is None:
+            return None
+        metadata = {}
+        try:
+            metadata = json.loads(row[8]) if row[8] else {}
+        except Exception:
+            metadata = {}
+        return {
+            "id": int(row[0]),
+            "song_key": row[1],
+            "filename": row[2] or "",
+            "tone_key": row[3],
+            "provider_id": row[4],
+            "provider_ref": row[5],
+            "label": row[6] or "",
+            "source": row[7] or "manual",
+            "metadata": metadata if isinstance(metadata, dict) else {},
+            "created_at": row[9] or "",
+            "updated_at": row[10] or "",
+            "active": bool(row[11]),
+        }
+
+    def _select_sql(self) -> str:
+        return """
+            SELECT m.id, m.song_key, m.filename, m.tone_key, m.provider_id,
+                   m.provider_ref, m.label, m.source, m.metadata_json,
+                   m.created_at, m.updated_at,
+                   CASE WHEN a.mapping_id IS NULL THEN 0 ELSE 1 END AS active
+            FROM audio_effect_mappings m
+            LEFT JOIN audio_effect_active_mappings a
+              ON a.song_key = m.song_key AND a.tone_key = m.tone_key AND a.mapping_id = m.id
+        """
+
+    def list(self, *, song_key: str = "", filename: str = "", tone_key: str = "", provider_id: str = "") -> list[dict]:
+        clauses: list[str] = []
+        params: list[str] = []
+        song_key = self._text(song_key, field="song_key", limit=240, allow_empty=True)
+        filename = self._text(filename, field="filename", limit=500, allow_empty=True)
+        tone_key = self._text(tone_key, field="tone_key", limit=160, allow_empty=True)
+        provider_id = self._text(provider_id, field="provider_id", limit=96, allow_empty=True)
+        if song_key and filename:
+            clauses.append("(m.song_key = ? OR m.filename = ?)")
+            params.extend([song_key, filename])
+        elif song_key:
+            clauses.append("m.song_key = ?")
+            params.append(song_key)
+        elif filename:
+            clauses.append("(m.song_key = ? OR m.filename = ?)")
+            params.extend([filename, filename])
+        if tone_key:
+            clauses.append("m.tone_key = ?")
+            params.append(tone_key)
+        if provider_id:
+            clauses.append("m.provider_id = ?")
+            params.append(provider_id)
+        sql = self._select_sql()
+        if clauses:
+            sql += " WHERE " + " AND ".join(clauses)
+        sql += " ORDER BY m.song_key COLLATE NOCASE, m.tone_key COLLATE NOCASE, m.provider_id COLLATE NOCASE"
+        with self._lock:
+            rows = self.conn.execute(sql, params).fetchall()
+        return [self._row(row) for row in rows]
+
+    def get(self, mapping_id: int) -> dict | None:
+        mapping_id = self._mapping_id(mapping_id)
+        if mapping_id is None:
+            return None
+        with self._lock:
+            row = self.conn.execute(self._select_sql() + " WHERE m.id = ?", (mapping_id,)).fetchone()
+        return self._row(row)
+
+    def upsert(self, data: dict) -> dict:
+        if not isinstance(data, dict):
+            raise ValueError("mapping body must be an object")
+        filename = self._text(data.get("filename", ""), field="filename", limit=500, allow_empty=True)
+        song_key_raw = self._field(data, "song_key", "songKey")
+        if song_key_raw is None or song_key_raw == "":
+            song_key_raw = filename
+        song_key = self._text(song_key_raw, field="song_key", limit=240)
+        tone_key = self._text(self._field(data, "tone_key", "toneKey"), field="tone_key", limit=160, allow_empty=True)
+        provider_id = self._text(self._field(data, "provider_id", "providerId"), field="provider_id", limit=96)
+        provider_ref = self._text(self._field(data, "provider_ref", "providerRef"), field="provider_ref", limit=240)
+        label = self._text(data.get("label", ""), field="label", limit=160, allow_empty=True)
+        source = self._text(data.get("source", "manual"), field="source", limit=40, allow_empty=True) or "manual"
+        metadata_json = self._metadata(data.get("metadata", {}))
+        with self._lock:
+            self.conn.execute(
+                """
+                INSERT INTO audio_effect_mappings
+                    (song_key, filename, tone_key, provider_id, provider_ref, label, source, metadata_json, updated_at)
+                VALUES (?, ?, ?, ?, ?, ?, ?, ?, datetime('now'))
+                ON CONFLICT(song_key, tone_key, provider_id) DO UPDATE SET
+                    -- Only overwrite filename when a non-empty one was supplied; an
+                    -- omitted/empty filename must preserve the stored value (it's an
+                    -- alternate lookup key for list(..., filename=...)).
+                    filename=CASE WHEN excluded.filename <> '' THEN excluded.filename ELSE audio_effect_mappings.filename END,
+                    provider_ref=excluded.provider_ref,
+                    label=excluded.label,
+                    source=excluded.source,
+                    metadata_json=excluded.metadata_json,
+                    updated_at=datetime('now')
+                """,
+                (song_key, filename, tone_key, provider_id, provider_ref, label, source, metadata_json),
+            )
+            row = self.conn.execute(
+                "SELECT id FROM audio_effect_mappings WHERE song_key = ? AND tone_key = ? AND provider_id = ?",
+                (song_key, tone_key, provider_id),
+            ).fetchone()
+            if row is None:
+                raise ValueError("failed to create audio-effects mapping")
+            mapping_id = int(row[0])
+            if data.get("active") is True:
+                self.conn.execute(
+                    """
+                    INSERT INTO audio_effect_active_mappings (song_key, tone_key, mapping_id, updated_at)
+                    VALUES (?, ?, ?, datetime('now'))
+                    ON CONFLICT(song_key, tone_key) DO UPDATE SET
+                        mapping_id=excluded.mapping_id,
+                        updated_at=datetime('now')
+                    """,
+                    (song_key, tone_key, mapping_id),
+                )
+            self.conn.commit()
+        return self.get(mapping_id)
+
+    def delete(self, mapping_id: int, *, provider_id: str = "") -> bool:
+        mapping_id = self._mapping_id(mapping_id)
+        if mapping_id is None:
+            return False
+        provider_id = self._text(provider_id, field="provider_id", limit=96, allow_empty=True)
+        with self._lock:
+            if provider_id:
+                cur = self.conn.execute(
+                    "DELETE FROM audio_effect_mappings WHERE id = ? AND provider_id = ?",
+                    (mapping_id, provider_id),
+                )
+            else:
+                cur = self.conn.execute("DELETE FROM audio_effect_mappings WHERE id = ?", (mapping_id,))
+            self.conn.commit()
+            return cur.rowcount > 0
+
+    def activate(self, mapping_id: int, *, provider_id: str = "") -> dict | None:
+        mapping_id = self._mapping_id(mapping_id)
+        if mapping_id is None:
+            return None
+        provider_id = self._text(provider_id, field="provider_id", limit=96, allow_empty=True)
+        with self._lock:
+            row = self.conn.execute(
+                self._select_sql() + " WHERE m.id = ?",
+                (mapping_id,),
+            ).fetchone()
+            mapping = self._row(row)
+            if not mapping or (provider_id and mapping["provider_id"] != provider_id):
+                return None
+            self.conn.execute(
+                """
+                INSERT INTO audio_effect_active_mappings (song_key, tone_key, mapping_id, updated_at)
+                VALUES (?, ?, ?, datetime('now'))
+                ON CONFLICT(song_key, tone_key) DO UPDATE SET
+                    mapping_id=excluded.mapping_id,
+                    updated_at=datetime('now')
+                """,
+                (mapping["song_key"], mapping["tone_key"], mapping_id),
+            )
+            self.conn.commit()
+            selected = self.conn.execute(self._select_sql() + " WHERE m.id = ?", (mapping_id,)).fetchone()
+        return self._row(selected)
+
+    def clear_active(self, *, song_key: str, tone_key: str) -> bool:
+        song_key = self._text(song_key, field="song_key", limit=240)
+        tone_key = self._text(tone_key, field="tone_key", limit=160, allow_empty=True)
+        with self._lock:
+            cur = self.conn.execute(
+                "DELETE FROM audio_effect_active_mappings WHERE song_key = ? AND tone_key = ?",
+                (song_key, tone_key),
+            )
+            self.conn.commit()
+            return cur.rowcount > 0

lib/dlc_paths.py

@@ -0,0 +1,99 @@
+"""DLC library path resolution — where the song files live, plus safe containment.
+
+Extracted from ``server.py`` (R3). ``_resolve_dlc_path`` is pure and moved
+verbatim. ``_get_dlc_dir`` reads the env-derived paths through the ``appstate``
+seam (``server.py`` configures ``dlc_dir``/``dlc_dir_env``/``config_dir`` at
+import, fresh on every re-import), so this module does no import-time IO and the
+pop-and-reimport fixtures keep working. ``server.py`` re-exports both names, so
+existing ``server._get_dlc_dir`` / ``server._resolve_dlc_path`` references
+(tests, other handlers) resolve unchanged.
+"""
+
+import json
+import os
+from pathlib import Path
+
+import appstate
+
+
+def _get_dlc_dir(cfg: dict | None = None) -> Path | None:
+    # Only consider DLC_DIR if the env var was non-empty. `Path("")` collapses
+    # to `.` and reports `.is_dir() == True`, which would silently shadow the
+    # config.json fallback. Checking the raw env string preserves
+    # `DLC_DIR=.` as a valid opt-in for cwd while keeping unset/empty out.
+    if appstate.dlc_dir_env and appstate.dlc_dir.is_dir():
+        return appstate.dlc_dir
+    if cfg is None:
+        config_file = appstate.config_dir / "config.json"
+        if config_file.exists():
+            try:
+                cfg = json.loads(config_file.read_text(encoding="utf-8"))
+            except Exception:
+                pass
+    if isinstance(cfg, dict):
+        raw = str(cfg.get("dlc_dir", "")).strip()
+        if raw:
+            p = Path(raw)
+            if p.is_dir():
+                return p
+    return None
+
+
+def _resolve_dlc_path(dlc: Path, filename: str) -> Path | None:
+    """Resolve `filename` under DLC_DIR and refuse anything that escapes.
+
+    `filename` arrives from `:path` route params and can contain `..`
+    segments. The Sloppak and archive paths happen to fail safely later
+    because their loaders raise on missing/invalid files, but loose-
+    folder format detection (`is_loose_song`) globs and parses XML on
+    disk first, which lets a crafted path trigger filesystem reads
+    outside DLC_DIR before any guard fires. Centralise the containment
+    check so every filename-bound handler validates before touching the
+    filesystem.
+
+    Containment here is LEXICAL (normalize `.`/`..` WITHOUT following
+    symlinks), not `safe_join`'s `.resolve()`-based check — because users
+    commonly mount their song library through a directory JUNCTION/symlink
+    (a library shared across app installs; the desktop app's own mounts).
+    `.resolve()` follows that junction to its real target, sees it sits
+    outside DLC_DIR, and wrongly rejects every song reached through it — the
+    scanner's `rglob` indexes those songs, but art/load then 403/404s (broken
+    covers, unplayable songs). Lexical normalization still rejects the only
+    escapes a `:path` filename can express — `..` traversal and absolute
+    paths — which the traversal tests pin. `safe_join` stays strict (it is
+    the zip-slip / plugin-asset guard, where following a symlink out IS the
+    defense); the loose-folder art handler keeps its own per-file symlink
+    re-check for defence-in-depth.
+
+    Returns the validated Path (not necessarily link-resolved), or None if
+    the filename is empty, contains a NUL, or escapes the DLC root.
+    """
+    if not filename:
+        return None
+    # Backslashes → forward slashes so a Windows-style `..\\x` traversal is
+    # rejected identically on POSIX (mirrors safe_join's normalisation).
+    safe = filename.replace("\\", "/")
+    if "\x00" in safe:
+        return None
+    # Reject drive-letter / absolute paths in BOTH conventions. A POSIX "/x" is
+    # caught by the containment check below (the `/` operator discards `root`),
+    # but a Windows drive-absolute "C:/x" is treated as a relative "C:" dir on
+    # POSIX and would otherwise slip in as `<root>/C:/x` — so the contract must
+    # hold cross-platform (a shared library is reached from either OS).
+    from pathlib import PurePosixPath, PureWindowsPath
+    if (PurePosixPath(safe).is_absolute()
+            or PureWindowsPath(safe).is_absolute()
+            or PureWindowsPath(safe).drive):
+        return None
+    try:
+        root = dlc.resolve()
+        # normpath collapses `.`/`..`/duplicate separators purely lexically —
+        # it never touches the filesystem, so an in-library junction component
+        # is preserved (allowed) while `..`/absolute segments still escape and
+        # get caught by the containment check below.
+        candidate = Path(os.path.normpath(root / safe))
+        if not candidate.is_relative_to(root):
+            return None
+    except (ValueError, OSError):
+        return None
+    return candidate

lib/gp2rs.py

@@ -1114,7 +1114,7 @@ def _build_xml(
     ET.SubElement(root, "arrangement").text = arrangement
     ET.SubElement(root, "offset").text = f"{audio_offset:.3f}"
     ET.SubElement(root, "songLength").text = f"{song_length:.3f}"
-    ET.SubElement(root, "startBeat").text = f"{beats[0].time:.3f}" if beats else "0.000"
+    ET.SubElement(root, "startBeat").text = f"{beats[0].time:.6f}" if beats else "0.000000"
     ET.SubElement(root, "averageTempo").text = str(tempo)
     ET.SubElement(root, "artistName").text = artist
     ET.SubElement(root, "albumName").text = album
@@ -1139,10 +1139,17 @@ def _build_xml(
         tuning_el.set(f"string{i}", str(tuning[i] if i < len(tuning) else 0))
     ET.SubElement(root, "capo").text = "0"
 
-    # Ebeats
+    # Ebeats — write beat times at MICROSECOND (6-decimal) precision, not
+    # millisecond (3-decimal). The editor/timeline DERIVES per-bar BPM from beat
+    # spans (bpm = beats·60/span), which amplifies any rounding: at 3 decimals a
+    # constant-tempo GP (e.g. 140) shows a spurious ±0.05–0.7 BPM per-bar drift
+    # (worse for fast/odd meters) because most bar lengths don't land on a ms
+    # boundary. gp2rs computes these times exactly from the GP tempo map, so the
+    # only loss is this format string — 6 decimals makes the derived tempo match
+    # GP's authored value. (Everything else stays at :.3f; only beats drive tempo.)
     ebeats = ET.SubElement(root, "ebeats", count=str(len(beats)))
     for b in beats:
-        ET.SubElement(ebeats, "ebeat", time=f"{b.time:.3f}", measure=str(b.measure))
+        ET.SubElement(ebeats, "ebeat", time=f"{b.time:.6f}", measure=str(b.measure))
 
     # Sections
     sections_el = ET.SubElement(root, "sections", count=str(len(sections)))
@@ -1836,9 +1843,10 @@ def convert_drum_track_to_drumtab(
     drum strings. Unknown percussion sounds (cowbell, tambourine etc.) are
     skipped — round-tripping them would require teaching `lib/drums.py` first.
     Callers can pass an empty dict as ``out_unmapped`` to receive a per-MIDI
-    record of every skipped note (``{midi: {"count": int, "times": [...]}}``,
-    times capped at 100 samples per note) so they can surface a warning or
-    offer a manual mapping UI.
+    record of every skipped note (``{midi: {"count": int, "times": [...],
+    "velocities": [...]}}``, times/velocities index-aligned and capped at
+    100 samples per note — velocities carry the source notes' real dynamics)
+    so they can surface a warning or offer a manual mapping UI.
 
     Honours GP repeat brackets and D.S./D.C./Coda/Fine jumps when
     ``expand_repeats`` is true — same `_build_playback_schedule` machinery
@@ -1894,18 +1902,29 @@ def convert_drum_track_to_drumtab(
                             # NB: do NOT shadow the outer `entry` loop
                             # variable from `for entry in schedule:`.
                             unmapped_rec = out_unmapped.setdefault(
-                                int(midi_note), {"count": 0, "times": []})
+                                int(midi_note),
+                                {"count": 0, "times": [], "velocities": []})
                             unmapped_rec["count"] += 1
                             if len(unmapped_rec["times"]) < 100:
                                 unmapped_rec["times"].append(round(t, 3))
+                                # Index-aligned with times: the note's real
+                                # dynamics (same 1-127 gate as mapped hits,
+                                # falling back to the 100 import default) so
+                                # a hand-mapping UI doesn't flatten them.
+                                _uv = int(getattr(note, "velocity", 0) or 0)
+                                unmapped_rec["velocities"].append(
+                                    _uv if 1 <= _uv <= 127 else 100)
                         continue
 
                     hit: dict = {"t": round(t, 3), "p": piece}
 
-                    # Velocity: GP stores 1-127 MIDI velocity directly; default
-                    # is 95 (Velocities.default). Pass through verbatim,
-                    # clamping defensively so a corrupt file can't poison the
-                    # wire format.
+                    # Velocity: GP stores 1-127 MIDI velocity directly. Note
+                    # this is GP's *authoring* default (95, Velocities.default)
+                    # — unrelated to the drumtab render default of 100
+                    # (DEFAULT_VELOCITY, lib/drums.py:179), which only applies
+                    # when `v` is omitted from a hit. Pass the GP value through
+                    # verbatim, clamping defensively so a corrupt file can't
+                    # poison the wire format.
                     vel = int(getattr(note, "velocity", 0) or 0)
                     if 1 <= vel <= 127:
                         hit["v"] = vel
@@ -1946,9 +1965,21 @@ def convert_drum_track_to_drumtab(
     # Times for unmapped notes were collected in beat-iteration order;
     # multi-voice measures can produce out-of-order beats, so sort each
     # entry's `times` list chronologically before returning to the caller.
+    # Velocities are index-aligned with times, so they must sort in
+    # LOCKSTEP — sorting times alone would silently reassign dynamics.
     if out_unmapped is not None:
         for _rec in out_unmapped.values():
-            _rec["times"].sort()
+            _vels = _rec.get("velocities")
+            if _vels and len(_vels) == len(_rec["times"]):
+                _pairs = sorted(zip(_rec["times"], _vels))
+                _rec["times"] = [p[0] for p in _pairs]
+                _rec["velocities"] = [p[1] for p in _pairs]
+            else:
+                # Belt-and-suspenders: times & velocities are always appended
+                # together under the same `len(times) < 100` guard above, so
+                # in practice the lengths can't diverge. Kept as a defensive
+                # fallback, not a real divergence case.
+                _rec["times"].sort()
 
     return {
         "version": drums_mod.SCHEMA_VERSION,

lib/gp_autosync.py

@@ -538,9 +538,32 @@ def _dtw_align(
     Returns wp where wp[i] = [score_frame_index, audio_frame_index].
     """
     import librosa
+    import numpy as np
     cs = _safe_normalise(chroma_score)
     ca = _safe_normalise(chroma_audio)
-    _D, wp = librosa.sequence.dtw(cs, ca, metric='cosine')
+    # Slope-constrained step pattern ([[1,1],[1,2],[2,1]], Müller's standard
+    # music-sync config): every step advances BOTH axes, bounding the local
+    # tempo ratio to 0.5x-2x. librosa's default steps allow pure
+    # horizontal/vertical runs, and on riff-based music (long self-similar
+    # chroma stretches, e.g. stoner/doom) the flat cost surface let the path
+    # collapse — whole minutes of score mapped onto a single audio frame,
+    # producing garbage sync points. The constrained pattern makes that
+    # degenerate path impossible.
+    steps = np.array([[1, 1], [1, 2], [2, 1]])
+    weights = np.array([1.0, 1.0, 1.0])
+    try:
+        _D, wp = librosa.sequence.dtw(
+            cs, ca, metric='cosine',
+            step_sizes_sigma=steps, weights_mul=weights,
+        )
+    except Exception as exc:
+        # The constrained pattern needs the global length ratio within its
+        # 0.5x-2x slope bounds; a pathological pairing (e.g. a 3-minute tab
+        # against a 20-minute video) is infeasible and librosa raises. Fall
+        # back to the unconstrained path rather than failing the whole sync.
+        _log.warning("gp_autosync: constrained DTW infeasible (%s) — "
+                     "falling back to unconstrained steps", exc)
+        _D, wp = librosa.sequence.dtw(cs, ca, metric='cosine')
     return wp[::-1]  # reverse to forward order
 
 # ── Sync point extraction from DTW path ──────────────────────────────────────

lib/midi_import.py

@@ -203,7 +203,13 @@ def convert_midi_track_to_keys_wire(
     #     a foreign track's tempo events do NOT apply to the chosen
     #     track. Merging would mis-time the notes — restrict the tempo
     #     scan to the selected track only.
-    ticks_per_beat = midi.ticks_per_beat
+    # ``ticks_per_beat`` is 0 for a malformed header and NEGATIVE for SMPTE
+    # division (mido returns the signed short as-is). Both feed the two
+    # divisions below (tempo-table build + tick_to_seconds), so guard here:
+    # 0 would raise ZeroDivisionError and a negative value would yield
+    # negative/garbage times. Use ``> 0`` (not ``or``) so the negative SMPTE
+    # case also falls back to the SMF default.
+    ticks_per_beat = midi.ticks_per_beat if midi.ticks_per_beat > 0 else 480
     raw_events: list[tuple[int, int]] = [(0, 500000)]  # default 120 BPM
     midi_type = getattr(midi, "type", 1)
     tempo_source = (
@@ -352,7 +358,14 @@ def _build_tick_to_seconds(midi: mido.MidiFile, track_index: int) -> Callable[[i
       - type 1: parallel tracks share the timeline; merge tempo events.
       - type 2: independent timelines; tempo only from the chosen track.
     """
-    ticks_per_beat = midi.ticks_per_beat
+    # A metrical header carries positive ticks-per-beat. mido reads the SMF
+    # division as a signed short, so an SMPTE-division file surfaces as a
+    # negative value and a malformed header as 0 — both make the two division
+    # sites below divide by a non-positive number (ZeroDivisionError, or
+    # negative seconds that send the bar walk off the rails). Fall back to the
+    # SMF default here, the single place every caller routes ticks through, so
+    # each caller's own fallback is real rather than cosmetic.
+    ticks_per_beat = midi.ticks_per_beat if midi.ticks_per_beat > 0 else 480
     raw_events: list[tuple[int, int]] = [(0, 500000)]  # default 120 BPM
     midi_type = getattr(midi, "type", 1)
     tempo_source = (
@@ -393,6 +406,141 @@ def _build_tick_to_seconds(midi: mido.MidiFile, track_index: int) -> Callable[[i
     return tick_to_seconds
 
 
+# Safety valve for the bar walk below: a malformed SMF (absurd tempo + long
+# trailing meta) could otherwise imply millions of bars. Real charts sit
+# orders of magnitude below this.
+_TEMPO_MAP_MAX_BARS = 20000
+
+
+def convert_midi_tempo_map(midi_path: str, track_index: int = 0) -> dict:
+    """Extract the song-timeline grid a `.mid` file carries: tempos, time
+    signatures, and a full beat grid — the data the note converters here
+    always computed internally (to bake note times) and then threw away,
+    which left every MIDI import with no bars, no measures, and an implied
+    4/4 no matter what the file said.
+
+    Returns ``{"tempos": [...], "time_signatures": [...], "beats": [...]}``:
+
+    - ``tempos``: ``{time, bpm}`` per tempo event (deduped per tick).
+    - ``time_signatures``: ``{time, ts: [num, den]}`` per signature event —
+      the song-timeline sidecar shape (feedpak-spec §7.4).
+    - ``beats``: one row per beat on the editor grid shape — downbeats carry
+      a running ``measure`` (1, 2, 3, …) plus a ``den`` hint (the signature
+      denominator), interior beats carry ``measure: -1``. The beat unit
+      follows the active signature (6/8 ⇒ six eighth-note rows per bar).
+
+    Event scope mirrors ``_build_tick_to_seconds``: SMF type 0/1 merge meta
+    from all tracks (shared timeline); type 2 reads ONLY ``track_index``
+    (independent timelines — callers must never share one grid across
+    type-2 tracks). Signature changes apply at the NEXT bar boundary when a
+    file places one mid-bar (ill-formed but seen in the wild). All times
+    are computed from absolute ticks through the cumulative tempo table and
+    rounded once at emit — rounding error never accumulates with song
+    length. An SMF with no note events yields empty ``beats``.
+    """
+    midi = mido.MidiFile(midi_path)
+    # Positive for metrical files; 0 (malformed) or negative (SMPTE division,
+    # read as a signed short) otherwise — fall back so beat_ticks below stays
+    # sane, mirroring the guard inside _build_tick_to_seconds.
+    ticks_per_beat = midi.ticks_per_beat if midi.ticks_per_beat > 0 else 480
+    midi_type = getattr(midi, "type", 1)
+    # Same scope both converters use: type 2 reads only the chosen track
+    # (independent timelines); type 0/1 merge all tracks (shared timeline).
+    source_tracks = (
+        [midi.tracks[track_index]] if midi_type == 2 else midi.tracks
+    )
+    tick_to_seconds = _build_tick_to_seconds(midi, track_index)
+
+    # ── collect meta + the end of musical content in one pass ────────────
+    sig_events: list[tuple[int, int, int]] = []
+    tempo_events: list[tuple[int, int]] = []
+    end_tick = 0
+    for tr in source_tracks:
+        abs_tick = 0
+        for msg in tr:
+            abs_tick += msg.time
+            if msg.type == "time_signature":
+                num = int(getattr(msg, "numerator", 4) or 4)
+                den = int(getattr(msg, "denominator", 4) or 4)
+                if num > 0 and den > 0:
+                    sig_events.append((abs_tick, num, den))
+            elif msg.type == "set_tempo":
+                tempo_events.append((abs_tick, int(msg.tempo)))
+            elif msg.type in ("note_on", "note_off"):
+                end_tick = max(end_tick, abs_tick)
+
+    # Dedupe at equal ticks (last wins), matching the tempo-table rule.
+    sig_events.sort(key=lambda e: e[0])
+    sigs: list[tuple[int, int, int]] = []
+    for ev in sig_events:
+        if sigs and sigs[-1][0] == ev[0]:
+            sigs[-1] = ev
+        else:
+            sigs.append(ev)
+    if not sigs or sigs[0][0] > 0:
+        sigs.insert(0, (0, 4, 4))
+
+    tempo_events.sort(key=lambda e: e[0])
+    seen_tempo_ticks: dict[int, int] = {}
+    for ev_tick, ev_tempo in tempo_events:
+        seen_tempo_ticks[ev_tick] = ev_tempo
+    sorted_tempo_ticks = sorted(seen_tempo_ticks)
+    tempos_out: list[dict] = []
+    # Seed the MIDI default (120 BPM) at time 0 when the first tempo event
+    # lands after the start (or there are none). The beat grid already runs
+    # at 120 for the head of the song, so the sidecar must say so too —
+    # symmetric with the (0, 4, 4) default seeded into the signatures above.
+    if not sorted_tempo_ticks or sorted_tempo_ticks[0] > 0:
+        tempos_out.append({"time": 0.0, "bpm": 120.0})
+    for ev_tick in sorted_tempo_ticks:
+        tempos_out.append({
+            "time": round(tick_to_seconds(ev_tick), 3),
+            "bpm": round(60_000_000.0 / seen_tempo_ticks[ev_tick], 3),
+        })
+
+    time_signatures_out = [
+        {"time": round(tick_to_seconds(t), 3), "ts": [num, den]}
+        for t, num, den in sigs
+    ]
+
+    # ── walk bars from tick 0 to the end of the notes ────────────────────
+    beats: list[dict] = []
+    if end_tick > 0:
+        cur_tick = 0.0
+        measure = 1
+        sig_idx = 0
+        while cur_tick < end_tick and measure <= _TEMPO_MAP_MAX_BARS:
+            # Active signature: the latest event at or before this bar's
+            # start. Mid-bar events wait for the next boundary by
+            # construction (we only re-read between bars).
+            while (sig_idx + 1 < len(sigs)
+                    and sigs[sig_idx + 1][0] <= cur_tick + 1e-6):
+                sig_idx += 1
+            _, num, den = sigs[sig_idx]
+            beat_ticks = ticks_per_beat * 4.0 / den
+            beats.append({
+                "time": round(tick_to_seconds(int(round(cur_tick))), 3),
+                "measure": measure,
+                "den": den,
+            })
+            for k in range(1, num):
+                sub_tick = cur_tick + k * beat_ticks
+                if sub_tick >= end_tick:
+                    break
+                beats.append({
+                    "time": round(tick_to_seconds(int(round(sub_tick))), 3),
+                    "measure": -1,
+                })
+            cur_tick += num * beat_ticks
+            measure += 1
+
+    return {
+        "tempos": tempos_out,
+        "time_signatures": time_signatures_out,
+        "beats": beats,
+    }
+
+
 # ── Drum track listing (channel-9 only) ──────────────────────────────────────
 
 # Velocity below this is treated as a ghost note. GM doesn't have an explicit
@@ -486,10 +634,12 @@ def convert_drum_track_from_midi(
 
     Callers can pass an empty dict as ``out_unmapped`` to receive a
     per-MIDI record of every channel-9 note_on that didn't resolve to a
-    piece-id (``{midi: {"count": int, "times": [float, ...]}}``, times
-    capped at 100 samples per note). The default path skips this
-    capture entirely so MIDIs heavy with cowbell/tambourine/etc. take
-    no extra work.
+    piece-id (``{midi: {"count": int, "times": [float, ...],
+    "velocities": [int, ...]}}``, times/velocities index-aligned and
+    capped at 100 samples per note — velocities carry the source notes'
+    real dynamics so a hand-mapping UI doesn't have to flatten them to a
+    default). The default path skips this capture entirely so MIDIs
+    heavy with cowbell/tambourine/etc. take no extra work.
     """
     offset = float(audio_offset)
     if not math.isfinite(offset):
@@ -527,10 +677,13 @@ def convert_drum_track_from_midi(
                     continue
                 t = tick_to_seconds(abs_tick) + offset
                 entry = out_unmapped.setdefault(
-                    midi_note, {"count": 0, "times": []})
+                    midi_note, {"count": 0, "times": [], "velocities": []})
                 entry["count"] += 1
                 if len(entry["times"]) < 100:
                     entry["times"].append(round(t, 3))
+                    # Index-aligned with times: the note's real dynamics,
+                    # so hand-mapping doesn't flatten everything to 100.
+                    entry["velocities"].append(int(msg.velocity))
                 continue
             # Mapped note: compute t once for the raw entry.
             t = tick_to_seconds(abs_tick) + offset

lib/reqfields.py

@@ -0,0 +1,13 @@
+"""Request-field coercion helpers shared by the raw-`dict` POST handlers.
+
+Extracted verbatim from ``server.py`` (R3). Pure — no IO, no globals — so it
+imports cleanly from both ``server`` and any ``routers/`` module.
+"""
+
+
+def _clean_str(value) -> str:
+    """Trim a request field to a string; non-strings (or missing) → ''.
+    Lets the raw-`dict` POST handlers treat wrong-typed JSON (an int/list/etc.
+    where a string was expected) as "empty" and answer 400, instead of raising
+    AttributeError/TypeError → 500 on a later .strip()/`in`."""
+    return value.strip() if isinstance(value, str) else ""

lib/routers/__init__.py

@@ -0,0 +1,31 @@
+"""FastAPI route modules extracted from ``server.py`` (R3).
+
+Each module here exposes a module-level ``router`` (a ``fastapi.APIRouter``)
+that ``server.py`` mounts with ``app.include_router(...)`` at the point in the
+file where those routes used to be defined — FastAPI matches routes in
+registration order, so keeping the mount site preserves it.
+
+**Routers must never ``import server``.** They reach core singletons through
+the injected seam instead::
+
+    import appstate
+
+    @router.get("/api/thing")
+    def get_thing():
+        return appstate.meta_db.thing()
+
+and always as a **module attribute, at call time** — never
+``from appstate import meta_db``, which freezes the binding and defeats both a
+later ``appstate.configure()`` and ``monkeypatch.setattr``. See ``appstate.py``.
+
+Dependencies flow one way: ``server -> routers -> appstate``.
+
+**Why this lives under ``lib/``.** ``lib/`` is the only core directory every
+packaging path already copies wholesale — the Dockerfile (``COPY lib/``),
+``docker-compose.yml``, and feedback-desktop's ``bundle-slopsmith.sh``
+(``cp -r lib``) — and all three put it on ``sys.path``. A root-level package
+ships in Docker but is silently dropped from the packaged desktop app, whose
+bundler copies a hardcoded file list. Route modules import nothing at module
+scope beyond FastAPI and ``appstate``, so they do no import-time IO and satisfy
+Principle V's rule for ``lib/``.
+"""

lib/routers/art.py

@@ -0,0 +1,513 @@
+"""Album-art routes: serve / cover-search / candidates / upload / url / remove
+(/api/song/{filename}/art*, /api/art/{filename}/override).
+
+Extracted verbatim from server.py (R3). Only the decorators (@app -> @router) and
+the seam reads change: meta_db -> appstate.meta_db, ART_CACHE_DIR ->
+appstate.art_cache_dir, and the three shared art helpers that stay in server.py
+(they are also used by the song/delete routes) -> appstate.<callable>
+(_song_pack_art_exists, _art_override_paths, _art_safe_name). The CAA / release
+search transport lives in lib/enrichment.py and is reached as enrichment.X.
+"""
+
+import asyncio
+import hashlib
+import ipaddress
+from pathlib import Path
+
+from fastapi import APIRouter, HTTPException, Request
+from fastapi.responses import FileResponse, JSONResponse, Response
+
+import appstate
+import enrichment
+import loosefolder as loosefolder_mod
+import sloppak as sloppak_mod
+from dlc_paths import _get_dlc_dir, _resolve_dlc_path
+
+import logging
+log = logging.getLogger("feedBack.server")
+router = APIRouter()
+
+def _if_none_match_hits(header: str | None, etag: str) -> bool:
+    """True if an If-None-Match header matches `etag` (weak comparison).
+
+    Handles the `*` wildcard and comma-separated lists, and ignores a weak
+    `W/` prefix on either side — the standard semantics for a conditional GET.
+    """
+    if not header:
+        return False
+    bare = etag.removeprefix("W/")
+    for tok in header.split(","):
+        t = tok.strip()
+        if t == "*" or t.removeprefix("W/") == bare:
+            return True
+    return False
+
+
+# Album art is served with a strong validator (an ETag on the sloppak byte
+# path; FileResponse's own ETag/Last-Modified on the file paths) and revalidated
+# with `no-cache`. That keeps re-scroll cheap — a conditional GET returns a
+# bodyless 304 — without ever serving a stale cover. A long `immutable` max-age
+# was rejected: the frontend's `?v=<mtime>` buster is only second-resolution, so
+# a same-second cover rewrite would keep the URL and pin the old bytes for the
+# cache lifetime. Validation cost is negligible for a localhost backend.
+_ART_CACHE_HEADERS = {"Cache-Control": "no-cache"}
+
+
+def _art_etag(path: Path) -> str | None:
+    """Strong validator for an art file: nanosecond mtime + size (so a
+    same-second rewrite still changes it). None if the file can't be stat'd."""
+    try:
+        st = path.stat()
+        return f'"{st.st_mtime_ns}-{st.st_size}"'
+    except OSError:
+        return None
+
+
+def _art_conditional(etag: str | None, request: Request | None):
+    """Return (headers, not_modified) for an art response. `not_modified` is
+    True when the client's If-None-Match already matches `etag` → caller should
+    return a bodyless 304. Starlette's FileResponse emits an ETag but does NOT
+    itself evaluate If-None-Match, so every art path routes through here to get
+    real conditional handling."""
+    headers = dict(_ART_CACHE_HEADERS)
+    if etag:
+        headers["ETag"] = etag
+    inm = request.headers.get("if-none-match") if request is not None else None
+    return headers, bool(etag) and _if_none_match_hits(inm, etag)
+
+
+def _file_art_response(path: Path, media_type: str, request: Request | None):
+    """FileResponse for an on-disk art file, with no-cache + ETag and a bodyless
+    304 when the client's validator still matches."""
+    headers, not_modified = _art_conditional(_art_etag(path), request)
+    if not_modified:
+        return Response(status_code=304, headers=headers)
+    return FileResponse(str(path), media_type=media_type, headers=headers)
+
+
+@router.get("/api/song/{filename:path}/art")
+async def get_song_art(filename: str, request: Request = None, source: str = ""):
+    """Serve album art for a song, walking the R3 override chain:
+
+      1. USER OVERRIDE (upload / URL-fetch, {safe_name}.gif|.png in the art
+         cache) — art the user explicitly pinned outranks everything, pack
+         art included. GIF is allowed HERE only: an animated cover is a
+         local-only bonus; packs stay jpg/png/webp and nothing ever writes
+         art into a pack file.
+      2. PACK ART — sloppak cover (single member read, no full unpack) or
+         the loose folder's discovered image.
+      3. COVER ART ARCHIVE cache — fetched by the enrichment art worker for
+         matched songs that lack pack art, keyed by release MBID.
+
+    `?source=pack` narrows the chain to step 2 only (no override, no CAA):
+    the cover picker's "Pack original" tile must show the pack's own art
+    even while a user override is what the plain route serves. 404 when the
+    song ships no art of its own.
+    """
+    dlc = _get_dlc_dir()
+    if not dlc:
+        return JSONResponse({"error": "not configured"}, 404)
+
+    song_path = _resolve_dlc_path(dlc, filename)
+    if song_path is None:
+        return JSONResponse({"error": "forbidden"}, 403)
+    if not song_path.exists():
+        return JSONResponse({"error": "not found"}, 404)
+
+    pack_only = source == "pack"
+
+    # 1. User override — GIF first (it wins over a stale PNG override).
+    if not pack_only:
+        for cached in appstate.art_override_paths(filename):
+            mt = "image/gif" if cached.suffix == ".gif" else "image/png"
+            return _file_art_response(cached, mt, request)
+
+    # 2a. Sloppak: read the cover (manifest-declared or default) straight from
+    # the package. For a zip-form sloppak this opens just the cover member —
+    # NOT the whole archive — so the library grid never triggers a full unpack
+    # of stems just to paint a thumbnail.
+    if sloppak_mod.is_sloppak(song_path):
+        # Read the cover (cheap — single member, no full unpack) and validate by
+        # its CONTENT. A stat-based ETag would be wrong for directory-form
+        # sloppaks: editing cover.jpg in place changes the file's mtime, not the
+        # directory's, so a dir-stat ETag could emit a stale 304. Content hashing
+        # is correct for both dir- and zip-form. Raw byte Response lacks
+        # FileResponse's validators, so we attach the ETag + honor If-None-Match.
+        try:
+            art = await asyncio.to_thread(sloppak_mod.read_cover_bytes, song_path)
+        except Exception:
+            art = None
+        if art is not None:
+            data, mt = art
+            etag = f'"{hashlib.sha1(data).hexdigest()}"'
+            headers, not_modified = _art_conditional(etag, request)
+            if not_modified:
+                return Response(status_code=304, headers=headers)
+            return Response(content=data, media_type=mt, headers=headers)
+
+    # 2b. Loose folder: serve the discovered art file directly.
+    # song_path is already validated against DLC_DIR by _resolve_dlc_path.
+    elif loosefolder_mod.is_loose_song(song_path):
+        art_path = loosefolder_mod.find_art(song_path)
+        if art_path:
+            # Re-resolve in case the matched file is a symlink — a crafted
+            # custom song could put `album_art.jpg` as a symlink to anywhere on
+            # disk. Insist the final target stays inside the song folder.
+            art_resolved = art_path.resolve()
+            try:
+                art_resolved.relative_to(song_path)
+            except ValueError:
+                return JSONResponse({"error": "forbidden"}, 403)
+            if art_resolved.is_file():
+                mt = {
+                    ".jpg": "image/jpeg", ".jpeg": "image/jpeg",
+                    ".png": "image/png", ".webp": "image/webp",
+                }.get(art_resolved.suffix.lower(), "image/jpeg")
+                return _file_art_response(art_resolved, mt, request)
+
+    # 3. Cover Art Archive cache (the enrichment art worker's fetch).
+    if not pack_only:
+        row = appstate.meta_db.get_enrichment(filename)
+        if row and row.get("art_state") == "caa" and row.get("art_cache_path"):
+            caa = Path(row["art_cache_path"])
+            if caa.is_file():
+                return _file_art_response(caa, "image/jpeg", request)
+
+    return JSONResponse({"error": "no art"}, 404)
+
+
+# ── Cover picker (PR-C): candidate assembly ───────────────────────────────────
+# Enumerated ON OPEN, never at scan time (charrette §8), and NO image bytes
+# are fetched here — Cover Art Archive release INDEX jsons only (1-3 throttled
+# calls on a cache miss); the tiles' thumbnails load straight from the archive
+# in the client. Applying a pick never grows a new write path: the client
+# POSTs the chosen thumb URL to the EXISTING …/art/url route (the override
+# lane — never evicted, survives a re-match), "Pack original" DELETEs the
+# override, uploads keep the existing upload route.
+_ART_PICKER_MAX_CAA = 12
+
+
+@router.get("/api/song/{filename:path}/art/cover-search")
+def api_art_cover_search(filename: str, q: str = ""):
+    """Search Cover Art Archive (via MusicBrainz release-groups) for album covers
+    — powers the Change-cover picker's search box, so a cover can be found even
+    for a song with no metadata match (the unmatched city-pop pile, where
+    /art/candidates is empty). `q` defaults to the song's own artist + album/
+    title (romaji fallback applied). Read-only; the picker renders the thumbs and
+    applies a pick through the existing /art/url route."""
+    query = (q or "").strip()
+    if not query:
+        pack = appstate.meta_db.pack_fields(appstate.meta_db._canonical_song_filename(filename))
+        query = " ".join(x for x in (pack.get("artist"), pack.get("album") or pack.get("title")) if x).strip()
+    if not query:
+        return {"query": "", "covers": []}
+    try:
+        return {"query": query, "covers": enrichment._mb_search_release_groups(query, limit=8)}
+    except enrichment.EnrichTransportError:
+        return {"query": query, "covers": [], "error": "unavailable"}
+
+
+@router.get("/api/song/{filename:path}/art/candidates")
+def get_song_art_candidates(filename: str):
+    """Everything the cover picker can offer for one song, without fetching a
+    single image: the current cover (with its provenance), the pack original
+    when the song ships art, and CAA candidates for the matched/manual
+    release plus any distinct releases among the stored review candidates.
+    Sync route on purpose (the CAA index fetch sleeps in the shared
+    throttle — FastAPI runs `def` routes in the threadpool). One response,
+    `pending` always False — the client shows a spinner for the request's own
+    latency; offline / CAA-down just means an empty caa tail (the instant
+    tiles keep working), never an error."""
+    from urllib.parse import quote
+    dlc = _get_dlc_dir()
+    song_path = _resolve_dlc_path(dlc, filename) if dlc else None
+    if song_path is None or not song_path.exists():
+        raise HTTPException(status_code=404, detail="unknown song")
+
+    row = appstate.meta_db.get_enrichment(filename) or {}
+    has_pack = appstate.song_pack_art_exists(filename)
+    art_url = f"/api/song/{quote(filename)}/art"
+
+    # What the plain art route would serve right now — the serve chain's
+    # order (override > pack > CAA cache) restated as provenance.
+    if appstate.art_override_paths(filename):
+        provenance = "yours"
+    elif has_pack:
+        provenance = "pack"
+    elif row.get("art_state") == "caa" and row.get("art_cache_path"):
+        provenance = "matched"
+    else:
+        provenance = "none"
+
+    candidates: list[dict] = [{
+        "id": "current", "kind": "current", "label": "Current",
+        "thumb_url": art_url, "provenance": provenance,
+    }]
+    if has_pack:
+        candidates.append({
+            "id": "pack", "kind": "pack", "label": "Pack original",
+            "thumb_url": art_url + "?source=pack", "provenance": "pack",
+        })
+
+    # Releases worth asking the archive about: the matched/manual release
+    # first (it seeds the best candidates), then any distinct release among
+    # the stored review candidates (a review row has no mb_release_id of its
+    # own — its releases live in the candidates JSON).
+    # Only spend the shared CAA rate budget on rows whose match warrants it:
+    # a matched/manual release seeds the best candidates, and a review row's
+    # stored candidates are still live proposals. A failed/rejected (or
+    # unscanned) row has no accepted match — asking would burn the budget and
+    # surface releases already rejected as non-matches. The Current + Pack
+    # tiles above serve regardless, so those songs still get a picker.
+    rids: list[str] = []
+    if row.get("match_state") in ("matched", "manual", "review"):
+        if row.get("match_state") in ("matched", "manual") and row.get("mb_release_id"):
+            rids.append(str(row["mb_release_id"]))
+        for cand in (row.get("candidates") or []):
+            rid = str(cand.get("release_id") or "") if isinstance(cand, dict) else ""
+            if rid and rid not in rids:
+                rids.append(rid)
+
+    caa_entries: list[dict] = []
+    for rid in rids:
+        if len(caa_entries) >= _ART_PICKER_MAX_CAA:
+            break
+        try:
+            imgs = enrichment._caa_index_cached(rid)
+        except enrichment.EnrichTransportError:
+            # Offline / archive down — stop asking (each further miss would
+            # only burn a timeout). The instant tiles still serve; a later
+            # picker-open retries naturally (failures are never cached).
+            break
+        # Front covers first, approved before pending, otherwise index order
+        # (the picker grammar is a RANKED list — §7/§9).
+        def _rank(img):
+            types = img.get("types") or []
+            is_front = bool(img.get("front")) or "Front" in types
+            return (not is_front, not bool(img.get("approved")))
+        for img in sorted((i for i in imgs if isinstance(i, dict)), key=_rank):
+            if len(caa_entries) >= _ART_PICKER_MAX_CAA:
+                break
+            thumbs = img.get("thumbnails") or {}
+            if not isinstance(thumbs, dict):
+                continue
+            thumb = (thumbs.get("500") or thumbs.get("large")
+                     or thumbs.get("250") or thumbs.get("small"))
+            if not thumb:
+                continue
+            types = [str(t) for t in (img.get("types") or []) if isinstance(t, str)]
+            caa_entries.append({
+                "id": f"caa-{rid}-{img.get('id', '')}",
+                "kind": "caa",
+                "label": ", ".join(types) or "Cover",
+                "thumb_url": str(thumb),
+                "provenance": "matched",
+                "types": types,
+                "approved": bool(img.get("approved")),
+                "release_id": rid,
+            })
+
+    return {"candidates": candidates + caa_entries, "pending": False}
+
+
+def _save_art_override(filename: str, img_data: bytes) -> dict:
+    """Persist a user art override into the art cache (R3). One override per
+    song: GIF input is validated and kept VERBATIM as .gif (animation intact —
+    the local-only bonus; it is never written into the pack file), everything
+    else is normalized to RGB PNG via PIL. Saving either kind removes the
+    other so the serve chain has exactly one user file to find."""
+    appstate.art_cache_dir.mkdir(parents=True, exist_ok=True)
+    stem = appstate.art_safe_name(filename)
+    png_path = appstate.art_cache_dir / f"{stem}.png"
+    gif_path = appstate.art_cache_dir / f"{stem}.gif"
+    from PIL import Image
+    import io as _io
+    if img_data[:6] in (b"GIF87a", b"GIF89a"):
+        try:
+            probe = Image.open(_io.BytesIO(img_data))
+            probe.verify()   # decodes headers/frames without keeping the image
+            if probe.format != "GIF":
+                raise ValueError("not a GIF")
+        except Exception as e:
+            return {"error": f"Invalid image: {e}"}
+        gif_path.write_bytes(img_data)
+        png_path.unlink(missing_ok=True)
+        return {"ok": True, "kind": "gif"}
+    try:
+        img = Image.open(_io.BytesIO(img_data)).convert("RGB")
+        img.save(str(png_path), "PNG")
+    except Exception as e:
+        return {"error": f"Invalid image: {e}"}
+    gif_path.unlink(missing_ok=True)
+    return {"ok": True, "kind": "png"}
+
+
+@router.post("/api/song/{filename:path}/art/upload")
+async def upload_song_art_b64(filename: str, data: dict):
+    """Upload a custom cover as base64 (PNG/JPG/WebP → normalized PNG;
+    GIF → kept animated, local-only). The override outranks pack art in the
+    serve chain; remove it via DELETE …/art/override."""
+    import base64
+    # Reject art for a filename that doesn't resolve to a real song (mirrors the
+    # url route's guard) — no writing stray override files for unknown keys.
+    dlc = _get_dlc_dir()
+    song_path = _resolve_dlc_path(dlc, filename) if dlc else None
+    if song_path is None or not song_path.exists():
+        raise HTTPException(status_code=404, detail="unknown song")
+    b64 = data.get("image", "")
+    if not b64:
+        return {"error": "No image data"}
+    # Strip data URL prefix if present
+    if "," in b64:
+        b64 = b64.split(",", 1)[1]
+    try:
+        img_data = base64.b64decode(b64)
+    except Exception:
+        return {"error": "Invalid base64"}
+    if len(img_data) > _ART_URL_MAX_BYTES:
+        raise HTTPException(status_code=400, detail="image larger than 10 MB")
+    return _save_art_override(filename, img_data)
+
+
+# Art-by-URL fetch cap — a cover, not a wallpaper pack.
+_ART_URL_MAX_BYTES = 10 * 1024 * 1024
+
+
+def _url_host_is_internal(url: str) -> bool:
+    """True when a user-supplied URL's host resolves to a loopback, private,
+    link-local, reserved, multicast or unspecified address — an SSRF target we
+    refuse to fetch on the user's behalf (e.g. 169.254.169.254 metadata, LAN
+    services). Fails CLOSED: an unresolvable or unparseable host is treated as
+    internal. Every resolved address must be public for the URL to pass."""
+    from urllib.parse import urlparse
+    import socket
+    host = urlparse(url).hostname
+    if not host:
+        return True
+    try:
+        infos = socket.getaddrinfo(host, None)
+    except OSError:
+        return True
+    if not infos:
+        return True
+    for info in infos:
+        raw = info[4][0].split("%", 1)[0]  # strip any zone id
+        try:
+            ip = ipaddress.ip_address(raw)
+        except ValueError:
+            return True
+        if (ip.is_private or ip.is_loopback or ip.is_link_local
+                or ip.is_reserved or ip.is_multicast or ip.is_unspecified):
+            return True
+    return False
+
+
+# Art-by-URL redirect budget. Cover hosts commonly answer with a redirect —
+# the Cover Art Archive (whose thumbs the cover picker applies through this
+# very route) 307s every image to archive.org — so redirects must work; 5
+# hops is generous for any real CDN chain while still bounding the walk.
+_ART_URL_MAX_REDIRECTS = 5
+
+
+def _fetch_art_url(url: str) -> bytes:
+    """The one place art-by-URL touches the network (tests fake this seam).
+    User-initiated, so not throttled like the background workers — but the
+    same offline guard applies (pytest can never fetch), the host is checked
+    against internal/reserved ranges (SSRF), redirects are followed MANUALLY
+    with the scheme + internal-host guard re-applied to every hop (so a
+    redirect can't smuggle the request to an internal target — a blanket
+    no-redirect rule would break every Cover Art Archive pick, which always
+    redirects to archive.org), and the size cap is enforced while streaming
+    so a huge response never fully downloads.
+
+    Residual, accepted: each hop's host is resolved here and again by
+    requests, so a rebinding DNS name is a theoretical TOCTOU. Not closed
+    with an IP-pinned connection because (a) this is a single-user, no-auth
+    app (constitution §I) and the route is demo-blocked, so there is no
+    untrusted submission path, and (b) no other in-tree client (MusicBrainz,
+    CAA) pins either — a bespoke pinned+SNI adapter here would be
+    inconsistent and disproportionate. The cheap guards above still stop the
+    realistic vectors (direct internal URL, redirect-to-internal)."""
+    if not enrichment._enrich_network_enabled():
+        raise enrichment.EnrichTransportError("art fetch disabled (offline)")
+    import requests
+    from urllib.parse import urljoin, urlparse
+    for _hop in range(_ART_URL_MAX_REDIRECTS + 1):
+        # Re-validate EVERY hop, not just the user's original URL: the whole
+        # point of handling redirects ourselves is that each target gets the
+        # same scheme + SSRF gate before any request is made.
+        if urlparse(url).scheme not in ("http", "https"):
+            raise ValueError("url must be http(s)")
+        if _url_host_is_internal(url):
+            raise ValueError("url host is not allowed")
+        try:
+            with requests.get(url, timeout=15, stream=True, allow_redirects=False,
+                              headers={"User-Agent": enrichment._enrich_user_agent()}) as resp:
+                if resp.status_code in (301, 302, 303, 307, 308):
+                    loc = resp.headers.get("Location") or ""
+                    if not loc:
+                        raise enrichment.EnrichTransportError(
+                            f"HTTP {resp.status_code} without a Location")
+                    url = urljoin(url, loc)
+                    continue
+                if resp.status_code != 200:
+                    raise enrichment.EnrichTransportError(f"HTTP {resp.status_code}")
+                data = b""
+                for chunk in resp.iter_content(65536):
+                    data += chunk
+                    if len(data) > _ART_URL_MAX_BYTES:
+                        raise ValueError("image larger than 10 MB")
+                return data
+        except requests.RequestException as e:
+            raise enrichment.EnrichTransportError(str(e)) from e
+    raise enrichment.EnrichTransportError("too many redirects")
+
+
+@router.post("/api/song/{filename:path}/art/url")
+def set_song_art_from_url(filename: str, data: dict):
+    """Paste-a-link cover art (the media-server idiom): the server fetches the
+    image and stores it as this song's local override — identical result to an
+    upload, including the GIF-stays-local rule. http(s) only."""
+    url = str((data or {}).get("url") or "").strip()
+    from urllib.parse import urlparse
+    parsed = urlparse(url)
+    if parsed.scheme not in ("http", "https") or not parsed.hostname:
+        raise HTTPException(status_code=400, detail="url must be http(s)")
+    dlc = _get_dlc_dir()
+    song_path = _resolve_dlc_path(dlc, filename) if dlc else None
+    if song_path is None or not song_path.exists():
+        raise HTTPException(status_code=404, detail="unknown song")
+    try:
+        img_data = _fetch_art_url(url)
+    except enrichment.EnrichTransportError as e:
+        return JSONResponse({"error": "could not fetch image", "detail": str(e)},
+                            status_code=502)
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e))
+    return _save_art_override(filename, img_data)
+
+
+@router.delete("/api/art/{filename:path}/override")
+def remove_song_art_override(filename: str):
+    """Drop the user art override — the serve chain falls back to pack art,
+    then the Cover Art Archive cache. Lives under /api/art (NOT /api/song) so
+    the greedy DELETE /api/song/{path} catch-all can't shadow it — the same
+    dodge the chart split/unsplit routes use."""
+    removed = False
+    for p in appstate.art_override_paths(filename):
+        try:
+            p.unlink()
+            removed = True
+        except OSError:
+            pass
+    if removed:
+        # The art worker may have settled this row as 'user' (override present,
+        # no pack art). Reset it so the next enrichment pass re-evaluates and the
+        # CAA fallback resumes — otherwise a removed override strands the row
+        # (enrichment_art_pending only re-queues art_state IS NULL) and the song
+        # is left with no art at all.
+        try:
+            appstate.meta_db.set_enrichment_art(filename, None, None)
+        except Exception:
+            log.exception("art override delete: failed to reset enrichment state")
+    return {"ok": True, "removed": removed}

lib/routers/artist_aliases.py

@@ -0,0 +1,68 @@
+"""Artist aliases / Tidy-up (P4) — canonicalize messy artist tags at DISPLAY
+("ACDC" -> "AC/DC") without touching feedpak files or the scanner-derived
+songs.artist. All DB-only.
+
+Extracted verbatim from ``server.py`` (R3); only the decorator receiver
+(``@app`` -> ``@router``) and the singleton read (``meta_db`` ->
+``appstate.meta_db``) changed. The read stays a module attribute so a re-imported
+``server`` re-publishes a fresh DB into the seam — see ``appstate.py``.
+"""
+
+from fastapi import APIRouter
+from fastapi.responses import JSONResponse
+
+import appstate
+
+router = APIRouter()
+
+
+@router.get("/api/artist-aliases")
+def list_artist_aliases():
+    """Existing raw→canonical overrides (the Tidy-up 'current merges' list)."""
+    return {"aliases": appstate.meta_db.list_artist_aliases()}
+
+
+@router.get("/api/artists/raw")
+def list_raw_artists(limit: int = 2000):
+    """Distinct RAW artist names + song counts + current canonical — the Tidy-up
+    picker (you merge raw variants into one canonical)."""
+    return {"artists": appstate.meta_db.raw_artists(limit)}
+
+
+@router.post("/api/artist-aliases")
+def set_artist_alias(data: dict):
+    """Upsert one override: {raw_name, canonical_name, mb_artist_id?}. A self-alias
+    (raw == canonical) clears the row instead (un-merge)."""
+    raw = (data.get("raw_name") or "").strip()
+    canon = (data.get("canonical_name") or "").strip()
+    if not raw or not canon:
+        return JSONResponse({"error": "raw_name and canonical_name are required"}, 400)
+    result = appstate.meta_db.set_artist_alias(raw, canon, (data.get("mb_artist_id") or None))
+    if not result.get("ok"):
+        # Would form a cycle (raw → … → raw) — refuse rather than corrupt the chain.
+        return JSONResponse(
+            {"error": "alias would create a cycle", "raw_name": raw, "canonical_name": canon},
+            409)
+    return {"ok": True, "raw_name": raw, "canonical_name": result.get("canonical_name", canon)}
+
+
+@router.post("/api/artist-aliases/merge")
+def merge_artist_aliases(data: dict):
+    """Merge several raw artist variants into one canonical:
+    {raw_names: [...], canonical_name}. The canonical's own self-alias is skipped.
+    Returns {merged: N}."""
+    canon = (data.get("canonical_name") or "").strip()
+    raws = data.get("raw_names")
+    if not canon:
+        return JSONResponse({"error": "canonical_name is required"}, 400)
+    if not isinstance(raws, list) or not raws:
+        return JSONResponse({"error": "raw_names must be a non-empty array"}, 400)
+    n = appstate.meta_db.merge_artists(raws, canon)
+    return {"merged": n, "canonical_name": canon}
+
+
+@router.delete("/api/artist-aliases/{raw_name:path}")
+def delete_artist_alias(raw_name: str):
+    """Remove one override so that raw artist stands on its own again."""
+    appstate.meta_db.remove_artist_alias(raw_name)
+    return {"ok": True}

lib/routers/audio_effects.py

@@ -0,0 +1,80 @@
+"""Audio-effects mapping API — the core-owned song/tone -> provider routing index.
+
+Extracted verbatim from ``server.py`` (R3); only the decorator receiver
+(``@app`` -> ``@router``) and the singleton read (``audio_effect_mappings`` ->
+``appstate.audio_effect_mappings``) changed. The read must stay a module
+attribute so a re-imported ``server`` re-publishes a fresh DB into the seam and
+`monkeypatch.setattr` reaches this module — see ``appstate.py``.
+"""
+
+from fastapi import APIRouter, Body, Query
+from fastapi.responses import JSONResponse
+
+import appstate
+
+router = APIRouter()
+
+
+def _audio_effects_error(exc: Exception):
+    return JSONResponse({"error": str(exc)}, status_code=400)
+
+
+@router.get("/api/audio-effects/mappings")
+def list_audio_effect_mappings(
+    song_key: str = Query(""),
+    filename: str = Query(""),
+    tone_key: str = Query(""),
+    provider_id: str = Query(""),
+):
+    try:
+        return {
+            "mappings": appstate.audio_effect_mappings.list(
+                song_key=song_key,
+                filename=filename,
+                tone_key=tone_key,
+                provider_id=provider_id,
+            )
+        }
+    except ValueError as exc:
+        return _audio_effects_error(exc)
+
+
+@router.post("/api/audio-effects/mappings")
+def upsert_audio_effect_mapping(data: dict = Body(...)):
+    try:
+        mapping = appstate.audio_effect_mappings.upsert(data)
+    except ValueError as exc:
+        return _audio_effects_error(exc)
+    return {"ok": True, "mapping": mapping}
+
+
+@router.delete("/api/audio-effects/mappings/{mapping_id}")
+def delete_audio_effect_mapping(mapping_id: int, provider_id: str = Query("")):
+    try:
+        deleted = appstate.audio_effect_mappings.delete(mapping_id, provider_id=provider_id)
+    except ValueError as exc:
+        return _audio_effects_error(exc)
+    if not deleted:
+        return JSONResponse({"error": "mapping not found"}, status_code=404)
+    return {"ok": True}
+
+
+@router.post("/api/audio-effects/mappings/{mapping_id}/activate")
+def activate_audio_effect_mapping(mapping_id: int, data: dict = Body(default_factory=dict)):
+    try:
+        provider_id = data.get("provider_id") if "provider_id" in data else data.get("providerId")
+        mapping = appstate.audio_effect_mappings.activate(mapping_id, provider_id="" if provider_id is None else provider_id)
+    except ValueError as exc:
+        return _audio_effects_error(exc)
+    if not mapping:
+        return JSONResponse({"error": "mapping not found"}, status_code=404)
+    return {"ok": True, "mapping": mapping}
+
+
+@router.delete("/api/audio-effects/active-mapping")
+def clear_audio_effect_active_mapping(song_key: str = Query(...), tone_key: str = Query("")):
+    try:
+        cleared = appstate.audio_effect_mappings.clear_active(song_key=song_key, tone_key=tone_key)
+    except ValueError as exc:
+        return _audio_effects_error(exc)
+    return {"ok": True, "cleared": cleared}

lib/routers/chart.py

@@ -0,0 +1,115 @@
+"""Chart-level endpoints — split/unsplit a chart from its work, resolve work
+membership, and the context-menu "Get info" file inspector.
+
+Extracted verbatim from ``server.py`` (R3); edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``. DLC path resolution comes from
+``dlc_paths``; sloppak/loose detection from the shared lib modules.
+"""
+
+from fastapi import APIRouter, HTTPException
+
+import appstate
+from dlc_paths import _get_dlc_dir, _resolve_dlc_path
+import sloppak as sloppak_mod
+import loosefolder as loosefolder_mod
+
+router = APIRouter()
+
+
+@router.post("/api/chart/{filename:path}/split")
+def api_split_chart(filename: str):
+    """'These aren't the same song' — split this chart out as its own singleton
+    work. Under /api/chart (NOT /api/song) so the DELETE /api/song/{path}
+    catch-all can't shadow it."""
+    key = appstate.meta_db._canonical_song_filename(filename)
+    appstate.meta_db.split_chart(key)
+    return {"ok": True, "filename": key}
+
+
+@router.post("/api/chart/{filename:path}/unsplit")
+def api_unsplit_chart(filename: str):
+    """Undo a split — rejoin the chart to its work."""
+    key = appstate.meta_db._canonical_song_filename(filename)
+    appstate.meta_db.unsplit_chart(key)
+    return {"ok": True, "filename": key}
+
+
+@router.get("/api/chart/{filename:path}/work")
+def api_get_chart_work(filename: str):
+    """Resolve a chart's work membership: {work_key, chart_count}. For openers
+    on rows that came from an ungrouped query (the tree view) — grouped grid
+    rows already carry both fields inline."""
+    return appstate.meta_db.chart_work(filename)
+
+
+@router.get("/api/chart/{filename:path}/fileinfo")
+def api_chart_fileinfo(filename: str):
+    """The context menu's "Get info": where the file lives + what the pack
+    contains. Under /api/chart — the GET /api/song/{path} catch-all would
+    swallow a /api/song/…/fileinfo suffix. Read-only; demo-mode blocks it
+    because it exposes filesystem paths."""
+    dlc = _get_dlc_dir()
+    if not dlc:
+        raise HTTPException(status_code=404, detail="not configured")
+    p = _resolve_dlc_path(dlc, filename)
+    if p is None:
+        raise HTTPException(status_code=403, detail="forbidden")
+    if not p.exists():
+        raise HTTPException(status_code=404, detail="not found")
+    # Restrict to actual charts — sloppak or loose song. Without this the route
+    # would stat ANY file the user happens to keep under DLC_DIR (e.g. notes),
+    # leaking its path/size; the app only recognises these two song formats.
+    is_pak = sloppak_mod.is_sloppak(p)
+    is_loose = loosefolder_mod.is_loose_song(p)
+    if not (is_pak or is_loose):
+        raise HTTPException(status_code=404, detail="not a chart")
+    st = p.stat()
+    info = {
+        "filename": filename,
+        "path": str(p),
+        "folder": str(p.parent),
+        "format": "sloppak" if is_pak else "loose",
+        # Directory-form songs report the tree's total (covers loose folders
+        # and dir-form paks); zip-form paks report the archive size. Symlinked
+        # entries are skipped so a link inside the folder can't pull in — or
+        # leak the size of — a file outside it.
+        "size": (st.st_size if p.is_file()
+                 else sum(f.stat().st_size for f in p.rglob("*")
+                          if f.is_file() and not f.is_symlink())),
+        "mtime": st.st_mtime,
+    }
+    if is_pak:
+        try:
+            m = sloppak_mod.load_manifest(p) or {}
+        except Exception:
+            m = {}
+        arrs = [str(a.get("name", a.get("id", ""))) for a in (m.get("arrangements") or [])
+                if isinstance(a, dict)]
+        stems = [str(s.get("id", "")) for s in (m.get("stems") or []) if isinstance(s, dict)]
+        try:
+            has_cover = sloppak_mod.read_cover_bytes(p, m) is not None
+        except Exception:
+            has_cover = False
+        # The optional identity/catalog keys, listed only when present — the
+        # Get-info panel's "what this pack carries vs what's missing" readout.
+        identity = {k: m.get(k) for k in
+                    ("mbid", "isrc", "genres", "track", "disc", "album_artist",
+                     "feedpak_version", "language")
+                    if m.get(k) not in (None, "", [])}
+        info["manifest"] = {
+            "title": str(m.get("title", "")), "artist": str(m.get("artist", "")),
+            "album": str(m.get("album", "")), "year": str(m.get("year", "") or ""),
+            "arrangements": arrs, "stems": stems,
+            "has_cover": has_cover, "has_lyrics": bool(m.get("lyrics")),
+            "authors": [a.get("name", "") if isinstance(a, dict) else str(a)
+                        for a in (m.get("authors") or [])],
+            "identity": identity,
+        }
+    # The enrichment verdict, so Get info can say "Matched (auto, 96%)" /
+    # "Pinned by you" / "Not matched" alongside the file facts.
+    row = appstate.meta_db.get_enrichment(filename)
+    if row:
+        info["match"] = {k: row.get(k) for k in
+                         ("match_state", "match_source", "match_score",
+                          "canon_artist", "canon_title", "canon_album", "canon_year")}
+    return info

lib/routers/diagnostics.py

@@ -0,0 +1,295 @@
+"""Diagnostic bundle export + hardware probe (/api/diagnostics/*).
+
+One-click "Export Diagnostics" in Settings produces a redacted zip combining
+server logs, system info, hardware (CPU/GPU/RAM), plugin inventory, and the
+browser-side console transcript + hardware probe. Bundle format is specified in
+docs/diagnostics-bundle-spec.md.
+
+Extracted verbatim from server.py (R3) except:
+  - the decorators (@app -> @router),
+  - CONFIG_DIR -> appstate.config_dir and _running_version() ->
+    appstate.running_version() (both read through the appstate seam),
+  - the builtin-plugins lookup in _diag_plugins_roots: Path(__file__).parent
+    (the app root when this lived at the top level) ->
+    Path(__file__).resolve().parents[2] (routers -> lib -> app root). The
+    plugins/ dir ships at the app root in every packaging path.
+
+The pure helpers + caps here are re-exported from server.py so the existing
+`server._diag_*` / `server._DIAG_*` tests keep resolving (none monkeypatch them).
+"""
+
+import json
+import logging
+import os
+from pathlib import Path
+
+from fastapi import APIRouter, Body, Response
+
+import appstate
+from dlc_paths import _get_dlc_dir
+from diagnostics_bundle import build_bundle as _diag_build, preview_bundle as _diag_preview
+from diagnostics_hardware import collect as _diag_hardware
+from env_compat import getenv_compat
+
+log = logging.getLogger("feedBack.server")
+router = APIRouter()
+
+
+def _diag_log_file() -> Path | None:
+    raw = os.environ.get("LOG_FILE", "").strip()
+    if not raw:
+        return None
+    return Path(raw)
+
+
+def _diag_plugins_roots() -> list[Path]:
+    """Return all plugin root directories for orphan scanning.
+
+    Includes both the built-in ``plugins/`` directory and
+    ``FEEDBACK_PLUGINS_DIR`` when set, so user-installed plugins and
+    orphans in the external dir are reflected in the bundle.
+    """
+    roots: list[Path] = []
+    user_dir = getenv_compat("FEEDBACK_PLUGINS_DIR", "").strip()
+    if user_dir:
+        p = Path(user_dir)
+        if p.is_dir():
+            roots.append(p)
+    builtin = Path(__file__).resolve().parents[2] / "plugins"  # R3: app root from lib/routers/
+    if builtin not in roots:
+        roots.append(builtin)
+    return roots
+
+
+def _diag_coerce_bool(v, *, default: bool = True) -> bool:
+    """Coerce a request-side value to bool, accepting both JSON booleans and
+    string representations.
+
+    - Falsy strings: ``"false"``, ``"0"``, ``"no"``, ``""`` → ``False``
+    - ``None`` → *default*
+    - Everything else (including ``"true"``, ``"1"``) → ``True``
+    """
+    if v is None:
+        return default
+    if isinstance(v, bool):
+        return v
+    if isinstance(v, str):
+        return v.strip().lower() not in ("false", "0", "no", "")
+    return bool(v)
+
+
+def _diag_normalize_include(include: dict | None) -> dict:
+    """Coerce request-side flags to the booleans build_bundle expects.
+    Missing keys default to True so a bare {} request still produces
+    the full bundle.
+
+    Accepts both JSON booleans (``true``/``false``) and string
+    representations so callers that serialize flags as strings behave
+    consistently with the preview endpoint:
+    - Falsy strings: ``"false"``, ``"0"``, ``"no"``, ``""`` → ``False``
+    - Everything else (including ``"true"``, ``"1"``, ``"yes"``) → ``True``
+    """
+    keys = ("system", "hardware", "logs", "console", "plugins")
+    if not isinstance(include, dict):
+        return {k: True for k in keys}
+
+    return {k: _diag_coerce_bool(include.get(k), default=True) for k in keys}
+
+
+# Server-side caps on client-supplied payload sections.  diagnostics.js
+# enforces a 500-entry / ~250 KB ring buffer on the browser side; these
+# bounds give generous headroom while still preventing a crafted POST from
+# forcing the server to allocate arbitrarily large in-memory bundles.
+_DIAG_MAX_CONSOLE_ENTRIES = 1000          # hard cap: truncate silently
+_DIAG_MAX_CONSOLE_BYTES = 2 * 1024 * 1024  # 2 MB hard cap on total console list
+_DIAG_MAX_CLIENT_PAYLOAD_BYTES = 2 * 1024 * 1024   # 2 MB per dict section
+_DIAG_MAX_CONTRIBUTIONS_BYTES = 4 * 1024 * 1024    # 4 MB aggregate cap for contributions
+
+
+def _diag_cap_console(v) -> list | None:
+    """Return *v* if it is a list, truncated to _DIAG_MAX_CONSOLE_ENTRIES entries
+    and _DIAG_MAX_CONSOLE_BYTES total.  Entries are accumulated until either cap
+    is reached; no partial-entry splitting occurs."""
+    if not isinstance(v, list):
+        return None
+    result = v[:_DIAG_MAX_CONSOLE_ENTRIES]
+    # Also enforce a byte cap — the count cap alone does not bound memory when
+    # entries contain arbitrarily large strings.
+    try:
+        out = []
+        total = 0
+        for entry in result:
+            encoded = json.dumps(entry, separators=(",", ":")).encode("utf-8", errors="replace")
+            if total + len(encoded) > _DIAG_MAX_CONSOLE_BYTES:
+                break
+            out.append(entry)
+            total += len(encoded)
+        return out
+    except (TypeError, ValueError):
+        return None
+
+
+def _diag_cap_dict(v) -> dict | None:
+    """Return *v* if it is a dict whose JSON serialisation fits within
+    _DIAG_MAX_CLIENT_PAYLOAD_BYTES, otherwise return None."""
+    if not isinstance(v, dict):
+        return None
+    try:
+        encoded = json.dumps(v, separators=(",", ":")).encode("utf-8", errors="replace")
+    except (TypeError, ValueError) as e:
+        log.warning("diagnostics client payload is not JSON-serialisable, dropping: %s", e)
+        return None
+    if len(encoded) > _DIAG_MAX_CLIENT_PAYLOAD_BYTES:
+        return None
+    return v
+
+
+def _diag_cap_contributions(v, known_ids=None) -> dict | None:
+    """Apply per-plugin and aggregate size caps on client_contributions.
+
+    Unlike _diag_cap_dict(), which drops the whole dict when any plugin
+    exceeds the limit, this function caps each plugin independently so
+    one noisy plugin does not silence every other plugin's contribution.
+
+    Parameters
+    ----------
+    v:
+        The raw contributions dict from the POST payload.
+    known_ids:
+        When provided, contributions from plugins not in this set are
+        skipped *before* serialisation, preventing a malicious caller
+        from forcing the server to JSON-encode hundreds of near-limit
+        payloads that ``build_bundle()`` would later discard anyway.
+        ``None`` means "accept all plugin ids" (used in tests / preview).
+    """
+    if not isinstance(v, dict):
+        return None
+    result = {}
+    total_bytes = 0
+    for pid, contribution in v.items():
+        if not isinstance(pid, str):
+            continue
+        # Filter unknown plugin ids early — before serialising — so a
+        # crafted request cannot force large allocations for plugins that
+        # build_bundle() would drop.
+        if known_ids is not None and pid not in known_ids:
+            continue
+        try:
+            encoded = json.dumps(contribution, separators=(",", ":")).encode("utf-8", errors="replace")
+        except (TypeError, ValueError) as e:
+            log.warning(
+                "client_contributions[%r] is not JSON-serialisable, dropping: %s", pid, e
+            )
+            continue
+        if len(encoded) > _DIAG_MAX_CLIENT_PAYLOAD_BYTES:
+            log.warning(
+                "client_contributions[%r] exceeds %d bytes, dropping",
+                pid, _DIAG_MAX_CLIENT_PAYLOAD_BYTES,
+            )
+            continue
+        if total_bytes + len(encoded) > _DIAG_MAX_CONTRIBUTIONS_BYTES:
+            log.warning(
+                "client_contributions aggregate size limit (%d bytes) reached, "
+                "dropping remaining entries",
+                _DIAG_MAX_CONTRIBUTIONS_BYTES,
+            )
+            break
+        result[pid] = contribution
+        total_bytes += len(encoded)
+    return result or None
+
+
+@router.post("/api/diagnostics/export")
+def export_diagnostics(payload: dict = Body(default_factory=dict)):
+    """Build a diagnostic bundle and stream it back as a zip download.
+
+    The browser layers in `client_console`, `client_hardware`,
+    `client_ua`, and `local_storage` before posting; the server adds
+    server logs, hardware, plugin inventory, and packages everything
+    into a single zip.
+
+    Errors during plugin diagnostics callables are caught and logged
+    to the bundle's manifest `notes` rather than failing the export.
+    """
+    from plugins import LOADED_PLUGINS, PLUGINS_LOCK
+
+    redact = _diag_coerce_bool(payload.get("redact", True), default=True)
+    include = _diag_normalize_include(payload.get("include"))
+    client_console = _diag_cap_console(payload.get("client_console"))
+    client_hardware = _diag_cap_dict(payload.get("client_hardware"))
+    client_ua = _diag_cap_dict(payload.get("client_ua"))
+    local_storage = _diag_cap_dict(payload.get("local_storage"))
+    # Fetch the plugin list first so we can filter contributions to known
+    # plugin ids before serialising — prevents a crafted request from
+    # forcing large allocations for plugins build_bundle() would drop.
+    with PLUGINS_LOCK:
+        plugins_snapshot = list(LOADED_PLUGINS)
+    known_ids = {p.get("id") for p in plugins_snapshot if isinstance(p.get("id"), str)}
+    client_contributions = _diag_cap_contributions(
+        payload.get("client_contributions"), known_ids=known_ids
+    )
+
+    zip_bytes, filename, _manifest = _diag_build(
+        feedBack_version=appstate.running_version(),
+        config_dir=appstate.config_dir,
+        dlc_dir=_get_dlc_dir(),
+        log_file=_diag_log_file(),
+        loaded_plugins=plugins_snapshot,
+        include=include,
+        redact=redact,
+        client_console=client_console,
+        client_hardware=client_hardware,
+        client_ua=client_ua,
+        local_storage=local_storage,
+        client_contributions=client_contributions,
+        log=log,
+        plugins_root=_diag_plugins_roots(),
+    )
+    return Response(
+        content=zip_bytes,
+        media_type="application/zip",
+        headers={"Content-Disposition": f'attachment; filename="{filename}"'},
+    )
+
+
+@router.get("/api/diagnostics/preview")
+def preview_diagnostics(
+    redact: bool = True,
+    system: bool = True,
+    hardware: bool = True,
+    logs: bool = True,
+    console: bool = True,
+    plugins: bool = True,
+):
+    """Return what `/api/diagnostics/export` would produce, minus the
+    actual file contents — file tree, sizes, schemas, redaction counts.
+    Lets the Settings UI show the user what's about to be sent."""
+    from plugins import LOADED_PLUGINS, PLUGINS_LOCK
+
+    include = {
+        "system": system,
+        "hardware": hardware,
+        "logs": logs,
+        "console": console,
+        "plugins": plugins,
+    }
+    with PLUGINS_LOCK:
+        plugins_snapshot = list(LOADED_PLUGINS)
+    return _diag_preview(
+        feedBack_version=appstate.running_version(),
+        config_dir=appstate.config_dir,
+        dlc_dir=_get_dlc_dir(),
+        log_file=_diag_log_file(),
+        loaded_plugins=plugins_snapshot,
+        include=include,
+        redact=redact,
+        log=log,
+        plugins_root=_diag_plugins_roots(),
+    )
+
+
+@router.get("/api/diagnostics/hardware")
+def diagnostics_hardware():
+    """Backend hardware probe (cross-platform). Reusable independently
+    of the bundle export — handy for "what's my GPU" plugin queries."""
+    return _diag_hardware()

lib/routers/library_extras.py

@@ -0,0 +1,75 @@
+"""Small meta_db-backed library / user-state endpoints — work keeper-chart
+prefs, favorites, personal tags, saved-for-later, and continue-playing.
+
+Extracted verbatim from ``server.py`` (R3); edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``, ``_clean_str`` from ``reqfields``. All paths
+are distinct and non-overlapping, so mounting them together (rather than at each
+original scattered site) does not change routing.
+"""
+
+from fastapi import APIRouter
+from fastapi.responses import JSONResponse
+
+import appstate
+from reqfields import _clean_str
+
+router = APIRouter()
+
+
+@router.get("/api/work/{work_key:path}/charts")
+def api_get_work_charts(work_key: str):
+    """All charts in a work + which is the keeper (your pick vs auto-pick)."""
+    return appstate.meta_db.work_charts(work_key)
+
+
+@router.put("/api/work/{work_key:path}/preferred")
+def api_set_work_preferred(work_key: str, data: dict):
+    """Set the keeper chart of a work: body {filename}. The filename must be a
+    current member of the work. Returns the refreshed chart list."""
+    fn = (data.get("filename") or "").strip()
+    if not fn:
+        return JSONResponse({"error": "filename is required"}, 400)
+    members = {c["filename"] for c in appstate.meta_db.work_charts(work_key)["charts"]}
+    if fn not in members:
+        return JSONResponse({"error": "filename is not a chart of this work"}, 400)
+    appstate.meta_db.set_chart_preferred(work_key, fn)
+    return appstate.meta_db.work_charts(work_key)
+
+
+@router.delete("/api/work/{work_key:path}/preferred")
+def api_reset_work_preferred(work_key: str):
+    """Reset a work to auto-pick (drop the explicit preferred)."""
+    appstate.meta_db.clear_chart_preferred(work_key)
+    return appstate.meta_db.work_charts(work_key)
+
+
+@router.post("/api/favorites/toggle")
+def toggle_favorite(data: dict):
+    """Toggle a song's favorite status."""
+    filename = data.get("filename", "")
+    if not filename:
+        return {"error": "No filename"}
+    new_state = appstate.meta_db.toggle_favorite(filename)
+    return {"favorite": new_state}
+
+
+@router.get("/api/tags")
+def list_tags():
+    """All personal tags in use (over still-present songs), most-used first —
+    powers the tag filter UI."""
+    return {"tags": appstate.meta_db.all_tags()}
+
+
+@router.post("/api/saved/toggle")
+def api_toggle_saved(data: dict):
+    """Add/remove a song on the reserved Saved-for-Later playlist."""
+    filename = _clean_str(data.get("filename"))
+    if not filename:
+        return JSONResponse({"error": "filename required"}, status_code=400)
+    return {"saved": appstate.meta_db.toggle_saved(filename)}
+
+
+@router.get("/api/session/continue")
+def api_session_continue():
+    """The Continue-Playing card's song (most recent play) or null."""
+    return appstate.meta_db.continue_session()

lib/routers/loops.py

@@ -0,0 +1,60 @@
+"""Practice loops — saved A/B regions per song.
+
+Extracted verbatim from ``server.py`` (R3); only the decorator receiver
+(``@app`` -> ``@router``) and the singleton reads (``meta_db`` ->
+``appstate.meta_db``) changed. See ``appstate.py`` for why the reads stay
+module attributes.
+"""
+
+from fastapi import APIRouter
+
+import appstate
+
+router = APIRouter()
+
+
+@router.get("/api/loops")
+def list_loops(filename: str):
+    # Hold the DB lock for the read: the shared single connection
+    # (check_same_thread=False) is serialized through meta_db._lock by every
+    # writer, so an unlocked SELECT here can overlap a POST/DELETE commit.
+    db = appstate.meta_db
+    with db._lock:
+        rows = db.conn.execute(
+            "SELECT id, name, start_time, end_time FROM loops WHERE filename = ? ORDER BY start_time",
+            (filename,)
+        ).fetchall()
+    return [{"id": r[0], "name": r[1], "start": r[2], "end": r[3]} for r in rows]
+
+
+@router.post("/api/loops")
+def save_loop(data: dict):
+    filename = data.get("filename", "")
+    name = data.get("name", "").strip()
+    start = data.get("start")
+    end = data.get("end")
+    if not filename or start is None or end is None:
+        return {"error": "Missing fields"}
+    db = appstate.meta_db
+    with db._lock:
+        # COUNT + INSERT under one lock so two unnamed POSTs can't read the same
+        # count and both mint "Loop N" (the count is only used to name the row).
+        if not name:
+            count = db.conn.execute(
+                "SELECT COUNT(*) FROM loops WHERE filename = ?", (filename,)
+            ).fetchone()[0]
+            name = f"Loop {count + 1}"
+        db.conn.execute(
+            "INSERT INTO loops (filename, name, start_time, end_time) VALUES (?, ?, ?, ?)",
+            (filename, name, float(start), float(end))
+        )
+        db.conn.commit()
+    return {"ok": True, "name": name}
+
+
+@router.delete("/api/loops/{loop_id}")
+def delete_loop(loop_id: int):
+    with appstate.meta_db._lock:
+        appstate.meta_db.conn.execute("DELETE FROM loops WHERE id = ?", (loop_id,))
+        appstate.meta_db.conn.commit()
+    return {"ok": True}

lib/routers/playlists.py

@@ -0,0 +1,267 @@
+"""Playlists + custom playlist covers (fee[dB]ack v0.3.0).
+
+Extracted verbatim from ``server.py`` (R3). Edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``, ``CONFIG_DIR`` -> ``appstate.config_dir``
+(both read at call time through the seam), and ``_clean_str`` now imports from
+``reqfields``. See ``appstate.py``.
+"""
+
+import logging
+import os
+import tempfile
+from pathlib import Path
+
+from fastapi import APIRouter
+from fastapi.responses import FileResponse, JSONResponse
+
+import appstate
+from reqfields import _clean_str
+
+log = logging.getLogger("feedBack.server")
+
+router = APIRouter()
+
+# Cache policy for the custom-cover file response: revalidate every time so a
+# replaced cover is never served stale (pairs with the mtime-ns URL token).
+_ART_CACHE_HEADERS = {"Cache-Control": "no-cache"}
+
+
+def _playlist_cover_path(pid) -> Path | None:
+    """Filesystem path of a playlist's optional custom cover image (PNG),
+    stored under CONFIG_DIR. Returns None for a non-integer id."""
+    try:
+        pid = int(pid)
+    except (TypeError, ValueError):
+        return None
+    return appstate.config_dir / "playlist_covers" / f"{pid}.png"
+
+
+def _playlist_cover_url(pid) -> str | None:
+    cover = _playlist_cover_path(pid)
+    if not cover or not cover.exists():
+        return None
+    try:
+        # Nanosecond mtime so a same-second replace/remove/re-upload still
+        # changes the cache-bust token (int seconds could collide → stale image).
+        mt = cover.stat().st_mtime_ns
+    except OSError:
+        mt = 0
+    return f"/api/playlists/{pid}/cover?v={mt}"
+
+
+@router.get("/api/playlists")
+def api_list_playlists():
+    lists = appstate.meta_db.list_playlists()
+    for pl in lists:
+        pl["cover_url"] = _playlist_cover_url(pl["id"])
+    return lists
+
+
+@router.post("/api/playlists")
+def api_create_playlist(data: dict):
+    name = _clean_str(data.get("name"))
+    if not (1 <= len(name) <= 100):
+        return JSONResponse({"error": "Playlist name must be 1–100 characters."}, status_code=400)
+    # kind='album' = a curated album (§7.2): hand-picked works, a chosen chart
+    # per slot, played front-to-back on the queue. Absent/None = a regular mix.
+    kind = _clean_str(data.get("kind")) or None
+    if kind not in (None, "album"):
+        return JSONResponse({"error": "kind must be 'album' or omitted"}, status_code=400)
+    return appstate.meta_db.create_playlist(name, kind=kind)
+
+
+@router.get("/api/playlists/{pid}")
+def api_get_playlist(pid: int):
+    pl = appstate.meta_db.get_playlist(pid)
+    if pl is None:
+        return JSONResponse({"error": "not found"}, status_code=404)
+    pl["cover_url"] = _playlist_cover_url(pid)
+    return pl
+
+
+@router.patch("/api/playlists/{pid}")
+def api_rename_playlist(pid: int, data: dict):
+    pl = appstate.meta_db.get_playlist(pid)
+    if pl is None:
+        return JSONResponse({"error": "not found"}, status_code=404)
+    if pl["system_key"]:
+        return JSONResponse({"error": "System playlists cannot be renamed."}, status_code=400)
+    name = _clean_str(data.get("name"))
+    if not (1 <= len(name) <= 100):
+        return JSONResponse({"error": "Playlist name must be 1–100 characters."}, status_code=400)
+    appstate.meta_db.rename_playlist(pid, name)
+    return appstate.meta_db.get_playlist(pid)
+
+
+@router.delete("/api/playlists/{pid}")
+def api_delete_playlist(pid: int):
+    pl = appstate.meta_db.get_playlist(pid)
+    if pl is None:
+        return JSONResponse({"error": "not found"}, status_code=404)
+    if pl["system_key"]:
+        return JSONResponse({"error": "System playlists cannot be deleted."}, status_code=400)
+    if not appstate.meta_db.delete_playlist(pid):   # vanished under us (concurrent delete)
+        return JSONResponse({"error": "not found"}, status_code=404)
+    cover = _playlist_cover_path(pid)       # drop any custom cover with the playlist
+    if cover and cover.exists():
+        try:
+            cover.unlink()
+        except OSError:
+            pass
+    return {"ok": True}
+
+
+@router.post("/api/playlists/{pid}/songs")
+def api_add_playlist_song(pid: int, data: dict):
+    if appstate.meta_db.get_playlist(pid) is None:
+        return JSONResponse({"error": "not found"}, status_code=404)
+    filename = _clean_str(data.get("filename"))
+    if not filename:
+        return JSONResponse({"error": "filename required"}, status_code=400)
+    if appstate.meta_db.add_playlist_song(pid, filename) is None:   # playlist vanished under us
+        return JSONResponse({"error": "not found"}, status_code=404)
+    pl = appstate.meta_db.get_playlist(pid)
+    return pl if pl is not None else JSONResponse({"error": "not found"}, status_code=404)
+
+
+@router.patch("/api/playlists/{pid}/songs/{filename:path}")
+def api_update_playlist_slot(pid: int, filename: str, data: dict):
+    """Edit one curated-album slot: {"arrangement": name|null} pins/clears the
+    slot's arrangement; {"chart_filename": fn} swaps the slot to another chart
+    of the same work (position + pin kept). Albums only — a mix has no slots."""
+    pl = appstate.meta_db.get_playlist(pid)
+    if pl is None:
+        return JSONResponse({"error": "not found"}, status_code=404)
+    if pl.get("kind") != "album":
+        return JSONResponse({"error": "Slot editing is for albums."}, status_code=400)
+    kwargs = {}
+    if "chart_filename" in data:
+        new_fn = _clean_str(data.get("chart_filename"))
+        if not new_fn:
+            return JSONResponse({"error": "chart_filename must be a filename"}, status_code=400)
+        kwargs["new_filename"] = new_fn
+    if "arrangement" in data:
+        arr = data.get("arrangement")
+        if arr is not None and not (isinstance(arr, str) and 1 <= len(arr.strip()) <= 100):
+            return JSONResponse({"error": "arrangement must be a name or null"}, status_code=400)
+        kwargs["arrangement"] = arr.strip() if isinstance(arr, str) else None
+    if not kwargs:
+        return JSONResponse({"error": "nothing to update"}, status_code=400)
+    if appstate.meta_db.update_playlist_slot(pid, filename, **kwargs) is None:
+        return JSONResponse(
+            {"error": "no such slot, or the chart isn't a version of this song"},
+            status_code=400)
+    return appstate.meta_db.get_playlist(pid)
+
+
+@router.delete("/api/playlists/{pid}/songs/{filename:path}")
+def api_remove_playlist_song(pid: int, filename: str):
+    if appstate.meta_db.get_playlist(pid) is None:
+        return JSONResponse({"error": "not found"}, status_code=404)
+    appstate.meta_db.remove_playlist_song(pid, filename)
+    pl = appstate.meta_db.get_playlist(pid)
+    return pl if pl is not None else JSONResponse({"error": "not found"}, status_code=404)
+
+
+@router.post("/api/playlists/{pid}/reorder")
+def api_reorder_playlist(pid: int, data: dict):
+    pl = appstate.meta_db.get_playlist(pid)
+    if pl is None:
+        return JSONResponse({"error": "not found"}, status_code=404)
+    order = data.get("order")
+    if not isinstance(order, list) or not all(isinstance(f, str) for f in order):
+        return JSONResponse({"error": "order must be a list of filenames"}, status_code=400)
+    # Require an exact permutation of the playlist's current songs: a list with
+    # duplicates, omissions, or extras would otherwise produce duplicate
+    # positions / a partial reorder while still returning 200.
+    current = [s["filename"] for s in pl["songs"]]
+    if len(order) != len(current) or sorted(order) != sorted(current):
+        return JSONResponse(
+            {"error": "order must be a permutation of the playlist's current songs"},
+            status_code=400,
+        )
+    appstate.meta_db.reorder_playlist(pid, order)
+    return appstate.meta_db.get_playlist(pid)
+
+
+@router.post("/api/playlists/{pid}/cover")
+async def api_set_playlist_cover(pid: int, data: dict):
+    """Set a playlist's custom cover from a base64 / data-URL image (PNG/JPG).
+    Overrides the content-dependent (song-art) cover. Stored as a small PNG
+    thumbnail under CONFIG_DIR/playlist_covers/."""
+    if appstate.meta_db.get_playlist(pid) is None:
+        return JSONResponse({"error": "not found"}, status_code=404)
+    import base64
+    import io
+    b64 = data.get("image", "")
+    # Guard the type before the `","` membership test — a non-string image
+    # (e.g. {"image": 123} / null) would otherwise raise TypeError → 500.
+    # Mirrors the avatar/song-art upload guard.
+    if not isinstance(b64, str) or not b64:
+        return JSONResponse({"error": "No image data"}, status_code=400)
+    if "," in b64:
+        b64 = b64.split(",", 1)[1]
+    if not b64:
+        return JSONResponse({"error": "No image data"}, status_code=400)
+    try:
+        img_data = base64.b64decode(b64)
+    except Exception:
+        return JSONResponse({"error": "Invalid base64"}, status_code=400)
+    cover = _playlist_cover_path(pid)
+    cover.parent.mkdir(parents=True, exist_ok=True)
+    # Decode/validate the image — a bad payload is a CLIENT error (400), and the
+    # message stays generic so it can't echo internals.
+    try:
+        from PIL import Image
+        img = Image.open(io.BytesIO(img_data)).convert("RGB")
+        img.thumbnail((640, 640))                  # covers stay small
+    except Exception:
+        return JSONResponse({"error": "Invalid image"}, status_code=400)
+    # Persist. A save/replace failure is a SERVER error (500, logged, no
+    # filesystem detail leaked) — the pre-split handler mislabeled these as 400
+    # and echoed the exception. A unique temp name in the cover dir (not a shared
+    # `{pid}.png.tmp`) means two concurrent uploads can't clobber each other's
+    # temp file; the atomic replace publishes. Re-check the playlist still exists
+    # just before publishing so a delete that raced the decode above can't leave
+    # an orphan cover — cheap belt-and-braces; FeedBack is single-user
+    # (Principle I), so a full per-playlist lock would be for a race the
+    # deployment model precludes.
+    tmp = None
+    try:
+        # mkstemp is inside the try too: an unwritable dir / full disk raises
+        # here, and that's the same class of persistence failure as save/replace.
+        fd, tmp_name = tempfile.mkstemp(prefix=f".{pid}.", suffix=".png.tmp", dir=str(cover.parent))
+        tmp = Path(tmp_name)
+        with os.fdopen(fd, "wb") as f:
+            img.save(f, "PNG")
+        if appstate.meta_db.get_playlist(pid) is None:
+            tmp.unlink(missing_ok=True)
+            return JSONResponse({"error": "not found"}, status_code=404)
+        tmp.replace(cover)
+    except Exception:
+        if tmp is not None:
+            tmp.unlink(missing_ok=True)
+        log.exception("playlist cover save failed (pid=%s)", pid)
+        return JSONResponse({"error": "could not save cover"}, status_code=500)
+    return {"ok": True, "cover_url": _playlist_cover_url(pid)}
+
+
+@router.get("/api/playlists/{pid}/cover")
+def api_get_playlist_cover(pid: int):
+    cover = _playlist_cover_path(pid)
+    if not cover or not cover.exists():
+        return JSONResponse({"error": "not found"}, status_code=404)
+    # no-cache (revalidate) like song art, so a replaced cover is never served
+    # stale — pairs with the mtime-ns cache-bust token on the URL.
+    return FileResponse(str(cover), media_type="image/png", headers=_ART_CACHE_HEADERS)
+
+
+@router.delete("/api/playlists/{pid}/cover")
+def api_delete_playlist_cover(pid: int):
+    cover = _playlist_cover_path(pid)
+    if cover and cover.exists():
+        try:
+            cover.unlink()
+        except OSError:
+            pass
+    return {"ok": True}

lib/routers/profile.py

@@ -0,0 +1,138 @@
+"""Player profile — identity, avatars (bundled + custom uploads), and progress.
+
+Extracted verbatim from ``server.py`` (R3); edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``, ``CONFIG_DIR``/``STATIC_DIR`` ->
+``appstate.config_dir``/``appstate.static_dir`` (seam), ``_clean_str`` from
+``reqfields``, ``_get_progression_content()`` ->
+``appstate.get_progression_content()``. The bundled-avatar lister moves with it.
+"""
+
+import logging
+import secrets
+
+from fastapi import APIRouter
+from fastapi.responses import FileResponse, JSONResponse
+
+import appstate
+from reqfields import _clean_str
+
+log = logging.getLogger("feedBack.server")
+
+router = APIRouter()
+
+
+def _list_bundled_avatars() -> list[str]:
+    """Bundled default avatar filenames under static/v3/avatars/."""
+    d = appstate.static_dir / "v3" / "avatars"
+    if not d.is_dir():
+        return []
+    exts = {".svg", ".png", ".webp"}
+    return sorted(
+        p.name for p in d.iterdir()
+        if p.is_file() and p.suffix.lower() in exts and not p.name.startswith(".")
+    )
+
+
+@router.get("/api/profile")
+def api_get_profile():
+    profile = appstate.meta_db.get_profile()
+    # Equipped cosmetics ride along (resolved to their payloads) so the theme
+    # and avatar frame apply at boot without an extra request. Never let a
+    # cosmetics/content problem break the profile read.
+    cosmetics = {}
+    try:
+        shop = appstate.get_progression_content()["shop"]
+        for slot, item_id in appstate.meta_db.get_equipped().items():
+            item = shop.get(item_id)
+            if item:
+                cosmetics[slot] = {"item_id": item_id, "payload": item["payload"]}
+    except Exception:
+        log.warning("profile cosmetics enrich failed", exc_info=True)
+    profile["cosmetics"] = cosmetics
+    return profile
+
+
+
+@router.post("/api/profile")
+def api_set_profile(data: dict):
+    """Set/update the player profile. Body: {display_name, avatar:{type,value}}.
+    avatar.type is 'default' (value = bundled filename) or 'upload' (value =
+    the /api/profile/avatar/<name> URL returned by the upload endpoint); omit
+    avatar to keep the existing one (name-only edit)."""
+    name = _clean_str(data.get("display_name"))
+    if not (1 <= len(name) <= 32):
+        return JSONResponse({"error": "Display name must be 1–32 characters."}, status_code=400)
+    avatar = data.get("avatar")
+    if avatar is None:
+        avatar = {}            # omitted → keep the current avatar (name-only edit)
+    elif not isinstance(avatar, dict):
+        return JSONResponse({"error": "avatar must be an object."}, status_code=400)
+    atype = avatar.get("type")
+    aval = _clean_str(avatar.get("value"))
+    avatar_url = None
+    if atype == "default":
+        if aval not in _list_bundled_avatars():
+            return JSONResponse({"error": "Unknown default avatar."}, status_code=400)
+        avatar_url = f"/static/v3/avatars/{aval}"
+    elif atype == "upload":
+        from safepath import safe_join
+        fname = aval.rsplit("/", 1)[-1] if aval.startswith("/api/profile/avatar/") else ""
+        target = safe_join(appstate.config_dir / "avatars", fname) if fname else None
+        if target is None or not target.is_file():
+            return JSONResponse({"error": "Uploaded avatar not found."}, status_code=400)
+        avatar_url = f"/api/profile/avatar/{fname}"
+    elif atype:
+        return JSONResponse({"error": "Unknown avatar type."}, status_code=400)
+    # atype None/missing → keep the current avatar (name-only edit).
+    return appstate.meta_db.set_profile(name, avatar_url)
+
+
+@router.get("/api/profile/avatars")
+def api_list_avatars():
+    return [{"name": n, "url": f"/static/v3/avatars/{n}"} for n in _list_bundled_avatars()]
+
+
+@router.post("/api/profile/avatar")
+def api_upload_avatar(data: dict):
+    """Upload a custom avatar as base64 (mirrors the album-art upload pattern).
+    Re-encodes to a ≤512px PNG under appstate.config_dir/avatars/."""
+    import base64
+    import io
+    b64 = data.get("image", "")
+    if not isinstance(b64, str) or not b64:
+        return JSONResponse({"error": "No image data"}, status_code=400)
+    if "," in b64:
+        b64 = b64.split(",", 1)[1]
+    try:
+        raw = base64.b64decode(b64)
+    except Exception:
+        return JSONResponse({"error": "Invalid base64"}, status_code=400)
+    if len(raw) > 6 * 1024 * 1024:
+        return JSONResponse({"error": "Image too large (max 6 MB)."}, status_code=400)
+    avatars_dir = appstate.config_dir / "avatars"
+    avatars_dir.mkdir(parents=True, exist_ok=True)
+    try:
+        from PIL import Image
+        img = Image.open(io.BytesIO(raw)).convert("RGB")
+        img.thumbnail((512, 512))
+        fname = f"upload-{secrets.token_hex(4)}.png"  # token busts caches on change
+        img.save(str(avatars_dir / fname), "PNG")
+    except Exception as e:
+        return JSONResponse({"error": f"Invalid image: {e}"}, status_code=400)
+    return {"url": f"/api/profile/avatar/{fname}"}
+
+
+@router.get("/api/profile/avatar/{name}")
+def api_get_avatar(name: str):
+    from safepath import safe_join
+    target = safe_join(appstate.config_dir / "avatars", name)
+    if target is None or not target.is_file():
+        return JSONResponse({"error": "not found"}, status_code=404)
+    return FileResponse(str(target), media_type="image/png")
+
+
+@router.get("/api/profile/progress")
+def api_profile_progress():
+    """One call for the whole profile badge: {level, xp, xp_in_level,
+    xp_to_next, current_streak, best_streak, last_active_date}."""
+    return appstate.meta_db.get_progress()

lib/routers/progression.py

@@ -0,0 +1,230 @@
+"""Progression (spec 010) — mastery rank, challenges, quests, onboarding paths.
+
+Extracted verbatim from ``server.py`` (R3); edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``, ``_clean_str`` from ``reqfields``, and the
+two shared server accessors read through the seam:
+``_get_progression_content()`` -> ``appstate.get_progression_content()`` and
+``_builtin_diagnostic_filename()`` -> ``appstate.builtin_diagnostic_filename()``.
+The exclusive helpers (_goal_ui_progress, _progression_overview) + the
+_PROGRESSION_EVENT_TYPES whitelist move with it.
+"""
+
+import math
+
+from fastapi import APIRouter
+from fastapi.responses import JSONResponse
+
+import appstate
+from reqfields import _clean_str
+
+router = APIRouter()
+
+
+def _goal_ui_progress(goal: dict, state: dict, streak: int, xp_total: int) -> tuple:
+    """(count, target) for a challenge/quest progress bar. Count goals show
+    n/target; threshold goals show how far the live stat is along the line."""
+    import progression as progression_mod
+    gtype = goal.get("type")
+    if gtype in progression_mod.COUNT_GOAL_TYPES:
+        target = int(goal.get("target") or 1)
+        count = target if state.get("completed") else min(int(state.get("count") or 0), target)
+        return count, target
+    if gtype == "streak_reached":
+        target = int(goal.get("days") or 1)
+        return (target if state.get("completed") else min(streak, target)), target
+    if gtype == "db_earned":
+        target = int(goal.get("amount") or 1)
+        return (target if state.get("completed") else min(xp_total, target)), target
+    return 0, 1
+
+
+def _progression_overview() -> dict:
+    """The full GET /api/progression payload (also the capability `inspect`
+    result): rank, onboarding, per-path challenge checklists, quests, wallet."""
+    import progression as progression_mod
+    from datetime import datetime as _dt
+    content = appstate.get_progression_content()
+    now = _dt.now()
+    appstate.meta_db.ensure_quest_period(content, now)
+
+    state = appstate.meta_db.get_progression_state()
+    player_paths = appstate.meta_db.get_player_paths()
+    challenge_state = appstate.meta_db.get_challenge_state()
+    wallet = appstate.meta_db.get_wallet()
+    streak_progress = appstate.meta_db.get_progress()
+    streak = int(streak_progress.get("current_streak") or 0)
+    xp_total = wallet["lifetime_db"]
+    keys = progression_mod.period_keys(now)
+
+    def _path_order(pid):
+        pdef = content["paths"].get(pid) or {}
+        return (pdef.get("order") or 0, pid)
+
+    paths_payload = []
+    for pid in sorted(player_paths, key=_path_order):
+        pdef = content["paths"].get(pid)
+        level = player_paths[pid]
+        if not pdef:
+            # Path selected under older content that no longer ships: keep its
+            # rank contribution visible rather than silently dropping it.
+            paths_payload.append({"id": pid, "name": pid, "icon": "", "level": level,
+                                  "max_level": level, "next": None})
+            continue
+        next_block = None
+        active = progression_mod.active_challenges(content, pid, level)
+        if active:
+            level_def = next(e for e in pdef["levels"] if e["level"] == level + 1)
+            challenges = []
+            completed_count = 0
+            for ch in active:
+                st = challenge_state.get(ch["id"]) or {}
+                count, target = _goal_ui_progress(ch["goal"], st, streak, xp_total)
+                if st.get("completed"):
+                    completed_count += 1
+                challenges.append({
+                    "id": ch["id"],
+                    "title": ch["title"],
+                    "description": ch["description"],
+                    "count": count,
+                    "target": target,
+                    "completed": bool(st.get("completed")),
+                    "completed_at": st.get("completed_at"),
+                })
+            next_block = {
+                "level": level + 1,
+                "required": level_def["required"],
+                "completed": completed_count,
+                "challenges": challenges,
+            }
+        paths_payload.append({
+            "id": pid,
+            "name": pdef["name"],
+            "icon": pdef["icon"],
+            "level": level,
+            "max_level": progression_mod.path_max_level(content, pid),
+            "next": next_block,
+        })
+
+    available = [
+        {"id": pid, "name": pdef["name"], "icon": pdef["icon"]}
+        for pid, pdef in sorted(content["paths"].items(), key=lambda kv: (kv[1].get("order") or 0, kv[0]))
+        if pid not in player_paths
+    ]
+
+    quest_rows = appstate.meta_db.get_quest_rows(keys)
+    quests_payload = {}
+    for period_type in ("daily", "weekly"):
+        pool = content["quests"][period_type]["pool"]
+        quests = []
+        for row in quest_rows:
+            if row["period_type"] != period_type:
+                continue
+            qdef = pool.get(row["quest_id"])
+            if not qdef:
+                continue  # removed from the pool mid-period: hide, keep the row
+            count, target = _goal_ui_progress(qdef["goal"], row, streak, xp_total)
+            quests.append({
+                "id": row["quest_id"],
+                "title": qdef["title"],
+                "description": qdef["description"],
+                "reward_db": row["reward_db"],
+                "count": count,
+                "target": target,
+                "completed": row["completed"],
+                "completed_at": row["completed_at"],
+            })
+        quests_payload[period_type] = {
+            "period_key": keys[period_type],
+            "resets_at": progression_mod.period_resets_at(period_type, now).isoformat(),
+            "quests": quests,
+        }
+
+    return {
+        "mastery_rank": progression_mod.mastery_rank(state["calibration_status"], player_paths),
+        "onboarding": {
+            "calibration_status": state["calibration_status"],
+            "calibration_completed_at": state["calibration_completed_at"],
+            "diagnostic_filename": appstate.builtin_diagnostic_filename(),
+        },
+        "paths": paths_payload,
+        "available_paths": available,
+        "quests": quests_payload,
+        "wallet": wallet,
+    }
+
+
+@router.get("/api/progression")
+def api_progression():
+    return _progression_overview()
+
+
+@router.post("/api/progression/paths")
+def api_progression_add_paths(data: dict):
+    """Select instrument paths. Body: {add: [path_id, ...]}. Idempotent;
+    removal is unsupported (Mastery Rank never decreases)."""
+    add = data.get("add")
+    if not isinstance(add, list) or not add:
+        return JSONResponse({"error": "add must be a non-empty list of path ids"}, status_code=400)
+    content = appstate.get_progression_content()
+    for pid in add:
+        if not isinstance(pid, str) or pid not in content["paths"]:
+            return JSONResponse({"error": f"unknown path: {pid!r}"}, status_code=400)
+    appstate.meta_db.add_player_paths(add)
+    return _progression_overview()
+
+
+@router.post("/api/progression/onboarding")
+def api_progression_onboarding(data: dict):
+    """Onboarding calibration choice. Body: {action: "skip"} — completing the
+    calibration needs no endpoint, it flows through the normal /api/stats path."""
+    if _clean_str(data.get("action")) != "skip":
+        return JSONResponse({"error": "action must be 'skip'"}, status_code=400)
+    # Spec invariant: onboarding requires picking at least one instrument path
+    # before finishing, so skipping straight to rank 1 with no paths would
+    # leave a rank that can never grow. Only enforced when the content bundle
+    # actually defines paths — broken/empty content must never brick onboarding.
+    if appstate.get_progression_content()["paths"] and not appstate.meta_db.get_player_paths():
+        return JSONResponse(
+            {"error": "select at least one instrument path before skipping calibration"},
+            status_code=400,
+        )
+    appstate.meta_db.skip_calibration()
+    return _progression_overview()
+
+
+# Externally postable progression events. song_completed is deliberately NOT
+# here: it is server-derived inside /api/stats so the scored-session authority
+# stays in one place.
+_PROGRESSION_EVENT_TYPES = {"minigame_run"}
+
+
+@router.post("/api/progression/events")
+def api_progression_events(data: dict):
+    """Generic progression-event intake for plugins (capability `record-event`).
+    Body: {type, payload}. Whitelisted types, scalar payload values only."""
+    etype = _clean_str(data.get("type"))
+    if etype not in _PROGRESSION_EVENT_TYPES:
+        return JSONResponse(
+            {"error": f"event type must be one of {sorted(_PROGRESSION_EVENT_TYPES)}"},
+            status_code=400,
+        )
+    payload = data.get("payload")
+    if payload is None:
+        payload = {}
+    if not isinstance(payload, dict) or len(payload) > 16:
+        return JSONResponse({"error": "payload must be a small object"}, status_code=400)
+    clean = {}
+    for key, value in payload.items():
+        if not isinstance(key, str) or len(key) > 64:
+            return JSONResponse({"error": "payload keys must be short strings"}, status_code=400)
+        if value is None:
+            continue
+        if isinstance(value, bool) or (
+            not isinstance(value, (int, float, str))
+        ) or (isinstance(value, float) and not math.isfinite(value)) or (
+            isinstance(value, str) and len(value) > 256
+        ):
+            return JSONResponse({"error": "payload values must be short strings or finite numbers"}, status_code=400)
+        clean[key] = value
+    summary = appstate.meta_db.record_progression_event(etype, clean, appstate.get_progression_content())
+    return {"ok": True, "progression": summary}

lib/routers/shop.py

@@ -0,0 +1,62 @@
+"""Cosmetics shop (spec 010) — buy/equip avatars & themes with earned currency.
+
+Extracted verbatim from ``server.py`` (R3); edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``, ``_get_progression_content()`` ->
+``appstate.get_progression_content()`` (the accessor is injected into the seam;
+its lazy content cache stays in server.py).
+"""
+
+from fastapi import APIRouter
+from fastapi.responses import JSONResponse
+
+import appstate
+from reqfields import _clean_str
+
+router = APIRouter()
+
+
+@router.get("/api/shop")
+def api_shop():
+    content = appstate.get_progression_content()
+    owned = appstate.meta_db.get_owned_items()
+    equipped = appstate.meta_db.get_equipped()
+    items = [
+        {**item, "owned": iid in owned, "equipped": equipped.get(item["slot"]) == iid}
+        for iid, item in sorted(content["shop"].items())
+    ]
+    return {"items": items, "wallet": appstate.meta_db.get_wallet()}
+
+
+@router.post("/api/shop/buy")
+def api_shop_buy(data: dict):
+    """Spend Decibels on a cosmetic. Atomic: balance check + spend + ownership
+    in one transaction. Decibels are earned by playing only — never purchasable."""
+    item_id = _clean_str(data.get("item_id"))
+    item = appstate.get_progression_content()["shop"].get(item_id)
+    if not item:
+        return JSONResponse({"error": f"unknown item: {item_id!r}"}, status_code=400)
+    status, wallet = appstate.meta_db.buy_shop_item(item)
+    if status == "owned":
+        return JSONResponse({"error": "already owned", "wallet": wallet}, status_code=409)
+    if status == "insufficient":
+        return JSONResponse({"error": "insufficient balance", "wallet": wallet}, status_code=402)
+    return {"ok": True, "item_id": item_id, "wallet": wallet}
+
+
+@router.post("/api/shop/equip")
+def api_shop_equip(data: dict):
+    """Equip an owned cosmetic into its slot. Body: {slot, item_id|null}
+    (null unequips, restoring the default look)."""
+    import progression as progression_mod
+    slot = _clean_str(data.get("slot"))
+    if slot not in progression_mod.SHOP_SLOTS:
+        return JSONResponse({"error": f"slot must be one of {sorted(progression_mod.SHOP_SLOTS)}"}, status_code=400)
+    item_id = data.get("item_id")
+    if item_id is not None:
+        item_id = _clean_str(item_id)
+        item = appstate.get_progression_content()["shop"].get(item_id)
+        if not item or item["slot"] != slot:
+            return JSONResponse({"error": f"unknown item for slot {slot}: {item_id!r}"}, status_code=400)
+        if item_id not in appstate.meta_db.get_owned_items():
+            return JSONResponse({"error": "item not owned"}, status_code=403)
+    return {"ok": True, "equipped": appstate.meta_db.equip_item(slot, item_id)}

lib/routers/stats.py

@@ -0,0 +1,233 @@
+"""Gameplay scoring — XP award + per-song practice stats (record / recent / best /
+top / per-song). The `/api/stats/{filename:path}` route is registered LAST so its
+catch-all doesn't shadow the fixed /recent /best /top paths.
+
+Extracted verbatim from ``server.py`` (R3); edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``, ``_get_progression_content()`` /
+``_builtin_diagnostic_filename()`` read through the seam.
+"""
+
+import logging
+import math
+
+from fastapi import APIRouter
+from fastapi.responses import JSONResponse
+
+import appstate
+from metadata_db import _as_int
+from reqfields import _clean_str
+
+log = logging.getLogger("feedBack.server")
+
+router = APIRouter()
+
+
+@router.post("/api/xp/award")
+def api_award_xp(data: dict):
+    """Award XP into the unified store. Body: {source, amount}. Returns the
+    new progress payload. The single XP authority — song-play, minigames, and
+    tutorials all feed this (no second curve)."""
+    try:
+        amount = _as_int(data.get("amount", 0))   # rejects bool / non-integral / inf
+    except (TypeError, ValueError, OverflowError):
+        return JSONResponse({"error": "amount must be an integer"}, status_code=400)
+    # Upper-bound it: an unbounded value overflows SQLite's 64-bit INTEGER on
+    # bind (→ 500) and no real run awards anywhere near this.
+    if not (0 <= amount <= 10_000_000):
+        return JSONResponse({"error": "amount must be between 0 and 10,000,000"}, status_code=400)
+    appstate.meta_db.award_xp(amount)
+    return appstate.meta_db.get_progress()
+
+
+@router.post("/api/stats")
+def api_record_stats(data: dict):
+    """Record a play. With `score`+`accuracy` → a scored session (plays += 1,
+    best_* = max, last_* = new) plus unified-XP + streak side-effects. With
+    only `lastPlayPosition`/`last_position` → a lightweight resume-position
+    touch (no plays change) so Continue-Playing works for non-scored plays."""
+    filename = _clean_str(data.get("filename"))
+    if not filename:
+        return JSONResponse({"error": "filename required"}, status_code=400)
+    # The recorder hands us URL-encoded filenames; canonicalize to the library
+    # key so stored rows line up with `songs` (and so the arrangement-count bound
+    # below resolves the real song). See MetadataDB._canonical_song_filename.
+    filename = appstate.meta_db._canonical_song_filename(filename)
+    arr_raw = data.get("arrangement", 0)
+    if arr_raw is None:
+        arrangement = 0
+    else:
+        try:
+            arrangement = _as_int(arr_raw)   # rejects bool / non-integral (1.9) / inf
+        except (TypeError, ValueError, OverflowError):
+            return JSONResponse({"error": "arrangement must be a non-negative integer"}, status_code=400)
+    # Reject (don't silently coerce to 0) so a malformed/out-of-range index
+    # can't corrupt arrangement 0's stats; also keeps it bindable to INTEGER.
+    if not (0 <= arrangement < 2**63):
+        return JSONResponse({"error": "arrangement must be a non-negative integer"}, status_code=400)
+    # Bound against the song's real arrangement count when it's a known library
+    # song, so a bad index can't create fake arrangement buckets that poison the
+    # per-song aggregate / Continue. Skipped when the song isn't in the library
+    # yet (count unknown — dead-song reads are filtered anyway).
+    _acount = appstate.meta_db.arrangement_count(filename)
+    if _acount and arrangement >= _acount:
+        return JSONResponse({"error": "arrangement out of range for this song"}, status_code=400)
+    score = data.get("score")
+    accuracy = data.get("accuracy")
+    last_pos = data.get("lastPlayPosition", data.get("last_position"))
+    if isinstance(last_pos, bool):   # float(False)=0.0 would otherwise store a bogus position
+        return JSONResponse({"error": "lastPlayPosition must be a finite number"}, status_code=400)
+
+    # A scored session needs BOTH score and accuracy. Exactly one provided is
+    # ambiguous — don't silently fall through to the position-only branch.
+    if (score is None) != (accuracy is None):
+        return JSONResponse({"error": "score and accuracy must be provided together"}, status_code=400)
+
+    if score is not None and accuracy is not None:
+        # Reject booleans explicitly — float(True) would otherwise record a play.
+        if isinstance(score, bool) or isinstance(accuracy, bool):
+            return JSONResponse({"error": "score/accuracy must be finite numbers"}, status_code=400)
+        # Reject NaN/Inf too: round(inf) raises OverflowError (→ 500), and a
+        # stored Inf/NaN later breaks JSON serialization of /api/stats reads.
+        try:
+            score = float(score)
+            accuracy = float(accuracy)
+            if not (math.isfinite(score) and math.isfinite(accuracy)):
+                raise ValueError("non-finite")
+            score = int(round(score))
+        except (TypeError, ValueError, OverflowError):
+            return JSONResponse({"error": "score/accuracy must be finite numbers"}, status_code=400)
+        # A huge-but-finite score passes isfinite() yet overflows SQLite's
+        # 64-bit INTEGER on bind (→ 500). Bound it to the int64 range.
+        if not (0 <= score < 2**63):
+            return JSONResponse({"error": "score out of range"}, status_code=400)
+        # accuracy is a 0..1 fraction (the recorder's contract); reject
+        # out-of-range values so they don't surface as >100% / negative in
+        # /api/stats/best and the badge UI.
+        if not (0 <= accuracy <= 1):
+            return JSONResponse({"error": "accuracy must be between 0 and 1"}, status_code=400)
+        # Validate the optional resume position in this branch too (the
+        # position-only branch below already rejects non-finite).
+        if last_pos is not None:
+            try:
+                last_pos = float(last_pos)
+                if not math.isfinite(last_pos):
+                    raise ValueError("non-finite")
+            except (TypeError, ValueError, OverflowError):
+                return JSONResponse({"error": "lastPlayPosition must be a finite number"}, status_code=400)
+        row = appstate.meta_db.record_session(filename, arrangement, score=score,
+                                     accuracy=accuracy, last_position=last_pos)
+        # Unified XP + streak side-effects — never let these drop the stat write.
+        progress = None
+        try:
+            from xp import xp_for_run
+            from datetime import date
+            appstate.meta_db.award_xp(xp_for_run(score))
+            appstate.meta_db.record_active_day(date.today().isoformat())
+            progress = appstate.meta_db.get_progress()
+        except Exception:
+            log.warning("stats side-effects (xp/streak) failed", exc_info=True)
+        # Progression engine (spec 010) — same never-drop-the-stat-write
+        # contract. Scored sessions are the server-derived `song_completed`
+        # authority (scored == note detection by construction); instrument is
+        # resolved from library arrangement metadata, after the XP award so
+        # db_earned goals see this run's Decibels.
+        progression_summary = None
+        try:
+            import progression as progression_mod
+            instrument = progression_mod.instrument_for_arrangement(
+                appstate.meta_db.arrangement_entry(filename, arrangement)
+            )
+            progression_summary = appstate.meta_db.record_progression_event(
+                "song_completed",
+                {
+                    "filename": filename,
+                    "instrument": instrument,
+                    "accuracy": accuracy,
+                    "score": score,
+                    "is_diagnostic": filename == appstate.builtin_diagnostic_filename(),
+                },
+                appstate.get_progression_content(),
+            )
+        except Exception:
+            log.warning("stats side-effects (progression) failed", exc_info=True)
+        return {"stats": row, "progress": progress, "progression": progression_summary}
+
+    # Position-only touch.
+    if last_pos is None:
+        return JSONResponse(
+            {"error": "provide score+accuracy (scored) or lastPlayPosition (resume)"},
+            status_code=400,
+        )
+    try:
+        pos = float(last_pos)
+        if not math.isfinite(pos):
+            raise ValueError("non-finite")
+        row = appstate.meta_db.touch_position(filename, arrangement, pos)
+    except (TypeError, ValueError, OverflowError):
+        return JSONResponse({"error": "lastPlayPosition must be a finite number"}, status_code=400)
+    # A resume session still counts as playing today: advance the streak (no XP —
+    # that's scoring-only) so a non-scored practice day keeps the streak alive,
+    # consistent with these sessions also surfacing in recent / continue.
+    progress = None
+    try:
+        from datetime import date
+        appstate.meta_db.record_active_day(date.today().isoformat())
+        progress = appstate.meta_db.get_progress()
+    except Exception:
+        log.warning("stats side-effects (streak) failed", exc_info=True)
+    return {"stats": row, "progress": progress}
+
+
+@router.get("/api/stats/recent")
+def api_recent_stats(limit: int = 12):
+    """Recently-played rows joined to song metadata for 'Jump back in'."""
+    from urllib.parse import quote
+    out = []
+    for r in appstate.meta_db.recent_stats(limit):
+        meta = appstate.meta_db.conn.execute(
+            "SELECT title, artist, tuning_name FROM songs WHERE filename = ?",
+            (r["filename"],),
+        ).fetchone()
+        title, artist, tuning_name = meta if meta else (None, None, None)
+        out.append({
+            **r,
+            "title": title or r["filename"],
+            "artist": artist or "",
+            "tuning_name": tuning_name or "",
+            "art_url": f"/api/song/{quote(r['filename'])}/art",
+        })
+    return out
+
+
+@router.get("/api/stats/best")
+def api_stats_best():
+    """{filename: best_accuracy} for all songs with a recorded best — one call
+    to badge the library grid (defined before the {filename} catch-all)."""
+    return appstate.meta_db.best_accuracy_map()
+
+
+@router.get("/api/stats/top")
+def api_top_stats(limit: int = 5):
+    """Top scored songs (best first), joined to song metadata, for the profile
+    'Your best scores' panel (defined before the {filename} catch-all)."""
+    from urllib.parse import quote
+    out = []
+    for r in appstate.meta_db.top_stats(limit):
+        meta = appstate.meta_db.conn.execute(
+            "SELECT title, artist, tuning_name FROM songs WHERE filename = ?",
+            (r["filename"],),
+        ).fetchone()
+        title, artist, tuning_name = meta if meta else (None, None, None)
+        out.append({
+            **r,
+            "title": title or r["filename"],
+            "artist": artist or "",
+            "tuning_name": tuning_name or "",
+            "art_url": f"/api/song/{quote(r['filename'])}/art",
+        })
+    return out
+
+
+@router.get("/api/stats/{filename:path}")
+def api_song_stats(filename: str):
+    return appstate.meta_db.get_song_stats(filename)

lib/routers/tunings.py

@@ -0,0 +1,46 @@
+"""The merged tuning catalog (/api/tunings).
+
+Extracted verbatim from server.py (R3) except @app->@router, CONFIG_DIR->
+appstate.config_dir, _load_config imported from lib/appconfig, and the tuning
+registry read through the appstate seam (appstate.tuning_providers — the same
+instance plugins register into via the plugin_context in server.py).
+"""
+
+from fastapi import APIRouter
+
+import appstate
+from appconfig import _load_config
+from tunings import DEFAULT_REFERENCE_PITCH, TUNING_PRESET_MIDIS, freqs_to_midis
+
+router = APIRouter()
+
+
+@router.get("/api/tunings")
+def get_tunings():
+    cfg = _load_config(appstate.config_dir / "config.json") or {}
+    ref = cfg.get("reference_pitch", DEFAULT_REFERENCE_PITCH)
+    try:
+        ref = float(ref)
+        if not (430.0 <= ref <= 450.0):
+            ref = DEFAULT_REFERENCE_PITCH
+    except (TypeError, ValueError):
+        ref = DEFAULT_REFERENCE_PITCH
+    merged = appstate.tuning_providers.get_merged(ref)
+    # tuningMidis: the same catalog as exact integer MIDI notes (low → high).
+    # Built-ins come straight from TUNING_PRESET_MIDIS (no float round-trip);
+    # provider-contributed entries are recovered from their frequencies at the
+    # served reference pitch. Every consumer today (the v3 badges, plugins)
+    # reconstructs midis client-side via log2 — a rounding footgun at non-440
+    # references — so serve the integers once, host-side. Additive: the
+    # existing referencePitch/tunings shape is unchanged.
+    tuning_midis: dict[str, dict[str, list[int]]] = {}
+    for key, names in merged.items():
+        builtin = TUNING_PRESET_MIDIS.get(key, {})
+        resolved: dict[str, list[int]] = {}
+        for name, freqs in names.items():
+            midis = builtin.get(name) or freqs_to_midis(freqs, ref)
+            if midis:
+                resolved[name] = list(midis)
+        if resolved:
+            tuning_midis[key] = resolved
+    return {"referencePitch": ref, "tunings": merged, "tuningMidis": tuning_midis}

lib/routers/version.py

@@ -0,0 +1,81 @@
+"""App version + source/license URLs (/api/version).
+
+Extracted verbatim from ``server.py`` (R3) except the decorator (``@app`` ->
+``@router``) and the VERSION-file lookup: ``Path(__file__).parent`` (app root
+when this lived at the top level) -> ``Path(__file__).resolve().parents[2]``
+(routers -> lib -> app root). VERSION ships at the app root in every packaging
+path (Dockerfile COPY, desktop bundle).
+"""
+
+import os
+from pathlib import Path
+
+from fastapi import APIRouter
+
+router = APIRouter()
+
+
+def _safe_http_url(raw):
+    """Return `raw` stripped + trailing-slash-stripped if it parses as an
+    http(s) URL with a non-empty host; else None.
+
+    Used to validate operator-supplied `APP_SOURCE_URL` / `APP_LICENSE_URL`
+    env vars before they reach `<a href>` in the UI. A bare prefix check
+    like `startswith(("http://","https://"))` accepts malformed inputs
+    such as `"https://"` (no host) or `"https:///foo"` (empty host) that
+    still produce broken hrefs — and, when used as a base for the default
+    `license_url`, garbage like `"https:///blob/main/LICENSE"`.
+    """
+    from urllib.parse import urlsplit
+    if not raw:
+        return None
+    s = raw.strip().rstrip("/")
+    if not s:
+        return None
+    try:
+        parsed = urlsplit(s)
+    except ValueError:
+        return None
+    if parsed.scheme.lower() not in ("http", "https"):
+        return None
+    # `netloc` includes any `user:pass@` and `:port` — strings like
+    # "http://:80/path" have non-empty netloc (":80") but no real
+    # hostname. Validate `hostname` so only URLs with an actual host
+    # are accepted.
+    if not parsed.hostname:
+        return None
+    return s
+
+
+@router.get("/api/version")
+def get_version():
+    env_version = os.environ.get("APP_VERSION", "").strip()
+    if env_version:
+        version = env_version
+    else:
+        version_file = Path(__file__).resolve().parents[2] / "VERSION"  # R3: app root from lib/routers/
+        version = "unknown"
+        if version_file.exists():
+            try:
+                version = version_file.read_text().strip()
+            except (OSError, UnicodeDecodeError):
+                pass
+    default_source_url = "https://github.com/got-feedback/feedBack"
+    # APP_SOURCE_URL / APP_LICENSE_URL flow straight into <a href> in the UI,
+    # so validate with urllib.parse rather than a bare prefix check — a prefix
+    # check accepts malformed values like "https://" (no host) which produce
+    # broken hrefs (and a constructed license_url like "https:///blob/main/LICENSE").
+    # _safe_http_url requires scheme in {http,https} AND a non-empty hostname
+    # (not just netloc — that would still accept port-only authorities like
+    # "http://:80/path"); fall back to the safe default otherwise.
+    source_url = _safe_http_url(os.environ.get("APP_SOURCE_URL")) or default_source_url
+    # APP_LICENSE_URL: explicit override for the LICENSE link. The default
+    # constructed value (source_url + "/blob/main/LICENSE") is GitHub-
+    # specific and assumes the repo's default branch is `main`; non-GitHub
+    # hosts (GitLab, Gitea, self-hosted) need an explicit value.
+    license_url = _safe_http_url(os.environ.get("APP_LICENSE_URL")) or (source_url + "/blob/main/LICENSE")
+    return {
+        "version": version,
+        "source_url": source_url,
+        "license_url": license_url,
+    }

lib/routers/wanted.py

@@ -0,0 +1,45 @@
+"""Wishlist / "wanted" API (feedBack#636) — songs the user wants but doesn't own.
+
+Extracted verbatim from ``server.py`` (R3); edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``, ``_clean_str`` from ``reqfields``.
+"""
+
+from fastapi import APIRouter
+from fastapi.responses import JSONResponse
+
+import appstate
+from reqfields import _clean_str
+
+router = APIRouter()
+
+
+@router.get("/api/wanted")
+def api_list_wanted():
+    """The wishlist — songs the user wants but doesn't own yet (newest first)."""
+    return {"wanted": appstate.meta_db.list_wanted()}
+
+
+@router.post("/api/wanted")
+def api_add_wanted(data: dict):
+    """Add a not-owned song to the wishlist. `artist`/`title` are required (at
+    least one non-empty); `source`/`source_ref`/`note` are optional. Idempotent
+    on identity so producers (find_more ownership-diff, manual add) can re-post."""
+    if not isinstance(data, dict):
+        return JSONResponse({"error": "body must be an object"}, status_code=400)
+    artist = _clean_str(data.get("artist"))
+    title = _clean_str(data.get("title"))
+    if not artist and not title:
+        return JSONResponse({"error": "artist or title required"}, status_code=400)
+    row = appstate.meta_db.add_wanted(
+        artist=artist, title=title,
+        source=_clean_str(data.get("source")) or "manual",
+        source_ref=_clean_str(data.get("source_ref")),
+        note=_clean_str(data.get("note")),
+    )
+    return {"ok": True, "wanted": row}
+
+
+@router.delete("/api/wanted/{wanted_id}")
+def api_remove_wanted(wanted_id: int):
+    """Remove a wishlist entry by id."""
+    return {"ok": appstate.meta_db.remove_wanted(wanted_id)}

lib/scan_worker.py

@@ -3,7 +3,7 @@
 This module is deliberately kept apart from ``server.py`` so that
 ``ProcessPoolExecutor`` workers can import and unpickle ``_scan_one``
 without dragging in ``server.py``'s import-time side effects
-(``configure_logging()``, ``meta_db = MetadataDB()`` opening/migrating
+(``configure_logging()``, ``meta_db = MetadataDB(CONFIG_DIR)`` opening/migrating
 SQLite, and ``register_plugin_api(app)`` registering routes).
 
 The background scan spawns its pool with the ``spawn`` start method (see

lib/sloppak.py

@@ -703,20 +703,32 @@ def load_song(
                     and isinstance(e.get("d"), (int, float))
                 ]
                 if song.lyrics:
-                    # Provenance — populated by the converter (xml/notechart),
-                    # the WhisperX fallback (whisperx), or hand-edits
-                    # (user). Validate against the closed enum so a
-                    # hand-edited (or otherwise malformed) manifest can't
-                    # propagate a YAML dict / list / arbitrary string
-                    # into the highway WS `lyrics.source` field and out
-                    # to plugin badges. Anything outside the enum (or
-                    # the wrong type) falls back to "xml" — the spec's
-                    # back-compat default — instead of being stringified
-                    # and trusted.
-                    _ALLOWED_LYRICS_SOURCES = {"xml", "notechart", "whisperx", "user"}
-                    # Legacy alias: older manifests labelled note-chart-derived
-                    # lyrics with the source format's name; normalise it.
-                    _LYRICS_SOURCE_ALIASES = {"sng": "notechart"}
+                    # Provenance. The feedpak spec (§7.1) vocabulary is
+                    # {authored, transcribed, user}; older manifests + the
+                    # in-tree readers also use the source-format names
+                    # (xml/notechart) and the WhisperX engine name
+                    # (whisperx). Accept the union so both spec-compliant
+                    # writers (e.g. the stem_splitter plugin emitting
+                    # `transcribed`) and legacy packs validate. Validate
+                    # against the closed enum so a hand-edited (or otherwise
+                    # malformed) manifest can't propagate a YAML dict / list /
+                    # arbitrary string into the highway WS `lyrics.source`
+                    # field and out to plugin badges. Anything outside the
+                    # enum (or the wrong type) falls back to "xml" — the
+                    # back-compat default — instead of being stringified and
+                    # trusted.
+                    # Post-alias values only: `whisperx` is normalised to
+                    # `transcribed` before the membership check below, so (like
+                    # `sng`) it is intentionally absent from this set.
+                    _ALLOWED_LYRICS_SOURCES = {
+                        "xml", "notechart", "user",
+                        "authored", "transcribed",
+                    }
+                    # Legacy aliases: older manifests labelled note-chart-derived
+                    # lyrics with the source format's name, and the WhisperX
+                    # fallback with the engine name — normalise both to the
+                    # spec vocabulary the badges now expect.
+                    _LYRICS_SOURCE_ALIASES = {"sng": "notechart", "whisperx": "transcribed"}
                     raw_source = manifest.get("lyrics_source")
                     if isinstance(raw_source, str):
                         raw_source = _LYRICS_SOURCE_ALIASES.get(raw_source, raw_source)

lib/tunings.py

@@ -98,6 +98,22 @@ def open_midis_to_freqs(midis: list[int], reference_pitch: float = DEFAULT_REFER
     return [round(midi_to_freq(m, reference_pitch), 2) for m in midis]
 
 
+def freqs_to_midis(freqs: list[float], reference_pitch: float = DEFAULT_REFERENCE_PITCH) -> list[int] | None:
+    """Return absolute open-string MIDI notes for frequencies at the supplied
+    A4 reference — the inverse of open_midis_to_freqs. None if any entry is
+    non-numeric or non-positive (a provider could hand us anything)."""
+    out: list[int] = []
+    for f in freqs:
+        try:
+            f = float(f)
+        except (TypeError, ValueError):
+            return None
+        if f <= 0:
+            return None
+        out.append(int(round(69 + 12 * math.log2(f / reference_pitch))))
+    return out
+
+
 def tuning_offsets_from_midis(instrument_key: str, midis: list[int]) -> list[int] | None:
     """Return semitone offsets from the instrument's standard open strings."""
     standard = STANDARD_OPEN_MIDIS.get(instrument_key)

package.json

@@ -8,9 +8,12 @@
     "test:headed": "playwright test --headed",
     "test:debug": "playwright test --debug",
     "test:js": "node --test tests/js/*.test.js 'tests/plugins/*/js/*.test.js'",
-    "install:playwright": "playwright install chromium"
+    "install:playwright": "playwright install chromium",
+    "lint": "eslint ."
   },
   "devDependencies": {
-    "@playwright/test": "^1.59.1"
+    "@playwright/test": "^1.59.1",
+    "eslint": "^9.39.4",
+    "eslint-plugin-import-x": "^4.17.1"
   }
 }

plugins/__init__.py

@@ -18,6 +18,54 @@ from safepath import safe_join
 log = logging.getLogger("feedBack.plugins")
 
 
+def _plugin_media_type(path: Path) -> str:
+    """Best-effort Content-Type for a served plugin file. `.js`/`.css` must come
+    back as JavaScript/CSS so `<script type=module>` / `addModule()` / a `<link>`
+    accept them; `mimetypes.guess_type` can miss these on a stripped platform
+    registry, so fall back explicitly (mirrors the assets/ route)."""
+    media_type = mimetypes.guess_type(path.name)[0]
+    if media_type is None and path.suffix == ".js":
+        return "application/javascript"
+    if media_type is None and path.suffix == ".css":
+        return "text/css"
+    return media_type or "application/octet-stream"
+
+
+def _plugin_file_etag(path: Path) -> str | None:
+    """Weak ETag from mtime+size — cheap, stable across reads, changes on edit.
+    This is what makes the live-edit loop work for module graphs: a conditional
+    GET revalidates and 304s unchanged files on refresh instead of re-downloading
+    the whole `src/` tree. Returns None if the file can't be stat'd."""
+    try:
+        st = path.stat()
+    except OSError:
+        return None
+    return f'W/"{st.st_mtime_ns:x}-{st.st_size:x}"'
+
+
+def _if_none_match(request: Request, etag: str) -> bool:
+    """True when the client's If-None-Match already holds `etag`."""
+    # ponytail: we serve one weak ETag; the browser echoes it back verbatim, so
+    # a direct compare is enough (comma-split tolerates a proxy concatenation).
+    return etag in [t.strip() for t in request.headers.get("if-none-match", "").split(",")]
+
+
+def _plugin_file_response(request: Request, path: Path, media_type: str) -> Response:
+    """Serve a plugin source/asset file with the live-edit cache contract:
+    `Cache-Control: no-cache` (browser may store but MUST revalidate) + a weak
+    ETag, and a bodyless 304 when the client's If-None-Match already matches.
+    Starlette's `FileResponse` emits an ETag but never evaluates If-None-Match
+    itself, so the conditional handling has to live here."""
+    headers = {"Cache-Control": "no-cache"}
+    etag = _plugin_file_etag(path)
+    if etag:
+        headers["ETag"] = etag
+        if _if_none_match(request, etag):
+            return Response(status_code=304, headers=headers)
+    # FileResponse sets etag/last-modified via setdefault, so the ETag above wins.
+    return FileResponse(path, media_type=media_type, headers=headers)
+
+
 PLUGINS_DIR = Path(__file__).parent
 # Holds only *ready* (loaded) plugins — those whose dependencies installed
 # and whose routes registered. A plugin GRADUATES from PENDING_PLUGINS into
@@ -1373,6 +1421,12 @@ def load_plugins(app: FastAPI, context: dict, progress_cb=None, route_setup_fn=N
             "version": manifest.get("version"),
             "has_screen": bool(manifest.get("screen")),
             "has_script": bool(manifest.get("script")),
+            # Module-migration (R0): `scriptType:"module"` tells the loader to
+            # inject screen.js as <script type="module">; `minHost` is the
+            # min core version a migrated plugin needs (passthrough only in R0 —
+            # enforcement is deferred to R4, master §4b). None when unset.
+            "script_type": manifest.get("scriptType"),
+            "min_host": manifest.get("minHost"),
             "has_settings": bool(manifest.get("settings")),
             "settings_category": _settings_category,
             # Drives the v3 shell's immersive (full-screen) mode for this
@@ -2089,6 +2143,11 @@ def register_plugin_api(app: FastAPI):
                 "fallback": p.get("fallback", False),
                 "has_screen": p["has_screen"],
                 "has_script": p["has_script"],
+                # Module-migration passthrough (R0). Re-read from the manifest
+                # like `version` above so stubbed test entries (built without
+                # _nav_entry) don't need the key.
+                "script_type": (p.get("_manifest") or {}).get("scriptType"),
+                "min_host": (p.get("_manifest") or {}).get("minHost"),
                 "has_settings": p["has_settings"],
                 # v3 immersive screen opt-in (full-screen plugin UI).
                 "fullscreen": p.get("fullscreen", False),
@@ -2142,6 +2201,9 @@ def register_plugin_api(app: FastAPI):
                 "fallback": False,
                 "has_screen": e.get("has_screen", False),
                 "has_script": e.get("has_script", False),
+                # Pending entries come from _nav_entry, so they carry these.
+                "script_type": e.get("script_type"),
+                "min_host": e.get("min_host"),
                 "has_settings": e.get("has_settings", False),
                 "settings_category": e.get("settings_category"),
                 "fullscreen": e.get("fullscreen", False),
@@ -2307,7 +2369,7 @@ def register_plugin_api(app: FastAPI):
         return HTMLResponse("", status_code=404)
 
     @app.get("/api/plugins/{plugin_id}/screen.js")
-    def plugin_screen_js(plugin_id: str):
+    def plugin_screen_js(request: Request, plugin_id: str):
         with PLUGINS_LOCK:
             snapshot = list(LOADED_PLUGINS)
         for p in snapshot:
@@ -2315,8 +2377,11 @@ def register_plugin_api(app: FastAPI):
                 if p.get("status", "ready") != "ready":
                     break
                 script_file = p["_dir"] / p["_manifest"].get("script", "screen.js")
-                if script_file.exists():
-                    return Response(script_file.read_text(encoding="utf-8"), media_type="application/javascript")
+                if script_file.is_file():
+                    # no-cache + ETag/304 so an edited screen.js reloads on
+                    # refresh while an unchanged one revalidates cheaply — the
+                    # same live-edit contract the src/ module graph relies on.
+                    return _plugin_file_response(request, script_file, "application/javascript")
         return Response("", status_code=404)
 
     @app.get("/api/plugins/{plugin_id}/settings.html")
@@ -2377,7 +2442,7 @@ def register_plugin_api(app: FastAPI):
         return Response("{}", status_code=404, media_type="application/json")
 
     @app.get("/api/plugins/{plugin_id}/assets/{asset_path:path}")
-    def plugin_asset(plugin_id: str, asset_path: str):
+    def plugin_asset(request: Request, plugin_id: str, asset_path: str):
         """Serve a static file a plugin bundles under its own ``assets/``
         directory (e.g. an AudioWorklet module, WASM, or image). Unlike the
         fixed screen.js/settings.html handlers above, this is a generic
@@ -2399,16 +2464,35 @@ def register_plugin_api(app: FastAPI):
                     log.warning("Plugin %r: asset path rejected: %r", plugin_id, asset_path)
                     break
                 if target.is_file():
-                    media_type = mimetypes.guess_type(target.name)[0]
-                    # .js must come back as JavaScript so addModule() / <script>
-                    # accept it; guess_type can miss this on some platforms.
-                    if media_type is None and target.suffix == ".js":
-                        media_type = "application/javascript"
-                    # .css must come back as text/css so a <link rel=stylesheet>
-                    # (the styles capability) is honoured; guess_type can miss it
-                    # on a stripped platform mimetypes registry, same as .js.
-                    elif media_type is None and target.suffix == ".css":
-                        media_type = "text/css"
-                    return FileResponse(target, media_type=media_type or "application/octet-stream")
+                    # no-cache + ETag/304 so a live-edited worklet/asset reloads
+                    # on refresh (bare FileResponse emits an ETag but never 304s).
+                    return _plugin_file_response(request, target, _plugin_media_type(target))
+                break
+        return Response("", status_code=404)
+
+    @app.get("/api/plugins/{plugin_id}/src/{src_path:path}")
+    def plugin_src(request: Request, plugin_id: str, src_path: str):
+        """Serve a file from a plugin's ES-module source tree under ``src/``.
+
+        This is the R0 host capability that lets a migrated plugin's
+        ``screen.js`` (a one-line ``import './src/main.js'``) load its whole
+        module graph. Containment mirrors the assets/ route exactly —
+        ``safe_join`` against ``<plugin>/src`` rejects ``..``, absolute paths,
+        and NUL bytes — and the live-edit cache contract (no-cache + ETag/304)
+        makes an edited module reload on refresh while unchanged ones 304.
+        Read-only; the src/ tree is source files, never executed server-side.
+        """
+        with PLUGINS_LOCK:
+            snapshot = list(LOADED_PLUGINS)
+        for p in snapshot:
+            if p["id"] == plugin_id:
+                if p.get("status", "ready") != "ready":
+                    break
+                target = safe_join(p["_dir"] / "src", src_path)
+                if target is None:
+                    log.warning("Plugin %r: src path rejected: %r", plugin_id, src_path)
+                    break
+                if target.is_file():
+                    return _plugin_file_response(request, target, _plugin_media_type(target))
                 break
         return Response("", status_code=404)

plugins/drum_highway_3d/plugin.json

@@ -1,7 +1,7 @@
 {
   "id": "drum_highway_3d",
   "name": "3D Drum Highway",
-  "version": "0.3.1",
+  "version": "0.3.2",
   "type": "visualization",
   "bundled": true,
   "script": "screen.js",

plugins/drum_highway_3d/screen.js

@@ -1361,6 +1361,41 @@
         } catch (_) { /* dispatch unavailable — persisted value applies next init */ }
     };
 
+    /* ======================================================================
+     *  Camera Director bridge resolver (pure — exported via createFactory.__test)
+     * ====================================================================== */
+
+    /**
+     * The active splitscreen API, defensive on the global-name rename in flight
+     * (feedBackSplitscreen is canonical; slopsmithSplitscreen is the legacy alias).
+     * @returns {object|null} the splitscreen API, or null when not present
+     */
+    function _ssApi() { return window.feedBackSplitscreen || window.slopsmithSplitscreen || null; }
+
+    /**
+     * Resolve the Camera Director camera for a canvas: this panel's camera under
+     * splitscreen, else the global, else null (Camera Director absent → stock
+     * framing). Throw-safe on panelIndexFor so a misbehaving splitscreen build
+     * can't break framing.
+     * @param {HTMLCanvasElement} canvas this renderer's highway canvas
+     * @param {object|null} ss the splitscreen API (see _ssApi)
+     * @param {object|null} panelsMap window.__h3dCamCtlPanels (per-panel cameras by index)
+     * @param {object|null} globalCam window.__h3dCamCtl (single global camera)
+     * @returns {object|null} the resolved free-camera bridge, or null
+     */
+    function _resolveFreeCam(canvas, ss, panelsMap, globalCam) {
+        if (panelsMap && ss && typeof ss.panelIndexFor === 'function') {
+            try {
+                const i = ss.panelIndexFor(canvas);
+                // Only a non-negative integer indexes the panel map — a non-int /
+                // negative / string index (or a prototype key) must not resolve an
+                // unintended/inherited property; fall through to the global then.
+                if (Number.isInteger(i) && i >= 0 && panelsMap[i]) return panelsMap[i];
+            } catch (e) { /* ignore */ }
+        }
+        return globalCam || null;
+    }
+
     /* ======================================================================
      *  Renderer factory
      * ====================================================================== */
@@ -1414,7 +1449,7 @@
         let _sparkPts = null, _sparkPos = null, _sparkCol = null, _sparkVel = null, _sparkLife = null;
         let _fxLastWall = 0;          // wall clock for FX integration (sparks, pulse decay)
         let _kickPulse = 0;           // kick-hit camera-dip + floor-wash envelope
-        let _camBaseH = 0, _camBaseD = 0;  // positionCamera's unpulsed pose
+        let _camBaseH = null, _camBaseD = null;  // positionCamera's unpulsed pose (null until it first runs; applyCamera's guard depends on this)
         let _gaussTex = null;         // shared soft-falloff texture for flash quads
         let _laneFlashQuads = [];     // pooled additive quad per hand lane (z=0)
         let _kickFlashQuad = null;    // full-width flash quad for the kick bar
@@ -2651,6 +2686,48 @@
             cam.lookAt(0, 0, -AHEAD * TS * 0.45);
         }
 
+        /**
+         * Camera Director bridge for THIS panel — delegates to the pure, unit-
+         * tested _resolveFreeCam / _ssApi (resolver block above the factory).
+         * Reads the live globals: per-panel map __h3dCamCtlPanels → this panel's
+         * camera, else the global __h3dCamCtl, else null (stock framing).
+         * @param {HTMLCanvasElement} canvas this panel's highway canvas
+         * @returns {object|null} the resolved free-camera bridge, or null
+         */
+        function _freeCamFor(canvas) {
+            return _resolveFreeCam(canvas, _ssApi(), window.__h3dCamCtlPanels, window.__h3dCamCtl);
+        }
+
+        // Per-frame camera write: static base pose (positionCamera) + kick-pulse Y
+        // dip, then layer Camera Director free-cam offsets (dolly/height/orbit on
+        // the camera-from-target vector; pan/pitch on the look target). Runs every
+        // frame so a live free-cam drag is smooth; allocation-free; NaN-safe; a
+        // null/disabled bridge reproduces the stock static+pulse pose exactly.
+        function applyCamera() {
+            if (_camBaseH == null) return;               // before first positionCamera()
+            const _dip = (_kickPulse > 0.001) ? (0.8 * K * _kickPulse * fx.hitFx) : 0;
+            let _cx = 0, _cy = _camBaseH - _dip, _cz = _camBaseD;
+            let _lx = 0, _ly = 0, _lz = -AHEAD * TS * 0.45;
+            const _fc = _freeCamFor(highwayCanvas);
+            if (_fc && _fc.enabled) {
+                const _dm = Number.isFinite(_fc.distMul) ? _fc.distMul : 1;
+                const _hm = Number.isFinite(_fc.heightMul) ? _fc.heightMul : 1;
+                const _yaw = Number.isFinite(_fc.yaw) ? _fc.yaw : 0;
+                let _vx = _cx - _lx, _vy = _cy - _ly, _vz = _cz - _lz;
+                _vx *= _dm; _vy *= _dm; _vz *= _dm;   // dolly (zoom)
+                _vy *= _hm;                            // height
+                const _cyw = Math.cos(_yaw), _syw = Math.sin(_yaw);
+                const _rx = _vx * _cyw - _vz * _syw, _rz = _vx * _syw + _vz * _cyw; // orbit around Y
+                _cx = _lx + _rx; _cy = _ly + _vy; _cz = _lz + _rz;
+                const _px = Number.isFinite(_fc.panX) ? _fc.panX : 0;
+                const _py = Number.isFinite(_fc.panY) ? _fc.panY : 0;
+                const _pt = Number.isFinite(_fc.pitch) ? _fc.pitch : 0;
+                _lx += _px * K; _ly += (_pt + _py) * K;
+            }
+            cam.position.set(_cx, _cy, _cz);
+            cam.lookAt(_lx, _ly, _lz);
+        }
+
         function buildLanes(_floorW, floorD) {
             laneGroup = new T.Group();
             laneStripeMats = [];
@@ -3431,15 +3508,18 @@
                             BG_STYLES[_bgState._style].update(_bgState.s, bands, fdt, nowMs / 1000);
                         } catch (_) { /* visual-only */ }
                     }
+                    // Kick pulse decays each frame; it drives the floor flash and,
+                    // via applyCamera(), the camera Y dip.
                     if (_kickPulse > 0.001) {
                         _kickPulse *= Math.exp(-fdt * 7);
-                        cam.position.y = _camBaseH - 0.8 * K * _kickPulse * fx.hitFx;
                         if (_floorFlash) _floorFlash.material.opacity = 0.25 * _kickPulse * fx.hitFx;
                     } else if (_kickPulse !== 0) {
                         _kickPulse = 0;
-                        cam.position.y = _camBaseH;
                         if (_floorFlash) _floorFlash.material.opacity = 0;
                     }
+                    // Write the camera every frame: static base pose + kick dip +
+                    // Camera Director free-cam offsets (per-panel-aware).
+                    applyCamera();
                 }
                 // Approach highlight: raise each lane stripe toward its next
                 // note (accumulated by the rebuildNotes walk above).
@@ -3565,6 +3645,8 @@
     // vm-loaded with no DOM/WebGL; everything here must stay side-effect
     // free to call).
     window.slopsmithViz_drum_highway_3d.__test = {
+        _resolveFreeCam,
+        _ssApi,
         _variantForHit,
         _classifyTiming,
         readFxSettings,

plugins/drum_highway_3d/tests/camera_bridge.test.js

@@ -0,0 +1,78 @@
+// Camera Director bridge resolver tests: per-panel select, global fallback,
+// null-when-absent, throw-safety, and the splitscreen global-name alias. Loads
+// screen.js in a bare vm window and exercises the __test exports (no DOM/WebGL).
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const vm = require('node:vm');
+
+function load() {
+    const window = {
+        console,
+        location: { protocol: 'http:', host: 'localhost' },
+        slopsmith: {},
+    };
+    window.window = window;
+    window.globalThis = window;
+    const context = vm.createContext(window);
+    const src = fs.readFileSync(path.join(__dirname, '..', 'screen.js'), 'utf8');
+    vm.runInContext(src, context, { filename: 'screen.js' });
+    return { window, __test: window.slopsmithViz_drum_highway_3d.__test };
+}
+
+test('_resolveFreeCam: per-panel camera under splitscreen', () => {
+    const { __test } = load();
+    const c0 = {}, c1 = {};
+    const ss = { panelIndexFor: (c) => (c === c0 ? 0 : 1) };
+    const map = { 0: { id: 'p0' }, 1: { id: 'p1' } };
+    assert.equal(__test._resolveFreeCam(c0, ss, map, { id: 'g' }).id, 'p0');
+    assert.equal(__test._resolveFreeCam(c1, ss, map, { id: 'g' }).id, 'p1');
+});
+
+test('_resolveFreeCam: falls back to global when there is no panel map', () => {
+    const { __test } = load();
+    const g = { id: 'global' };
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => 0 }, null, g), g);
+});
+
+test('_resolveFreeCam: falls back to global when the panel has no map entry', () => {
+    const { __test } = load();
+    const g = { id: 'global' };
+    const ss = { panelIndexFor: () => 3 };            // index 3 absent from map
+    assert.equal(__test._resolveFreeCam({}, ss, { 0: {} }, g), g);
+});
+
+test('_resolveFreeCam: null when Camera Director is absent (no global)', () => {
+    const { __test } = load();
+    assert.equal(__test._resolveFreeCam({}, null, null, null), null);
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => 0 }, {}, undefined), null);
+});
+
+test('_resolveFreeCam: throw-safe on panelIndexFor → falls back to global', () => {
+    const { __test } = load();
+    const g = { id: 'global' };
+    const ss = { panelIndexFor: () => { throw new Error('boom'); } };
+    assert.equal(__test._resolveFreeCam({}, ss, { 0: {} }, g), g);
+});
+
+test('_resolveFreeCam: NaN/negative/float/string index → falls back to global', () => {
+    const { __test } = load();
+    const g = { id: 'global' };
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => NaN }, { 0: {} }, g), g);
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => -1 }, { 0: {} }, g), g);
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => 0.5 }, { 0: {} }, g), g);
+    // A string/prototype key must not resolve an inherited property (e.g. toString).
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => 'toString' }, {}, g), g);
+});
+
+test('_ssApi: null when neither global set; slopsmith alias; feedBack canonical wins', () => {
+    const { window, __test } = load();
+    assert.equal(__test._ssApi(), null);
+    const legacy = { panelIndexFor: () => 0 };
+    window.slopsmithSplitscreen = legacy;
+    assert.equal(__test._ssApi(), legacy);            // legacy alias picked up
+    const current = { panelIndexFor: () => 1 };
+    window.feedBackSplitscreen = current;
+    assert.equal(__test._ssApi(), current);           // canonical name takes precedence
+});

plugins/highway_3d/plugin.json

@@ -1,7 +1,7 @@
 {
     "id": "highway_3d",
     "name": "3D Highway",
-    "version": "3.31.2",
+    "version": "3.31.5",
     "type": "visualization",
     "bundled": true,
     "script": "screen.js",

plugins/highway_3d/screen.js

@@ -548,9 +548,20 @@
             ctrl.ownsActx = !(fogAudio && fogAudio.ctx);
             ctrl.actx = (fogAudio && fogAudio.ctx) || new Ctx();
             if (ctrl.actx.state === 'suspended' && ctrl.actx.resume) ctrl.actx.resume().catch(() => {});
+            // Seed the DRAWING BUFFER (canvas.width/height) to the device-pixel
+            // render size and report that SAME size to Butterchurn. Its on-screen
+            // pass viewports to the reported size but never sizes the output canvas
+            // itself — leaving the buffer at the 300x150 default blits the whole
+            // visualizer into a corner that CSS then stretches across the highway.
+            // pixelRatio:1 because DPR is now folded into the reported size, so
+            // buffer == viewport == internal texsize (no double-counting).
+            const _bcRatio0 = Math.min(window.devicePixelRatio || 1, 1.5);
+            const _bcW0 = Math.max(1, Math.round((sz.w || 1280) * _bcRatio0));
+            const _bcH0 = Math.max(1, Math.round((sz.h || 720) * _bcRatio0));
+            canvas.width = _bcW0; canvas.height = _bcH0;
             ctrl.viz = bc.createVisualizer(ctrl.actx, canvas, {
-                width: sz.w || 1280, height: sz.h || 720,
-                pixelRatio: Math.min(window.devicePixelRatio || 1, 1.5), textureRatio: 1,
+                width: _bcW0, height: _bcH0,
+                pixelRatio: 1, textureRatio: 1,
             });
             if (_bcIsDesktop()) {
                 try {
@@ -584,6 +595,27 @@
             ctrl.actx = null; ctrl.viz = null; ctrl.dead = true;
             _bcControllers.delete(ctrl);
         });
+        // Size the Butterchurn output: set the canvas DRAWING BUFFER to the
+        // device-pixel render size AND report that same size, so buffer ==
+        // on-screen viewport == full fill. Butterchurn never sizes the output
+        // canvas itself; the previous code set only CSS size, leaving the buffer
+        // at the 300x150 default -> the viz showed a stretched lower-left corner
+        // (worse the larger the panel). Ratio reuses the highway's DPR budget.
+        function _bcApplySize(cssW, cssH) {
+            if (!(cssW > 0 && cssH > 0)) return;
+            ctrl.lastW = cssW; ctrl.lastH = cssH;
+            const ratio = Math.min(window.devicePixelRatio || 1, 1.5);
+            const bw = Math.max(1, Math.round(cssW * ratio)), bh = Math.max(1, Math.round(cssH * ratio));
+            if (canvas.width !== bw) canvas.width = bw;
+            if (canvas.height !== bh) canvas.height = bh;
+            const wpx = cssW + 'px', hpx = cssH + 'px';
+            // Confine ALL layers to exactly the highway-canvas rect so the opaque
+            // backdrop can't bleed over the transport bar above the highway.
+            [ctrl.canvas, ctrl.backdrop, ctrl.scrim, ctrl.tint].forEach((el) => {
+                if (el) { el.style.width = wpx; el.style.height = hpx; el.style.right = 'auto'; el.style.bottom = 'auto'; }
+            });
+            if (ctrl.viz && ctrl.viz.setRendererSize) { try { ctrl.viz.setRendererSize(bw, bh); } catch (e) {} }
+        }
         return {
             applySettings() { ctrl.applySettings(); },
             dead() { return ctrl.dead; },
@@ -612,18 +644,11 @@
                 if (!ctrl.viz || !s.enabled) return; // skip GPU work when the bg is off
                 const sz = sizeProvider && sizeProvider();
                 if (sz && sz.w > 0 && sz.h > 0 && (sz.w !== ctrl.lastW || sz.h !== ctrl.lastH)) {
-                    ctrl.lastW = sz.w; ctrl.lastH = sz.h;
-                    const wpx = sz.w + 'px', hpx = sz.h + 'px';
-                    // Confine ALL layers to exactly the highway-canvas rect so the opaque
-                    // backdrop can't bleed over the transport bar above the highway.
-                    [ctrl.canvas, ctrl.backdrop, ctrl.scrim, ctrl.tint].forEach((el) => {
-                        if (el) { el.style.width = wpx; el.style.height = hpx; el.style.right = 'auto'; el.style.bottom = 'auto'; }
-                    });
-                    try { ctrl.viz.setRendererSize(sz.w, sz.h); } catch (e) {}
+                    _bcApplySize(sz.w, sz.h);
                 }
                 try { ctrl.viz.render(); } catch (e) {}
             },
-            resize(w, h) { if (ctrl.viz && ctrl.viz.setRendererSize) { try { ctrl.viz.setRendererSize(w, h); } catch (e) {} ctrl.lastW = w; ctrl.lastH = h; } },
+            resize(w, h) { _bcApplySize(w, h); },
             destroy() {
                 ctrl.dead = true;
                 _bcControllers.delete(ctrl);
@@ -2595,10 +2620,51 @@
     }
     const FRET_NUMBER_GHOST_SCOPE_IDS = ['chords', 'all'];
 
+    /**
+     * localStorage panel key for per-panel background settings ('main' or
+     * 'panel<index>'). Defensive on the splitscreen global-name rename in flight,
+     * and throw-safe on panelIndexFor — same as _freeCamFor — so a misbehaving
+     * splitscreen build can't take down background-settings resolution. Only a
+     * non-negative integer index yields a 'panel<N>' key; anything else (null,
+     * NaN, negative, non-integer) falls back to 'main' so a bad index can never
+     * mint a bogus "panelNaN"-style key.
+     * @param {HTMLCanvasElement} canvas this renderer's highway canvas
+     * @returns {string} 'main' or 'panel<index>'
+     */
     function _bgPanelKey(canvas) {
-        const ss = window.feedBackSplitscreen;
-        const idx = (ss && typeof ss.panelIndexFor === 'function') ? ss.panelIndexFor(canvas) : null;
-        return (idx == null) ? 'main' : 'panel' + idx;
+        const ss = window.feedBackSplitscreen || window.slopsmithSplitscreen;
+        let idx = null;
+        if (ss && typeof ss.panelIndexFor === 'function') {
+            try { idx = ss.panelIndexFor(canvas); } catch (e) { idx = null; }
+        }
+        return (Number.isInteger(idx) && idx >= 0) ? 'panel' + idx : 'main';
+    }
+
+    /**
+     * Camera Director bridge resolver. Prefers THIS panel's per-panel camera under
+     * splitscreen (window.__h3dCamCtlPanels[panelIndex]) and falls back to the
+     * single global (window.__h3dCamCtl); returns null when Camera Director is
+     * absent → 100% stock framing. Defensive on the splitscreen global-name rename
+     * in flight (feedBackSplitscreen vs slopsmithSplitscreen); throw-safe on
+     * panelIndexFor. Mirrors the panel resolution in _bgPanelKey.
+     * @param {HTMLCanvasElement} canvas this renderer's highway canvas
+     * @returns {object|null} the resolved free-camera bridge, or null
+     */
+    function _freeCamFor(canvas) {
+        const map = window.__h3dCamCtlPanels;
+        if (map) {
+            const ss = window.feedBackSplitscreen || window.slopsmithSplitscreen;
+            if (ss && typeof ss.panelIndexFor === 'function') {
+                try {
+                    const i = ss.panelIndexFor(canvas);
+                    // Only a non-negative integer indexes the map (same hardening
+                    // as _bgPanelKey) — a non-int / negative / string index must not
+                    // resolve an unintended/inherited property; fall through then.
+                    if (Number.isInteger(i) && i >= 0 && map[i]) return map[i];
+                } catch (e) { /* ignore */ }
+            }
+        }
+        return window.__h3dCamCtl || null;
     }
     // In-memory fallback for when localStorage is blocked (private mode,
     // sandboxed iframes, some test runners). _bgWriteGlobal stages the
@@ -3747,6 +3813,15 @@
         // ── Per-instance Three.js state ───────────────────────────────────
         let scene = null, cam = null, ren = null;
         let wrap = null;
+        // WebGL context-loss recovery. Switching the active window / alt-tabbing
+        // (especially on Windows) can trigger a GPU context reset; with no
+        // handler the lost context escalates into a render-process crash. The
+        // listeners (bound in initScene on ren.domElement, removed in teardown)
+        // preventDefault the loss so the browser keeps the context restorable,
+        // _ctxLost gates draw() off the dead context, and on restore we reset the
+        // viewport + resume (Three re-uploads scene resources on the next render).
+        let _ctxLost = false;
+        let _onCtxLost = null, _onCtxRestored = null;
         let bcCtrl = null; // Butterchurn audio-reactive background (the 'butterchurn' bg-style)
         let _chartEnv = 0, _chartPrevT = -1, _bcBeatIdx = 0, _bcNoteIdx = 0, _bcChordIdx = 0, _bcTintTarget = null;
         let _tintR = 20, _tintG = 24, _tintB = 40; // smoothed instrument-color tint for the bg
@@ -6526,6 +6601,26 @@
             ren.setClearColor(0x101820, _bcActive() ? 0 : 1);
             wrap.appendChild(ren.domElement);
 
+            // WebGL context-loss recovery (see the _ctxLost declaration). Bound
+            // on Three's own canvas — the context that actually resets on a GPU
+            // reset / alt-tab. preventDefault() keeps the context restorable
+            // instead of letting the loss escalate to a render-process crash;
+            // _ctxLost then makes draw() bail so no GL work runs on the dead
+            // context; on restore we reset the viewport and resume (Three
+            // re-uploads geometry/materials/textures lazily on the next render).
+            _onCtxLost = (e) => {
+                if (e && typeof e.preventDefault === 'function') e.preventDefault();
+                _ctxLost = true;
+                console.warn('[3D-Hwy] WebGL context lost — pausing render until it is restored.');
+            };
+            _onCtxRestored = () => {
+                _ctxLost = false;
+                console.warn('[3D-Hwy] WebGL context restored — resuming render.');
+                try { const s = canvasSize(highwayCanvas); if (s.w > 0 && s.h > 0) applySize(s.w, s.h); } catch (err) {}
+            };
+            ren.domElement.addEventListener('webglcontextlost', _onCtxLost, false);
+            ren.domElement.addEventListener('webglcontextrestored', _onCtxRestored, false);
+
             lyricsCanvas = document.createElement('canvas');
             lyricsCanvas.style.cssText = 'position:absolute;top:0;left:0;pointer-events:none;z-index:1;';
             lyricsCtx = lyricsCanvas.getContext('2d');
@@ -14635,7 +14730,10 @@
             // suppressed while the Camera Director owns the view (it wins).
             const _startAspect = (_tune && Number.isFinite(_tune.startAspect) && _tune.startAspect > 0)
                 ? _tune.startAspect : HORPLUS_START_ASPECT;
-            const _dirActive = !!(window.__h3dCamCtl && window.__h3dCamCtl.enabled);
+            // Resolve the Camera Director bridge once (per-panel under splitscreen,
+            // else global). Used both for the wide-pane gate and the transforms below.
+            const _freeCam = _freeCamFor(highwayCanvas);
+            const _dirActive = !!(_freeCam && _freeCam.enabled);
             const _wide = !!(_tune && _paneAspect > _startAspect) && !_dirActive;
             const _poseHMul = (_wide && Number.isFinite(_tune.heightMul)) ? _tune.heightMul : 1;
             const _poseDMul = (_wide && Number.isFinite(_tune.distMul)) ? _tune.distMul : 1;
@@ -14662,13 +14760,16 @@
             if (_poseHMul !== 1) _camY *= _poseHMul;
             if (_poseDMul !== 1) _camZ *= _poseDMul;
             // ── Free-camera user tweaks (orbit / height / zoom / pan) ──
-            // Driven by the Camera Director plugin via window.__h3dCamCtl.
+            // Driven by the Camera Director plugin via the camera bridge:
+            // window.__h3dCamCtlPanels[panelIndexFor(canvas)] when split (this
+            // panel's own camera), falling back to the global window.__h3dCamCtl.
             // Layered ON TOP of the auto-framing so note tracking still works.
             // The bridge is read once into _freeCam and reused for both the
             // position and the look-at transforms; every field is coerced to a
             // finite number before use so a malformed object can never feed NaN
             // into cam.position / cam.lookAt.
-            const _freeCam = window.__h3dCamCtl;
+            // _freeCam resolved above via _freeCamFor(highwayCanvas): the
+            // per-panel __h3dCamCtlPanels entry, else global __h3dCamCtl, else null.
             const _lookAtZ = -FOCUS_D * 0.35 * _poseLookZMul;
             if (_freeCam && _freeCam.enabled) {
                 const _distMul = Number.isFinite(_freeCam.distMul) ? _freeCam.distMul : 1;
@@ -14829,6 +14930,15 @@
             // mid-teardown settings change doesn't try to rebuild a torn-
             // down scene; then dispose the active style's resources.
             if (_bgListener) { _bgUnsubscribe(_bgListener); _bgListener = null; }
+            // WebGL context-loss listeners (bound in initScene on ren.domElement).
+            // Remove before ren is disposed below so a torn-down instance can't
+            // keep firing them; reset the flag so a reused instance starts clean.
+            if (ren && ren.domElement) {
+                if (_onCtxLost) { try { ren.domElement.removeEventListener('webglcontextlost', _onCtxLost, false); } catch (e) {} }
+                if (_onCtxRestored) { try { ren.domElement.removeEventListener('webglcontextrestored', _onCtxRestored, false); } catch (e) {} }
+            }
+            _onCtxLost = _onCtxRestored = null;
+            _ctxLost = false;
             // Notedetect listeners (issue #9). Remove on destroy so a
             // panel that stops doesn't keep accumulating marks. Marks
             // arrays are cleared too — they hold stale chart positions
@@ -15154,6 +15264,7 @@
 
             draw(bundle) {
                 if (!_isReady) return;
+                if (_ctxLost) return;   // GPU context lost (alt-tab / reset) — skip until restored
                 if (!_chartPrewarmed) {
                     _chartPrewarmed = true;
                     _prewarmChart(bundle);

plugins/keys_highway_3d/README.md

@@ -3,12 +3,34 @@
 RS+-style falling-note 3D piano highway for [Slopsmith](https://github.com/got-feedback/feedback), fed by the **Sloppak Notation Format** (sloppak-spec §5.3) — part of the piano/keys first-class epic (slopsmith#828, plugin workstream slopsmith#824).
 
 - Consumes the `notation_info` / `notation_measures` highway-WS stream over a private per-instance socket and flattens measure → staff → voice → beat → note into `{midi, t, durSec, hand}` (durations derived from written `dur`/`dot`/`tu` at the running tempo; ties extend; overlap-clamped).
-- 3D perspective highway to a vanishing point with a real white/black-key keyboard; per-key **pitch-class colours** (Synthesia convention — C red, D yellow, E blue, …) with hand (rh/lh) as a secondary brightness cue.
+- 3D perspective highway to a vanishing point with a real white/black-key keyboard; per-key **pitch-class colors** (Synthesia convention — C red, D yellow, E blue, …) with hand (rh/lh) as a secondary brightness cue. Selectable **note-color palettes** (settings → Note colors, `keys3d_bg_palette`, default the per-octave scheme): a per-octave rainbow (each octave its own hue, darker sharps), the original per-pitch "Rainbow" table, vivid/pastel per-pitch variants, and single-hue two-tone palettes (uniform naturals, darker sharps) for players who want "black key coming" to read at a glance; notes, key glow, lane guides and hit flames all follow the pick live.
 - Full RS+ visual treatment: key **letter glyphs** printed on the active-range key tops (cached CanvasTextures), **bevelled gem-style note blocks** (ExtrudeGeometry, geometry/material caches keyed by size and pitch-class×hand), **floating bar numbers** scrolling with the notes, **active-range lane dimming** so the playable span pops, and a **glowing pulsing hit-line** (layered additive gradient planes — no postprocessing).
 - Performance discipline: no per-frame allocations or DOM queries in `draw()`. Chart-scoped resources — note geometries/materials, bar-number and glow textures — are cached and disposed on chart teardown; the key-letter glyph `CanvasTexture`s live in a shared module-level cache that survives teardown and is reused across instances.
 - Auto-selected for arrangements with notation via `matchesArrangement(songInfo.has_notation)`; capability-native `visualization` provider declaration.
+- **Camera settings**: camera-rig presets (`keys3d_bg_camera` — classic low rig / elevated / overhead; default overhead, applied live, adaptive pan-zoom preserved) with base-rig fine-tune sliders for height, distance and tilt (`keys3d_bg_camHeight` / `camDist` / `camTilt`) that nudge the vantage point the follow-motion orbits. Numeric FX keys clamp to per-key declared ranges (`FX_RANGES`, default 0–1).
+- **Highway-layout options** (settings → Highway layout). **Sharps & flats**
+  (`keys3d_bg_sharpMode`, string; default `realistic`) picks the sharp layout:
+  `floating` (original raised-plane sharps, white-only lanes); `flat` (one plane,
+  zero-overlap piano-shaped tiled lanes — white lanes trimmed where a sharp adjoins
+  them, and each sharp leaned toward the edge natural beside it so the naturals come
+  out close to even: C/D/E/F/B equal, G/A a hair smaller since G# can't lean; pure
+  `laneSpanFlat()`); `realistic` (one plane, bars sized like the physical keys — full
+  naturals always rendered full, full black keys drawn on top and only occluding a
+  natural where a sharp note actually coincides in time; pure `laneSpanReal()`).
+  **Lane color opacity** (`keys3d_bg_laneOpacity`, 0–1, default 0) fades the
+  pitch-class lane tint; at 0 (default) the strips are a dark floor with guide lines
+  only at the key-block boundaries (E→F and each octave B→C), so each block is bounded
+  rather than every lane — the notes keep their colors; toward 1 it fills in full,
+  vivid colored lanes. The strips, per-lane separators and block lines crossfade with
+  this value. **Octave separators** (`keys3d_bg_octaveGaps`, default on) widens the
+  gap a touch at each B→C octave boundary. **Octave line contrast**
+  (`keys3d_bg_octaveContrast`, 0–1, default 0.5) scales how hard the B→C octave line
+  reads; it is drawn as a dark layer (scaled by lane opacity) plus a bright layer
+  (scaled by its inverse), so it auto-shifts dark→bright as the lanes fade — no mode
+  switch needed. All are geometry-time — applied on the next chart build via
+  `init()`'s re-read.
 - **Web MIDI input scoring**: module-level MIDI singleton (one access per tab, focused-instance routing) with device auto-connect by saved id+name, loopback blocklist, channel filter, transpose and CC64 sustain (`keys3d_` localStorage prefix; `window.keysH3d*` settings API). Hit detection matches played MIDI against the flattened chart notes within ±0.10 s with per-note dedupe and a missed-note sweep (only while a device is connected — never retroactive across a mid-song connect).
-- **Live hit feedback on the MIDI path** (not the chart): key depress (~4° back-edge pivot, ~120 ms spring; the key letter rides along), wrong-note red key flash, and a vertical flame flare on hits (pooled additive sprites, white-hot base fading into the pitch-class colour, ~400 ms).
+- **Live hit feedback on the MIDI path** (not the chart): key depress (~4° back-edge pivot, ~120 ms spring; the key letter rides along), wrong-note red key flash, and a vertical flame flare on hits (pooled additive sprites, white-hot base fading into the pitch-class color, ~400 ms).
 - **End-of-run stats**: POSTs `/api/stats` `{filename, arrangement, score, accuracy}` exactly once per run with the same formula as the guitar notedetect path (`accuracy = hits / max(1, hits+misses)`, `score = round(hits·100·accuracy)`), then notifies the progression core when present.
 - **Capability wiring** (all guarded for servers without the hosts): registers as a note-detection `midi` provider (`keys-midi`, `verify.target`), opens a per-song binding scoped to the chart's keys range, reports hit/miss observability events, and exposes Web MIDI inputs to the audio-input domain with pseudonymized labels (`midi-input-1`, …) via `source.enumerate/describe/open/close`.
 - Headless test hook: `window.__keysHwTest = { injectNoteOn(midi, when), getScore() }`.

plugins/keys_highway_3d/plugin.json

@@ -1,7 +1,7 @@
 {
   "id": "keys_highway_3d",
   "name": "Keys Highway 3D",
-  "version": "0.1.1",
+  "version": "0.2.1",
   "description": "RS+-style 3D falling-note piano highway fed by the Sloppak Notation Format, with Web MIDI input scoring.",
   "type": "visualization",
   "bundled": true,

plugins/keys_highway_3d/settings.html

@@ -12,6 +12,22 @@
     <div class="mt-3">
         <h4 class="text-xs font-medium text-gray-300 mb-2">Graphics</h4>
 
+        <label for="keysh3d-fx-palette" class="text-xs font-medium text-gray-400 mb-1 block">Note colors</label>
+        <select id="keysh3d-fx-palette"
+            onchange="window.keys3dSetPalette && window.keys3dSetPalette(this.value)"
+            class="w-full bg-dark-700 border border-gray-800 rounded-lg px-3 py-2 text-xs text-gray-300 outline-none">
+            <option value="octaves" selected>Octaves (color per octave, darker sharps)</option>
+            <option value="emerald">Emerald (green, darker sharps)</option>
+            <option value="ice">Ice (blue, darker sharps)</option>
+            <option value="classic">Rainbow (per-pitch)</option>
+            <option value="vivid">Vivid (per-pitch, punchier)</option>
+            <option value="pastel">Pastel (per-pitch, soft)</option>
+        </select>
+        <p class="text-xs text-gray-500 mt-1 mb-3">
+            Choose the color scheme for the falling notes, key glow, lane
+            guides and hit flames. Each option is described in its own label.
+        </p>
+
         <label for="keysh3d-fx-theme" class="text-xs font-medium text-gray-400 mb-1 block">Scene theme</label>
         <select id="keysh3d-fx-theme"
             onchange="window.keys3dSetTheme && window.keys3dSetTheme(this.value)"
@@ -30,7 +46,117 @@
         </select>
         <p class="text-xs text-gray-500 mt-1 mb-3">
             Background gradient, floor and lane rails — the same theme names
-            as the guitar highway. Pitch-class note colours never change.
+            as the guitar highway. Note colors come from the
+            "Note colors" palette above.
+        </p>
+
+        <label for="keysh3d-fx-camera" class="text-xs font-medium text-gray-400 mb-1 block">Camera angle</label>
+        <select id="keysh3d-fx-camera"
+            onchange="window.keys3dSetCamera && window.keys3dSetCamera(this.value)"
+            class="w-full bg-dark-700 border border-gray-800 rounded-lg px-3 py-2 text-xs text-gray-300 outline-none">
+            <option value="classic">Classic (low, deep runway)</option>
+            <option value="elevated">Elevated (higher, more board)</option>
+            <option value="overhead" selected>Overhead (top-down reading view)</option>
+        </select>
+        <p class="text-xs text-gray-500 mt-1 mb-3">
+            Where the camera sits. Classic is the original low rig; Elevated
+            lifts it for a fuller view of the keybed; Overhead looks down the
+            lanes for a sheet-reading feel. Applies live, keeps the
+            auto-pan/zoom that follows your hands.
+        </p>
+
+        <label for="keysh3d-fx-camheight" class="text-xs font-medium text-gray-400 mb-1 block">
+            Camera height <span id="keysh3d-fx-camheight-val" class="text-gray-500 font-mono">1.00</span>
+        </label>
+        <input type="range" id="keysh3d-fx-camheight"
+            min="0.4" max="2.2" step="0.02" value="1"
+            oninput="window.keys3dSetFx && window.keys3dSetFx('camHeight', this.value); document.getElementById('keysh3d-fx-camheight-val').textContent = parseFloat(this.value).toFixed(2)"
+            class="w-full">
+        <p class="text-xs text-gray-500 mt-1">
+            Raise or lower the camera around the angle above (higher = more
+            top-down). Fine-tunes the base view; the follow-motion stays.
+        </p>
+
+        <label for="keysh3d-fx-camdist" class="text-xs font-medium text-gray-400 mb-1 mt-3 block">
+            Camera distance <span id="keysh3d-fx-camdist-val" class="text-gray-500 font-mono">1.00</span>
+        </label>
+        <input type="range" id="keysh3d-fx-camdist"
+            min="0.4" max="2.2" step="0.02" value="1"
+            oninput="window.keys3dSetFx && window.keys3dSetFx('camDist', this.value); document.getElementById('keysh3d-fx-camdist-val').textContent = parseFloat(this.value).toFixed(2)"
+            class="w-full">
+        <p class="text-xs text-gray-500 mt-1">
+            Pull the camera back or push it in (larger = further away, smaller
+            = closer).
+        </p>
+
+        <label for="keysh3d-fx-camtilt" class="text-xs font-medium text-gray-400 mb-1 mt-3 block">
+            Camera tilt <span id="keysh3d-fx-camtilt-val" class="text-gray-500 font-mono">0.00</span>
+        </label>
+        <input type="range" id="keysh3d-fx-camtilt"
+            min="-1" max="1" step="0.02" value="0"
+            oninput="window.keys3dSetFx && window.keys3dSetFx('camTilt', this.value); document.getElementById('keysh3d-fx-camtilt-val').textContent = parseFloat(this.value).toFixed(2)"
+            class="w-full">
+        <p class="text-xs text-gray-500 mt-1 mb-3">
+            Tilt the view up (+) or down (−) without moving the camera —
+            aims higher up the runway or down toward the keys. 0 = neutral.
+        </p>
+
+        <h4 class="text-xs font-medium text-gray-300 mb-2 mt-4">Highway layout</h4>
+
+        <label for="keysh3d-fx-sharpmode" class="text-xs font-medium text-gray-400 mb-1 block">Sharps &amp; flats</label>
+        <select id="keysh3d-fx-sharpmode"
+            onchange="window.keys3dSetSharpMode && window.keys3dSetSharpMode(this.value)"
+            class="w-full bg-dark-700 border border-gray-800 rounded-lg px-3 py-2 text-xs text-gray-300 outline-none">
+            <option value="floating">Floating</option>
+            <option value="flat">Non-floating</option>
+            <option value="realistic" selected>Realistic key sizes (default — best with no colored lanes)</option>
+        </select>
+        <p class="text-xs text-gray-500 mt-1 mb-3">
+            How sharps and flats are drawn. <em>Floating</em>: they ride a raised
+            plane above the naturals. <em>Non-floating</em>: everything on one
+            plane, each key its own even piano-shaped lane. <em>Realistic key
+            sizes</em>: one plane, bars sized like the real keys (full naturals,
+            full black keys on top). Applies next time you open a song.
+        </p>
+
+        <label for="keysh3d-fx-laneopacity" class="text-xs font-medium text-gray-400 mb-1 block">
+            Lane color opacity <span id="keysh3d-fx-laneopacity-val" class="text-gray-500 font-mono">0.00</span>
+        </label>
+        <input type="range" id="keysh3d-fx-laneopacity"
+            min="0" max="1" step="0.05" value="0"
+            oninput="window.keys3dSetFx && window.keys3dSetFx('laneOpacity', this.value); document.getElementById('keysh3d-fx-laneopacity-val').textContent = parseFloat(this.value).toFixed(2)"
+            class="w-full">
+        <p class="text-xs text-gray-500 mt-1 mb-3">
+            How strongly each lane is tinted its note color. 0.00 (default) is a
+            dark floor with plain guide lines only between the key blocks (at E–F
+            and each octave); the notes keep their colors and pop off the floor.
+            Raise toward 1.00 for full, vivid colored lanes. Applies next time you
+            open a song.
+        </p>
+
+        <label for="keysh3d-fx-octavegaps" class="flex items-center gap-2 text-xs text-gray-300 cursor-pointer mt-3">
+            <input type="checkbox" id="keysh3d-fx-octavegaps" checked
+                onchange="window.keys3dSetFx && window.keys3dSetFx('octaveGaps', this.checked)">
+            Octave separators
+        </label>
+        <p class="text-xs text-gray-500 mt-1 mb-3">
+            Widen the gap a little at each octave boundary (every B to the C
+            above it) so octaves are easier to read. Applies next time you open
+            a song.
+        </p>
+
+        <label for="keysh3d-fx-octavecontrast" class="text-xs font-medium text-gray-400 mb-1 mt-3 block">
+            Octave line contrast <span id="keysh3d-fx-octavecontrast-val" class="text-gray-500 font-mono">0.50</span>
+        </label>
+        <input type="range" id="keysh3d-fx-octavecontrast"
+            min="0" max="1" step="0.05" value="0.5"
+            oninput="window.keys3dSetFx && window.keys3dSetFx('octaveContrast', this.value); document.getElementById('keysh3d-fx-octavecontrast-val').textContent = parseFloat(this.value).toFixed(2)"
+            class="w-full">
+        <p class="text-xs text-gray-500 mt-1 mb-3">
+            How strongly the octave line (every B to C) stands out. It adapts to
+            the lane color opacity automatically — darkening the line against
+            bright lanes and brightening it as you fade them toward the dark
+            floor. Applies next time you open a song.
         </p>
 
         <label for="keysh3d-fx-cinematic" class="flex items-center gap-2 text-xs text-gray-300 cursor-pointer">
@@ -116,7 +242,7 @@
         <label for="keysh3d-fx-timing" class="flex items-center gap-2 text-xs text-gray-300 cursor-pointer mt-3">
             <input type="checkbox" id="keysh3d-fx-timing" checked
                 onchange="window.keys3dSetFx && window.keys3dSetFx('timingFx', this.checked)">
-            Timing colours
+            Timing colors
         </label>
         <p class="text-xs text-gray-500 mt-1">
             Tint the sparks by timing — on-time green, early cyan, late
@@ -179,6 +305,9 @@
             hydrateFxBool('cinematic', 'keysh3d-fx-cinematic');
             hydrateFxBool('bgReactive', 'keysh3d-fx-bgreactive');
             hydrateFxBool('scoreFx', 'keysh3d-fx-scorefx');
+            // Highway-layout: octaveGaps defaults ON (bool); laneOpacity /
+            // octaveContrast are 0-1 sliders hydrated with hydrateFxRange below.
+            hydrateFxBool('octaveGaps', 'keysh3d-fx-octavegaps');
             const hydrateFxRange = (key, elId, valId) => {
                 const n = parseFloat(localStorage.getItem('keys3d_bg_' + key));
                 if (!Number.isFinite(n)) return;
@@ -190,6 +319,26 @@
             hydrateFxRange('vibrancy', 'keysh3d-fx-vibrancy', 'keysh3d-fx-vibrancy-val');
             hydrateFxRange('glow', 'keysh3d-fx-glow', 'keysh3d-fx-glow-val');
             hydrateFxRange('bgIntensity', 'keysh3d-fx-bgintensity', 'keysh3d-fx-bgintensity-val');
+            hydrateFxRange('laneOpacity', 'keysh3d-fx-laneopacity', 'keysh3d-fx-laneopacity-val');
+            hydrateFxRange('octaveContrast', 'keysh3d-fx-octavecontrast', 'keysh3d-fx-octavecontrast-val');
+            // Camera fine-tune sliders live outside 0-1 — clamp to the
+            // control's own min/max (mirrors screen.js FX_RANGES).
+            const hydrateFxRangeIn = (key, elId, valId) => {
+                const n = parseFloat(localStorage.getItem('keys3d_bg_' + key));
+                if (!Number.isFinite(n)) return;
+                const el = document.getElementById(elId);
+                const v = Math.min(parseFloat(el.max), Math.max(parseFloat(el.min), n));
+                el.value = String(v);
+                document.getElementById(valId).textContent = v.toFixed(2);
+            };
+            hydrateFxRangeIn('camHeight', 'keysh3d-fx-camheight', 'keysh3d-fx-camheight-val');
+            hydrateFxRangeIn('camDist', 'keysh3d-fx-camdist', 'keysh3d-fx-camdist-val');
+            hydrateFxRangeIn('camTilt', 'keysh3d-fx-camtilt', 'keysh3d-fx-camtilt-val');
+            const storedCamera = localStorage.getItem('keys3d_bg_camera');
+            const cameraSel = document.getElementById('keysh3d-fx-camera');
+            if (storedCamera && Array.from(cameraSel.options).some(o => o.value === storedCamera)) {
+                cameraSel.value = storedCamera;
+            }
             const storedStyle = localStorage.getItem('keys3d_bg_style');
             const styleSel = document.getElementById('keysh3d-fx-bgstyle');
             if (storedStyle && Array.from(styleSel.options).some(o => o.value === storedStyle)) {
@@ -200,6 +349,16 @@
             if (storedTheme && Array.from(themeSel.options).some(o => o.value === storedTheme)) {
                 themeSel.value = storedTheme;
             }
+            const storedPalette = localStorage.getItem('keys3d_bg_palette');
+            const paletteSel = document.getElementById('keysh3d-fx-palette');
+            if (storedPalette && Array.from(paletteSel.options).some(o => o.value === storedPalette)) {
+                paletteSel.value = storedPalette;
+            }
+            const storedSharp = localStorage.getItem('keys3d_bg_sharpMode');
+            const sharpSel = document.getElementById('keysh3d-fx-sharpmode');
+            if (storedSharp && Array.from(sharpSel.options).some(o => o.value === storedSharp)) {
+                sharpSel.value = storedSharp;
+            }
         } catch (e) {
             console.warn('[Keys-Hwy3D settings] hydration failed:', e);
         }

plugins/keys_highway_3d/tests/camera_bridge.test.js

@@ -0,0 +1,78 @@
+// Camera Director bridge resolver tests: per-panel select, global fallback,
+// null-when-absent, throw-safety, and the splitscreen global-name alias. Loads
+// screen.js in a bare vm window and exercises the __test exports (no DOM/WebGL).
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const vm = require('node:vm');
+
+function load() {
+    const window = {
+        console,
+        location: { protocol: 'http:', host: 'localhost' },
+        slopsmith: {},
+    };
+    window.window = window;
+    window.globalThis = window;
+    const context = vm.createContext(window);
+    const src = fs.readFileSync(path.join(__dirname, '..', 'screen.js'), 'utf8');
+    vm.runInContext(src, context, { filename: 'screen.js' });
+    return { window, __test: window.slopsmithViz_keys_highway_3d.__test };
+}
+
+test('_resolveFreeCam: per-panel camera under splitscreen', () => {
+    const { __test } = load();
+    const c0 = {}, c1 = {};
+    const ss = { panelIndexFor: (c) => (c === c0 ? 0 : 1) };
+    const map = { 0: { id: 'p0' }, 1: { id: 'p1' } };
+    assert.equal(__test._resolveFreeCam(c0, ss, map, { id: 'g' }).id, 'p0');
+    assert.equal(__test._resolveFreeCam(c1, ss, map, { id: 'g' }).id, 'p1');
+});
+
+test('_resolveFreeCam: falls back to global when there is no panel map', () => {
+    const { __test } = load();
+    const g = { id: 'global' };
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => 0 }, null, g), g);
+});
+
+test('_resolveFreeCam: falls back to global when the panel has no map entry', () => {
+    const { __test } = load();
+    const g = { id: 'global' };
+    const ss = { panelIndexFor: () => 3 };            // index 3 absent from map
+    assert.equal(__test._resolveFreeCam({}, ss, { 0: {} }, g), g);
+});
+
+test('_resolveFreeCam: null when Camera Director is absent (no global)', () => {
+    const { __test } = load();
+    assert.equal(__test._resolveFreeCam({}, null, null, null), null);
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => 0 }, {}, undefined), null);
+});
+
+test('_resolveFreeCam: throw-safe on panelIndexFor → falls back to global', () => {
+    const { __test } = load();
+    const g = { id: 'global' };
+    const ss = { panelIndexFor: () => { throw new Error('boom'); } };
+    assert.equal(__test._resolveFreeCam({}, ss, { 0: {} }, g), g);
+});
+
+test('_resolveFreeCam: NaN/negative/float/string index → falls back to global', () => {
+    const { __test } = load();
+    const g = { id: 'global' };
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => NaN }, { 0: {} }, g), g);
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => -1 }, { 0: {} }, g), g);
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => 0.5 }, { 0: {} }, g), g);
+    // A string/prototype key must not resolve an inherited property (e.g. toString).
+    assert.equal(__test._resolveFreeCam({}, { panelIndexFor: () => 'toString' }, {}, g), g);
+});
+
+test('_ssApi: null when neither global set; slopsmith alias; feedBack canonical wins', () => {
+    const { window, __test } = load();
+    assert.equal(__test._ssApi(), null);
+    const legacy = { panelIndexFor: () => 0 };
+    window.slopsmithSplitscreen = legacy;
+    assert.equal(__test._ssApi(), legacy);            // legacy alias picked up
+    const current = { panelIndexFor: () => 1 };
+    window.feedBackSplitscreen = current;
+    assert.equal(__test._ssApi(), current);           // canonical name takes precedence
+});

plugins/keys_highway_3d/tests/data_layer.test.js

@@ -188,3 +188,99 @@ test('measureMarkers extracts idx/t pairs', () => {
         [{ idx: 1, t: 0 }, { idx: 2, t: 2.5 }],
     );
 });
+
+test('_pickMidiTarget: no plugin-local pick defers to the domain-wide selection, not "first device"', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [
+        { id: 'a', name: 'Device A', key: 'web-midi::a' },
+        { id: 'b', name: 'Device B', key: 'web-midi::b' },
+    ];
+    // Fresh install / never picked here — must use the Input Setup global,
+    // NOT fall through to inputs[0].
+    const target = _pickMidiTarget(inputs, null, 'web-midi::b', true);
+    assert.equal(target.id, 'b');
+});
+
+test('_pickMidiTarget: the domain-wide selection is the source of truth — it wins over a stale plugin-local pick', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [
+        { id: 'a', name: 'Device A', key: 'web-midi::a' },
+        { id: 'b', name: 'Device B', key: 'web-midi::b' },
+    ];
+    // A stale local pick (e.g. left by a pre-fix build's auto-connect) must
+    // NOT override the device the user configured in Settings → Input Setup.
+    const target = _pickMidiTarget(inputs, { id: 'a', name: 'Device A', key: 'web-midi::a' }, 'web-midi::b', true);
+    assert.equal(target.id, 'b');
+});
+
+test('_pickMidiTarget: local pick is used as a fallback when no global is configured', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [
+        { id: 'a', name: 'Device A', key: 'web-midi::a' },
+        { id: 'b', name: 'Device B', key: 'web-midi::b' },
+    ];
+    const target = _pickMidiTarget(inputs, { id: 'a', name: 'Device A', key: 'web-midi::a' }, null, true);
+    assert.equal(target.id, 'a');
+});
+
+test('_pickMidiTarget: local pick name-recovers when its logicalSourceKey went stale (id regeneration)', () => {
+    const { _pickMidiTarget } = load();
+    // Same physical device, new id/key across a reload; the saved key/id miss
+    // but the name still matches.
+    const inputs = [{ id: 'a2', name: 'Device A', key: 'web-midi::a2' }];
+    const target = _pickMidiTarget(inputs, { id: 'a1', name: 'Device A', key: 'web-midi::a1' }, null, true);
+    assert.equal(target.id, 'a2');
+});
+
+test('_pickMidiTarget: domain-wide selection is ignored if it names a blocklisted loopback port', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [
+        { id: 'thru', name: 'IAC Driver Bus 1', key: 'web-midi::thru' },
+        { id: 'b', name: 'Device B', key: 'web-midi::b' },
+    ];
+    const target = _pickMidiTarget(inputs, null, 'web-midi::thru', true);
+    assert.equal(target.id, 'b'); // falls through to the first non-loopback device
+});
+
+test('_pickMidiTarget: when every present device is a loopback, connect to nothing (never a dead port)', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [
+        { id: 'thru', name: 'MIDI Through Port-0', key: 'web-midi::thru' },
+        { id: 'iac', name: 'IAC Driver Bus 1', key: 'web-midi::iac' },
+    ];
+    // No non-loopback device exists — must NOT fall back to inputs[0] (a port
+    // that carries no input and would silently eat every note).
+    const target = _pickMidiTarget(inputs, null, null, true);
+    assert.equal(target, null);
+});
+
+test('_pickMidiTarget: explicit "None" opt-out still wins over any global default', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [{ id: 'a', name: 'Device A', key: 'web-midi::a' }];
+    const target = _pickMidiTarget(inputs, { id: '', name: '' }, 'web-midi::a', true);
+    assert.equal(target, null);
+});
+
+test('_pickMidiTarget: a present global wins even during hotplug recovery', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [{ id: 'b', name: 'Device B', key: 'web-midi::b' }];
+    // The configured global device is present — reconnect to it, don't bail.
+    const target = _pickMidiTarget(inputs, null, 'web-midi::b', false);
+    assert.equal(target.id, 'b');
+});
+
+test('_pickMidiTarget: recovery (allowFallback=false) preserves an absent configured device instead of grabbing a random one', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [{ id: 'b', name: 'Device B', key: 'web-midi::b' }];
+    // The configured device ('x', global) is currently unplugged; a transient
+    // recovery must NOT switch to the unrelated device that is present.
+    const target = _pickMidiTarget(inputs, null, 'web-midi::x', false);
+    assert.equal(target, null);
+});
+
+test('_pickMidiTarget: recovery with no preference at all still allows a first-hotplug grab', () => {
+    const { _pickMidiTarget } = load();
+    const inputs = [{ id: 'b', name: 'Device B', key: 'web-midi::b' }];
+    const target = _pickMidiTarget(inputs, null, null, false);
+    assert.equal(target.id, 'b');
+});

plugins/keys_highway_3d/tests/fx_settings.test.js

@@ -148,3 +148,405 @@ test('FX defaults: ambience + score FX ship enabled', () => {
     assert.equal(FX_DEFAULTS.bgIntensity, 0.5);
     assert.equal(FX_DEFAULTS.bgReactive, true);
 });
+
+/* ── Note-colour palettes (feat/keys3d-note-palettes) ────────────────── */
+
+test('note palettes: 12 entries each, classic IS the stock table', () => {
+    const { NOTE_PALETTES, PITCH_CLASS_COLORS } =
+        load().slopsmithViz_keys_highway_3d.__test;
+    assert.deepEqual(Object.keys(NOTE_PALETTES),
+        ['classic', 'emerald', 'vivid', 'pastel', 'ice']);
+    for (const [id, colors] of Object.entries(NOTE_PALETTES)) {
+        assert.equal(colors.length, 12, id + ' has one colour per pitch class');
+        for (const c of colors) {
+            assert.ok(Number.isInteger(c) && c >= 0 && c <= 0xffffff,
+                id + ' colours are 24-bit ints');
+        }
+    }
+    // 'classic' preserves the shipped look byte-identically — it is the
+    // same array, not a copy that could drift.
+    assert.equal(NOTE_PALETTES.classic, PITCH_CLASS_COLORS);
+    assert.equal(PITCH_CLASS_COLORS[0], 0xff3030); // C stays red in classic
+});
+
+test('note palettes: two-tone tables use darker sharps than naturals', () => {
+    const { NOTE_PALETTES } = load().slopsmithViz_keys_highway_3d.__test;
+    const luma = (c) =>
+        0.2126 * ((c >> 16) & 0xff) + 0.7152 * ((c >> 8) & 0xff) + 0.0722 * (c & 0xff);
+    for (const id of ['emerald', 'ice']) {
+        const p = NOTE_PALETTES[id];
+        for (const sharp of [1, 3, 6, 8, 10]) {
+            assert.ok(luma(p[sharp]) < luma(p[0]),
+                id + ' sharp pc ' + sharp + ' darker than naturals');
+        }
+    }
+});
+
+test('readPaletteSetting: octaves default, validated overrides only', () => {
+    // No localStorage in the vm → the plug-and-play default.
+    const bare = load().slopsmithViz_keys_highway_3d.__test;
+    assert.equal(bare.readPaletteSetting(), 'octaves');
+    // An explicit non-default value (classic) overrides.
+    const store = { keys3d_bg_palette: 'classic' };
+    const win = load({
+        localStorage: {
+            getItem: (k) => (k in store ? store[k] : null),
+            setItem: (k, v) => { store[k] = v; },
+        },
+    });
+    const { readPaletteSetting } = win.slopsmithViz_keys_highway_3d.__test;
+    assert.equal(readPaletteSetting(), 'classic');
+    // Corrupt/foreign value → the default rather than an undefined scheme.
+    store.keys3d_bg_palette = 'banana';
+    assert.equal(readPaletteSetting(), 'octaves');
+});
+
+test('keys3dSetPalette: persists + dispatches valid ids, ignores unknown', () => {
+    const store = {};
+    const events = [];
+    const win = load({
+        localStorage: {
+            getItem: (k) => (k in store ? store[k] : null),
+            setItem: (k, v) => { store[k] = v; },
+        },
+        dispatchEvent: (ev) => { events.push(ev); return true; },
+        CustomEvent: class CustomEvent {
+            constructor(type, opts) { this.type = type; this.detail = opts && opts.detail; }
+        },
+    });
+    win.keys3dSetPalette('emerald');
+    assert.equal(store.keys3d_bg_palette, 'emerald');
+    assert.equal(events.length, 1);
+    assert.equal(events[0].type, 'keys3d:settings');
+    assert.equal(events[0].detail.palette, 'emerald');
+    // Unknown id: no write, no event.
+    win.keys3dSetPalette('banana');
+    assert.equal(store.keys3d_bg_palette, 'emerald');
+    assert.equal(events.length, 1);
+    // 'octaves' (procedural, not a 12-array) is a valid selectable id.
+    win.keys3dSetPalette('octaves');
+    assert.equal(store.keys3d_bg_palette, 'octaves');
+    assert.equal(events.length, 2);
+});
+
+test('PALETTE_IDS: the array palettes plus the procedural octaves scheme', () => {
+    const { PALETTE_IDS, NOTE_PALETTES } = load().slopsmithViz_keys_highway_3d.__test;
+    assert.deepEqual([...PALETTE_IDS],
+        [...Object.keys(NOTE_PALETTES), 'octaves']);
+    assert.ok(PALETTE_IDS.indexOf('octaves') !== -1);
+    assert.ok(!('octaves' in NOTE_PALETTES)); // it is NOT a 12-entry table
+});
+
+test('octaveNoteColor: hue steps per octave, loops, sharps darker, sub-C1 distinct', () => {
+    const { octaveNoteColor, OCTAVE_HUES } = load().slopsmithViz_keys_highway_3d.__test;
+    const luma = (c) =>
+        0.2126 * ((c >> 16) & 0xff) + 0.7152 * ((c >> 8) & 0xff) + 0.0722 * (c & 0xff);
+    // C1 (midi 24) = first hue; C2 (36) = second; C8 (108) = 8th (index 7).
+    assert.equal(octaveNoteColor(24), OCTAVE_HUES[0]);   // C1 red
+    assert.equal(octaveNoteColor(35), OCTAVE_HUES[0]);   // B1 still octave 1
+    assert.equal(octaveNoteColor(36), OCTAVE_HUES[1]);   // C2 orange
+    assert.equal(octaveNoteColor(60), OCTAVE_HUES[3]);   // C4 (middle C)
+    assert.equal(octaveNoteColor(108), OCTAVE_HUES[7]);  // C8 last hue
+    // Naturals across one octave (C1..B1 whites) all share the octave hue.
+    for (const nat of [24, 26, 28, 29, 31, 33, 35]) {
+        assert.equal(octaveNoteColor(nat), OCTAVE_HUES[0], 'natural ' + nat);
+    }
+    // Sharps in an octave are a DARKER shade of that same hue.
+    for (const sharp of [25, 27, 30, 32, 34]) { // C#1..A#1
+        assert.ok(luma(octaveNoteColor(sharp)) < luma(OCTAVE_HUES[0]),
+            'sharp ' + sharp + ' darker than the octave natural');
+    }
+    // The three keys below C1 (A0/A#0/B0) share a distinct sub-C1 colour,
+    // different from the red octave-1 start.
+    assert.equal(octaveNoteColor(21), octaveNoteColor(23)); // A0 == B0 hue
+    assert.notEqual(octaveNoteColor(21), OCTAVE_HUES[0]);
+    // Loop: an octave past the table wraps (safety for out-of-88 midi).
+    assert.equal(octaveNoteColor(24 + 12 * OCTAVE_HUES.length), OCTAVE_HUES[0]);
+});
+
+/* ── Camera presets + fine-tune (feat/keys3d-camera) ─────────────────── */
+
+test('FX defaults: camera height/distance/tilt all neutral (preset carries the tuned aim)', () => {
+    const { FX_DEFAULTS, FX_RANGES } = load().slopsmithViz_keys_highway_3d.__test;
+    assert.equal(FX_DEFAULTS.camHeight, 1.0);
+    assert.equal(FX_DEFAULTS.camDist, 1.0);
+    // Tilt ships NEUTRAL (0): the tuned plug-and-play aim now lives in
+    // CAM_PRESETS.overhead.lookY, so the fine-tune only nudges from a preset
+    // and 'classic' + this default reproduces the exact historical rig.
+    assert.equal(FX_DEFAULTS.camTilt, 0.0);
+    assert.ok(FX_DEFAULTS.camTilt >= FX_RANGES.camTilt[0] && FX_DEFAULTS.camTilt <= FX_RANGES.camTilt[1]);
+    // Height/distance bracket 1 (can go lower AND higher); tilt spans 0.
+    assert.ok(FX_RANGES.camHeight[0] < 1 && 1 < FX_RANGES.camHeight[1]);
+    assert.ok(FX_RANGES.camDist[0] < 1 && 1 < FX_RANGES.camDist[1]);
+    assert.ok(FX_RANGES.camTilt[0] < 0 && 0 < FX_RANGES.camTilt[1]);
+});
+
+test('camTilt: negative values survive the clamp (down-tilt must be reachable)', () => {
+    const store = {};
+    const win = load({
+        localStorage: {
+            getItem: (k) => (k in store ? store[k] : null),
+            setItem: (k, v) => { store[k] = v; },
+        },
+        dispatchEvent: () => true,
+        CustomEvent: class { constructor(t, o) { this.type = t; this.detail = o && o.detail; } },
+    });
+    const { FX_RANGES } = win.slopsmithViz_keys_highway_3d.__test;
+    win.keys3dSetFx('camTilt', -0.5);
+    assert.equal(store.keys3d_bg_camTilt, '-0.5');   // NOT crushed to 0 by a 0-1 clamp
+    win.keys3dSetFx('camTilt', -99);
+    assert.equal(parseFloat(store.keys3d_bg_camTilt), FX_RANGES.camTilt[0]);
+});
+
+test('FX ranges: reader + setter clamp to the declared range, not 0-1', () => {
+    const store = { keys3d_bg_camHeight: '5', keys3d_bg_camDist: '0.01' };
+    const events = [];
+    const win = load({
+        localStorage: {
+            getItem: (k) => (k in store ? store[k] : null),
+            setItem: (k, v) => { store[k] = v; },
+        },
+        dispatchEvent: (ev) => { events.push(ev); return true; },
+        CustomEvent: class CustomEvent {
+            constructor(type, opts) { this.type = type; this.detail = opts && opts.detail; }
+        },
+    });
+    const { readFxSettings, FX_RANGES } = win.slopsmithViz_keys_highway_3d.__test;
+    // Reader: corrupt/out-of-range writes clamp to the declared bounds.
+    assert.equal(readFxSettings().camHeight, FX_RANGES.camHeight[1]);
+    assert.equal(readFxSettings().camDist, FX_RANGES.camDist[0]);
+    // Setter: same clamp on the way in; a value above 1 must survive
+    // (the historical 0-1 clamp would have crushed 1.3 to 1).
+    win.keys3dSetFx('camHeight', 1.3);
+    assert.equal(store.keys3d_bg_camHeight, '1.3');
+    win.keys3dSetFx('camDist', 99);
+    assert.equal(parseFloat(store.keys3d_bg_camDist), FX_RANGES.camDist[1]);
+    // Un-ranged keys keep the historical 0-1 clamp.
+    win.keys3dSetFx('vibrancy', 2);
+    assert.equal(store.keys3d_bg_vibrancy, '1');
+});
+
+test('scrollZ: distance-to-hitline scales linearly with the speed argument', () => {
+    const { scrollZ } = load().slopsmithViz_keys_highway_3d.__test;
+    const hitZ = 0;
+    const d1 = scrollZ(2, 0, hitZ, 130) - hitZ;   // 2s ahead at stock speed
+    const d2 = scrollZ(2, 0, hitZ, 260) - hitZ;   // same note at 2x speed
+    assert.equal(d2, d1 * 2);
+    // At the hit moment the note is at the hit-line regardless of speed.
+    assert.equal(scrollZ(5, 5, hitZ, 130), hitZ);
+    assert.equal(scrollZ(5, 5, hitZ, 260), hitZ);
+});
+
+test('camera presets: classic preserves the stock rig, overhead is the default', () => {
+    const { CAM_PRESETS, readCameraSetting } = load().slopsmithViz_keys_highway_3d.__test;
+    assert.deepEqual(Object.keys(CAM_PRESETS), ['classic', 'elevated', 'overhead']);
+    // 'classic' preserves the historical constants (pre-K units) even though
+    // it is no longer the default — anyone who picks it gets the old rig back
+    // EXACTLY, because camTilt now defaults to 0 (neutral): effective aim =
+    // classic.lookY + 0*CAM_TILT_UNITS = 8, the historical LOOK_Y.
+    assert.deepEqual({ ...CAM_PRESETS.classic },
+        { fov: 40, y: 46, z: 112, lookY: 8, lookZ: -165 });
+    for (const [id, p] of Object.entries(CAM_PRESETS)) {
+        for (const f of ['fov', 'y', 'z', 'lookY', 'lookZ']) {
+            assert.ok(Number.isFinite(p[f]), id + '.' + f + ' is a number');
+        }
+        assert.ok(p.y > 0 && p.z > 0, id + ' sits above and behind the keys');
+    }
+    assert.equal(readCameraSetting(), 'overhead'); // no localStorage in the vm → tuned default
+});
+
+test('camera default look is unchanged: overhead bakes the old tuned tilt, camTilt is neutral', () => {
+    const { CAM_PRESETS, FX_DEFAULTS } = load().slopsmithViz_keys_highway_3d.__test;
+    const CAM_TILT_UNITS = 55; // full-swing of the camTilt offset at ±1 (screen.js)
+    // The shipped default look = overhead preset + the default camTilt. Before,
+    // that was lookY 0 + (−0.6 × 55) = −33; the tuned aim now lives in the
+    // preset (lookY −33) with a neutral camTilt (0), so the effective aim — and
+    // thus the out-of-the-box framing — is byte-identical.
+    const effOverhead = CAM_PRESETS.overhead.lookY + FX_DEFAULTS.camTilt * CAM_TILT_UNITS;
+    assert.equal(effOverhead, -33);
+    // 'classic' + the neutral default reproduces the historical LOOK_Y (8) —
+    // the "pick Classic for the original look" promise, now actually true.
+    const effClassic = CAM_PRESETS.classic.lookY + FX_DEFAULTS.camTilt * CAM_TILT_UNITS;
+    assert.equal(effClassic, 8);
+});
+
+test('keys3dSetCamera: persists + dispatches valid ids, ignores unknown', () => {
+    const store = {};
+    const events = [];
+    const win = load({
+        localStorage: {
+            getItem: (k) => (k in store ? store[k] : null),
+            setItem: (k, v) => { store[k] = v; },
+        },
+        dispatchEvent: (ev) => { events.push(ev); return true; },
+        CustomEvent: class CustomEvent {
+            constructor(type, opts) { this.type = type; this.detail = opts && opts.detail; }
+        },
+    });
+    win.keys3dSetCamera('overhead');
+    assert.equal(store.keys3d_bg_camera, 'overhead');
+    assert.equal(events.length, 1);
+    assert.equal(events[0].type, 'keys3d:settings');
+    assert.equal(events[0].detail.camera, 'overhead');
+    win.keys3dSetCamera('helicopter');
+    assert.equal(store.keys3d_bg_camera, 'overhead');
+    assert.equal(events.length, 1);
+    const { readCameraSetting } = win.slopsmithViz_keys_highway_3d.__test;
+    assert.equal(readCameraSetting(), 'overhead');
+    store.keys3d_bg_camera = 'garbage';
+    assert.equal(readCameraSetting(), 'overhead');
+});
+
+/* ── Flat-sharps / piano-shaped lanes (feat/keys3d-flat-lanes) ───────── */
+
+test('FX defaults: octave separators on, lanes off (minimal default look)', () => {
+    const { FX_DEFAULTS } = load().slopsmithViz_keys_highway_3d.__test;
+    assert.equal(FX_DEFAULTS.octaveGaps, true);   // octave separators ship on
+    assert.equal(FX_DEFAULTS.laneOpacity, 0.0);   // dark floor + guide lines by default
+    assert.equal(FX_DEFAULTS.octaveContrast, 0.5);
+    // Sharp LAYOUT is a string setting, not an FX bool.
+    assert.equal('flatSharps' in FX_DEFAULTS, false);
+    assert.equal('laneColors' in FX_DEFAULTS, false); // superseded by laneOpacity
+});
+
+test('keys3dSetFx: highway-layout controls persist (bool + sliders)', () => {
+    const store = {};
+    const win = load({
+        localStorage: {
+            getItem: (k) => (k in store ? store[k] : null),
+            setItem: (k, v) => { store[k] = v; },
+        },
+        dispatchEvent: () => true,
+        CustomEvent: class { constructor(t, o) { this.type = t; this.detail = o && o.detail; } },
+    });
+    win.keys3dSetFx('octaveGaps', true);
+    assert.equal(store.keys3d_bg_octaveGaps, '1');
+    // laneOpacity / octaveContrast are 0-1 numbers, persisted verbatim + clamped.
+    win.keys3dSetFx('laneOpacity', 0.35);
+    assert.equal(store.keys3d_bg_laneOpacity, '0.35');
+    win.keys3dSetFx('laneOpacity', 5); // clamps to the 0-1 range
+    assert.equal(store.keys3d_bg_laneOpacity, '1');
+    win.keys3dSetFx('octaveContrast', 0.8);
+    assert.equal(store.keys3d_bg_octaveContrast, '0.8');
+});
+
+test('sharpMode: realistic default, validated ids, persists + dispatches', () => {
+    const bare = load().slopsmithViz_keys_highway_3d.__test;
+    assert.deepEqual([...bare.SHARP_MODES], ['floating', 'flat', 'realistic']);
+    assert.equal(bare.readSharpModeSetting(), 'realistic'); // no localStorage → default
+    const store = {};
+    const events = [];
+    const win = load({
+        localStorage: {
+            getItem: (k) => (k in store ? store[k] : null),
+            setItem: (k, v) => { store[k] = v; },
+        },
+        dispatchEvent: (ev) => { events.push(ev); return true; },
+        CustomEvent: class { constructor(t, o) { this.type = t; this.detail = o && o.detail; } },
+    });
+    win.keys3dSetSharpMode('flat'); // a non-default id, to exercise persistence
+    assert.equal(store.keys3d_bg_sharpMode, 'flat');
+    assert.equal(events[0].detail.sharpMode, 'flat');
+    assert.equal(win.slopsmithViz_keys_highway_3d.__test.readSharpModeSetting(), 'flat');
+    // Unknown id ignored (no write, no event).
+    win.keys3dSetSharpMode('bogus');
+    assert.equal(store.keys3d_bg_sharpMode, 'flat');
+    assert.equal(events.length, 1);
+});
+
+test('laneSpanFlat (V5): lanes tile with zero overlap and even the naturals', () => {
+    const { laneSpanFlat, _isBlackPc } = load().slopsmithViz_keys_highway_3d.__test;
+    const sh = 2.2, shift = 2.2 / 3;
+    const dims = { whiteW: 12, sharpHalf: sh, shift, octGap: 0.9 }; // mirrors shipped LANE_DIMS_FLAT
+    // cx for one octave: whites on integer slots, blacks on half-slots — the
+    // same slot geometry keyLayout/keyX produce (cx = slot * whiteW=12).
+    const CX = {
+        60: 0, 61: 6, 62: 12, 63: 18, 64: 24, 65: 36, 66: 42,
+        67: 48, 68: 54, 69: 60, 70: 66, 71: 72, 72: 84,
+    };
+    const midis = [60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72];
+    const spans = midis.map((m) => laneSpanFlat(m, _isBlackPc(m), CX[m], dims, false));
+    const wOf = (s) => s.right - s.left;
+    const w = (m) => wOf(spans[midis.indexOf(m)]);
+    // Zero-overlap tiling: every lane abuts the previous one (no gap, no overlap).
+    for (let i = 1; i < spans.length; i++) {
+        assert.ok(Math.abs(spans[i].left - spans[i - 1].right) < 1e-9, 'lane ' + midis[i] + ' abuts');
+    }
+    // Sharps are all the same width.
+    for (const m of [61, 63, 66, 68, 70]) {
+        assert.ok(Math.abs(w(m) - 2 * sh) < 1e-9, 'sharp ' + m + ' width');
+    }
+    // The lean evens the naturals: C, D, E, F, B all come out equal.
+    for (const m of [62, 64, 65, 71]) {
+        assert.ok(Math.abs(w(m) - w(60)) < 1e-9, 'natural ' + m + ' == C (evened)');
+    }
+    // G and A are the only slightly-smaller naturals (G# can't lean) — still
+    // clearly wider than a sharp, and MUCH closer to the rest than plain V2
+    // (which would leave D at 12−2·sh, far below C's 12−sh).
+    assert.ok(Math.abs(w(67) - w(69)) < 1e-9, 'G == A');
+    assert.ok(w(67) < w(60) && w(67) > 2 * sh, 'G/A a touch smaller, still wider than a sharp');
+    assert.ok(w(60) - w(67) < sh, 'natural spread is under one sharp-width');
+});
+
+test('laneSpanReal (V4): naturals uniform, sharps full-width and overlapping', () => {
+    const { laneSpanReal } = load().slopsmithViz_keys_highway_3d.__test;
+    const dims = { natHalf: 5.64, sharpHalf: 3.2, octGap: 0.9 }; // mirrors LANE_DIMS_REAL
+    const wOf = (s) => s.right - s.left;
+    // Every natural is the same full width, whatever its neighbours.
+    for (const [midi, slot] of [[60, 0], [62, 1], [64, 2], [67, 4], [71, 6]]) {
+        assert.ok(Math.abs(wOf(laneSpanReal(midi, false, slot * 12, dims, false)) - 2 * 5.64) < 1e-9,
+            'natural ' + midi + ' uniform');
+    }
+    // Sharps are the full (wider) black-key width and overlap their naturals.
+    const C = laneSpanReal(60, false, 0, dims, false);
+    const Cs = laneSpanReal(61, true, 6, dims, false);
+    assert.ok(Math.abs(wOf(Cs) - 2 * 3.2) < 1e-9, 'sharp full width');
+    assert.ok(Cs.left < C.right, 'sharp overlaps (tucks over) the natural');
+});
+
+test('laneSpanFlat (V5): octaveGaps widens B→C by octGap, sharps unaffected', () => {
+    const { laneSpanFlat } = load().slopsmithViz_keys_highway_3d.__test;
+    const dims = { whiteW: 12, sharpHalf: 2.2, shift: 2.2 / 3, octGap: 0.9 };
+    const gapOff = laneSpanFlat(72, false, 84, dims, false).left - laneSpanFlat(71, false, 72, dims, false).right;
+    const gapOn = laneSpanFlat(72, false, 84, dims, true).left - laneSpanFlat(71, false, 72, dims, true).right;
+    assert.ok(Math.abs((gapOn - gapOff) - dims.octGap) < 1e-9, 'B→C divider grows by octGap');
+    // Sharps are unaffected by the octave-gap option.
+    const s = laneSpanFlat(61, true, 6, dims, true);
+    assert.ok(Math.abs((s.right - s.left) - 2 * dims.sharpHalf) < 1e-9, 'sharp width unchanged by gaps');
+});
+
+test('laneSpanFlat (V5): active-range boundary key is NOT trimmed by an out-of-range neighbor sharp', () => {
+    const { laneSpanFlat } = load().slopsmithViz_keys_highway_3d.__test;
+    const dims = { whiteW: 12, sharpHalf: 2.2, shift: 2.2 / 3, octGap: 0.9 }; // mirrors LANE_DIMS_FLAT
+    // F (midi 65, cx 36): its upper neighbor F# (66) is a sharp. When F sits
+    // at range.activeHigh and F# is excluded from the active range, F# never
+    // gets a lane drawn (see the activeLow/activeHigh skip around the
+    // lane-strip loop) — trimming F's right edge for it would leave a dark,
+    // unfilled sliver. The edge should stay full instead.
+    const highBoundary = { activeLow: 60, activeHigh: 65 };
+    const fAtBoundary = laneSpanFlat(65, false, 36, dims, false, highBoundary);
+    assert.ok(Math.abs(fAtBoundary.right - (36 + dims.whiteW / 2)) < 1e-9,
+        'F right edge stays full when F# is out of the active range');
+    // Same key, but now F# IS in the active range: normal zero-overlap
+    // tiling applies — the trim matches the ungated (no-range) call exactly,
+    // so in-range geometry is unaffected by this fix.
+    const highIncluded = { activeLow: 60, activeHigh: 66 };
+    const fWithSharpInRange = laneSpanFlat(65, false, 36, dims, false, highIncluded);
+    const fUngated = laneSpanFlat(65, false, 36, dims, false);
+    assert.ok(Math.abs(fWithSharpInRange.right - fUngated.right) < 1e-9,
+        'F trims normally once F# is back in range');
+    assert.ok(fWithSharpInRange.right < fAtBoundary.right, 'in-range trim is narrower than the boundary full edge');
+
+    // Symmetric case on the low edge: D (midi 62, cx 12), lower neighbor C#
+    // (61) excluded when D sits at range.activeLow.
+    const lowBoundary = { activeLow: 62, activeHigh: 72 };
+    const dAtBoundary = laneSpanFlat(62, false, 12, dims, false, lowBoundary);
+    assert.ok(Math.abs(dAtBoundary.left - (12 - dims.whiteW / 2)) < 1e-9,
+        'D left edge stays full when C# is out of the active range');
+    const lowIncluded = { activeLow: 61, activeHigh: 72 };
+    const dWithSharpInRange = laneSpanFlat(62, false, 12, dims, false, lowIncluded);
+    const dUngated = laneSpanFlat(62, false, 12, dims, false);
+    assert.ok(Math.abs(dWithSharpInRange.left - dUngated.left) < 1e-9,
+        'D trims normally once C# is back in range');
+});
+

plugins/tuner/plugin.json

@@ -1,7 +1,7 @@
 {
   "id": "tuner",
   "name": "Guitar/Bass Tuner",
-  "version": "1.3.3",
+  "version": "1.3.4",
   "bundled": true,
   "private": false,
   "script": "screen.js",

plugins/tuner/utils/ui.js

@@ -869,8 +869,15 @@ window._tunerUI = function(state, actions) {
         btn.textContent = 'Tuner';
         btn.title = 'Open Tuner';
         btn.onclick = window.tuner.toggle;
-        const closeBtn = isV3 ? null : controls.querySelector('button:last-child');
-        if (closeBtn) controls.insertBefore(btn, closeBtn);
+        // Anchor to the last DIRECT-child button of `controls` (the classic
+        // transport's close/exit button). A bare `button:last-child` can match
+        // a NESTED button that is not a direct child of `controls`, and
+        // `insertBefore()` then throws NotFoundError — which propagated out of
+        // the player-screen transition and aborted its render (feedBack#800).
+        // `:scope > button:last-of-type` restricts the anchor to a direct child;
+        // the parentNode check is a belt-and-suspenders guard before insertBefore.
+        const closeBtn = isV3 ? null : controls.querySelector(':scope > button:last-of-type');
+        if (closeBtn && closeBtn.parentNode === controls) controls.insertBefore(btn, closeBtn);
         else controls.appendChild(btn);
         updatePlayerButton();
     }

scripts/perf-baseline.mjs

@@ -0,0 +1,177 @@
+// Perf-baseline harness for the module-migration refactor (R0).
+//
+// Rerun this after every phase (R0 → R3c) to prove the split does not regress
+// screen-entry, frame-time, memory, or server latency. It writes a markdown
+// results block to stdout; paste it into docs/perf-baseline.md (or redirect).
+//
+// Usage:
+//   node scripts/perf-baseline.mjs --base http://127.0.0.1:8000 [--n 60] [--soak 30]
+//   node scripts/perf-baseline.mjs --base http://127.0.0.1:8300 --song "Arcturus ….feedpak"
+//
+// With --song, it additionally measures the 2D highway's PER-FRAME DRAW cost:
+// it wraps requestAnimationFrame before any page script runs, tags the frames
+// in which the highway actually painted (via highway.addDrawHook), starts
+// playback, and reports draw-frame p50/p95/p99 over --frames seconds. Tagging
+// matters — roughly half the rAF callbacks belong to other cheap loops, and
+// averaging them in hides a renderer regression behind ~0.1 ms no-op frames.
+// This is the metric that gates the highway.js split (R3c); run it before AND
+// after each highway change on the same machine.
+//
+// Maintainer/CI-only dev tooling (uses the committed @playwright/test browser);
+// never part of the serve or Docker path. Metrics that need a seeded library
+// with charts (playback frame-time, screen-entry into a live highway) are
+// clearly labelled — run those against an environment with real songs.
+
+import { createRequire } from 'module';
+const require = createRequire(import.meta.url);
+const { chromium } = require('@playwright/test');
+
+const args = new Map();
+for (let i = 2; i < process.argv.length; i += 2) args.set(process.argv[i].replace(/^--/, ''), process.argv[i + 1]);
+const BASE = args.get('base') || 'http://127.0.0.1:8000';
+const N = parseInt(args.get('n') || '60', 10);
+const SOAK_S = parseInt(args.get('soak') || '30', 10);
+const SONG = args.get('song') || null;
+const FRAME_S = parseInt(args.get('frames') || '10', 10);
+const RUNS = parseInt(args.get('runs') || '3', 10);   // repeat frame sampling to show spread
+
+const pct = (xs, p) => {
+    if (!xs.length) return null;
+    const s = [...xs].sort((a, b) => a - b);
+    return s[Math.min(s.length - 1, Math.floor((p / 100) * s.length))];
+};
+const ms = (x) => (x == null ? '—' : `${x.toFixed(1)}`);
+
+// ── Server latency: p50/p95/p99 over N requests per endpoint ──────────────────
+async function serverLatency(paths) {
+    const rows = [];
+    for (const path of paths) {
+        const t = [];
+        let status = 0;
+        for (let i = 0; i < N; i++) {
+            const t0 = performance.now();
+            try {
+                const r = await fetch(BASE + path);
+                status = r.status;
+                await r.arrayBuffer();
+            } catch { status = -1; }
+            t.push(performance.now() - t0);
+        }
+        rows.push({ path, status, p50: pct(t, 50), p95: pct(t, 95), p99: pct(t, 99) });
+    }
+    return rows;
+}
+
+// ── Client: cold boot-to-interactive + idle memory after a soak ───────────────
+async function clientMetrics() {
+    const browser = await chromium.launch();
+    const page = await browser.newPage();
+    const t0 = Date.now();
+    await page.goto(BASE, { waitUntil: 'networkidle', timeout: 60000 });
+    const bootMs = Date.now() - t0;
+
+    // performance.memory is Chromium-only; JS heap after settle.
+    const mem0 = await page.evaluate(() => (performance.memory ? performance.memory.usedJSHeapSize : null));
+    await page.waitForTimeout(SOAK_S * 1000);
+    const mem1 = await page.evaluate(() => (performance.memory ? performance.memory.usedJSHeapSize : null));
+
+    const scripts = await page.evaluate(() =>
+        document.querySelectorAll('script[data-plugin-id]').length);
+
+    await browser.close();
+    return { bootMs, memStartMB: mem0 && mem0 / 1048576, memSoakMB: mem1 && mem1 / 1048576, scripts };
+}
+
+// ── 2D highway per-frame draw cost (needs --song + a seeded library) ──────────
+async function frameTimeOnce(browser) {
+    const page = await browser.newPage();
+    let f, t2, notes;
+    try {
+        // Wrap rAF before any page script; mark frames the highway actually drew.
+        await page.addInitScript(() => {
+            window.__f = [];
+            window.__drew = false;
+            const raf = window.requestAnimationFrame.bind(window);
+            window.requestAnimationFrame = (cb) => raf((t) => {
+                window.__drew = false;
+                const t0 = performance.now();
+                try { cb(t); } finally { window.__f.push({ ms: performance.now() - t0, drew: window.__drew }); }
+            });
+        });
+        await page.goto(BASE, { waitUntil: 'networkidle', timeout: 60000 });
+        await page.evaluate(() => document.getElementById('v3-onboarding')?.remove());
+        await page.evaluate((s) => window.playSong(s), SONG);
+        await page.waitForFunction(() => (window.highway?.getNotes?.() || []).length >= 0 && window.highway?.getSongInfo?.(),
+            null, { timeout: 45000 }).catch(() => {});
+        await page.waitForFunction(() => (window.highway?.getNotes?.() || []).length > 0, null, { timeout: 45000 });
+        await page.evaluate(() => window.highway.addDrawHook(() => { window.__drew = true; }));
+        // Start playback so draw() leaves its paused-throttle path; confirm the clock advances.
+        await page.evaluate(async () => { const a = window.highway.getAudioElement?.(); if (a) a.muted = true; await a?.play?.(); });
+        await page.waitForTimeout(1500);
+        const t1 = await page.evaluate(() => window.highway.getTime());
+        await page.evaluate(() => { window.__f.length = 0; });
+        await page.waitForTimeout(FRAME_S * 1000);
+        ({ f, t2, notes } = await page.evaluate(() => ({
+            f: window.__f.slice(), t2: window.highway.getTime(), notes: window.highway.getNotes().length,
+        })));
+        if (!(t2 > t1 + 1)) throw new Error(`clock did not advance (${t1}→${t2}) — measured the paused path`);
+    } finally {
+        // Always close, even when an await above throws — otherwise a failing
+        // run leaks its page until the final browser.close().
+        await page.close();
+    }
+    const drew = f.filter((x) => x.drew).map((x) => x.ms);
+    return { drew, total: f.length, notes };
+}
+
+async function frameTime() {
+    const browser = await chromium.launch({ args: ['--autoplay-policy=no-user-gesture-required'] });
+    const rows = [];
+    for (let i = 0; i < RUNS; i++) {
+        try {
+            const r = await frameTimeOnce(browser);
+            rows.push({
+                p50: pct(r.drew, 50), p95: pct(r.drew, 95), p99: pct(r.drew, 99),
+                max: Math.max(...r.drew), n: r.drew.length, total: r.total, notes: r.notes,
+            });
+        } catch (e) { rows.push({ error: String(e.message || e) }); }
+    }
+    await browser.close();
+    return rows;
+}
+
+const server = await serverLatency([
+    '/api/version',
+    '/api/plugins',
+    '/api/library?limit=60',
+    '/api/library/artists',
+]);
+const client = await clientMetrics();
+
+const now = new Date().toISOString();
+let out = `\n<!-- generated by scripts/perf-baseline.mjs @ ${now} against ${BASE} (n=${N}, soak=${SOAK_S}s) -->\n\n`;
+out += `### Server latency (ms)\n\n| Endpoint | status | p50 | p95 | p99 |\n|---|---|---|---|---|\n`;
+for (const r of server) out += `| \`${r.path}\` | ${r.status} | ${ms(r.p50)} | ${ms(r.p95)} | ${ms(r.p99)} |\n`;
+out += `\n### Client\n\n| Metric | Value |\n|---|---|\n`;
+out += `| Cold boot → networkidle | ${client.bootMs} ms |\n`;
+out += `| JS heap after load | ${client.memStartMB ? client.memStartMB.toFixed(1) + ' MB' : '—'} |\n`;
+out += `| JS heap after ${SOAK_S}s idle soak | ${client.memSoakMB ? client.memSoakMB.toFixed(1) + ' MB' : '—'} |\n`;
+out += `| Plugin scripts injected | ${client.scripts} |\n`;
+if (SONG) {
+    const frames = await frameTime();
+    out += `\n### 2D highway per-frame draw cost — \`${SONG}\` (${RUNS} runs × ${FRAME_S}s)\n\n`;
+    out += `| run | draw frames | p50 | p95 | p99 | max |\n|---|---|---|---|---|---|\n`;
+    for (let i = 0; i < frames.length; i++) {
+        const r = frames[i];
+        if (r.error) { out += `| ${i + 1} | — | \`${r.error}\` | | | |\n`; continue; }
+        out += `| ${i + 1} | ${r.n}/${r.total} | ${ms(r.p50)} | ${ms(r.p95)} | ${ms(r.p99)} | ${ms(r.max)} |\n`;
+    }
+    const p95s = frames.filter((r) => !r.error).map((r) => r.p95);
+    if (p95s.length) out += `\n**p95 spread across runs: ${ms(Math.min(...p95s))}–${ms(Math.max(...p95s))} ms**\n`;
+} else {
+    out += `\n> **Requires a seeded library** (not captured by this run): playback frame-time p95\n`;
+    out += `> on the 2D highway — pass \`--song "<filename in DLC_DIR>"\` to capture it.\n`;
+    out += `> (3D highway_3d + screen-entry timings are a separate R4 concern.)\n`;
+}
+
+console.log(out);

static/app.js

@@ -1110,6 +1110,7 @@ const _LIB_VIEW_VALUES = new Set(['grid', 'tree', 'folder']);
 const _LIB_SORT_VALUES = new Set([
     'artist', 'artist-desc', 'title', 'title-desc',
     'recent', 'year-desc', 'year', 'tuning',
+    'difficulty', 'difficulty-desc',
 ]);
 const _LIB_FORMAT_VALUES = new Set(['', 'sloppak', 'loose']);
 // Tree-view expand/collapse persistence. Three states per tree:
@@ -2078,6 +2079,7 @@ function renderGridCards(songs, containerId = 'lib-grid', mode = 'replace') {
                     ${(() => { const _nm = _getArrangementNamingMode(); return (song.arrangements || []).map(a => _arrangementBadgeHtml(a, _nm)).join(''); })()}
                     ${tuning ? `<span class="px-1.5 py-0.5 rounded ${tuning === 'E Standard' ? 'bg-green-900/30 text-green-400' : 'bg-yellow-900/30 text-yellow-400'}">${esc(tuning)}</span>` : ''}
                     ${song.has_lyrics ? `<span class="px-1.5 py-0.5 bg-purple-900/30 rounded text-purple-300">Lyrics</span>` : ''}
+                    ${song.user_difficulty != null ? `<span class="px-1.5 py-0.5 bg-blue-900/30 rounded text-blue-300" title="Your difficulty rating">◆${esc(song.user_difficulty)}</span>` : ''}
                     ${duration ? `<span class="text-gray-600">${duration}</span>` : ''}
                 </div>
                 ${retuneBtn}
@@ -2277,6 +2279,8 @@ async function renderTreeInto(containerId, countId, stats, letter, q, favoritesO
                     html += `<span class="px-1.5 py-0.5 rounded ${tuning === 'E Standard' ? 'bg-green-900/30 text-green-400' : 'bg-yellow-900/30 text-yellow-400'}">${esc(tuning)}</span>`;
                 if (song.has_lyrics)
                     html += `<span class="px-1.5 py-0.5 bg-purple-900/30 rounded text-purple-300">Lyrics</span>`;
+                if (song.user_difficulty != null)
+                    html += `<span class="px-1.5 py-0.5 bg-blue-900/30 rounded text-blue-300" title="Your difficulty rating">◆${esc(song.user_difficulty)}</span>`;
                 if (duration)
                     html += `<span class="text-gray-600 w-10 text-right">${duration}</span>`;
                 if (stdRetune)
@@ -2870,6 +2874,10 @@ const HWC_DEFAULT_FALLBACK = { lowE: '#cc0000', A: '#cca800', D: '#0066cc', G: '
 //   - colorblind: the Okabe–Ito accessible qualitative palette (vermillion,
 //     orange, yellow, bluish-green, sky-blue, blue, reddish-purple), the most
 //     distinguishable option for deuteranopia/protanopia.
+//   - colorblind_deuteranope: a deuteranope-tuned variant of the Okabe–Ito set
+//     above, contributed by a deuteranopic player who still found that set hard
+//     to separate. Retunes the six main strings (red / yellow-green / blue /
+//     orange / teal / deep-purple) and keeps its 7/8-string colors unchanged.
 //   - neon: electric, max-saturation hues whose LIGHTNESS deliberately zig-zags
 //     between neighbours (bright→bright→brightest→dark blue→bright green→dark
 //     violet) so adjacent strings separate harder than vivid — a stage/stream
@@ -2906,6 +2914,10 @@ const HWC_PRESETS = [
         id: 'colorblind', label: 'Colorblind-friendly',
         colors: { lowE: '#d55e00', A: '#e69f00', D: '#f0e442', G: '#009e73', B: '#56b4e9', highE: '#cc79a7', low7: '#0072b2', low8: '#999999' },
     },
+    {
+        id: 'colorblind_deuteranope', label: 'Colorblind (deuteranope)',
+        colors: { lowE: '#aa1414', A: '#88de00', D: '#1889e3', G: '#c6601c', B: '#00f5b2', highE: '#4d2173', low7: '#0072b2', low8: '#999999' },
+    },
     {
         id: 'neon', label: 'Neon',
         colors: { lowE: '#ff1f4e', A: '#ff9d00', D: '#e9ff00', G: '#1844ff', B: '#00ff84', highE: '#d000ff', low7: '#ff00aa', low8: '#00f0ff' },
@@ -4371,7 +4383,7 @@ async function uploadSongs(fileList) {
         if (lower.endsWith('.feedpak') || lower.endsWith('.sloppak')) {
             files.push(f);
         } else {
-            failures.push(`${f.name}: only .feedpak accepted`);
+            failures.push(`${f.name}: only .feedpak or .sloppak accepted`);
         }
     }
     if (files.length === 0) {
@@ -4852,6 +4864,65 @@ window.jucePlayer = jucePlayer;
     // (a network blip on /api/audio-local-path, an isAudioRunning() race
     // during a device restart) are deliberately NOT memoised so they retry.
     let _rerouteRejectedUrl = null;
+    // Exclusive-style output backends silence every other client on the
+    // endpoint — including our own <audio> element. The share mode IS the
+    // JUCE output device type: "Windows Audio (Exclusive Mode)" is a
+    // hardcoded, unlocalised JUCE type name; ASIO drivers typically hold
+    // the endpoint exclusively too. "Windows Audio (Low Latency Mode)" is
+    // shared and must NOT match.
+    function _isExclusiveOutputType(t) {
+        return t === 'Windows Audio (Exclusive Mode)' || t === 'ASIO';
+    }
+    // [feedpak-route] diagnostics: log the raw outputType string once per
+    // value change (this runs on a 350ms poll — logging every tick would
+    // flood the diagnostics buffer).
+    let _loggedOutputType;
+    // [asio-diag] verbose diagnostics, gated on --debug (preload exposes
+    // audio.debugEnabled). Resolved once at install; until it resolves the
+    // flag stays false and verbose lines are skipped. Shared with the
+    // renderer-bus feeder below via window._asioDiagEnabled.
+    let _asioDiag = false;
+    if (typeof juceApi.debugEnabled === 'function') {
+        juceApi.debugEnabled().then((v) => { _asioDiag = !!v; }).catch(() => {});
+    }
+    window._asioDiagEnabled = () => _asioDiag;
+    async function _outputIsExclusive() {
+        if (typeof juceApi.getCurrentDevice !== 'function') {
+            if (_loggedOutputType !== '<no-getCurrentDevice>') {
+                _loggedOutputType = '<no-getCurrentDevice>';
+                console.warn('[feedpak-route] juceApi.getCurrentDevice missing — cannot detect exclusive output');
+            }
+            return false;
+        }
+        try {
+            const dev = await juceApi.getCurrentDevice();
+            const t = dev?.outputType || dev?.type || '';
+            const excl = _isExclusiveOutputType(t);
+            if (t !== _loggedOutputType) {
+                _loggedOutputType = t;
+                console.log('[feedpak-route] outputType=', JSON.stringify(t), '→ exclusive=', excl);
+                // [asio-diag] full device object on every type change — shows
+                // the exact strings the predicate saw (inputType vs outputType,
+                // device names, duplex), so a driver reporting a non-'ASIO'
+                // type name is visible in tester logs.
+                if (_asioDiag) {
+                    try {
+                        console.log('[asio-diag] getCurrentDevice=', JSON.stringify(dev));
+                    } catch (_) { /* circular/hostile object — skip */ }
+                }
+            }
+            return excl;
+        } catch (e) {
+            if (_loggedOutputType !== '<getCurrentDevice-failed>') {
+                _loggedOutputType = '<getCurrentDevice-failed>';
+                console.warn('[feedpak-route] getCurrentDevice failed:', e);
+            }
+            return false;
+        }
+    }
+    // highway.js's initial song-load routing consults this for the same
+    // feedpak-under-exclusive decision the watcher makes below.
+    window._juceOutputIsExclusive = _outputIsExclusive;
     // Returns true when window._currentSongAudio no longer references the exact
     // snapshot object captured at reroute entry — i.e. the song was swapped (or
     // cleared) mid-flight. Staleness is detected by object-reference identity,
@@ -4892,8 +4963,12 @@ window.jucePlayer = jucePlayer;
         audio.pause();
         try {
             const res = await fetch(`/api/audio-local-path?url=${encodeURIComponent(url)}`);
-            if (!res.ok) throw new Error('HTTP ' + res.status);
+            if (!res.ok) {
+                console.warn('[feedpak-route] audio-local-path HTTP', res.status, 'for', url);
+                throw new Error('HTTP ' + res.status);
+            }
             const { path } = await res.json();
+            console.log('[feedpak-route] audio-local-path resolved:', (typeof path === 'string' && path.split(/[\\/]/).pop()) || '<missing>');
             if (_isStale(songAudio)) return 'stale';   // song changed mid-fetch
             const ok = await juceApi.loadBackingTrack(path);
             if (ok === false) {
@@ -5111,8 +5186,12 @@ window.jucePlayer = jucePlayer;
     async function _reevaluateJuceRouting() {
         if (_rerouteInFlight) return;
         const songAudio = window._currentSongAudio;
-        // Only /audio/ songs are JUCE-routable; sloppak stems stay on HTML5.
-        if (!songAudio || !songAudio.juceEligible) return;
+        // /audio/ songs are always JUCE-routable. A feedpak full-mix
+        // (single-mix pack, no stems) is routable ONLY under an
+        // exclusive-style output — in shared mode it must stay on HTML5 so
+        // the stem mixer / WebAudio path keeps working. Sloppak stem URLs
+        // are never routable (per-stem mix can't ride a single transport).
+        if (!songAudio || (!songAudio.juceEligible && !songAudio.feedpakFullMix)) return;
         // Don't race highway.js's own initial song-load routing: it owns
         // _juceMode until _juceRoutingPromise settles. Re-running our switch
         // concurrently would double-call loadBackingTrack for the same URL.
@@ -5130,13 +5209,30 @@ window.jucePlayer = jucePlayer;
             try { running = await juceApi.isAudioRunning(); }
             catch (_) { return; }
             if (_isStale(songAudio)) return;               // song changed during IPC
-            if (!!running === !!window._juceMode) return;  // routing already consistent
-
-            const wantJuce = running && !window._juceMode;
+            // Eligibility is evaluated per tick, not snapshotted at song load:
+            // the output share mode can change mid-song (device switch in the
+            // Audio Engine panel), and a feedpak full-mix must follow it —
+            // exclusive → ride the engine; back to shared → return to HTML5.
+            let eligible = !!songAudio.juceEligible;
+            if (!eligible && songAudio.feedpakFullMix && running) {
+                eligible = await _outputIsExclusive();
+                if (_isStale(songAudio)) return;           // song changed during IPC
+            }
+            const wantJuce = !!(running && eligible);
+            // [feedpak-route] diagnostics: one line per decision change (the
+            // watcher polls at 350ms; steady state must not spam the buffer).
+            const _decision = 'running=' + running + ' eligible=' + eligible
+                + ' feedpakFullMix=' + !!songAudio.feedpakFullMix
+                + ' juceMode=' + !!window._juceMode + ' url=' + songAudio.url;
+            if (_decision !== window._lastFeedpakRouteDecision) {
+                window._lastFeedpakRouteDecision = _decision;
+                console.log('[feedpak-route] watcher:', _decision);
+            }
+            if (wantJuce === !!window._juceMode) return;   // routing already consistent
             // Don't keep retrying a track JUCE explicitly rejected.
             if (wantJuce && songAudio.url === _rerouteRejectedUrl) return;
 
-            if (running) {
+            if (wantJuce) {
                 const outcome = await _switchHtml5ToJuce(songAudio);
                 // Memoise ONLY an explicit hard JUCE reject. A successful
                 // switch clears the memo; a 'stale' abort (song changed
@@ -5151,9 +5247,10 @@ window.jucePlayer = jucePlayer;
                 // outcome === 'stale': leave _rerouteRejectedUrl as-is.
             } else {
                 await _switchJuceToHtml5(songAudio);
-                // The engine just stopped. Clear any hard-reject memo so a
-                // later engine restart re-evaluates the track at least once —
-                // the rejection may have been a transient device/decoder state.
+                // The engine stopped (or a feedpak's output left exclusive
+                // mode). Clear any hard-reject memo so a later engine restart
+                // or mode change re-evaluates the track at least once — the
+                // rejection may have been a transient device/decoder state.
                 _rerouteRejectedUrl = null;
             }
         } catch (e) {
@@ -5185,6 +5282,234 @@ window.jucePlayer = jucePlayer;
     }, 350);
 })();
 
+// Renderer-audio bus feeder (desktop Phase 2): when the engine holds the
+// output endpoint in an exclusive-style mode, Chromium cannot reach the
+// device, so any song audio still played by the renderer goes silent. The
+// Phase 1 watcher above already migrates what a single-file transport can
+// carry (loose /audio/ songs, feedpak full-mixes) onto the native backing
+// transport. This feeder covers the rest — the stems plugin's multi-stem
+// WebAudio graph, plus <audio>-element songs the native transport could not
+// take (e.g. a codec loadBackingTrack rejected).
+//
+// Mechanism: capture the renderer-side master with an AudioWorklet tap,
+// re-point the owning AudioContext at a null sink so it keeps rendering
+// without a device, and push ~10 ms chunks over IPC into the engine's
+// renderer bus, where they are mixed into the exclusive output like a
+// backing track (~10-20 ms added latency on song audio only; the guitar
+// monitoring path is untouched). Validated by the fix12 tester spike:
+// null-sink rendering works, clocks hold (drift → 0), no overflow.
+//
+// Docker sphere: window.feedBackDesktop is undefined → this whole block is
+// inert. Shared-mode desktop: the bus stays disabled (no double audio) and
+// captured contexts keep/regain their default sink.
+(function _installRendererBusFeeder() {
+    const api = window.feedBackDesktop?.audio;
+    if (!api || typeof api.setRendererBus !== 'function'
+             || typeof api.pushRendererAudio !== 'function') return;
+
+    const TAP_WORKLET = `
+        class FeedbackBusTap extends AudioWorkletProcessor {
+            process(inputs) {
+                const inp = inputs[0];
+                if (inp && inp[0]) {
+                    const L = inp[0], R = inp[1] || inp[0];
+                    const out = new Float32Array(L.length * 2);
+                    for (let i = 0; i < L.length; i++) { out[i*2] = L[i]; out[i*2+1] = R[i]; }
+                    this.port.postMessage(out, [out.buffer]);
+                }
+                return true;
+            }
+        }
+        registerProcessor('feedback-bus-tap', FeedbackBusTap);
+    `;
+    const _tapModuleUrl = URL.createObjectURL(new Blob([TAP_WORKLET], { type: 'application/javascript' }));
+    const _tapModuleLoaded = new WeakSet();   // AudioContexts with the module added
+
+    // One tap per captured graph. `active` gates the push (the worklet keeps
+    // running when inactive — it's silent bookkeeping, not audio).
+    function _makeTap(ctx) {
+        const state = { node: null, active: false, batch: [], batchFrames: 0 };
+        state.attach = async (sourceNode) => {
+            if (!_tapModuleLoaded.has(ctx)) {
+                await ctx.audioWorklet.addModule(_tapModuleUrl);
+                _tapModuleLoaded.add(ctx);
+            }
+            if (!state.node) {
+                state.node = new AudioWorkletNode(ctx, 'feedback-bus-tap', { numberOfInputs: 1, channelCount: 2 });
+                const BATCH = Math.round(ctx.sampleRate / 100);   // ~10 ms
+                state.node.port.onmessage = (e) => {
+                    if (!state.active) { state.batch = []; state.batchFrames = 0; return; }
+                    state.batch.push(e.data);
+                    state.batchFrames += e.data.length / 2;
+                    if (state.batchFrames >= BATCH) {
+                        const merged = new Float32Array(state.batchFrames * 2);
+                        let o = 0;
+                        for (const c of state.batch) { merged.set(c, o); o += c.length; }
+                        api.pushRendererAudio(merged, ctx.sampleRate);
+                        state.batch = []; state.batchFrames = 0;
+                    }
+                };
+            }
+            sourceNode.connect(state.node);
+            // No onward connection: the tap is a sink-side observer; audibility
+            // in shared mode comes from the graph's own destination path.
+        };
+        state.detach = (sourceNode) => {
+            state.active = false;
+            state.batch = []; state.batchFrames = 0;
+            if (state.node && sourceNode) {
+                try { sourceNode.disconnect(state.node); } catch (_) { /* already gone */ }
+            }
+        };
+        return state;
+    }
+
+    // ── Core <audio> element capture ─────────────────────────────────────────
+    // createMediaElementSource permanently reroutes the element into its
+    // context, so it is created lazily — only the first time an exclusive
+    // device actually needs it — and never torn down. From then on the element
+    // always plays through _elCtx; sink toggling routes it to the speakers
+    // (shared mode) or the null sink + bus (exclusive mode).
+    let _elCtx = null, _elSource = null, _elTap = null;
+    async function _ensureElementCapture() {
+        if (_elCtx) return;
+        const el = document.getElementById('audio');
+        if (!el) throw new Error('no core audio element');
+        _elCtx = new AudioContext();
+        _elSource = _elCtx.createMediaElementSource(el);
+        _elSource.connect(_elCtx.destination);
+        _elTap = _makeTap(_elCtx);
+        await _elTap.attach(_elSource);
+    }
+
+    // ── Engagement state machine ─────────────────────────────────────────────
+    // 'off' | 'element' | 'stems'
+    let _mode = 'off';
+    let _stemsGraph = null;   // { context, masterNode } snapshot while engaged
+    let _stemsTap = null;
+    const _stemsTaps = new WeakMap();  // context → tap (stems ctx is reused across songs)
+    let _busy = false;
+
+    async function _setSink(ctx, exclusive) {
+        if (typeof ctx.setSinkId !== 'function') throw new Error('setSinkId unsupported');
+        await ctx.setSinkId(exclusive ? { type: 'none' } : '');
+        if (ctx.state !== 'running') await ctx.resume().catch(() => {});
+        // [asio-diag] a context left on the default sink while the bus is
+        // engaged is exactly the "song on the wrong device" symptom — record
+        // every successful sink flip (failures throw and are logged upstream).
+        if (window._asioDiagEnabled?.()) {
+            console.log('[asio-diag] setSink:', exclusive ? 'null-sink' : 'default',
+                'state=', ctx.state, 'rate=', ctx.sampleRate);
+        }
+    }
+
+    async function _disengage() {
+        if (_mode === 'off') return;
+        const prev = _mode;
+        _mode = 'off';
+        try { await api.setRendererBus(false, 0); } catch (_) { /* engine gone */ }
+        if (prev === 'element' && _elCtx) {
+            _elTap.active = false;
+            await _setSink(_elCtx, false).catch(() => {});
+        } else if (prev === 'stems' && _stemsGraph) {
+            if (_stemsTap) _stemsTap.detach(_stemsGraph.masterNode);
+            await _setSink(_stemsGraph.context, false).catch(() => {});
+            _stemsGraph = null; _stemsTap = null;
+        }
+        console.log('[renderer-bus] disengaged (' + prev + ')');
+    }
+
+    async function _engageStems(graph) {
+        await _setSink(graph.context, true);
+        let tap = _stemsTaps.get(graph.context);
+        if (!tap) { tap = _makeTap(graph.context); _stemsTaps.set(graph.context, tap); }
+        await tap.attach(graph.masterNode);
+        await api.setRendererBus(true, 1.0);
+        tap.active = true;
+        _stemsGraph = graph; _stemsTap = tap;
+        _mode = 'stems';
+        console.log('[renderer-bus] engaged: stems graph → engine bus');
+    }
+
+    async function _engageElement() {
+        await _ensureElementCapture();
+        await _setSink(_elCtx, true);
+        await api.setRendererBus(true, 1.0);
+        _elTap.active = true;
+        _mode = 'element';
+        console.log('[renderer-bus] engaged: <audio> element → engine bus');
+    }
+
+    async function _reevaluate() {
+        if (_busy) return;
+        _busy = true;
+        try {
+            let running = false, exclusive = false;
+            try {
+                running = await api.isAudioRunning();
+            } catch (_) { /* engine unreachable → treat as not running */ }
+            if (running) {
+                // Reuse the Phase 1 predicate installed by the routing watcher
+                // (getCurrentDevice + exclusive-type check with change-logged
+                // diagnostics). Fail closed if it is somehow absent.
+                exclusive = !!(await window._juceOutputIsExclusive?.());
+            }
+
+            // The stems plugin publishes its live graph while a multi-stem
+            // song is loaded (and removes it on teardown).
+            const stems = (window.feedBack || window.slopsmith)?.stems?.audioGraph || null;
+            // Element songs: a song is loaded, it is NOT riding the native
+            // transport (Phase 1 owns those), and the stems graph is not the
+            // player. Covers native-transport rejects (codec) in exclusive
+            // mode — without this they would be silent.
+            const songAudio = window._currentSongAudio;
+            const elementSong = !!songAudio && !window._juceMode && !stems;
+
+            let want = 'off';
+            if (running && exclusive) {
+                if (stems) want = 'stems';
+                else if (elementSong) want = 'element';
+            }
+
+            // [asio-diag] full decision vector, change-gated (500ms poll —
+            // steady state must not flood the buffer). This is the feeder-side
+            // counterpart of the watcher's [feedpak-route] decision line: it
+            // shows WHY the bus did or didn't engage (exclusive predicate,
+            // stems graph presence, native transport ownership, element song).
+            if (window._asioDiagEnabled?.()) {
+                const d = 'running=' + running + ' exclusive=' + exclusive
+                    + ' stems=' + !!stems + ' songAudio=' + !!songAudio
+                    + ' juceMode=' + !!window._juceMode
+                    + ' elementSong=' + elementSong
+                    + ' want=' + want + ' mode=' + _mode;
+                if (d !== window._lastRendererBusDecision) {
+                    window._lastRendererBusDecision = d;
+                    console.log('[asio-diag] renderer-bus:', d);
+                }
+            }
+
+
+            const stemsGraphChanged = _mode === 'stems' && stems !== _stemsGraph;
+            if (want !== _mode || stemsGraphChanged) {
+                await _disengage();
+                if (want === 'stems') await _engageStems(stems);
+                else if (want === 'element') await _engageElement();
+            }
+        } catch (e) {
+            console.warn('[renderer-bus] reevaluate failed (will retry):', e);
+            _mode = 'off';
+        } finally {
+            _busy = false;
+        }
+    }
+
+    // Same cadence/rationale as the routing watcher above. Also re-check on
+    // visibility return so a device switch made while hidden is reconciled.
+    setInterval(() => { if (!document.hidden) void _reevaluate(); }, 500);
+    document.addEventListener('visibilitychange', () => { if (!document.hidden) void _reevaluate(); });
+    window._reevaluateRendererBus = _reevaluate;
+})();
+
 // Desktop JUCE backing uses an empty <audio> element; plugins such as Section Map
 // still seek via audio.currentTime / pause / play. Mirror those onto jucePlayer
 // while _juceMode is active. Same-tick pause+seek coalesce into a single seek
@@ -5556,9 +5881,24 @@ function _playbackApi() {
         : null;
 }
 
+// Bridge hits are a "this legacy surface is still in use" signal, not a call
+// counter — but recordBridgeHit is not cheap (compat-shim bookkeeping, a
+// playback:bridge-hit event, and a diagnostics snapshot rebuild per call).
+// Plugins legitimately poll read surfaces like window.feedBack.getLoop() from
+// HUD ticks (note_detect polled at ~30 Hz), which turned every tick into a
+// snapshot serialization on the main thread and saturated the inspector's
+// hitCount. Throttle per surface: the first call records immediately, repeats
+// within the window are dropped.
+const _bridgeRecordLast = new Map();
+const _BRIDGE_RECORD_MIN_MS = 5000;
 function _recordPlaybackBridge(bridgeId, legacySurface, reason) {
     const playback = _playbackApi();
     if (!playback || typeof playback.recordBridgeHit !== 'function') return;
+    const key = `${bridgeId}|${legacySurface}`;
+    const now = Date.now();
+    const last = _bridgeRecordLast.get(key);
+    if (last != null && now - last < _BRIDGE_RECORD_MIN_MS) return;
+    _bridgeRecordLast.set(key, now);
     playback.recordBridgeHit({
         bridgeId,
         legacySurface,
@@ -7932,6 +8272,10 @@ function setLoopEnd() {
     if (loopB <= loopA) { loopB = null; return; }
     document.getElementById('btn-loop-b').className = 'px-3 py-1.5 bg-green-900/50 rounded-lg text-xs text-green-300 transition';
     updateLoopUI();
+    // Manual A/B arming is a loop mutation like setLoop()'s — emit the same
+    // transport event so event-driven consumers (note_detect drill sync) see
+    // button-armed loops without having to poll getLoop().
+    window.feedBack?.playback?.transportEvent?.('loop-set', { requesterId: 'core.loop', loopA, loopB, loop: { startTime: loopA, endTime: loopB, enabled: true, state: 'active' } });
 }
 
 function clearLoop(options) {
@@ -8092,6 +8436,26 @@ function _resolveEditRegion() {
     return { a: Math.max(0, t - 4), b: t + 4 };
 }
 
+/* @pure:editor-pending-view:start */
+function _buildEditorPendingViewPure(filename, arrangement, region, opts) {
+    const options = opts || {};
+    const view = {
+        filename,
+        arrangement: Number.isFinite(arrangement) && arrangement >= 0 ? arrangement : 0,
+        barSel: region ? { startTime: region.a, endTime: region.b } : null,
+    };
+    if (options.returnToHighway) view.returnToHighway = true;
+    if (typeof options.cursorTime === 'number') {
+        view.cursorTime = options.cursorTime;
+    } else if (region && typeof region.a === 'number') {
+        view.cursorTime = region.a;
+    }
+    if (typeof options.scrollX === 'number') view.scrollX = Math.max(0, options.scrollX);
+    if (typeof options.zoom === 'number' && options.zoom > 0) view.zoom = options.zoom;
+    return view;
+}
+/* @pure:editor-pending-view:end */
+
 // Enable "Edit region" whenever the editor plugin is present and a song is
 // loaded; show "↩ Editor" only while a return context is pending.
 function _updateEditRegionBtn() {
@@ -8118,12 +8482,9 @@ function editRegionInEditor() {
             arrangement = si.arrangement_index;
         }
     } catch (_) { /* default to 0 */ }
-    window._editorPendingView = {
-        filename: currentFilename,
-        arrangement,
-        barSel: { startTime: region.a, endTime: region.b },
+    window._editorPendingView = _buildEditorPendingViewPure(currentFilename, arrangement, region, {
         returnToHighway: true,
-    };
+    });
     window.editSong(currentFilename);
 }
 window.editRegionInEditor = editRegionInEditor;
@@ -8135,14 +8496,14 @@ function returnToEditorFromHighway() {
     const ctx = window._highwayReturnCtx;
     if (!ctx || typeof window.editSong !== 'function') return;
     window._highwayReturnCtx = null;
-    window._editorPendingView = {
-        filename: ctx.filename,
-        arrangement: ctx.arrangement,
+    const region = ctx.barSel
+        ? { a: ctx.barSel.startTime, b: ctx.barSel.endTime }
+        : null;
+    window._editorPendingView = _buildEditorPendingViewPure(ctx.filename, ctx.arrangement, region, {
         scrollX: ctx.scrollX,
         zoom: ctx.zoom,
         cursorTime: ctx.cursorTime,
-        barSel: ctx.barSel,
-    };
+    });
     window.editSong(ctx.filename);
 }
 window.returnToEditorFromHighway = returnToEditorFromHighway;
@@ -11519,6 +11880,14 @@ async function loadPlugins() {
                         // URL ?v=mtime convention elsewhere in this file).
                         const v = encodeURIComponent(wantedVersion);
                         script.src = `/api/plugins/${plugin.id}/screen.js${v ? `?v=${v}` : ''}`;
+                        // Module-migration (R0): a migrated plugin declares
+                        // scriptType:"module" and its screen.js is `import
+                        // './src/main.js'`. A <script type="module"> fires load
+                        // only after its whole static-import graph evaluates, so
+                        // the await-onload completion + _loadingPluginId contract
+                        // below is preserved (a classic-IIFE dynamic import()
+                        // would not). Classic plugins are unaffected.
+                        if (plugin.script_type === 'module') script.type = 'module';
                         script.dataset.pluginId = plugin.id;
                         script.dataset.pluginVersion = wantedVersion;
                         window.feedBack._loadingPluginId = plugin.id;

static/capabilities/audio-effects.js

@@ -9,6 +9,8 @@
 
     const SCHEMA = 'feedBack.audio_effects.diagnostics.v1';
     const PLAN_SCHEMA = 'feedBack.audio_effects.chain_plan.v1';
+// Pre-rebrand plugins (rig_builder <= 2.9.x) still send the old schema id — accept it as an alias.
+const LEGACY_PLAN_SCHEMA = 'slopsmith.audio_effects.chain_plan.v1';
     const OWNER_ID = 'core.audio.effects';
     const DEFAULT_ROUTE_KEY = 'desktop-main';
     const DEFAULT_TIMEOUT_MS = 2000;
@@ -734,7 +736,7 @@
         const errors = [];
         const source = _plainObject(rawPlan);
         const schema = _string(source.schema || source.version, PLAN_SCHEMA);
-        if (schema !== PLAN_SCHEMA && schema !== '1') errors.push('Unsupported chain plan schema');
+        if (schema !== PLAN_SCHEMA && schema !== LEGACY_PLAN_SCHEMA && schema !== '1') errors.push('Unsupported chain plan schema');
         const planRoute = _safeRoute(source.routeKey || source.route || routeKey);
         if (planRoute !== routeKey) errors.push('Chain plan route does not match selected route');
         const providerId = _safeId(source.providerId || provider.providerId, provider.providerId);

static/index.html

@@ -119,6 +119,8 @@
                         <option value="year-desc">Year (newest)</option>
                         <option value="year">Year (oldest)</option>
                         <option value="tuning">Tuning</option>
+                        <option value="difficulty">Difficulty (easiest first)</option>
+                        <option value="difficulty-desc">Difficulty (hardest first)</option>
                     </select>
                     <!-- Format filter (shared) -->
                     <select id="lib-format" onchange="sortLibrary()"

static/v3/badges.js

@@ -451,6 +451,12 @@
                 pill('inst', v, v[0].toUpperCase() + v.slice(1), settings.instrument === v)).join('')) +
             instRow('Strings', STRING_COUNTS[settings.instrument].map((v) =>
                 pill('strings', v, v + '', settings.string_count === v)).join('')) +
+            // Handedness — a left-hander flips the whole highway (frets mirror).
+            // Lives with the other player-orientation choices so it's part of the
+            // same "Choose your instrument" step the onboarding tour spotlights —
+            // i.e. set before you ever tune up or calibrate.
+            instRow('Handedness', pill('hand', 'right', 'Right', !_leftyPref()) +
+                pill('hand', 'left', 'Left', _leftyPref())) +
             '<div><div class="text-[0.625rem] uppercase tracking-wider text-fb-textDim mb-1">Tuning</div>' +
             '<select data-inst-tuning class="w-full bg-gray-800/50 border border-gray-700 rounded-md px-2 py-1.5 text-xs text-fb-text outline-none focus:border-fb-primary">' +
             // An offset-array tuning has no named option — surface it as a
@@ -513,6 +519,10 @@
             setWorkingInstrument(settings.instrument, newSc);
             renderInstrument(); keepOpen();
         }));
+        menu.querySelectorAll('[data-pill="hand"]').forEach((b) => b.addEventListener('click', () => {
+            _setLeftyPref(b.getAttribute('data-val') === 'left');
+            renderInstrument(); keepOpen();   // reflect the active pill; keep the menu open
+        }));
         menu.querySelector('[data-inst-tuning]').addEventListener('change', (e) => saveSettings({ tuning: e.target.value }));
         menu.querySelector('[data-inst-pathway]').addEventListener('change', (e) => saveSettings({ pathway: e.target.value }));
         const ref = menu.querySelector('[data-inst-ref]');
@@ -528,6 +538,22 @@
     function instRow(label, inner) {
         return '<div><div class="text-[0.625rem] uppercase tracking-wider text-fb-textDim mb-1">' + label + '</div><div class="flex flex-wrap gap-1">' + inner + '</div></div>';
     }
+    // Handedness (left-handed) preference. The canonical store is the highway's
+    // `lefty` localStorage key; when a live highway exists, setLefty() also flips
+    // it immediately. Feature-detected so it works on the dashboard before any
+    // highway has been created (the value is read on the highway's next init).
+    function _leftyPref() {
+        try { if (window.highway && typeof window.highway.getLefty === 'function') return !!window.highway.getLefty(); } catch (_) { /* */ }
+        try { return localStorage.getItem('lefty') === '1'; } catch (_) { return false; }
+    }
+    function _setLeftyPref(on) {
+        try {
+            if (window.highway && typeof window.highway.setLefty === 'function') window.highway.setLefty(!!on);
+            else localStorage.setItem('lefty', on ? '1' : '0');
+        } catch (_) { /* storage blocked — the pill still reflects the choice via re-render */ }
+        // Keep the Settings "Left-handed" checkbox in sync when it's mounted.
+        try { const cb = document.getElementById('setting-lefty'); if (cb) cb.checked = !!on; } catch (_) { /* */ }
+    }
     function pill(group, val, label, active) {
         return '<button type="button" data-pill="' + group + '" data-val="' + val + '" class="px-2 py-1 rounded-md text-xs ' +
             (active ? 'bg-fb-primary text-white' : 'bg-gray-800/50 text-fb-textDim hover:text-fb-text') + '">' + esc(label) + '</button>';

static/v3/image-picker.js

@@ -138,6 +138,17 @@
             '<div class="flex flex-wrap gap-3">' + SKELETON_TILE + SKELETON_TILE + SKELETON_TILE + '</div>' +
             '<div class="text-xs text-fb-textDim pt-2">Fetching covers… the source is rate-limited.</div>' +
             '</div>' +
+            // Search Cover Art Archive — find an album cover even when the song has
+            // no match (the auto candidates above are empty then). Pre-filled from
+            // the song's artist + album/title; the source is rate-limited.
+            '<div class="space-y-2 pt-1">' +
+            '<div class="text-xs font-semibold uppercase tracking-wider text-fb-textDim">Search covers</div>' +
+            '<div class="flex gap-2">' +
+            '<input data-ip-search-input type="text" value="' + esc(_cur.query || '') + '" placeholder="artist album" class="flex-1 bg-gray-800/50 border border-gray-700 rounded-md px-2 py-1 text-sm text-fb-text outline-none focus:border-fb-primary">' +
+            '<button data-ip-search-go class="text-sm text-fb-primary hover:text-fb-primaryHi border border-fb-primary/40 rounded-md px-3">Search</button>' +
+            '</div>' +
+            '<div data-ip-search-results class="flex flex-wrap gap-3"></div>' +
+            '</div>' +
             '<div data-ip-status class="hidden text-xs text-fb-accent"></div>' +
             '</div></div>' +
             '<input type="file" accept="image/*" data-ip-file class="hidden">';
@@ -185,9 +196,47 @@
                 }
             });
         });
+        const searchInput = panel.querySelector('[data-ip-search-input]');
+        const runSearch = () => coverSearch(panel, (searchInput && searchInput.value) || '');
+        panel.querySelector('[data-ip-search-go]')?.addEventListener('click', runSearch);
+        searchInput?.addEventListener('keydown', (e) => { if (e.key === 'Enter') { e.preventDefault(); runSearch(); } });
         panel.querySelector('[data-ip-close]')?.focus();
     }
 
+    // Search Cover Art Archive (via the song-scoped cover-search endpoint) and
+    // render the album covers as pickable tiles — the same apply('url') path as
+    // the auto candidates. Covers with no CAA art self-hide (img onerror).
+    async function coverSearch(panel, query) {
+        const out = panel.querySelector('[data-ip-search-results]');
+        const fn = _cur && _cur.filename;
+        if (!out || !fn) return;
+        out.innerHTML = '<div class="flex flex-wrap gap-3">' + SKELETON_TILE + SKELETON_TILE + '</div>';
+        let body = null;
+        try {
+            const r = await fetch('/api/song/' + enc(fn) + '/art/cover-search?q=' + enc(String(query).trim()));
+            if (r.ok) body = await r.json();
+        } catch (_) { /* falls through to the empty state */ }
+        if (!_cur || _cur.filename !== fn) return;   // closed / changed song while searching
+        const covers = (body && body.covers) || [];
+        if (!covers.length) {
+            out.innerHTML = '<div class="text-xs text-fb-textDim">' +
+                ((body && body.error) ? 'Cover search is unavailable right now.' : 'No covers found — try a different search.') +
+                '</div>';
+            return;
+        }
+        out.innerHTML = covers.map((c, i) =>
+            tileHtml('data-ip-cover="' + i + '"', imgFace(c.thumb_url), c.label || 'Cover')).join('');
+        out.querySelectorAll('[data-ip-cover]').forEach((btn) => {
+            const img = btn.querySelector('img');
+            if (img) img.onerror = () => btn.classList.add('hidden');   // no CAA art for this album → hide
+            btn.addEventListener('click', () => {
+                if (_busy) return;
+                const c = covers[Number(btn.getAttribute('data-ip-cover'))];
+                if (c) apply('url', c.thumb_url);
+            });
+        });
+    }
+
     // The one candidates fetch, cancelled if the modal closes first. Failure
     // (offline, demo mode, aborted) is silent: the skeletons just clear and
     // the instant tiles remain — never an error wall.
@@ -281,7 +330,13 @@
         const filename = opts && opts.filename;
         if (!filename) return;
         _lastFocus = document.activeElement;
-        _cur = { filename: filename, title: (opts && opts.title) || filename };
+        const title = (opts && opts.title) || filename;
+        const artist = (opts && opts.artist) || '';
+        const album = (opts && opts.album) || '';
+        // Pre-fill the cover search: "artist album" when the album is known, else
+        // just the artist, else the title — the server default backs it up.
+        const query = [artist, album].filter(Boolean).join(' ').trim() || title;
+        _cur = { filename: filename, title: title, query: query };
         _busy = false;
         const m = ensureModal();
         const panel = document.getElementById('v3-imgpick-panel');

static/v3/index.html

@@ -194,7 +194,7 @@
 
     <!-- Hidden file input shared by the navbar "Upload" link. Kept at body
          level so it stays reachable regardless of which screen is active. -->
-    <input type="file" id="upload-songs-file" accept=".sloppak" multiple class="hidden" onchange="uploadSongs(this.files); this.value=''">
+    <input type="file" id="upload-songs-file" accept=".feedpak,.sloppak" multiple class="hidden" onchange="uploadSongs(this.files); this.value=''">
 
     <!-- ══ HOME (Hero + Library) — reused as the v3 "Songs" screen ════════ -->
     <div id="home" class="screen">
@@ -641,7 +641,12 @@
                             </div>
                         </div>
                         <div class="fb-srow-control">
+                            <!-- Autosave on blur/enter via a single-key POST (like every other v3
+                                 setting), so setting the address never depends on the shared Save
+                                 button — whose bundled dlc_dir could otherwise block it. Save button
+                                 kept for discoverability. -->
                             <input type="text" id="demucs-server-url" placeholder="http://192.168.1.100:7865"
+                                onchange="persistSetting('demucs_server_url', this.value.trim())"
                                 class="bg-dark-700 border border-gray-800 rounded-xl px-4 py-2.5 text-sm text-gray-300 placeholder-gray-600 focus:border-accent/50 outline-none">
                             <button onclick="saveSettings()" class="bg-accent hover:bg-accent-light px-6 py-2.5 rounded-xl text-sm font-semibold text-white transition">Save</button>
                         </div>

static/v3/match-review.js

@@ -303,6 +303,7 @@
             '<span class="text-xs text-fb-textDim shrink-0">' + esc(pct) + '</span></span>' +
             '<span class="block text-xs text-fb-textDim truncate">' + esc(meta) + '</span>' +
             diffChips(song, c) +
+            (_single ? '<span class="block text-xs text-fb-primary pt-1">Use these values →</span>' : '') +
             '</button>';
     }
 
@@ -461,7 +462,11 @@
     // Each field sits on its pack value: editing above the pack makes it an
     // override ("Yours"); a lock pins it so an auto-match can't recanonicalize
     // it; revert (↺) drops back to the pack value.
-    const DETAIL_FIELDS = [['title', 'Title'], ['artist', 'Artist'], ['album', 'Album'], ['year', 'Year']];
+    const DETAIL_FIELDS = [['title', 'Title'], ['artist', 'Artist'], ['album', 'Album'], ['year', 'Year'], ['genre', 'Genre']];
+    // Only these four are written into the pack file; genre is a library-only
+    // overlay (drives the genre filter/facet + the auto-match lock), never baked
+    // to the file — so Write to file leaves genre's override in place.
+    const WRITE_FIELDS = ['title', 'artist', 'album', 'year'];
 
     async function renderDetailsTab(body, song) {
         body.innerHTML = '<div class="p-5"><p class="text-sm text-fb-textDim">Loading…</p></div>';
@@ -483,7 +488,47 @@
             };
         }
         song._detailsState = st;
+        // Match→Details bridge: a candidate picked with "Use these values" lands
+        // its fields here as the pending (unsaved) input values, shown pre-filled
+        // for review — the grid never adopts a match silently, so the user still
+        // Saves (or Writes to file).
+        const adopted = song._pendingDetails;
+        if (adopted) {
+            for (const [f] of DETAIL_FIELDS) {
+                if (f in adopted) st[f].value = String(adopted[f] || '');
+            }
+            song._pendingDetails = null;
+        }
         paintDetails(body, song);
+        if (adopted) {
+            const s = body.querySelector('[data-df-status]');
+            if (s) { s.className = 'text-xs leading-relaxed text-fb-textDim'; s.textContent = 'Filled from the match — review, then Save or Write to file.'; }
+        }
+    }
+
+    // Match→Details bridge: adopt a candidate's display fields into the Details
+    // tab (opt-in — never silent). Pin the match too so the art/canon follow,
+    // then land on Details pre-filled for review.
+    async function useTheseValues(song, cand) {
+        if (!cand) return;
+        // Smart adopt for an English base: KEEP the readable name + title the card
+        // already shows (the author's romaji, e.g. "Junko Yagami / BAY CITY") — the
+        // match is often native script (kanji/kana). Take only what the pack lacks
+        // — album / year / genre — from the match; the pin below still brings the
+        // correct art + identity. The user can still edit any field.
+        song._pendingDetails = {
+            artist: String(song.artist || cand.artist || ''),
+            title:  String(song.title  || cand.title  || ''),
+            album:  String(cand.album  || song.album  || ''),
+            year:   String(cand.year   || song.year   || ''),
+            genre:  String((Array.isArray(cand.genres) && cand.genres[0]) || cand.genre || ''),
+        };
+        try {
+            await post('/api/enrichment/review/' + enc(song.filename) + '/pick', { candidate: cand });
+        } catch (_) { /* pin is best-effort; the values still populate Details */ }
+        try { window.feedBack?.emit('library:changed', { reason: 'match' }); } catch (_) { }
+        _tab = 'details';
+        renderTabbed();
     }
 
     function paintDetails(body, song) {
@@ -514,7 +559,7 @@
             '<div class="p-5 space-y-4 overflow-y-auto v3-scroll min-h-0">' +
             '<div class="flex items-start gap-3">' +
             '<img src="' + esc(artUrl(song)) + '" alt="" onerror="this.style.visibility=\'hidden\'" class="w-14 h-14 rounded-lg object-cover bg-fb-card shrink-0">' +
-            '<p class="text-xs text-fb-textDim pt-1"><span class="text-fb-text">Save</span> keeps edits as a reversible library overlay — the song files aren\'t touched. <span class="text-fb-text">Write to file</span> bakes them into the pack itself. Lock a field to keep an auto-match from changing it.</p>' +
+            '<p class="text-xs text-fb-textDim pt-1"><span class="text-fb-text">Save</span> keeps edits as a reversible library overlay — the song files aren\'t touched. <span class="text-fb-text">Write to file</span> bakes the title, artist, album and year into the pack (genre stays a library-only tag). Lock a field to keep an auto-match from changing it.</p>' +
             '</div>' +
             DETAIL_FIELDS.map(row).join('') +
             '<p data-df-status class="text-xs leading-relaxed"></p>' +
@@ -584,7 +629,7 @@
     async function writeToFile(body, song) {
         const st = song._detailsState;
         const fields = {};
-        for (const [f] of DETAIL_FIELDS) fields[f] = String(st[f].value || '').trim();
+        for (const f of WRITE_FIELDS) fields[f] = String(st[f].value || '').trim();
         const status = body.querySelector('[data-df-status]');
         const writeBtn = body.querySelector('[data-df-write]');
         const saveBtn = body.querySelector('[data-df-save]');
@@ -617,11 +662,11 @@
             const yr = /^[+-]?\d+$/.test(applied.year) ? parseInt(applied.year, 10) : 0;
             applied.year = yr ? String(yr) : '';
         }
-        for (const [f] of DETAIL_FIELDS) song[f] = applied[f];
+        for (const f of WRITE_FIELDS) song[f] = applied[f];
         try { window.feedBack?.emit('library:changed', { reason: 'write' }); } catch (_) { }
         if (persisted) {
             const clear = {};
-            for (const [f] of DETAIL_FIELDS) clear[f] = { value: null, locked: !!st[f].locked };
+            for (const f of WRITE_FIELDS) clear[f] = { value: null, locked: !!st[f].locked };
             try {
                 await fetch('/api/song/' + enc(song.filename) + '/overrides', {
                     method: 'PUT',
@@ -651,7 +696,7 @@
             '</div>';
         body.querySelector('[data-cover-open]')?.addEventListener('click', () => {
             if (window.__fbOpenImagePicker) {
-                window.__fbOpenImagePicker({ filename: song.filename, title: song.title || song.filename });
+                window.__fbOpenImagePicker({ filename: song.filename, title: song.title || song.filename, artist: song.artist, album: song.album });
             }
         });
     }
@@ -705,6 +750,7 @@
             btn.addEventListener('click', async () => {
                 const cand = cands[Number(btn.getAttribute('data-mr-cand'))];
                 if (!cand) return;
+                if (_single) { useTheseValues(song, cand); return; }   // popup → adopt into Details
                 await post('/api/enrichment/review/' + enc(song.filename) + '/pick',
                     { candidate: cand });
                 settle(song);
@@ -757,6 +803,7 @@
             btn.addEventListener('click', async () => {
                 const cand = cands[Number(btn.getAttribute('data-mr-cand'))];
                 if (!cand) return;
+                if (_single) { useTheseValues(song, cand); return; }   // popup → adopt into Details
                 await post('/api/enrichment/review/' + enc(song.filename) + '/pick',
                     { candidate: cand });
                 settle(song);

static/v3/onboarding-tour.js

@@ -42,7 +42,7 @@
                 id: 'instrument', shape: 'spotlight', position: 'bottom',
                 selector: '#v3-instrument-wrap', waitFor: '#v3-instrument-wrap',
                 title: 'Choose your instrument',
-                content: 'Set your instrument, string count and tuning here. The highway, tuner and scoring all adapt to this selection.',
+                content: 'Set your instrument, string count and tuning here — and if you play left-handed, flip Handedness to Left so the whole highway mirrors. The highway, tuner and scoring all adapt to this selection.',
             },
             {
                 id: 'tuner', shape: 'spotlight', position: 'bottom',

static/v3/songs.js

@@ -38,6 +38,9 @@
         // Mastery = best accuracy across arrangements (song_stats); unscored songs
         // sort last either way. Ascending surfaces what needs work; never default.
         ['mastery', 'Needs practice first'], ['mastery-desc', 'Most mastered first'],
+        // Personal difficulty (song_user_meta.user_difficulty, 1-5); unrated
+        // songs sort last either way.
+        ['difficulty', 'Difficulty (easiest first)'], ['difficulty-desc', 'Difficulty (hardest first)'],
     ];
     const FORMATS = [['', 'All formats'], ['sloppak', 'Feedpak'], ['loose', 'Folder']];
     const ARRANGEMENTS = ['Lead', 'Rhythm', 'Bass', 'Combo', 'Vocals'];
@@ -166,15 +169,15 @@
         const f = saved.filters;
         if (f && typeof f === 'object') {
             const arr = (x) => (Array.isArray(x) ? x.slice() : []);
-            // mastery + match are session-only facets (deliberately not
+            // mastery + match + genre are session-only facets (deliberately not
             // persisted), but the restored object must still CARRY the keys —
-            // the filter drawer indexes f.mastery/f.match unconditionally, so
-            // dropping them here breaks the drawer for anyone with saved prefs.
+            // the filter drawer indexes f.mastery/f.match/f.genre unconditionally,
+            // so dropping them here breaks the drawer for anyone with saved prefs.
             state.filters = {
                 arr_has: arr(f.arr_has), arr_lacks: arr(f.arr_lacks),
                 stem_has: arr(f.stem_has), stem_lacks: arr(f.stem_lacks),
                 lyrics: f.lyrics || '', tunings: arr(f.tunings),
-                mastery: [], match: [],
+                mastery: [], match: [], genre: [],
             };
         }
     }
@@ -515,15 +518,22 @@
             done:     ['bg-fb-good/90 text-black', '✓ Updated', ''],
             nochange: ['bg-black/60 text-fb-textDim', '— No match', ''],
             // Resting indicator: subtle, so a mostly-unmatched library isn't a
-            // wall of loud badges; points at the manual fix.
-            nomatch:  ['bg-black/60 text-fb-textDim', 'No match', 'No metadata match found — right-click to fix it by hand'],
+            // wall of loud badges. Clickable — a one-click handoff into the
+            // Fix-metadata popup for this song (see the [data-meta-fix] wiring).
+            nomatch:  ['bg-black/60 text-fb-textDim', 'No match', 'Click to fix the metadata by hand'],
         };
         const conf = M[st] || M.queued;
+        const fixable = st === 'nomatch';   // resting badge → opens Fix-metadata
         // top-10 clears the tuning chip (top-2) in both normal and select mode;
-        // z-20 sits it above the art. Non-interactive so it never eats a click.
-        return '<span class="v3-meta-tile absolute top-10 left-2 z-20 ' + conf[0] +
-            ' text-[0.5625rem] font-bold px-1.5 py-0.5 rounded-sm leading-tight pointer-events-none"' +
-            (conf[2] ? ' title="' + conf[2] + '"' : '') + '>' + conf[1] + '</span>';
+        // z-20 sits it above the art. Batch states are non-interactive; the
+        // resting "no match" badge is the handoff into the popup.
+        const cls = 'v3-meta-tile absolute top-10 left-2 z-20 ' + conf[0] +
+            ' text-[0.5625rem] font-bold px-1.5 py-0.5 rounded-sm leading-tight ' +
+            (fixable ? 'pointer-events-auto cursor-pointer hover:bg-fb-primary hover:text-white transition-colors' : 'pointer-events-none');
+        return '<span class="' + cls + '"' +
+            (fixable ? ' data-meta-fix="1"' : '') +
+            (conf[2] ? ' title="' + conf[2] + '"' : '') +
+            '>' + conf[1] + '</span>';
     }
 
     // After a song is scored, the badge for that card is stale until the next
@@ -1000,7 +1010,7 @@
             // the group's work_key/chart_count and pre-ticks the shown chart.)
             if (id === '__fixmatch') { if (window.__fbFixMatch) window.__fbFixMatch(playTarget); return; }
             if (id === '__cover') {
-                if (window.__fbOpenImagePicker) window.__fbOpenImagePicker({ filename: playTarget.filename, title: playTarget.title || playTarget.filename });
+                if (window.__fbOpenImagePicker) window.__fbOpenImagePicker({ filename: playTarget.filename, title: playTarget.title || playTarget.filename, artist: playTarget.artist, album: playTarget.album });
                 return;
             }
             if (id === '__refreshmeta') {
@@ -1467,6 +1477,13 @@
                 e.stopPropagation();
                 openChartsDrawer(e.currentTarget.getAttribute('data-charts'), song);
             });
+            // "No match" badge → straight into the Fix-metadata popup for this
+            // song (the batch → fix handoff). stopPropagation so it doesn't also
+            // trigger the card's play. Follows the displayed chart, like the menu.
+            el.querySelector('[data-meta-fix]')?.addEventListener('click', (e) => {
+                e.stopPropagation();
+                if (window.__fbFixMatch) window.__fbFixMatch(playTarget);
+            });
             // Artist line → the artist page (PR-B). In select mode the grid's
             // capture-phase toggle intercepts first, so selection still wins.
             el.querySelector('[data-v3-artist]')?.addEventListener('click', (e) => {
@@ -2807,7 +2824,7 @@
             '<div class="flex items-center justify-between"><h3 class="text-lg font-semibold text-fb-text">Filters</h3>' +
             '<button data-drawer-close class="text-fb-textDim hover:text-fb-text">✕</button></div>' +
             section('Arrangements', ARRANGEMENTS.map((a) => triPill('arr', a, a, triState(f.arr_has, f.arr_lacks, a))).join('')) +
-            section('Stems (sloppak)', STEMS.map((s) => triPill('stem', s, s, triState(f.stem_has, f.stem_lacks, s))).join('')) +
+            section('Stems (feedpak)', STEMS.map((s) => triPill('stem', s, s, triState(f.stem_has, f.stem_lacks, s))).join('')) +
             section('Lyrics', ['', '1', '0'].map((v) => '<button data-lyrics="' + v + '" class="px-2 py-1 rounded-md text-xs border ' + (f.lyrics === v ? 'bg-fb-primary text-white border-fb-primary' : 'bg-gray-800/50 text-fb-textDim border-gray-700') + '">' + (v === '' ? 'Any' : v === '1' ? 'Has lyrics' : 'No lyrics') + '</button>').join('')) +
             // Progress (mastery bands) — multi-select; server filters via song_stats.
             section('Progress', [['mastered', 'Mastered'], ['in_progress', 'In progress'], ['not_started', 'Not started']].map((it) => '<button data-mastery="' + it[0] + '" class="px-2 py-1 rounded-md text-xs border ' + (f.mastery.includes(it[0]) ? 'bg-fb-primary text-white border-fb-primary' : 'bg-gray-800/50 text-fb-textDim border-gray-700') + '">' + it[1] + '</button>').join('')) +
@@ -3112,7 +3129,7 @@
             // when image-picker.js isn't loaded.
             artWrap.addEventListener('click', () => {
                 if (window.__fbOpenImagePicker) {
-                    window.__fbOpenImagePicker({ filename: song.filename, title: song.title || song.filename });
+                    window.__fbOpenImagePicker({ filename: song.filename, title: song.title || song.filename, artist: song.artist, album: song.album });
                 } else {
                     artFile.click();
                 }

tests/conftest.py

@@ -9,6 +9,36 @@ import structlog
 _LOGGING_NAMES = ("feedBack", "uvicorn", "uvicorn.error", "uvicorn.access")
 
 
+@pytest.fixture(autouse=True)
+def _reset_enrichment_state():
+    """Reset the enrichment worker's process-global state between tests.
+
+    The `server` fixtures pop-and-reimport `server`, but `lib/enrichment.py`
+    (which now owns the worker) stays imported for the whole session, so its
+    module globals — the cancel Event, the status dict, the caches — would
+    otherwise leak across tests. A test that set `_enrich_cancel` (or a stale
+    `running` status) could silently short-circuit a later direct
+    `_background_enrich()` call. Clear it up front so each test starts clean.
+    """
+    try:
+        import enrichment
+    except ImportError:
+        yield
+        return
+    enrichment._enrich_cancel.clear()
+    enrichment._enrich_pending_pass = False
+    enrichment._enrich_status.update(
+        {"running": False, "processed": 0, "last_pass_at": None,
+         "total": 0, "matched": 0, "current": None})
+    enrichment._enrich_last_fetch = 0.0
+    enrichment._artist_alias_cache.clear()
+    # _caa_index_locks is deliberately left alone: it's guarded by
+    # _caa_index_locks_guard, so clearing it here (unlocked) would race a
+    # still-alive worker thread, and its entries are stateless per-release
+    # mutexes that don't leak test state anyway.
+    yield
+
+
 @pytest.fixture()
 def isolate_logging():
     """Restore feedBack / uvicorn logger state after each test.

tests/js/badges_handedness.test.js

@@ -0,0 +1,47 @@
+// Pins the onboarding handedness control: a Right/Left choice lives in the
+// instrument selector (the "Choose your instrument" onboarding step, which the
+// tour spotlights BEFORE the tuner/audio-calibration steps) and writes the
+// highway 'lefty' preference. Source-level, matching the other tests/js/
+// browser-heavy regression guards (the runtime path is DOM/WebGL-heavy).
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const ROOT = path.join(__dirname, '..', '..');
+const BADGES = fs.readFileSync(path.join(ROOT, 'static', 'v3', 'badges.js'), 'utf8');
+const TOUR = fs.readFileSync(path.join(ROOT, 'static', 'v3', 'onboarding-tour.js'), 'utf8');
+
+test('instrument selector offers a Handedness Right/Left choice', () => {
+    assert.match(BADGES, /instRow\('Handedness'/, 'a Handedness row must be in the instrument menu');
+    assert.match(BADGES, /pill\('hand',\s*'right'/, 'Right handedness pill');
+    assert.match(BADGES, /pill\('hand',\s*'left'/, 'Left handedness pill');
+});
+
+test('clicking a handedness pill writes the lefty preference from its value', () => {
+    assert.match(
+        BADGES,
+        /\[data-pill="hand"\][\s\S]*?_setLeftyPref\(\s*b\.getAttribute\('data-val'\)\s*===\s*'left'\s*\)/,
+        'the handedness click handler sets lefty from the pill value');
+});
+
+test('_setLeftyPref prefers highway.setLefty and falls back to the lefty localStorage key', () => {
+    const setter = BADGES.match(/function _setLeftyPref\(on\)\s*\{[\s\S]*?\n    \}/);
+    assert.ok(setter, '_setLeftyPref must exist');
+    assert.match(setter[0], /highway\.setLefty/, 'prefers highway.setLefty (flips a live highway + persists)');
+    assert.match(setter[0], /localStorage\.setItem\('lefty'/, 'falls back to the lefty localStorage key the highway reads on init');
+});
+
+test('_leftyPref reads highway.getLefty with a localStorage fallback', () => {
+    assert.match(
+        BADGES,
+        /function _leftyPref\(\)\s*\{[\s\S]*?getLefty[\s\S]*?localStorage\.getItem\('lefty'\)/,
+        '_leftyPref reads the current handedness with a storage fallback');
+});
+
+test('onboarding instrument step calls out left-handed players + the Handedness control', () => {
+    assert.match(TOUR, /Choose your instrument/);
+    assert.match(TOUR, /left-handed/i, 'the instrument step must call out left-handed players');
+    assert.match(TOUR, /Handedness/, 'and name the Handedness control');
+});

tests/js/beats_loaded.test.js

@@ -42,7 +42,7 @@ test('beats:loaded emit is wired into the WS beats case', () => {
     );
     assert.match(
         block,
-        /count:\s*beats\.length/,
+        /count:\s*hwState\.beats\.length/,
         'beats:loaded payload must include count = beats.length',
     );
 });

tests/js/editor_pending_view.test.js

@@ -0,0 +1,47 @@
+'use strict';
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const src = fs.readFileSync(path.join(__dirname, '..', '..', 'static', 'app.js'), 'utf8');
+const m = src.match(/\/\* @pure:editor-pending-view:start \*\/[\s\S]*?\/\* @pure:editor-pending-view:end \*\//);
+if (!m) throw new Error('pending-view helper block not found');
+
+const api = new Function('"use strict";' + m[0] + '\nreturn { _buildEditorPendingViewPure };')();
+
+test('edit-region handoff defaults cursor to region start and marks return path', () => {
+    const out = api._buildEditorPendingViewPure('song.sloppak', 2, { a: 12.5, b: 20 }, { returnToHighway: true });
+    assert.deepStrictEqual(out, {
+        filename: 'song.sloppak',
+        arrangement: 2,
+        barSel: { startTime: 12.5, endTime: 20 },
+        returnToHighway: true,
+        cursorTime: 12.5,
+    });
+});
+
+test('return-trip handoff preserves explicit viewport state', () => {
+    const out = api._buildEditorPendingViewPure('song.sloppak', 1, { a: 8, b: 14 }, {
+        scrollX: -4,
+        zoom: 160,
+        cursorTime: 9.25,
+    });
+    assert.deepStrictEqual(out, {
+        filename: 'song.sloppak',
+        arrangement: 1,
+        barSel: { startTime: 8, endTime: 14 },
+        cursorTime: 9.25,
+        scrollX: 0,
+        zoom: 160,
+    });
+});
+
+test('missing region still produces a stable pending view shell', () => {
+    const out = api._buildEditorPendingViewPure('song.sloppak', -1, null, {});
+    assert.deepStrictEqual(out, {
+        filename: 'song.sloppak',
+        arrangement: 0,
+        barSel: null,
+    });
+});

tests/js/handshapes_pipeline.test.js

@@ -33,7 +33,7 @@ test('handshapes WS case accumulates incoming chunks into handShapes', () => {
     const block = getCaseBlock(src, 'handshapes');
     assert.match(
         block,
-        /handShapes\s*=\s*handShapes\.concat\(\s*msg\.data\s*\)/,
+        /hwState\.handShapes\s*=\s*hwState\.handShapes\.concat\(\s*msg\.data\s*\)/,
         'handshapes case must concat msg.data into the handShapes accumulator',
     );
 });
@@ -62,7 +62,7 @@ test('bundle exposes handShapes to renderers with flat-list fallback', () => {
     const src = fs.readFileSync(HIGHWAY_JS, 'utf8');
     assert.match(
         src,
-        /\bhandShapes\s*[:=]\s*\([^)]*_filteredHandShapes[^)]*\)\s*\?\s*_filteredHandShapes\s*:\s*handShapes\b/,
+        /\bhandShapes\s*[:=]\s*\([^)]*hwState\._filteredHandShapes[^)]*\)\s*\?\s*hwState\._filteredHandShapes\s*:\s*hwState\.handShapes\b/,
         'bundle must expose handShapes with the _filteredHandShapes-vs-handShapes ternary fallback',
     );
 });

tests/js/highway_3d_context_loss.test.js

@@ -0,0 +1,45 @@
+// Contract test: 3D Highway WebGL context-loss recovery.
+//
+// Switching the active window / alt-tabbing (especially on Windows) can trigger
+// a GPU context reset. Without a handler the lost WebGL context escalates into a
+// render-process crash. The renderer owns its own WebGL canvas + heavy Three.js
+// lifecycle (too much to construct in a vm sandbox), so — like the other
+// highway_* source-contract tests here — this pins the wiring at the source
+// level: the loss must be preventDefault()'d (so the browser restores it), draw
+// must bail while lost, and the listeners must be torn down.
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const SCREEN_JS = path.join(__dirname, '..', '..', 'plugins', 'highway_3d', 'screen.js');
+const src = fs.readFileSync(SCREEN_JS, 'utf8');
+
+test('binds webglcontextlost + webglcontextrestored on the renderer canvas', () => {
+    assert.match(src, /ren\.domElement\.addEventListener\(\s*['"]webglcontextlost['"]/,
+        'must listen for webglcontextlost on ren.domElement (the WebGL canvas)');
+    assert.match(src, /ren\.domElement\.addEventListener\(\s*['"]webglcontextrestored['"]/,
+        'must listen for webglcontextrestored on ren.domElement');
+});
+
+test('the context-lost handler preventDefaults and pauses drawing', () => {
+    // Without preventDefault() the browser will not attempt to restore the
+    // context and the loss can escalate to a renderer crash.
+    const m = src.match(/_onCtxLost\s*=\s*\(e\)\s*=>\s*\{[\s\S]*?\};/);
+    assert.ok(m, '_onCtxLost handler must exist');
+    assert.match(m[0], /preventDefault\(\)/, 'context-lost handler must call preventDefault()');
+    assert.match(m[0], /_ctxLost\s*=\s*true/, 'context-lost handler must set _ctxLost = true');
+});
+
+test('draw() early-returns while the context is lost', () => {
+    assert.match(src, /draw\(bundle\)\s*\{[\s\S]*?if\s*\(_ctxLost\)\s*return;/,
+        'draw() must bail while _ctxLost is set so no GL work runs on a dead context');
+});
+
+test('teardown removes the context-loss listeners', () => {
+    assert.match(src, /removeEventListener\(\s*['"]webglcontextlost['"]/,
+        'teardown must remove the webglcontextlost listener');
+    assert.match(src, /removeEventListener\(\s*['"]webglcontextrestored['"]/,
+        'teardown must remove the webglcontextrestored listener');
+});

tests/js/highway_3d_lefty.test.js

@@ -20,7 +20,7 @@ function src(file) {
 test('highway renderer bundles surface the core lefty flag', () => {
     assert.match(
         src(HIGHWAY_JS),
-        /lefty\s*[:=]\s*_lefty/,
+        /lefty\s*[:=]\s*hwState\._lefty/,
         'custom renderer bundles must include lefty: _lefty',
     );
 });

tests/js/highway_3d_smooth_clock_pause.test.js

@@ -49,12 +49,12 @@ test('core _makeBundle exposes isPlaying derived from the chart-clock anchor', (
     // within the interp cap.
     assert.match(
         fn,
-        /isPlaying\s*[:=]\s*!Number\.isNaN\(\s*_chartAnchorPerfNow\s*\)/,
+        /isPlaying\s*[:=]\s*!Number\.isNaN\(\s*hwState\._chartAnchorPerfNow\s*\)/,
         'isPlaying must gate on a live anchor (_chartAnchorPerfNow not NaN)',
     );
     assert.match(
         fn,
-        /_chartLastAdvanceAt\s*\)\s*<=\s*_CHART_MAX_INTERP_MS/,
+        /hwState\._chartLastAdvanceAt\s*\)\s*<=\s*_CHART_MAX_INTERP_MS/,
         'isPlaying must require the clock advanced within _CHART_MAX_INTERP_MS',
     );
 });

tests/js/highway_adaptive_scale.test.js

@@ -29,7 +29,7 @@ function extractBlock(src, signature) {
 
 test('highway declares adaptive-scale state with a floor', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
-    assert.match(src, /let\s+_autoScale\s*=\s*1/, 'missing _autoScale multiplier');
+    assert.match(src, /hwState\._autoScale\s*=\s*1/, 'missing _autoScale multiplier');
     assert.match(src, /const\s+_AUTO_SCALE_MIN\s*=\s*0?\.25/, 'missing _AUTO_SCALE_MIN floor (0.25)');
     assert.match(src, /const\s+_DRAW_BUDGET_HI_MS\s*=\s*\d+/, 'missing high draw budget');
     assert.match(src, /const\s+_DRAW_BUDGET_LO_MS\s*=\s*\d+/, 'missing low draw budget');
@@ -49,18 +49,18 @@ test('_effectiveRenderScale clamps user ceiling * auto factor to [MIN, 1]', () =
 test('min render scale floor is user-configurable + exposed on the api (#654)', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
     // Hard floor constant kept; configurable floor read from localStorage.
-    assert.match(src, /let\s+_autoScaleMin\s*=/, 'missing configurable _autoScaleMin');
+    assert.match(src, /hwState\._autoScaleMin\s*=/, 'missing configurable _autoScaleMin');
     assert.match(src, /localStorage\.getItem\('highwayMinRenderScale'\)/,
         'configurable floor must load from localStorage.highwayMinRenderScale');
     assert.match(src, /setMinRenderScale\(/, 'api.setMinRenderScale missing');
-    assert.match(src, /getMinRenderScale\(\)\s*\{\s*return\s+_autoScaleMin/, 'api.getMinRenderScale missing');
+    assert.match(src, /getMinRenderScale\(\)\s*\{\s*return\s+hwState\._autoScaleMin/, 'api.getMinRenderScale missing');
     // Floor is clamped to the user ceiling so it can never exceed the manual cap.
     const eff = extractBlock(src, 'function _effectiveRenderScale()');
-    assert.match(eff, /Math\.min\(\s*_autoScaleMin\s*,\s*user\s*\)/,
+    assert.match(eff, /Math\.min\(\s*hwState\._autoScaleMin\s*,\s*user\s*\)/,
         'effective scale must clamp the floor to the user ceiling');
     // _adaptRenderScale must cap the lo bound at 1 so _autoScale stays in [_,1].
     const adapt = extractBlock(src, 'function _adaptRenderScale(');
-    assert.match(adapt, /Math\.min\(\s*1\s*,\s*_autoScaleMin\s*\/\s*_renderScale\s*\)/,
+    assert.match(adapt, /Math\.min\(\s*1\s*,\s*hwState\._autoScaleMin\s*\/\s*hwState\._renderScale\s*\)/,
         'lo bound must be capped at 1 to keep _autoScale a [0,1] multiplier');
 });
 

tests/js/highway_chord_render_cache.test.js

@@ -34,9 +34,9 @@ test('_ensureChordRenderCache keys off src, _inverted, AND chordTemplates', () =
     const neqEither = (a, b) => new RegExp(
         `\\b${a}\\b\\s*!==\\s*\\b${b}\\b|\\b${b}\\b\\s*!==\\s*\\b${a}\\b`
     );
-    assert.match(src, eqEither('_chordRenderCacheSrc', 'src'), 'cache must key on src');
-    assert.match(src, eqEither('_chordRenderCacheInverted', '_inverted'), 'cache must key on _inverted');
-    assert.match(src, neqEither('_chordRenderCacheTemplates', 'chordTemplates'),
+    assert.match(src, eqEither('hwState\\._chordRenderCacheSrc', 'src'), 'cache must key on src');
+    assert.match(src, eqEither('hwState\\._chordRenderCacheInverted', 'hwState\\._inverted'), 'cache must key on _inverted');
+    assert.match(src, neqEither('hwState\\._chordRenderCacheTemplates', 'hwState\\.chordTemplates'),
         'cache must key on chordTemplates (detected via !== for change-flag)');
 });
 
@@ -50,9 +50,9 @@ test('chordTemplates change resets fretline preview and frame-mismatch warner',
     // block inside the `if (templatesChanged) { … }` branch (e.g. an
     // inner conditional reset) doesn't break the match by introducing
     // a `}` before the symbol we're checking for.
-    assert.match(src, /if\s*\(\s*templatesChanged\s*\)\s*\{[\s\S]*?_chordFretLineNotes\s*=\s*\[\][\s\S]*?\}/,
+    assert.match(src, /if\s*\(\s*templatesChanged\s*\)\s*\{[\s\S]*?hwState\._chordFretLineNotes\s*=\s*\[\][\s\S]*?\}/,
         'templatesChanged branch must reset _chordFretLineNotes');
-    assert.match(src, /if\s*\(\s*templatesChanged\s*\)\s*\{[\s\S]*?_lastChordOnFretLine\s*=\s*null[\s\S]*?\}/,
+    assert.match(src, /if\s*\(\s*templatesChanged\s*\)\s*\{[\s\S]*?hwState\._lastChordOnFretLine\s*=\s*null[\s\S]*?\}/,
         'templatesChanged branch must null _lastChordOnFretLine');
     assert.match(src, /if\s*\(\s*templatesChanged\s*\)\s*\{[\s\S]*?_frameMismatchWarned\.clear\(\)[\s\S]*?\}/,
         'templatesChanged branch must clear _frameMismatchWarned');

tests/js/highway_filtered_notes.test.js

@@ -23,7 +23,7 @@ test('getFilteredNotes falls through to notes when _filteredNotes is null', () =
     const src = fs.readFileSync(highwayJs, 'utf8');
     assert.match(
         src,
-        /getFilteredNotes\s*\(\s*\)\s*\{[^}]*_filteredNotes[^}]*:\s*notes/,
+        /getFilteredNotes\s*\(\s*\)\s*\{[^}]*_filteredNotes[^}]*:\s*hwState\.notes/,
         'getFilteredNotes must return notes as fallback',
     );
 });
@@ -41,7 +41,7 @@ test('getFilteredChords falls through to chords when _filteredChords is null', (
     const src = fs.readFileSync(highwayJs, 'utf8');
     assert.match(
         src,
-        /getFilteredChords\s*\(\s*\)\s*\{[^}]*_filteredChords[^}]*:\s*chords/,
+        /getFilteredChords\s*\(\s*\)\s*\{[^}]*_filteredChords[^}]*:\s*hwState\.chords/,
         'getFilteredChords must return chords as fallback',
     );
 });

tests/js/highway_monotonic_clock.test.js

@@ -35,7 +35,10 @@ function extractBlock(src, signature) {
 // + getTime methods so behavioral tests can exercise the real
 // implementation in isolation.
 function buildClockSandbox(perfNowImpl) {
-    const sandbox = {
+    // The lifted per-instance state now lives on `hwState` (the R3c H lift);
+    // the extracted setTime/getTime bodies reference hwState.<slot>. The const
+    // _CHART_MAX_INTERP_MS was NOT lifted, so it stays a top-level global here.
+    const hwState = {
         chartTime: 0,
         currentTime: 0,
         avOffsetSec: 0,
@@ -50,6 +53,9 @@ function buildClockSandbox(perfNowImpl) {
         _chartAnchorPerfNow: NaN,
         _chartLastAdvanceAt: 0,
         _chartObservedRate: 1,
+    };
+    const sandbox = {
+        hwState,
         _CHART_MAX_INTERP_MS: 100,
         performance: { now: perfNowImpl },
     };
@@ -72,10 +78,10 @@ test('highway declares chart anchor + stall-detect + rate state', () => {
     // particular MUST start as NaN, not 0, otherwise setTime(0) on the
     // very first 60 Hz tick fails the `t !== _chartAnchorAudioT` check
     // and never re-anchors, leaving the clock uninitialized.
-    assert.match(src, /let\s+_chartAnchorAudioT\s*=\s*NaN/, 'missing _chartAnchorAudioT (NaN sentinel)');
-    assert.match(src, /let\s+_chartAnchorPerfNow\s*=\s*NaN/, 'missing _chartAnchorPerfNow (NaN sentinel)');
-    assert.match(src, /let\s+_chartLastAdvanceAt\s*=\s*0/, 'missing _chartLastAdvanceAt (pause detection)');
-    assert.match(src, /let\s+_chartObservedRate\s*=\s*1/, 'missing _chartObservedRate (playback rate awareness)');
+    assert.match(src, /hwState\._chartAnchorAudioT\s*=\s*NaN/, 'missing _chartAnchorAudioT (NaN sentinel)');
+    assert.match(src, /hwState\._chartAnchorPerfNow\s*=\s*NaN/, 'missing _chartAnchorPerfNow (NaN sentinel)');
+    assert.match(src, /hwState\._chartLastAdvanceAt\s*=\s*0/, 'missing _chartLastAdvanceAt (pause detection)');
+    assert.match(src, /hwState\._chartObservedRate\s*=\s*1/, 'missing _chartObservedRate (playback rate awareness)');
     assert.match(src, /const\s+_CHART_MAX_INTERP_MS\s*=\s*100/, 'missing _CHART_MAX_INTERP_MS cap');
 });
 
@@ -86,7 +92,7 @@ test('getTime scales interpolation by _chartObservedRate (speed-slider safe)', (
     const slice = m[0];
     assert.match(
         slice,
-        /_chartObservedRate\s*\*\s*elapsedMs/,
+        /hwState\._chartObservedRate\s*\*\s*elapsedMs/,
         'getTime must scale interpolation by observed rate so audio.playbackRate != 1 stays accurate',
     );
 });
@@ -100,12 +106,12 @@ test('setTime re-anchors and updates _chartLastAdvanceAt only when t actually ch
     // The implementation may capture performance.now() into a local
     // (e.g. newPerfNow) and assign that to both fields; accept either
     // direct or via-local writes.
-    const m = src.match(/if\s*\(\s*t\s*!==\s*_chartAnchorAudioT\s*\)\s*\{[\s\S]+?\}\s*\},/);
+    const m = src.match(/if\s*\(\s*t\s*!==\s*hwState\._chartAnchorAudioT\s*\)\s*\{[\s\S]+?\}\s*\},/);
     assert.ok(m, 'if (t !== _chartAnchorAudioT) block not found inside setTime');
     const block = m[0];
-    assert.match(block, /_chartAnchorAudioT\s*=\s*t/, 'must assign _chartAnchorAudioT = t');
-    assert.match(block, /_chartAnchorPerfNow\s*=/, 'must assign _chartAnchorPerfNow');
-    assert.match(block, /_chartLastAdvanceAt\s*=/, 'must assign _chartLastAdvanceAt');
+    assert.match(block, /hwState\._chartAnchorAudioT\s*=\s*t/, 'must assign _chartAnchorAudioT = t');
+    assert.match(block, /hwState\._chartAnchorPerfNow\s*=/, 'must assign _chartAnchorPerfNow');
+    assert.match(block, /hwState\._chartLastAdvanceAt\s*=/, 'must assign _chartLastAdvanceAt');
 });
 
 test('getTime falls back to chartTime when audio has stalled (paused)', () => {
@@ -119,7 +125,7 @@ test('getTime falls back to chartTime when audio has stalled (paused)', () => {
     // Must check stall-since-last-advance against the cap.
     assert.match(
         slice,
-        /nowP\s*-\s*_chartLastAdvanceAt\s*>\s*_CHART_MAX_INTERP_MS/,
+        /nowP\s*-\s*hwState\._chartLastAdvanceAt\s*>\s*_CHART_MAX_INTERP_MS/,
         'getTime must short-circuit when audio has stalled past the cap',
     );
     // Must interpolate when active.
@@ -127,7 +133,7 @@ test('getTime falls back to chartTime when audio has stalled (paused)', () => {
     // Rate-scaled formula: _chartAnchorAudioT + (_chartObservedRate * elapsedMs) / 1000
     assert.match(
         slice,
-        /_chartAnchorAudioT\s*\+\s*\(\s*_chartObservedRate\s*\*\s*elapsedMs\s*\)\s*\/\s*1000/,
+        /_chartAnchorAudioT\s*\+\s*\(\s*hwState\._chartObservedRate\s*\*\s*elapsedMs\s*\)\s*\/\s*1000/,
         'getTime must compute anchor + rate-scaled elapsed during play',
     );
 });
@@ -138,10 +144,10 @@ test('api.stop() clears the chart anchor state so re-init starts fresh', () => {
     // the actual stop() body — a fixed-size slice would falsely match
     // resets that landed in an adjacent method.
     const stopBlock = extractBlock(src, 'stop() {');
-    assert.match(stopBlock, /_chartAnchorAudioT\s*=\s*NaN/, 'stop() must reset _chartAnchorAudioT to the NaN sentinel');
-    assert.match(stopBlock, /_chartAnchorPerfNow\s*=\s*NaN/, 'stop() must reset _chartAnchorPerfNow to the NaN sentinel');
-    assert.match(stopBlock, /_chartLastAdvanceAt\s*=\s*0/, 'stop() must reset _chartLastAdvanceAt');
-    assert.match(stopBlock, /_chartObservedRate\s*=\s*1/, 'stop() must reset _chartObservedRate to 1x');
+    assert.match(stopBlock, /hwState\._chartAnchorAudioT\s*=\s*NaN/, 'stop() must reset _chartAnchorAudioT to the NaN sentinel');
+    assert.match(stopBlock, /hwState\._chartAnchorPerfNow\s*=\s*NaN/, 'stop() must reset _chartAnchorPerfNow to the NaN sentinel');
+    assert.match(stopBlock, /hwState\._chartLastAdvanceAt\s*=\s*0/, 'stop() must reset _chartLastAdvanceAt');
+    assert.match(stopBlock, /hwState\._chartObservedRate\s*=\s*1/, 'stop() must reset _chartObservedRate to 1x');
 });
 
 // ── Behavioral tests (run extracted setTime/getTime in vm sandbox) ──────
@@ -195,12 +201,12 @@ test('behavior: seek discontinuity resets observed rate to 1x', () => {
     sb.setTime(10);
     now = 50;
     sb.setTime(10.025); // observed rate ≈ 0.5
-    assert.ok(Math.abs(sb._chartObservedRate - 0.5) < 0.001, `prior segment must measure ≈0.5, got ${sb._chartObservedRate}`);
+    assert.ok(Math.abs(sb.hwState._chartObservedRate - 0.5) < 0.001, `prior segment must measure ≈0.5, got ${sb.hwState._chartObservedRate}`);
     // Seek: large t jump in same perf delta — observed-rate clamp
     // rejects this segment, resets to 1.
     now = 70;
     sb.setTime(120); // dPerf=20ms, dT=110s → observed=5500 (out of clamp)
-    assert.equal(sb._chartObservedRate, 1, 'seek must reset rate to 1x');
+    assert.equal(sb.hwState._chartObservedRate, 1, 'seek must reset rate to 1x');
 });
 
 test('behavior: getTime caps interpolation at _CHART_MAX_INTERP_MS', () => {
@@ -225,8 +231,8 @@ test('behavior: setTime(0) on first tick anchors correctly (boot edge case)', ()
     const sb = buildClockSandbox(() => now);
     sb.setTime(0);
     // Anchor must now be initialized.
-    assert.equal(sb._chartAnchorAudioT, 0, 'setTime(0) on first tick must set anchor.audioT');
-    assert.equal(sb._chartAnchorPerfNow, 16, 'setTime(0) on first tick must set anchor.perfNow');
+    assert.equal(sb.hwState._chartAnchorAudioT, 0, 'setTime(0) on first tick must set anchor.audioT');
+    assert.equal(sb.hwState._chartAnchorPerfNow, 16, 'setTime(0) on first tick must set anchor.perfNow');
     // getTime should return a finite value, not NaN.
     const t = sb.getTime();
     assert.ok(!Number.isNaN(t), `getTime must not return NaN after setTime(0); got ${t}`);
@@ -252,10 +258,10 @@ test('behavior: long anchor gap resets observed rate to 1x', () => {
     sb.setTime(10);
     now = 50;
     sb.setTime(10.025); // observed rate ≈ 0.5
-    assert.ok(Math.abs(sb._chartObservedRate - 0.5) < 0.001, 'first segment measured 0.5x');
+    assert.ok(Math.abs(sb.hwState._chartObservedRate - 0.5) < 0.001, 'first segment measured 0.5x');
     // Long gap (1 second) before next setTime — out of the dPerf < 0.5
     // window, so the rate must reset to 1.
     now = 1100;
     sb.setTime(10.5);
-    assert.equal(sb._chartObservedRate, 1, 'long anchor gap must reset rate to 1x');
+    assert.equal(sb.hwState._chartObservedRate, 1, 'long anchor gap must reset rate to 1x');
 });

tests/js/highway_note_state.test.js

@@ -34,16 +34,16 @@ function extractBlock(src, signature) {
 
 test('highway declares the note-state provider slot', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
-    assert.match(src, /let\s+_noteStateProvider\s*=\s*null/, 'missing _noteStateProvider (provider slot, null = none)');
+    assert.match(src, /hwState\._noteStateProvider\s*=\s*null/, 'missing _noteStateProvider (provider slot, null = none)');
 });
 
 test('public API exposes setNoteStateProvider / getNoteStateProvider / getNoteState / isDefaultRenderer', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
-    assert.match(src, /setNoteStateProvider\s*\(\s*fn\s*\)\s*\{[^}]*_noteStateProvider\s*=/, 'setNoteStateProvider must assign _noteStateProvider');
+    assert.match(src, /setNoteStateProvider\s*\(\s*fn\s*\)\s*\{[^}]*hwState\._noteStateProvider\s*=/, 'setNoteStateProvider must assign _noteStateProvider');
     assert.match(src, /setNoteStateProvider\s*\(\s*fn\s*\)\s*\{[^}]*typeof\s+fn\s*===\s*['"]function['"][^}]*:\s*null/, 'setNoteStateProvider must coerce non-functions (incl. null) to null');
-    assert.match(src, /getNoteStateProvider\s*\(\s*\)\s*\{\s*return\s+_noteStateProvider/, 'getNoteStateProvider must return the slot');
+    assert.match(src, /getNoteStateProvider\s*\(\s*\)\s*\{\s*return\s+hwState\._noteStateProvider/, 'getNoteStateProvider must return the slot');
     assert.match(src, /getNoteState\s*\(\s*note\s*,\s*chartTime\s*\)\s*\{\s*return\s+_noteState\s*\(/, 'getNoteState must delegate to _noteState');
-    assert.match(src, /isDefaultRenderer\s*\(\s*\)\s*\{\s*return\s+_renderer\s*===\s*_defaultRenderer\s*\|\|\s*_renderer\s*==\s*null/, 'isDefaultRenderer must be (_renderer === _defaultRenderer || _renderer == null)');
+    assert.match(src, /isDefaultRenderer\s*\(\s*\)\s*\{\s*return\s+hwState\._renderer\s*===\s*_defaultRenderer\s*\|\|\s*hwState\._renderer\s*==\s*null/, 'isDefaultRenderer must be (_renderer === _defaultRenderer || _renderer == null)');
 });
 
 test('_makeBundle exposes getNoteState (stable reference, no per-frame alloc)', () => {
@@ -72,7 +72,7 @@ test('_makeBundle exposes getNoteStateProvider as a stable reference (feedBack#2
     // slot, so renderers see a live "is a provider registered?" view.
     assert.match(
         src,
-        /function\s+_getNoteStateProvider\s*\(\s*\)\s*\{\s*return\s+_noteStateProvider\s*;?\s*\}/,
+        /function\s+_getNoteStateProvider\s*\(\s*\)\s*\{\s*return\s+hwState\._noteStateProvider\s*;?\s*\}/,
         '_getNoteStateProvider must be defined as a stable named function returning _noteStateProvider'
     );
 });
@@ -80,7 +80,7 @@ test('_makeBundle exposes getNoteStateProvider as a stable reference (feedBack#2
 test('_noteState normalizes provider output as documented', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
     const fn = extractBlock(src, 'function _noteState(note, chartTime)');
-    assert.match(fn, /if\s*\(\s*!_noteStateProvider\s*\)\s*return\s+null/, 'must short-circuit when no provider is registered');
+    assert.match(fn, /if\s*\(\s*!hwState\._noteStateProvider\s*\)\s*return\s+null/, 'must short-circuit when no provider is registered');
     assert.match(fn, /try\s*\{[\s\S]*_noteStateProvider\s*\([\s\S]*catch[\s\S]*return\s+null/, 'must call the provider inside try/catch and return null on throw');
     assert.match(fn, /state\s*!==\s*['"]hit['"]\s*&&\s*state\s*!==\s*['"]active['"]\s*&&\s*state\s*!==\s*['"]miss['"]/, 'must reject states other than hit/active/miss');
     assert.match(fn, /Math\.max\(\s*0\s*,\s*Math\.min\(\s*1\s*,\s*raw\.alpha\s*\)\s*\)/, 'must clamp alpha to [0,1]');

tests/js/highway_pause_throttle.test.js

@@ -32,7 +32,7 @@ function extractBlock(src, signature) {
 test('highway declares the paused-render throttle state', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
     assert.match(src, /const\s+_PAUSED_FRAME_INTERVAL_MS\s*=\s*\d+/, 'missing _PAUSED_FRAME_INTERVAL_MS cap');
-    assert.match(src, /let\s+_lastPausedDrawAt\s*=\s*0/, 'missing _lastPausedDrawAt accumulator');
+    assert.match(src, /hwState\._lastPausedDrawAt\s*=\s*0/, 'missing _lastPausedDrawAt accumulator');
 });
 
 test('draw() throttles full renders while the audio clock is stalled', () => {
@@ -42,7 +42,7 @@ test('draw() throttles full renders while the audio clock is stalled', () => {
     assert.match(fn, /_chartLastAdvanceAt/, 'throttle must key off _chartLastAdvanceAt (the advance timestamp)');
     assert.match(fn, /_CHART_MAX_INTERP_MS/, 'throttle must reuse the _CHART_MAX_INTERP_MS pause threshold');
     assert.match(fn, /_PAUSED_FRAME_INTERVAL_MS/, 'throttle must cap paused draws to _PAUSED_FRAME_INTERVAL_MS');
-    assert.match(fn, /_lastPausedDrawAt\s*=\s*_nowP/, 'throttle must record the last paused draw time');
+    assert.match(fn, /hwState\._lastPausedDrawAt\s*=\s*_nowP/, 'throttle must record the last paused draw time');
 });
 
 test('throttle runs after the ready gate, before bundle/draw', () => {
@@ -51,7 +51,7 @@ test('throttle runs after the ready gate, before bundle/draw', () => {
     // Regex landmarks (not exact-string indexOf) so harmless spacing /
     // semicolon changes don't break the ordering guard — matches the
     // search-based style of the other highway source-guard tests.
-    const readyIdx = fn.search(/if\s*\(\s*!ready\s*\)\s*return;/);
+    const readyIdx = fn.search(/if\s*\(\s*!hwState\.ready\s*\)\s*return;/);
     const throttleIdx = fn.search(/_PAUSED_FRAME_INTERVAL_MS/);
     const drawIdx = fn.search(/_renderer\.draw\s*\(/);
     assert.ok(readyIdx !== -1, 'ready gate not found');

tests/js/highway_phrases.test.js

@@ -22,7 +22,7 @@ test('getPhrases returns null when _phrases is falsy or empty', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
     assert.match(
         src,
-        /getPhrases\s*\(\s*\)\s*\{[^}]*!\s*_phrases[^}]*return null/,
+        /getPhrases\s*\(\s*\)\s*\{[^}]*!\s*hwState\._phrases[^}]*return null/,
         'getPhrases must return null when no phrase data is available',
     );
 });

tests/js/highway_renderer_swap_canvas_reset.test.js

@@ -44,9 +44,9 @@ test('_setRenderer captures the outgoing renderer before overwriting it', () =>
     // prev must be captured BEFORE _destroyCurrentIfInited and the
     // `_renderer = next` assignment, otherwise the swap detection below
     // would always compare next against itself.
-    const prevIdx = fn.search(/const\s+prev\s*=\s*_renderer/);
+    const prevIdx = fn.search(/const\s+prev\s*=\s*hwState\._renderer/);
     const destroyIdx = fn.search(/_destroyCurrentIfInited\(\)/);
-    const assignIdx = fn.search(/^\s*_renderer\s*=\s*next\s*;/m);
+    const assignIdx = fn.search(/^\s*hwState\._renderer\s*=\s*next\s*;/m);
     assert.ok(prevIdx !== -1, 'must capture `const prev = _renderer`');
     assert.ok(destroyIdx !== -1, 'must call _destroyCurrentIfInited');
     assert.ok(assignIdx !== -1, 'must assign `_renderer = next`');
@@ -67,7 +67,7 @@ test('_setRenderer replaces the canvas on a context-type change OR a viz change'
     );
     assert.match(
         fn,
-        /if\s*\(\s*nextType\s*!==\s*_currentCanvasContextType\s*\|\|\s*_vizChanged\s*\)\s*\{\s*_replaceCanvas\(nextType\)/,
+        /if\s*\(\s*nextType\s*!==\s*hwState\._currentCanvasContextType\s*\|\|\s*_vizChanged\s*\)\s*\{\s*_replaceCanvas\(nextType\)/,
         'replace guard must be `nextType !== _currentCanvasContextType || _vizChanged`',
     );
 });

tests/js/highway_string_colors.test.js

@@ -40,20 +40,20 @@ test('2D palette arrays are mutable (let) with frozen DEFAULT_* originals', () =
     assert.match(src, /const\s+DEFAULT_STRING_COLORS\s*=/, 'DEFAULT_STRING_COLORS must exist for reset');
     assert.match(src, /const\s+DEFAULT_STRING_DIM\s*=/, 'DEFAULT_STRING_DIM must exist for reset');
     assert.match(src, /const\s+DEFAULT_STRING_BRIGHT\s*=/, 'DEFAULT_STRING_BRIGHT must exist for reset');
-    assert.match(src, /let\s+STRING_COLORS\s*=\s*DEFAULT_STRING_COLORS\.slice\(\)/, 'STRING_COLORS must be a mutable copy of the defaults');
-    assert.match(src, /let\s+STRING_DIM\s*=\s*DEFAULT_STRING_DIM\.slice\(\)/, 'STRING_DIM must be a mutable copy of the defaults');
-    assert.match(src, /let\s+STRING_BRIGHT\s*=\s*DEFAULT_STRING_BRIGHT\.slice\(\)/, 'STRING_BRIGHT must be a mutable copy of the defaults');
+    assert.match(src, /hwState\.STRING_COLORS\s*=\s*DEFAULT_STRING_COLORS\.slice\(\)/, 'STRING_COLORS must be a mutable copy of the defaults');
+    assert.match(src, /hwState\.STRING_DIM\s*=\s*DEFAULT_STRING_DIM\.slice\(\)/, 'STRING_DIM must be a mutable copy of the defaults');
+    assert.match(src, /hwState\.STRING_BRIGHT\s*=\s*DEFAULT_STRING_BRIGHT\.slice\(\)/, 'STRING_BRIGHT must be a mutable copy of the defaults');
 });
 
 test('2D public API exposes getStringColors / setStringColors', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
-    assert.match(src, /getStringColors\s*\(\s*\)\s*\{\s*return\s+STRING_COLORS\.slice\(\)/, 'getStringColors must return a copy');
+    assert.match(src, /getStringColors\s*\(\s*\)\s*\{\s*return\s+hwState\.STRING_COLORS\.slice\(\)/, 'getStringColors must return a copy');
     const fn = extractBlock(src, 'setStringColors(arr)');
     // Each provided index sets base + derived dim/bright; missing → default.
-    assert.match(fn, /STRING_COLORS\[i\]\s*=\s*base/, 'setStringColors must set the base color');
-    assert.match(fn, /STRING_DIM\[i\]\s*=\s*_darken\(/, 'setStringColors must derive the dim variant');
-    assert.match(fn, /STRING_BRIGHT\[i\]\s*=\s*_lighten\(/, 'setStringColors must derive the bright variant');
-    assert.match(fn, /STRING_COLORS\[i\]\s*=\s*DEFAULT_STRING_COLORS\[i\]/, 'setStringColors must restore defaults for missing/invalid indices');
+    assert.match(fn, /hwState\.STRING_COLORS\[i\]\s*=\s*base/, 'setStringColors must set the base color');
+    assert.match(fn, /hwState\.STRING_DIM\[i\]\s*=\s*_darken\(/, 'setStringColors must derive the dim variant');
+    assert.match(fn, /hwState\.STRING_BRIGHT\[i\]\s*=\s*_lighten\(/, 'setStringColors must derive the bright variant');
+    assert.match(fn, /hwState\.STRING_COLORS\[i\]\s*=\s*DEFAULT_STRING_COLORS\[i\]/, 'setStringColors must restore defaults for missing/invalid indices');
 });
 
 // ── 3D highway (plugins/highway_3d/screen.js) ─────────────────────────────

tests/js/highway_visibility.test.js

@@ -32,14 +32,14 @@ function extractBlock(src, signature) {
 
 test('highway declares visibility state (_visibleOverride + _lastVisible)', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
-    assert.match(src, /let\s+_visibleOverride\s*=\s*null/, 'missing _visibleOverride (override sentinel)');
-    assert.match(src, /let\s+_lastVisible\s*=\s*null/, 'missing _lastVisible (last-emitted state)');
+    assert.match(src, /hwState\._visibleOverride\s*=\s*null/, 'missing _visibleOverride (override sentinel)');
+    assert.match(src, /hwState\._lastVisible\s*=\s*null/, 'missing _lastVisible (last-emitted state)');
 });
 
 test('_isHighwayVisible respects _visibleOverride and falls back to offsetParent', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
     const fn = extractBlock(src, 'function _isHighwayVisible()');
-    assert.match(fn, /_visibleOverride\s*!==\s*null/, 'must check the override before the DOM');
+    assert.match(fn, /hwState\._visibleOverride\s*!==\s*null/, 'must check the override before the DOM');
     assert.match(fn, /canvas\.offsetParent\s*!==\s*null/, 'DOM fallback must use offsetParent !== null');
 });
 
@@ -47,9 +47,9 @@ test('_emitVisibilityIfChanged is transition-only (no per-frame spam)', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
     const fn = extractBlock(src, 'function _emitVisibilityIfChanged()');
     // Must short-circuit when the current state equals the cached one.
-    assert.match(fn, /v\s*===\s*_lastVisible/, 'must compare current vs _lastVisible and bail when equal');
+    assert.match(fn, /v\s*===\s*hwState\._lastVisible/, 'must compare current vs _lastVisible and bail when equal');
     // Must update the cache and emit the event with the documented payload shape.
-    assert.match(fn, /_lastVisible\s*=\s*v/, 'must update _lastVisible after a transition');
+    assert.match(fn, /hwState\._lastVisible\s*=\s*v/, 'must update _lastVisible after a transition');
     assert.match(
         fn,
         /window\.feedBack\.emit\(\s*['"]highway:visibility['"][\s\S]*?visible:\s*v[\s\S]*?canvas/,
@@ -66,7 +66,7 @@ test('rAF draw() loop calls _emitVisibilityIfChanged and skips when hidden', ()
     // transitions during loading/reconnect windows still propagate.
     const emitIdx = fn.search(/_emitVisibilityIfChanged\(\)/);
     const skipIdx = fn.search(/if\s*\(\s*!_rendering\s*\)\s*return/);
-    const readyIdx = fn.search(/if\s*\(\s*!ready\s*\)\s*return/);
+    const readyIdx = fn.search(/if\s*\(\s*!hwState\.ready\s*\)\s*return/);
     const drawIdx = fn.search(/_renderer\.draw\(/);
     assert.ok(emitIdx !== -1 && skipIdx !== -1 && readyIdx !== -1 && drawIdx !== -1, 'all four landmarks must be present');
     assert.ok(emitIdx < readyIdx, 'emit must run BEFORE the !ready gate (transitions during loading must still fire)');
@@ -84,19 +84,19 @@ test('draw() keeps an active custom renderer painting through an override-hide (
     const src = fs.readFileSync(highwayJs, 'utf8');
     const fn = extractBlock(src, 'function draw()');
     // Single render decision drives both the perf-HUD reset and the gate.
-    assert.match(fn, /let\s+_rendering\s*=\s*_lastVisible/, 'must derive a single _rendering decision from _lastVisible');
+    assert.match(fn, /let\s+_rendering\s*=\s*hwState\._lastVisible/, 'must derive a single _rendering decision from _lastVisible');
     // Assert the exact boolean RELATIONSHIP, not just the tokens (CodeRabbit):
     // the exemption must AND together override-hide, an active custom renderer,
     // and the canvas still in layout. A weakened guard (e.g. `||`, or a dropped
     // offsetParent clause) must fail this — that's the regression being fixed.
     assert.match(
         fn,
-        /!_rendering\s*&&\s*_visibleOverride\s*===\s*false\s*&&\s*_renderer\s*!==\s*_defaultRenderer\s*&&\s*canvas\s*&&\s*canvas\.offsetParent\s*!==\s*null/,
+        /!_rendering\s*&&\s*hwState\._visibleOverride\s*===\s*false\s*&&\s*hwState\._renderer\s*!==\s*_defaultRenderer\s*&&\s*hwState\.canvas\s*&&\s*hwState\.canvas\.offsetParent\s*!==\s*null/,
         'exemption must AND override-hide + active custom renderer + canvas-in-layout (genuine off-screen still pauses, #246)',
     );
     // Both the HUD reset and the gate key off _rendering, not _lastVisible,
     // so the HUD doesn\'t churn while the custom renderer is actually drawing.
-    assert.match(fn, /_perfHud\s*&&\s*\(\s*!_rendering/, 'perf-HUD reset must key off _rendering, not _lastVisible');
+    assert.match(fn, /hwState\._perfHud\s*&&\s*\(\s*!_rendering/, 'perf-HUD reset must key off _rendering, not _lastVisible');
     assert.match(fn, /if\s*\(\s*!_rendering\s*\)\s*return/, 'the draw gate must bail on !_rendering');
 });
 

tests/js/juce_engine_reroute.test.js

@@ -40,7 +40,7 @@ function extractWatcherIIFE(src) {
 
 // Build a sandbox with fakes and run the watcher IIFE inside it. Returns the
 // sandbox so tests can drive window._reevaluateJuceRouting and inspect state.
-function makeSandbox({ isAudioRunning, loadBackingTrack }) {
+function makeSandbox({ isAudioRunning, loadBackingTrack, outputType = 'Windows Audio' }) {
     const calls = { loadBackingTrack: [], jucePlay: 0, jucePause: 0, audioPlay: 0 };
 
     const audio = {
@@ -65,6 +65,7 @@ function makeSandbox({ isAudioRunning, loadBackingTrack }) {
     const juceApi = {
         isAudioRunning: () => Promise.resolve(isAudioRunning()),
         loadBackingTrack: (p) => { calls.loadBackingTrack.push(p); return Promise.resolve(loadBackingTrack()); },
+        getCurrentDevice: () => Promise.resolve({ outputType: typeof outputType === 'function' ? outputType() : outputType }),
         getBackingDuration: () => Promise.resolve(180),
         seekBacking: () => Promise.resolve(),
         startBacking: () => Promise.resolve(),
@@ -152,6 +153,87 @@ test('non-JUCE-eligible song (sloppak stems) is never rerouted', async () => {
     assert.equal(sb.__calls.loadBackingTrack.length, 0);
 });
 
+test('feedpak full-mix + exclusive output → migrates to JUCE', async () => {
+    const sb = makeSandbox({
+        isAudioRunning: () => true,
+        loadBackingTrack: () => true,
+        outputType: 'Windows Audio (Exclusive Mode)',
+    });
+    sb.window._juceMode = false;
+    sb.window._currentSongAudio = {
+        url: '/api/sloppak/song.sloppak/file/stems/full.ogg',
+        juceEligible: false,
+        feedpakFullMix: true,
+    };
+
+    await sb.window._reevaluateJuceRouting();
+
+    assert.equal(sb.window._juceMode, true, 'feedpak full-mix rides the engine under exclusive output');
+    assert.equal(sb.__calls.loadBackingTrack.length, 1);
+});
+
+test('feedpak full-mix + ASIO output → migrates to JUCE', async () => {
+    const sb = makeSandbox({
+        isAudioRunning: () => true,
+        loadBackingTrack: () => true,
+        outputType: 'ASIO',
+    });
+    sb.window._juceMode = false;
+    sb.window._currentSongAudio = {
+        url: '/api/sloppak/song.sloppak/file/stems/full.ogg',
+        juceEligible: false,
+        feedpakFullMix: true,
+    };
+
+    await sb.window._reevaluateJuceRouting();
+
+    assert.equal(sb.window._juceMode, true, 'ASIO is exclusive-style; feedpak rides the engine');
+});
+
+test('feedpak full-mix + shared output → stays on HTML5 (stem mixer untouched)', async () => {
+    for (const shared of ['Windows Audio', 'Windows Audio (Low Latency Mode)', 'DirectSound']) {
+        const sb = makeSandbox({
+            isAudioRunning: () => true,
+            loadBackingTrack: () => true,
+            outputType: shared,
+        });
+        sb.window._juceMode = false;
+        sb.window._currentSongAudio = {
+            url: '/api/sloppak/song.sloppak/file/stems/full.ogg',
+            juceEligible: false,
+            feedpakFullMix: true,
+        };
+
+        await sb.window._reevaluateJuceRouting();
+
+        assert.equal(sb.window._juceMode, false, `stays on HTML5 for shared type "${shared}"`);
+        assert.equal(sb.__calls.loadBackingTrack.length, 0);
+    }
+});
+
+test('feedpak on JUCE + output leaves exclusive mode → migrates back to HTML5', async () => {
+    let type = 'Windows Audio (Exclusive Mode)';
+    const sb = makeSandbox({
+        isAudioRunning: () => true,
+        loadBackingTrack: () => true,
+        outputType: () => type,
+    });
+    const url = '/api/sloppak/song.sloppak/file/stems/full.ogg';
+    sb.window._juceMode = true;
+    sb.window._juceAudioUrl = url;
+    sb.window._currentSongAudio = { url, juceEligible: false, feedpakFullMix: true };
+
+    // Still exclusive: routing is consistent, no switch.
+    await sb.window._reevaluateJuceRouting();
+    assert.equal(sb.window._juceMode, true, 'consistent while exclusive');
+
+    // Device switched to shared mid-song: must return to HTML5.
+    type = 'Windows Audio';
+    await sb.window._reevaluateJuceRouting();
+    assert.equal(sb.window._juceMode, false, 'returned to HTML5 after leaving exclusive mode');
+    assert.equal(sb.audio.src, url, 'HTML5 element re-pointed at the song');
+});
+
 test('JUCE hard-reject is memoised → not retried on the next poll', async () => {
     const sb = makeSandbox({ isAudioRunning: () => true, loadBackingTrack: () => false });
     sb.window._juceMode = false;

tests/js/plugin_loader_script_type.test.js

@@ -0,0 +1,59 @@
+// Guards the R0 module-migration loader change in static/app.js: a migrated
+// plugin (manifest scriptType:"module", surfaced as plugin.script_type) must be
+// injected as <script type="module"> so its screen.js `import './src/main.js'`
+// graph loads, while classic plugins stay untouched.
+//
+// The injection is a single line inside the large async loadPlugins() closure
+// (it depends on loadedScripts, _removePluginScriptTags, and the
+// _loadingPluginId completion window), so a faithful behavioural harness would
+// need to stub the whole loader. Instead this asserts the *structural*
+// contract in source — the guard exists, is gated (not unconditional), and sits
+// inside the screen.js injection block before appendChild. The behavioural proof
+// is the R0 end-to-end live-edit check (a real module plugin booting in-browser).
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const APP_JS = path.join(__dirname, '..', '..', 'static', 'app.js');
+const src = fs.readFileSync(APP_JS, 'utf8');
+
+// Isolate the screen.js <script> injection block: from where its src is built
+// to where the element is appended.
+function injectionBlock() {
+    const start = src.indexOf('/api/plugins/${plugin.id}/screen.js');
+    assert.ok(start !== -1, 'screen.js injection src not found — loader moved?');
+    const end = src.indexOf('document.body.appendChild(script)', start);
+    assert.ok(end !== -1, 'appendChild(script) not found after screen.js src');
+    return src.slice(start, end);
+}
+
+test('module plugins are injected as <script type="module">', () => {
+    const block = injectionBlock();
+    assert.match(
+        block,
+        /if\s*\(\s*plugin\.script_type\s*===\s*['"]module['"]\s*\)\s*script\.type\s*=\s*['"]module['"]\s*;/,
+        'expected a guarded `script.type = "module"` keyed on plugin.script_type === "module"',
+    );
+});
+
+test('the module type is gated, never set unconditionally', () => {
+    const block = injectionBlock();
+    // Every assignment of script.type in the block must be on the same line as
+    // the plugin.script_type guard (i.e. no bare `script.type = 'module'`).
+    for (const line of block.split('\n')) {
+        if (/script\.type\s*=/.test(line)) {
+            assert.match(line, /plugin\.script_type\s*===\s*['"]module['"]/,
+                `unguarded script.type assignment: ${line.trim()}`);
+        }
+    }
+});
+
+test('the module guard sits before appendChild, after the src assignment', () => {
+    const guardAt = src.indexOf('script.type = \'module\'');
+    const srcAt = src.indexOf('/api/plugins/${plugin.id}/screen.js');
+    const appendAt = src.indexOf('document.body.appendChild(script)', srcAt);
+    assert.ok(guardAt > srcAt && guardAt < appendAt,
+        'the module guard must live inside the screen.js injection block');
+});

tests/js/renderer_bus_feeder.test.js

@@ -0,0 +1,195 @@
+// Behavioral tests for the renderer-audio bus feeder in static/app.js.
+//
+// The feeder (an IIFE, `_installRendererBusFeeder`) captures renderer-side
+// song audio (stems-plugin WebAudio master, or the core <audio> element) and
+// pushes it into the desktop engine's renderer bus while the output device is
+// exclusive-style — the Phase 2 path for audio the native backing transport
+// cannot carry. These tests extract that IIFE from source and exercise
+// `window._reevaluateRendererBus` against fakes, covering: stems engagement
+// under exclusive output, disengagement on return to shared mode, inertness
+// in shared mode / while the native transport owns the song, and the
+// element-capture fallback.
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const vm = require('node:vm');
+
+const APP_JS = path.join(__dirname, '..', '..', 'static', 'app.js');
+
+function extractFeederIIFE(src) {
+    const marker = '(function _installRendererBusFeeder() {';
+    const start = src.indexOf(marker);
+    assert.ok(start !== -1, 'feeder IIFE not found in app.js');
+    const openBrace = src.indexOf('{', start);
+    let depth = 1;
+    let i = openBrace + 1;
+    while (i < src.length && depth > 0) {
+        const ch = src[i];
+        if (ch === '{') depth++;
+        else if (ch === '}') depth--;
+        i++;
+    }
+    assert.ok(depth === 0, 'unbalanced braces in feeder IIFE');
+    const tail = src.slice(i, i + 5);
+    assert.match(tail, /^\)\(\)/, 'feeder IIFE not immediately invoked');
+    return src.slice(start, i) + ')();';
+}
+
+function makeFakeContext(sampleRate = 48000) {
+    const ctx = {
+        sampleRate,
+        state: 'running',
+        sinkIdCalls: [],
+        destination: { isDestination: true },
+        setSinkId(v) { this.sinkIdCalls.push(v); return Promise.resolve(); },
+        resume() { this.state = 'running'; return Promise.resolve(); },
+        audioWorklet: { addModule: () => Promise.resolve() },
+        createMediaElementSource(el) {
+            this.mediaSourceEl = el;
+            return { connect() {}, disconnect() {} };
+        },
+    };
+    return ctx;
+}
+
+function makeSandbox({ isAudioRunning = () => true, exclusive = () => true } = {}) {
+    const calls = { setRendererBus: [], pushRendererAudio: [] };
+
+    const api = {
+        isAudioRunning: () => Promise.resolve(isAudioRunning()),
+        setRendererBus: (en, g) => { calls.setRendererBus.push([en, g]); return Promise.resolve(); },
+        pushRendererAudio: (buf, rate) => { calls.pushRendererAudio.push([buf.length, rate]); },
+    };
+
+    class FakeWorkletNode {
+        constructor() { this.port = { onmessage: null }; }
+        connect() {}
+        disconnect() {}
+    }
+
+    const sandbox = {
+        console: { log() {}, warn() {}, error() {} },
+        URL: { createObjectURL: () => 'blob:tap', revokeObjectURL() {} },
+        Blob: class { constructor() {} },
+        AudioWorkletNode: FakeWorkletNode,
+        AudioContext: function () { const c = makeFakeContext(); sandbox.__createdContexts.push(c); return c; },
+        WeakSet, WeakMap, Promise, Float32Array, Math,
+        setInterval: () => 0,
+        document: {
+            hidden: false,
+            addEventListener() {},
+            getElementById: () => sandbox.__audioEl,
+        },
+        __createdContexts: [],
+        __audioEl: { id: 'audio' },
+        __calls: calls,
+        window: null,
+    };
+    sandbox.window = {
+        feedBackDesktop: { audio: api },
+        _juceOutputIsExclusive: () => Promise.resolve(exclusive()),
+        _juceMode: false,
+        _currentSongAudio: null,
+        feedBack: { stems: {} },
+    };
+    sandbox.globalThis = sandbox;
+
+    const src = fs.readFileSync(APP_JS, 'utf8');
+    vm.createContext(sandbox);
+    vm.runInContext(extractFeederIIFE(src), sandbox);
+    assert.equal(typeof sandbox.window._reevaluateRendererBus, 'function',
+        'feeder must expose window._reevaluateRendererBus');
+    return sandbox;
+}
+
+function makeStemsGraph() {
+    return {
+        context: makeFakeContext(),
+        masterNode: { connect() {}, disconnect() {} },
+    };
+}
+
+test('stems graph + exclusive output → bus enabled, stems ctx null-sinked', async () => {
+    const sb = makeSandbox({ exclusive: () => true });
+    const graph = makeStemsGraph();
+    sb.window.feedBack.stems.audioGraph = graph;
+
+    await sb.window._reevaluateRendererBus();
+
+    assert.deepEqual(sb.__calls.setRendererBus.at(-1), [true, 1.0], 'bus enabled');
+    assert.equal(graph.context.sinkIdCalls.at(-1)?.type, 'none', 'stems ctx re-pointed at null sink');
+});
+
+test('output returns to shared → bus disabled, sink restored', async () => {
+    let excl = true;
+    const sb = makeSandbox({ exclusive: () => excl });
+    const graph = makeStemsGraph();
+    sb.window.feedBack.stems.audioGraph = graph;
+
+    await sb.window._reevaluateRendererBus();
+    excl = false;
+    await sb.window._reevaluateRendererBus();
+
+    assert.deepEqual(sb.__calls.setRendererBus.at(-1), [false, 0], 'bus disabled');
+    assert.equal(graph.context.sinkIdCalls.at(-1), '', 'default sink restored');
+});
+
+test('stems graph + shared output → feeder stays off (no double audio)', async () => {
+    const sb = makeSandbox({ exclusive: () => false });
+    sb.window.feedBack.stems.audioGraph = makeStemsGraph();
+
+    await sb.window._reevaluateRendererBus();
+
+    assert.equal(sb.__calls.setRendererBus.length, 0, 'bus never touched in shared mode');
+});
+
+test('element song + exclusive → element captured into bus', async () => {
+    const sb = makeSandbox({ exclusive: () => true });
+    sb.window._currentSongAudio = { url: '/api/sloppak/x.sloppak/file/stems/full.ogg' };
+    sb.window._juceMode = false;
+
+    await sb.window._reevaluateRendererBus();
+
+    assert.equal(sb.__createdContexts.length, 1, 'capture context created');
+    assert.equal(sb.__createdContexts[0].mediaSourceEl, sb.__audioEl, 'element source captured');
+    assert.deepEqual(sb.__calls.setRendererBus.at(-1), [true, 1.0], 'bus enabled');
+});
+
+test('song riding the native transport (_juceMode) → feeder stays off', async () => {
+    const sb = makeSandbox({ exclusive: () => true });
+    sb.window._currentSongAudio = { url: '/audio/song.ogg' };
+    sb.window._juceMode = true;
+
+    await sb.window._reevaluateRendererBus();
+
+    assert.equal(sb.__calls.setRendererBus.length, 0, 'native transport owns the song');
+    assert.equal(sb.__createdContexts.length, 0, 'no capture context created');
+});
+
+test('stems graph replaced mid-engagement → re-engages on the new graph', async () => {
+    const sb = makeSandbox({ exclusive: () => true });
+    const g1 = makeStemsGraph();
+    sb.window.feedBack.stems.audioGraph = g1;
+    await sb.window._reevaluateRendererBus();
+
+    const g2 = makeStemsGraph();
+    sb.window.feedBack.stems.audioGraph = g2;
+    await sb.window._reevaluateRendererBus();
+
+    assert.equal(g2.context.sinkIdCalls.at(-1)?.type, 'none', 'new graph null-sinked');
+    assert.deepEqual(sb.__calls.setRendererBus.at(-1), [true, 1.0], 're-enabled for new graph');
+});
+
+test('engine stops → bus disabled', async () => {
+    let running = true;
+    const sb = makeSandbox({ isAudioRunning: () => running, exclusive: () => true });
+    sb.window.feedBack.stems.audioGraph = makeStemsGraph();
+    await sb.window._reevaluateRendererBus();
+
+    running = false;
+    await sb.window._reevaluateRendererBus();
+
+    assert.deepEqual(sb.__calls.setRendererBus.at(-1), [false, 0], 'bus disabled after engine stop');
+});

tests/plugins/tuner/js/inject_player_button.test.js

@@ -0,0 +1,191 @@
+// Regression test for feedBack#800: tuner injectPlayerButton() must anchor the
+// injected button to a DIRECT-child button of #player-controls. The old
+// `controls.querySelector('button:last-child')` could resolve to a NESTED
+// button, and `controls.insertBefore(btn, nestedButton)` then throws
+// NotFoundError — which propagated out of the player-screen transition and
+// aborted its render.
+//
+// Same isolation strategy as the core tests/js suite: extract the real function
+// from source with extractFunction() and run it in a vm sandbox over a small
+// but faithful DOM model. The model's insertBefore() enforces the real DOM
+// invariant (reference node must be a direct child, else NotFoundError), and
+// querySelector() implements the exact semantics of both the old
+// (`button:last-child`) and new (`:scope > button:last-of-type`) selectors — so
+// reverting the fix makes this test throw.
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const vm = require('node:vm');
+
+const { extractFunction } = require('../../../js/test_utils');
+
+const UI_JS = path.join(__dirname, '..', '..', '..', '..', 'plugins', 'tuner', 'utils', 'ui.js');
+const SRC = fs.readFileSync(UI_JS, 'utf8');
+const FN_SRC = extractFunction(SRC, 'function injectPlayerButton(');
+
+// ── Minimal, faithful DOM model ──────────────────────────────────────────────
+
+class El {
+    constructor(tag, id = '') {
+        this.tagName = tag.toUpperCase();
+        this.id = id;
+        this.children = [];
+        this.parentNode = null;
+        this.textContent = '';
+        this.title = '';
+        this.onclick = null;
+    }
+    appendChild(node) {
+        node.parentNode = this;
+        this.children.push(node);
+        return node;
+    }
+    insertBefore(node, ref) {
+        const idx = this.children.indexOf(ref);
+        if (ref == null || idx === -1) {
+            // Faithful to the browser: ref must be a direct child.
+            const e = new Error(
+                "Failed to execute 'insertBefore' on 'Node': The node before which the "
+                + 'new node is to be inserted is not a child of this node.'
+            );
+            e.name = 'NotFoundError';
+            throw e;
+        }
+        node.parentNode = this;
+        this.children.splice(idx, 0, node);
+        return node;
+    }
+    querySelector(sel) {
+        if (sel === ':scope > button:last-of-type') {
+            // Last direct-child <button>.
+            const btns = this.children.filter((c) => c.tagName === 'BUTTON');
+            return btns.length ? btns[btns.length - 1] : null;
+        }
+        if (sel === 'button:last-child') {
+            // First descendant <button> (document order) that is the last child
+            // of its own parent — the buggy legacy anchor.
+            let found = null;
+            const walk = (node) => {
+                for (const c of node.children) {
+                    if (found) return;
+                    const isLast = c.parentNode.children[c.parentNode.children.length - 1] === c;
+                    if (c.tagName === 'BUTTON' && isLast) { found = c; return; }
+                    walk(c);
+                }
+            };
+            walk(this);
+            return found;
+        }
+        throw new Error(`unhandled selector in stub: ${sel}`);
+    }
+}
+
+function findById(node, id) {
+    if (!node) return null;
+    if (node.id === id) return node;
+    for (const c of node.children) {
+        const r = findById(c, id);
+        if (r) return r;
+    }
+    return null;
+}
+
+// Run the extracted injectPlayerButton() against a given controls tree.
+// Returns { controls, threw }.
+function run({ controls, isV3 = false, slot = null }) {
+    const roots = [controls, slot].filter(Boolean);
+    const document = {
+        getElementById(id) {
+            if (id === 'player-controls') return controls;
+            for (const r of roots) {
+                const hit = findById(r, id);
+                if (hit) return hit;
+            }
+            return null;
+        },
+        createElement(tag) { return new El(tag); },
+    };
+    const window = {
+        feedBack: isV3
+            ? { uiVersion: 'v3', ui: { playerControlSlot: () => slot } }
+            : { uiVersion: 'v2' },
+        tuner: { toggle: () => {} },
+    };
+    const sandbox = {
+        window,
+        document,
+        Element: El,
+        updatePlayerButton: () => {},
+    };
+    vm.createContext(sandbox);
+    let threw = null;
+    try {
+        vm.runInContext(FN_SRC + '\nglobalThis.__run = injectPlayerButton;\n__run();', sandbox);
+    } catch (e) {
+        threw = e;
+    }
+    return { controls, slot, threw };
+}
+
+// ── Tests ────────────────────────────────────────────────────────────────────
+
+test('does not throw when the last button is nested (feedBack#800 repro)', () => {
+    // controls > div.transport > [play, close]; `close` is button:last-child of
+    // the div but NOT a direct child of controls. The old anchor threw here.
+    const controls = new El('div', 'player-controls');
+    const transport = new El('div');
+    transport.appendChild(new El('button', 'play'));
+    transport.appendChild(new El('button', 'close'));
+    controls.appendChild(transport);
+
+    const { threw } = run({ controls });
+    assert.equal(threw, null, threw && threw.message);
+    // With no direct-child button, it appends to controls.
+    assert.ok(findById(controls, 'btn-tuner-player'), 'tuner button was added');
+    assert.equal(controls.children[controls.children.length - 1].id, 'btn-tuner-player');
+});
+
+test('inserts before the last direct-child button when one exists', () => {
+    const controls = new El('div', 'player-controls');
+    controls.appendChild(new El('button', 'play'));
+    controls.appendChild(new El('button', 'close'));
+
+    const { threw } = run({ controls });
+    assert.equal(threw, null, threw && threw.message);
+    const ids = controls.children.map((c) => c.id);
+    // tuner button sits immediately before the last direct-child button.
+    assert.deepEqual(ids, ['play', 'btn-tuner-player', 'close']);
+});
+
+test('appends when controls has no buttons at all', () => {
+    const controls = new El('div', 'player-controls');
+    controls.appendChild(new El('span'));
+    const { threw } = run({ controls });
+    assert.equal(threw, null, threw && threw.message);
+    assert.equal(controls.children[controls.children.length - 1].id, 'btn-tuner-player');
+});
+
+test('is idempotent — a second call does not add a duplicate', () => {
+    const controls = new El('div', 'player-controls');
+    controls.appendChild(new El('button', 'close'));
+    run({ controls });
+    run({ controls });
+    const injected = controls.children.filter((c) => c.id === 'btn-tuner-player');
+    assert.equal(injected.length, 1);
+});
+
+test('v3 mounts into the plugin-control slot and never uses the legacy anchor', () => {
+    const slot = new El('div', 'plugin-control-slot');
+    // A nested button in the slot would trip the legacy anchor; v3 must ignore it.
+    const inner = new El('div');
+    inner.appendChild(new El('button', 'other'));
+    slot.appendChild(inner);
+    const controls = new El('div', 'player-controls');
+
+    const { threw } = run({ controls, isV3: true, slot });
+    assert.equal(threw, null, threw && threw.message);
+    assert.ok(findById(slot, 'btn-tuner-player'), 'tuner button mounted into the slot');
+    assert.equal(findById(controls, 'btn-tuner-player'), null, 'not mounted into #player-controls');
+});

tests/test_appstate.py

@@ -0,0 +1,153 @@
+"""The router seam (`appstate.py`).
+
+The load-bearing assertion here is `test_server_wires_the_seam`: that `server`
+actually calls `appstate.configure(...)`. Every other test in this file would
+pass just fine against a seam nothing ever wires up — the same class of silent
+no-op that bit the frontend refactor twice when a scripted `setHostHooks` edit
+stopped matching its anchor. Unit tests cannot see wiring unless you make them
+look at it.
+"""
+
+import importlib
+import sys
+
+import pytest
+
+import appstate
+
+
+def _close_server_dbs(mod):
+    conn = getattr(getattr(mod, "meta_db", None), "conn", None)
+    if conn is not None:
+        getattr(mod, "_join_background_db_threads", lambda: None)()
+        conn.close()
+    ae_conn = getattr(getattr(mod, "audio_effect_mappings", None), "conn", None)
+    if ae_conn is not None:
+        ae_conn.close()
+
+
+@pytest.fixture()
+def isolated_server(tmp_path, monkeypatch):
+    """A freshly imported `server` bound to a throwaway CONFIG_DIR.
+
+    Importing `server` constructs `MetadataDB` + `AudioEffectsMappingDB` at
+    module level, so it MUST be re-imported under a patched CONFIG_DIR — an
+    unguarded `import server` would create/mutate the developer's real
+    `~/.local/share/feedback` databases. Same idiom as the other ~49
+    server-importing suites.
+
+    Teardown restores the appstate slots as well as closing the connections:
+    leaving `appstate.meta_db` published but pointing at a closed sqlite handle
+    would hand a later test (or router) a live-looking, dead singleton.
+    """
+    previous = (appstate.meta_db, appstate.audio_effect_mappings)
+    monkeypatch.setenv("CONFIG_DIR", str(tmp_path))
+    sys.modules.pop("server", None)
+    mod = importlib.import_module("server")
+    yield mod
+    _close_server_dbs(mod)
+    # Leave no half-torn-down `server` behind: the next fixture re-imports it.
+    sys.modules.pop("server", None)
+    appstate.configure(meta_db=previous[0], audio_effect_mappings=previous[1])
+
+
+def test_import_is_side_effect_free():
+    """`import appstate` must construct nothing and touch no disk.
+
+    This is why the ~49 fixtures that `sys.modules.pop("server")` and re-import
+    (to rebuild `meta_db` under a patched CONFIG_DIR) keep working untouched:
+    server owns construction, appstate only mirrors it. A singleton *owned*
+    here would survive that pop and go stale.
+    """
+    sys.modules.pop("appstate", None)
+    fresh = importlib.import_module("appstate")
+    try:
+        assert fresh.meta_db is None
+        assert fresh.audio_effect_mappings is None
+    finally:
+        sys.modules["appstate"] = appstate
+
+
+def test_configure_publishes_known_slots():
+    sentinel = object()
+    original = appstate.meta_db
+    try:
+        appstate.configure(meta_db=sentinel)
+        assert appstate.meta_db is sentinel
+    finally:
+        appstate.configure(meta_db=original)
+
+
+def test_configure_is_idempotent():
+    """server re-imports call configure() again; the last write must win."""
+    original = appstate.meta_db
+    try:
+        appstate.configure(meta_db="first")
+        appstate.configure(meta_db="second")
+        assert appstate.meta_db == "second"
+    finally:
+        appstate.configure(meta_db=original)
+
+
+def test_configure_rejects_an_unknown_slot():
+    """A typo'd or stale keyword must raise, not silently create a global that
+    nothing reads. A seam whose wiring can no-op undetected is worse than none."""
+    with pytest.raises(TypeError, match="unknown slot"):
+        appstate.configure(met_db="typo")
+    assert not hasattr(appstate, "met_db")
+
+
+def test_late_bound_read_sees_a_later_configure():
+    """Routers must read `appstate.meta_db`, never `from appstate import meta_db`.
+    This pins the property that makes that rule work."""
+    def router_style_read():
+        return appstate.meta_db          # module attribute, resolved at call time
+
+    original = appstate.meta_db
+    try:
+        appstate.configure(meta_db="before")
+        assert router_style_read() == "before"
+        appstate.configure(meta_db="after")
+        assert router_style_read() == "after"
+    finally:
+        appstate.configure(meta_db=original)
+
+
+def test_server_wires_the_seam(isolated_server):
+    """The one that catches a dropped `appstate.configure(...)` call.
+
+    Identity, not truthiness, so a stray re-assignment or a half-applied edit
+    fails here rather than in some router months later.
+    """
+    assert appstate.meta_db is isolated_server.meta_db
+    assert appstate.audio_effect_mappings is isolated_server.audio_effect_mappings
+    assert appstate.meta_db is not None
+
+
+def test_reimporting_server_republishes_the_fresh_singletons(
+    isolated_server, tmp_path, monkeypatch
+):
+    """The 49-fixture contract, exercised end to end.
+
+    Those fixtures `sys.modules.pop("server")` + re-import to rebuild `meta_db`
+    under a new CONFIG_DIR, and know nothing about appstate. So the seam must
+    re-publish on that second import. This is the test that would fail if
+    `appstate` ever *owned* the singletons: a module-level `meta_db` there
+    survives the pop and the assertions below would still see the FIRST DB.
+    """
+    first_db = isolated_server.meta_db
+    assert appstate.meta_db is first_db
+    assert str(tmp_path) in first_db.db_path
+
+    second_config = tmp_path / "second"
+    monkeypatch.setenv("CONFIG_DIR", str(second_config))
+    sys.modules.pop("server", None)
+    second_server = importlib.import_module("server")
+    try:
+        assert second_server.meta_db is not first_db          # genuinely rebuilt
+        assert str(second_config) in second_server.meta_db.db_path
+        assert appstate.meta_db is second_server.meta_db      # ...and re-published
+        assert appstate.audio_effect_mappings is second_server.audio_effect_mappings
+    finally:
+        _close_server_dbs(second_server)
+        sys.modules.pop("server", None)

tests/test_art_candidates.py

@@ -12,6 +12,8 @@ tests/test_art_layer.py.
 """
 
 import importlib
+import enrichment
+from routers import art
 import io as _io
 import sys
 
@@ -119,8 +121,8 @@ def caa_index(server, monkeypatch):
         calls.append(release_id)
         return indexes.get(release_id)   # unknown release → None (a CAA 404)
     fake.calls, fake.indexes = calls, indexes
-    monkeypatch.setattr(server, "_caa_release_index", fake)
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(enrichment, "_caa_release_index", fake)
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
     return fake
 
 
@@ -251,7 +253,7 @@ def test_caa_candidates_capped_at_12(server, client, caa_index):
     caa_index.indexes["rel-big"] = {
         "images": [_img(300 + i, front=(i == 0)) for i in range(20)]}
     _match_row(server, "a.sloppak", release_id="rel-big")
-    assert len(_caa(_get(client))) == server._ART_PICKER_MAX_CAA == 12
+    assert len(_caa(_get(client))) == art._ART_PICKER_MAX_CAA == 12
 
 
 def test_demo_mode_blocks_candidates(server, client, monkeypatch):
@@ -274,10 +276,10 @@ def test_malicious_release_id_rejected_no_fetch_no_write(server, caa_index):
     """A crafted release id (path traversal) never matches _CAA_ID_RE, so it
     yields no images, opens no socket, and writes no cache file — inside the
     art dir or anywhere else."""
-    art_dir = server._enrichment_art_dir()
+    art_dir = enrichment._enrichment_art_dir()
     before = set(art_dir.glob("*"))
-    assert not server._CAA_ID_RE.match("../../etc/x")
-    assert server._caa_index_cached("../../etc/x") == []
+    assert not enrichment._CAA_ID_RE.match("../../etc/x")
+    assert enrichment._caa_index_cached("../../etc/x") == []
     assert caa_index.calls == []                       # the seam was never asked
     assert set(art_dir.glob("*")) == before            # nothing written
     # And nothing landed at the traversal target beside the cache dir either.
@@ -340,10 +342,10 @@ def test_fetch_art_url_follows_redirects_validating_each_hop(server, monkeypatch
         return _FakeResp(200, chunks=[b"IMGDATA"])
 
     monkeypatch.setattr(requests, "get", fake_get)
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
-    monkeypatch.setattr(server, "_url_host_is_internal",
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(art, "_url_host_is_internal",
                         lambda u: (checked.append(u), False)[1])
-    data = server._fetch_art_url("https://coverartarchive.example/release/x/front-500")
+    data = art._fetch_art_url("https://coverartarchive.example/release/x/front-500")
     assert data == b"IMGDATA"
     assert fetched == ["https://coverartarchive.example/release/x/front-500",
                        "https://archive.example/img.png"]
@@ -354,18 +356,18 @@ def test_fetch_art_url_blocks_redirect_to_internal(server, monkeypatch):
     import requests
     monkeypatch.setattr(requests, "get", lambda url, **kw: _FakeResp(
         302, {"Location": "http://internal.example/x.png"}))
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
-    monkeypatch.setattr(server, "_url_host_is_internal",
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(art, "_url_host_is_internal",
                         lambda u: "internal" in u)
     with pytest.raises(ValueError):
-        server._fetch_art_url("https://public.example/x.png")
+        art._fetch_art_url("https://public.example/x.png")
 
 
 def test_fetch_art_url_redirect_budget(server, monkeypatch):
     import requests
     monkeypatch.setattr(requests, "get", lambda url, **kw: _FakeResp(
         307, {"Location": "https://public.example/next.png"}))
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
-    monkeypatch.setattr(server, "_url_host_is_internal", lambda u: False)
-    with pytest.raises(server.EnrichTransportError):
-        server._fetch_art_url("https://public.example/x.png")
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(art, "_url_host_is_internal", lambda u: False)
+    with pytest.raises(enrichment.EnrichTransportError):
+        art._fetch_art_url("https://public.example/x.png")

tests/test_art_layer.py

@@ -7,6 +7,8 @@ here opens a socket, and the offline default is itself asserted.
 """
 
 import importlib
+import enrichment
+from routers import art
 import io as _io
 import sys
 
@@ -121,7 +123,7 @@ def test_bad_upload_rejected(server, client):
 
 def test_art_url_fetches_and_overrides(server, client, monkeypatch):
     make_sloppak(server, "a.sloppak", with_cover=True)
-    monkeypatch.setattr(server, "_fetch_art_url", lambda url: png_bytes((9, 9, 9)))
+    monkeypatch.setattr(art, "_fetch_art_url", lambda url: png_bytes((9, 9, 9)))
     body = client.post("/api/song/a.sloppak/art/url",
                        json={"url": "https://example.com/cover.png"}).json()
     assert body == {"ok": True, "kind": "png"}
@@ -138,7 +140,7 @@ def test_art_url_validation(server, client, monkeypatch):
     # Oversize → 400 (the seam raises ValueError at the cap).
     def _huge(url):
         raise ValueError("image larger than 10 MB")
-    monkeypatch.setattr(server, "_fetch_art_url", _huge)
+    monkeypatch.setattr(art, "_fetch_art_url", _huge)
     assert client.post("/api/song/a.sloppak/art/url",
                        json={"url": "https://example.com/x.png"}).status_code == 400
 
@@ -176,15 +178,15 @@ def caa(server, monkeypatch):
         calls.append(release_id)
         return art.get(release_id)
     fake.calls, fake.art = calls, art
-    monkeypatch.setattr(server, "_caa_http_get", fake)
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(enrichment, "_caa_http_get", fake)
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
     return fake
 
 
 def test_caa_fetch_fills_missing_art(server, client, caa):
     make_sloppak(server, "a.sloppak")                 # no pack art
     _match_row(server, "a.sloppak")
-    server._background_enrich()
+    enrichment._background_enrich()
     row = server.meta_db.get_enrichment("a.sloppak")
     assert row["art_state"] == "caa"
     assert row["art_cache_path"] and row["art_cache_path"].endswith("caa_rel-1.jpg")
@@ -193,7 +195,7 @@ def test_caa_fetch_fills_missing_art(server, client, caa):
     assert r.headers["content-type"] == "image/jpeg"
     # Settled: the next pass never re-fetches.
     n = len(caa.calls)
-    server._background_enrich()
+    enrichment._background_enrich()
     assert len(caa.calls) == n
 
 
@@ -204,7 +206,7 @@ def test_caa_skips_pack_art_and_dedupes_by_release(server, caa):
     _match_row(server, "haspack.sloppak")
     _match_row(server, "b.sloppak")                   # same release as c
     _match_row(server, "c.sloppak")
-    server._background_enrich()
+    enrichment._background_enrich()
     assert server.meta_db.get_enrichment("haspack.sloppak")["art_state"] == "pack"
     assert server.meta_db.get_enrichment("b.sloppak")["art_state"] == "caa"
     assert server.meta_db.get_enrichment("c.sloppak")["art_state"] == "caa"
@@ -214,10 +216,10 @@ def test_caa_skips_pack_art_and_dedupes_by_release(server, caa):
 def test_caa_404_marks_none(server, caa):
     make_sloppak(server, "a.sloppak")
     _match_row(server, "a.sloppak", release_id="rel-missing")
-    server._background_enrich()
+    enrichment._background_enrich()
     assert server.meta_db.get_enrichment("a.sloppak")["art_state"] == "none"
     n = len(caa.calls)
-    server._background_enrich()
+    enrichment._background_enrich()
     assert len(caa.calls) == n                        # never re-hammered
 
 
@@ -226,13 +228,13 @@ def test_caa_transport_error_leaves_row_unevaluated(server, caa, monkeypatch):
     _match_row(server, "a.sloppak")
 
     def _down(release_id):
-        raise server.EnrichTransportError("down")
-    monkeypatch.setattr(server, "_caa_http_get", _down)
-    server._background_enrich()
+        raise enrichment.EnrichTransportError("down")
+    monkeypatch.setattr(enrichment, "_caa_http_get", _down)
+    enrichment._background_enrich()
     assert server.meta_db.get_enrichment("a.sloppak")["art_state"] is None
     # Network back → next pass completes it.
-    monkeypatch.setattr(server, "_caa_http_get", caa)
-    server._background_enrich()
+    monkeypatch.setattr(enrichment, "_caa_http_get", caa)
+    enrichment._background_enrich()
     assert server.meta_db.get_enrichment("a.sloppak")["art_state"] == "caa"
 
 
@@ -240,22 +242,22 @@ def test_offline_default_skips_art_worker(server, monkeypatch):
     """Under the plain test env the whole art phase is skipped with the rest
     of the network work."""
     calls = []
-    monkeypatch.setattr(server, "_caa_http_get", lambda rid: calls.append(rid))
+    monkeypatch.setattr(enrichment, "_caa_http_get", lambda rid: calls.append(rid))
     make_sloppak(server, "a.sloppak")
     _match_row(server, "a.sloppak")
-    server._background_enrich()
+    enrichment._background_enrich()
     assert calls == []
     assert server.meta_db.get_enrichment("a.sloppak")["art_state"] is None
 
 
 def test_lru_prune_evicts_oldest_and_resets_rows(server, caa, monkeypatch):
-    monkeypatch.setattr(server, "_CAA_CACHE_CAP_BYTES", 1)   # everything over cap
+    monkeypatch.setattr(enrichment, "_CAA_CACHE_CAP_BYTES", 1)   # everything over cap
     make_sloppak(server, "a.sloppak", title="One")
     make_sloppak(server, "b.sloppak", title="Two")
     caa.art["rel-2"] = png_bytes((1, 1, 1))
     _match_row(server, "a.sloppak", release_id="rel-1")
     _match_row(server, "b.sloppak", release_id="rel-2")
-    server._background_enrich()
+    enrichment._background_enrich()
     # With a 1-byte cap every fetch immediately evicts — the rows that pointed
     # at evicted files were reset to unevaluated.
     caa_files = list(server.ART_CACHE_DIR.glob("caa_*.jpg"))
@@ -282,13 +284,13 @@ def test_delete_override_restores_caa_fallback(server, client, caa):
     _match_row(server, "a.sloppak")
     # Pin an override BEFORE the art worker runs → the pass stamps art_state='user'.
     client.post("/api/song/a.sloppak/art/upload", json={"image": b64(png_bytes())})
-    server._background_enrich()
+    enrichment._background_enrich()
     assert server.meta_db.get_enrichment("a.sloppak")["art_state"] == "user"
     # Remove it → the row resets to unevaluated…
     assert client.delete("/api/art/a.sloppak/override").json()["removed"]
     assert server.meta_db.get_enrichment("a.sloppak")["art_state"] is None
     # …and the next pass fetches + serves the release's front cover.
-    server._background_enrich()
+    enrichment._background_enrich()
     assert server.meta_db.get_enrichment("a.sloppak")["art_state"] == "caa"
     r = client.get("/api/song/a.sloppak/art")
     assert r.status_code == 200
@@ -302,7 +304,7 @@ def test_upload_rejects_unknown_song_and_oversize(server, client):
     assert server._art_override_paths("ghost.sloppak") == []
     # Oversize decoded payload → 400 (bounds the base64 upload path).
     make_sloppak(server, "a.sloppak")
-    huge = b64(b"\x00" * (server._ART_URL_MAX_BYTES + 1))
+    huge = b64(b"\x00" * (art._ART_URL_MAX_BYTES + 1))
     assert client.post("/api/song/a.sloppak/art/upload",
                        json={"image": huge}).status_code == 400
 
@@ -310,10 +312,10 @@ def test_upload_rejects_unknown_song_and_oversize(server, client):
 def test_fetch_art_url_blocks_internal_hosts(server):
     """The SSRF guard refuses loopback / link-local / private targets before
     any request is made (the real seam, not the faked one)."""
-    assert server._url_host_is_internal("http://127.0.0.1/x.png")
-    assert server._url_host_is_internal("http://localhost/x.png")
-    assert server._url_host_is_internal("http://169.254.169.254/latest/meta-data")
-    assert server._url_host_is_internal("http://10.0.0.5/x.png")
-    assert server._url_host_is_internal("http://[::1]/x.png")
-    assert server._url_host_is_internal("http://nonexistent.invalid/x.png")  # unresolvable → closed
-    assert not server._url_host_is_internal("http://93.184.216.34/x.png")    # public literal
+    assert art._url_host_is_internal("http://127.0.0.1/x.png")
+    assert art._url_host_is_internal("http://localhost/x.png")
+    assert art._url_host_is_internal("http://169.254.169.254/latest/meta-data")
+    assert art._url_host_is_internal("http://10.0.0.5/x.png")
+    assert art._url_host_is_internal("http://[::1]/x.png")
+    assert art._url_host_is_internal("http://nonexistent.invalid/x.png")  # unresolvable → closed
+    assert not art._url_host_is_internal("http://93.184.216.34/x.png")    # public literal

tests/test_artist_page.py

@@ -10,7 +10,7 @@ Two halves, mirroring the design's split:
 
 * GET /api/artist/{name}/links + POST .../links/refresh — the lazy, cached,
   opt-in external-links layer. The HTTP transport is a fake over
-  `server._mb_http_get` (the ONE network seam — same pattern as
+  `enrichment._mb_http_get` (the ONE network seam — same pattern as
   tests/test_mb_enrichment.py), so nothing here opens a socket. Covers the
   url-rel whitelist mapping, the http(s) scheme gate (a hostile javascript:
   resource never reaches a link slot), cache-hit second calls making no
@@ -19,6 +19,7 @@ Two halves, mirroring the design's split:
 """
 
 import importlib
+import enrichment
 import json
 import sys
 from urllib.parse import quote
@@ -88,7 +89,7 @@ class FakeMBArtist:
 
     def __call__(self, path, params):
         if self.raise_transport:
-            raise self._srv.EnrichTransportError("fake network down")
+            raise enrichment.EnrichTransportError("fake network down")
         self.calls.append((path, dict(params)))
         if path == f"artist/{MBID}":
             return self.doc
@@ -100,8 +101,8 @@ def mb_artist(server, monkeypatch):
     """Install the fake transport AND enable the network flag (the test env
     disables it by default — see test_links_offline_returns_empty)."""
     fake = FakeMBArtist(server)
-    monkeypatch.setattr(server, "_mb_http_get", fake)
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(enrichment, "_mb_http_get", fake)
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
     return fake
 
 

tests/test_audio_local_path.py

@@ -103,12 +103,98 @@ def test_returns_404_for_nonexistent_file(client_and_server):
     assert "error" in r.json()
 
 
-# ── rejected non-/audio/ inputs ───────────────────────────────────────────────
+# ── sloppak URLs (feedpak full-mix, desktop exclusive-mode routing) ──────────
 
-def test_rejects_sloppak_url(client_and_server):
+@pytest.fixture()
+def dlc_client(tmp_path, monkeypatch):
+    """Loopback TestClient with a temp DLC_DIR for sloppak resolution."""
+    dlc = tmp_path / "dlc"
+    dlc.mkdir()
+    monkeypatch.setenv("DLC_DIR", str(dlc))
+    monkeypatch.setenv("CONFIG_DIR", str(tmp_path / "cfg"))
+    monkeypatch.setenv("FEEDBACK_SYNC_STARTUP", "1")
+    sys.modules.pop("server", None)
+    server = importlib.import_module("server")
+    # Module-level sloppak source-dir cache survives re-import; clear it so a
+    # prior test's filename key can't shadow this test's temp DLC_DIR.
+    server.sloppak_mod._source_cache.clear()
+    monkeypatch.setattr(server, "load_plugins", lambda *a, **kw: None)
+    monkeypatch.setattr(server, "startup_scan", lambda: None)
+    static_tmp = tmp_path / "static"
+    static_tmp.mkdir()
+    monkeypatch.setattr(server, "STATIC_DIR", static_tmp)
+    tc = TestClient(server.app, client=("127.0.0.1", 50000))
+    try:
+        yield tc, server, dlc
+    finally:
+        tc.close()
+        meta_db = getattr(server, "meta_db", None)
+        conn = getattr(meta_db, "conn", None)
+        if conn is not None:
+            getattr(__import__("sys").modules.get("server"), "_join_background_db_threads", lambda: None)()
+            conn.close()
+
+
+def _make_sloppak(dlc, name="song.sloppak"):
+    """Create a minimal directory-form sloppak with a full-mix file."""
+    pak = dlc / name
+    (pak / "stems").mkdir(parents=True)
+    (pak / "stems" / "full.ogg").write_bytes(b"OggS-fake")
+    return pak
+
+
+def test_sloppak_url_resolves_to_local_path(dlc_client):
+    tc, _server, dlc = dlc_client
+    pak = _make_sloppak(dlc)
+    r = tc.get(
+        "/api/audio-local-path",
+        params={"url": "/api/sloppak/song.sloppak/file/stems/full.ogg"},
+    )
+    assert r.status_code == 200, r.text
+    assert r.json()["path"] == str((pak / "stems" / "full.ogg").resolve())
+
+
+def test_sloppak_url_percent_encoded_segments_decode(dlc_client):
+    tc, _server, dlc = dlc_client
+    _make_sloppak(dlc, name="My Song.sloppak")
+    r = tc.get(
+        "/api/audio-local-path",
+        params={"url": "/api/sloppak/My%20Song.sloppak/file/stems/full.ogg"},
+    )
+    assert r.status_code == 200, r.text
+
+
+def test_sloppak_url_rel_traversal_is_403(dlc_client):
+    tc, _server, dlc = dlc_client
+    _make_sloppak(dlc)
+    (dlc / "secret.txt").write_text("top secret")
+    r = tc.get(
+        "/api/audio-local-path",
+        params={"url": "/api/sloppak/song.sloppak/file/..%2Fsecret.txt"},
+    )
+    assert r.status_code == 403, r.text
+
+
+def test_sloppak_url_filename_traversal_is_403(dlc_client):
+    tc, _server, _dlc = dlc_client
+    r = tc.get(
+        "/api/audio-local-path",
+        params={"url": "/api/sloppak/..%2F..%2F..%2Fetc/file/passwd"},
+    )
+    assert r.status_code == 403, r.text
+
+
+def test_sloppak_url_without_dlc_configured_is_404(client_and_server):
+    """No DLC_DIR in the base fixture — resolver reports 'not configured'."""
     client, _ = client_and_server
-    r = client.get("/api/audio-local-path", params={"url": "/api/sloppak/mysong/file/stems/full.ogg"})
-    assert r.status_code == 400
+    r = client.get(
+        "/api/audio-local-path",
+        params={"url": "/api/sloppak/mysong/file/stems/full.ogg"},
+    )
+    assert r.status_code == 404
+
+
+# ── rejected non-/audio/ inputs ───────────────────────────────────────────────
 
 
 def test_rejects_empty_url(client_and_server):

tests/test_context_menu_api.py

@@ -4,6 +4,7 @@ contents). The refresh flow reuses the P8 fake-transport pattern — nothing
 here opens a socket."""
 
 import importlib
+import enrichment
 import sys
 
 import pytest
@@ -85,9 +86,9 @@ def test_refresh_resets_even_a_manual_pin_and_rematches(server, client, monkeypa
                           "status": "Official", "date": "1990-09-24",
                           "release-group": {"primary-type": "Album"}}],
         }]}
-    monkeypatch.setattr(server, "_mb_http_get", fake)
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
-    server._background_enrich()
+    monkeypatch.setattr(enrichment, "_mb_http_get", fake)
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
+    enrichment._background_enrich()
     assert server.meta_db.get_enrichment("a.sloppak")["mb_recording_id"] == "rec-new"
 
 

tests/test_enrichment_plumbing.py

@@ -5,6 +5,7 @@ contracts it will inherit: rename-survivable idempotent hashing, manual rows
 never auto-reset, never purged on rescan, purged on explicit delete."""
 
 import importlib
+import enrichment
 import sys
 
 import pytest
@@ -58,7 +59,7 @@ def test_pending_covers_new_unscanned_and_changed(server):
     _put(server, "a.archive")
     assert [r["filename"] for r in server.meta_db.enrichment_pending()] == ["a.archive"]
     # stubbed → still unscanned → still pending (the matcher hasn't run)
-    server._background_enrich()
+    enrichment._background_enrich()
     assert [r["filename"] for r in server.meta_db.enrichment_pending()] == ["a.archive"]
     # a matched row with the CURRENT hash is settled…
     h = server.meta_db.enrichment_content_hash("Artist", "Song", "", 100)
@@ -76,7 +77,7 @@ def test_pending_covers_new_unscanned_and_changed(server):
 def test_hash_change_resets_matched_but_never_manual(server):
     _put(server, "a.archive")
     _put(server, "b.archive", title="Other")
-    server._background_enrich()
+    enrichment._background_enrich()
     with server.meta_db._lock:
         server.meta_db.conn.execute(
             "UPDATE song_enrichment SET match_state = 'matched' WHERE filename = 'a.archive'")
@@ -86,7 +87,7 @@ def test_hash_change_resets_matched_but_never_manual(server):
     # identity edits…
     _put(server, "a.archive", title="Song v2")
     _put(server, "b.archive", title="Other v2")
-    server._background_enrich()
+    enrichment._background_enrich()
     a = server.meta_db.get_enrichment("a.archive")
     b = server.meta_db.get_enrichment("b.archive")
     # …drop a stale MATCH back to unscanned with the fresh hash
@@ -99,7 +100,7 @@ def test_hash_change_resets_matched_but_never_manual(server):
 
 def test_failed_rows_not_requeued_by_pending(server):
     _put(server, "a.archive")
-    server._background_enrich()
+    enrichment._background_enrich()
     with server.meta_db._lock:
         server.meta_db.conn.execute(
             "UPDATE song_enrichment SET match_state = 'failed' WHERE filename = 'a.archive'")
@@ -113,7 +114,7 @@ def test_failed_rows_not_requeued_by_pending(server):
 def test_enrich_pass_stamps_every_song(server):
     for i in range(5):
         _put(server, f"s{i}.archive", title=f"Song {i}")
-    server._background_enrich()
+    enrichment._background_enrich()
     for i in range(5):
         row = server.meta_db.get_enrichment(f"s{i}.archive")
         assert row is not None
@@ -126,7 +127,7 @@ def test_enrich_pass_stamps_every_song(server):
 
 def test_rescan_never_purges_enrichment(server):
     _put(server, "a.archive")
-    server._background_enrich()
+    enrichment._background_enrich()
     server.meta_db.delete_missing(set())          # file vanished from a scan snapshot
     assert server.meta_db.get_enrichment("a.archive") is not None   # row survives
     # …and is invisible in the read-time-filtered counts
@@ -138,7 +139,7 @@ def test_rescan_never_purges_enrichment(server):
 def test_status_endpoint_counts(client, server):
     _put(server, "a.archive")
     _put(server, "b.archive", title="Other")
-    server._background_enrich()
+    enrichment._background_enrich()
     body = client.get("/api/enrichment/status").json()
     assert body["states"] == {"unscanned": 2}
     assert body["total_songs"] == 2
@@ -147,7 +148,7 @@ def test_status_endpoint_counts(client, server):
 
 
 def test_art_cache_dir_created(server):
-    d = server._enrichment_art_dir()
+    d = enrichment._enrichment_art_dir()
     assert d.is_dir()
     assert d.name == "art_cache"
 
@@ -156,7 +157,7 @@ def test_art_cache_dir_created(server):
 
 def test_states_for_returns_only_known_filenames(server):
     _put(server, "a.archive")
-    server._background_enrich()
+    enrichment._background_enrich()
     got = server.meta_db.enrichment_states_for(["a.archive", "nope.archive"])
     assert got == {"a.archive": "unscanned"}          # unknown filename absent
     assert server.meta_db.enrichment_states_for([]) == {}
@@ -165,7 +166,7 @@ def test_states_for_returns_only_known_filenames(server):
 def test_states_endpoint(client, server):
     _put(server, "a.archive")
     _put(server, "b.archive", title="Other")
-    server._background_enrich()
+    enrichment._background_enrich()
     body = client.post("/api/enrichment/states",
                        json={"filenames": ["a.archive", "zzz.missing"]}).json()
     assert body["states"] == {"a.archive": "unscanned"}
@@ -175,7 +176,7 @@ def test_states_endpoint(client, server):
 
 def test_status_exposes_progress_fields(client, server):
     _put(server, "a.archive")
-    server._background_enrich()
+    enrichment._background_enrich()
     body = client.get("/api/enrichment/status").json()
     for k in ("total", "matched", "current", "cancelling"):
         assert k in body
@@ -186,7 +187,7 @@ def test_cancel_is_noop_when_idle(client, server):
     body = client.post("/api/enrichment/cancel").json()
     assert body == {"ok": True, "was_running": False}
     # A no-op must not arm the flag (which would then poison the next pass).
-    assert server._enrich_cancel.is_set() is False
+    assert enrichment._enrich_cancel.is_set() is False
 
 
 def test_cancel_flag_halts_matching_loop_between_songs(server, monkeypatch):
@@ -195,28 +196,28 @@ def test_cancel_flag_halts_matching_loop_between_songs(server, monkeypatch):
     # Force the matcher path on (the test env is offline by default) and stub the
     # per-song matcher so nothing touches the network — it just trips Stop after
     # the first song, exactly as the /cancel route would mid-pass.
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
     calls = []
 
     def fake_enrich_one(row, **_kw):
         calls.append(row["filename"])
-        server._enrich_cancel.set()
+        enrichment._enrich_cancel.set()
 
-    monkeypatch.setattr(server, "_enrich_one", fake_enrich_one)
-    server._enrich_cancel.clear()
-    server._background_enrich()
+    monkeypatch.setattr(enrichment, "_enrich_one", fake_enrich_one)
+    enrichment._enrich_cancel.clear()
+    enrichment._background_enrich()
     # The loop checks cancel BEFORE each song, so exactly one is processed before
     # it breaks — not the whole 4-row queue.
     assert calls == ["s0.archive"]
-    assert server._enrich_status["total"] == 4
-    assert server._enrich_status["matched"] == 1
+    assert enrichment._enrich_status["total"] == 4
+    assert enrichment._enrich_status["matched"] == 1
 
 
 def test_rematch_requeues_visible_but_skips_manual(server, client):
     _put(server, "a.archive")                       # will be 'matched'
     _put(server, "b.archive", title="Other")        # will be 'failed'
     _put(server, "c.archive", title="Pinned")       # will be 'manual' — untouchable
-    server._background_enrich()
+    enrichment._background_enrich()
     with server.meta_db._lock:
         server.meta_db.conn.execute(
             "UPDATE song_enrichment SET match_state='matched' WHERE filename='a.archive'")
@@ -240,7 +241,7 @@ def test_rematch_requeues_visible_but_skips_manual(server, client):
 # ── filename-derived artist/title fallback (blank-artist packs) ───────────────
 
 def test_filename_artist_title_parse(server):
-    f = server._artist_title_from_filename
+    f = enrichment._artist_title_from_filename
     assert f("CDLC/0 - City Pop/Tatsuro-Yamashita_Ride-On-Time_v1_p.feedpak") == \
         {"artist": "Tatsuro Yamashita", "title": "Ride On Time"}
     assert f("Anri_Windy-Summer_v1_p.feedpak") == {"artist": "Anri", "title": "Windy Summer"}
@@ -255,18 +256,18 @@ def test_blank_artist_seeds_match_from_filename(server, monkeypatch):
     server.meta_db.put("Tatsuro-Yamashita_Ride-On-Time_v1_p.feedpak", 0, 0, {
         "title": "Tatsuro-Yamashita_Ride-On-Time_v1_p", "artist": "", "album": "",
         "duration": 240, "arrangements": [{"name": "Bass", "index": 0}]})
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
-    monkeypatch.setattr(server, "_manifest_exact_ids", lambda fn: {})
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(enrichment, "_manifest_exact_ids", lambda fn: {})
     seen = {}
 
     def fake_search(artist, title, limit=8):
         seen["artist"], seen["title"] = artist, title
         return []
 
-    monkeypatch.setattr(server, "_mb_search_recordings", fake_search)
+    monkeypatch.setattr(enrichment, "_mb_search_recordings", fake_search)
     row = next(r for r in server.meta_db.enrichment_pending()
                if r["filename"].startswith("Tatsuro"))
-    server._enrich_one(row)
+    enrichment._enrich_one(row)
     # the blank pack artist was replaced by the filename-derived identity for
     # the search (this is exactly what rescues the 'failed' pile)
     assert seen == {"artist": "Tatsuro Yamashita", "title": "Ride On Time"}
@@ -276,18 +277,18 @@ def test_present_artist_is_not_overridden_by_filename(server, monkeypatch):
     server.meta_db.put("Weird-Filename_x_y.feedpak", 0, 0, {
         "title": "Real Title", "artist": "Real Artist", "album": "", "duration": 100,
         "arrangements": [{"name": "Lead", "index": 0}]})
-    monkeypatch.setattr(server, "_enrich_network_enabled", lambda: True)
-    monkeypatch.setattr(server, "_manifest_exact_ids", lambda fn: {})
+    monkeypatch.setattr(enrichment, "_enrich_network_enabled", lambda: True)
+    monkeypatch.setattr(enrichment, "_manifest_exact_ids", lambda fn: {})
     seen = {}
 
     def fake_search(artist, title, limit=8):
         seen["artist"], seen["title"] = artist, title
         return []
 
-    monkeypatch.setattr(server, "_mb_search_recordings", fake_search)
+    monkeypatch.setattr(enrichment, "_mb_search_recordings", fake_search)
     row = next(r for r in server.meta_db.enrichment_pending()
                if r["filename"].startswith("Weird"))
-    server._enrich_one(row)
+    enrichment._enrich_one(row)
     # a pack that DOES carry an artist keeps it — the filename is never consulted
     assert seen == {"artist": "Real Artist", "title": "Real Title"}
 
@@ -295,7 +296,7 @@ def test_present_artist_is_not_overridden_by_filename(server, monkeypatch):
 def test_kick_clears_a_stale_cancel(server):
     # A cancelled-then-rekicked pass must start clean: _kick_enrich clears the
     # flag so the fresh pass isn't aborted the instant it checks.
-    server._enrich_cancel.set()
-    server._kick_enrich()
+    enrichment._enrich_cancel.set()
+    enrichment._kick_enrich()
     server._join_background_db_threads()
-    assert server._enrich_cancel.is_set() is False
+    assert enrichment._enrich_cancel.is_set() is False

tests/test_feedpak_extension.py

@@ -14,6 +14,7 @@ back-compat for `.sloppak` libraries or stop accepting the new `.feedpak`:
 from __future__ import annotations
 
 import importlib
+from routers import settings as settings_router
 import io
 import sys
 import zipfile
@@ -242,7 +243,7 @@ def test_settings_dlc_count_includes_both_suffixes(tmp_path, settings_server):
     (dlc / "c.FEEDPAK").write_bytes(b"")   # case-insensitive (suffix.lower())
     (dlc / "notes.txt").write_bytes(b"")   # ignored
 
-    result = settings_server.save_settings({"dlc_dir": str(dlc)})
+    result = settings_router.save_settings({"dlc_dir": str(dlc)})
 
     assert "error" not in result, result
     # save_settings joins its notices into a single ``message`` string.