chore(release): bump to 0.2.0

Minor bump rather than patch: Android gains working equalizer, volume normalization and gapless playback, which are new user-facing capabilities. CHANGELOG entry written by hand rather than from `bun run release:notes`. The generated draft lists "Crossfade between audio tracks (UR-031)" as a feature of this release, which is false — the trace graph cannot distinguish code that plumbs a setting (settings.rs clamping, the backend.rs trait method, both legitimately tagged DR-034) from code that implements it, and crossfade is implemented nowhere. The release-notes tool documents its output as a reviewed draft; this is a concrete case of why. v0.1.3-v0.1.5 have no CHANGELOG entries; noted in the file rather than backfilled.
feat(android): implement audio settings (EQ, normalization, gapless)
2026-07-28 23:08:05 +02:00 · 2026-07-28 23:03:31 +02:00 · 2026-07-28 23:03:17 +02:00 · 2026-07-28 01:33:58 +02:00 · 2026-07-28 01:33:20 +02:00 · 2026-07-28 01:33:10 +02:00
26 changed files with 3127 additions and 880 deletions
@@ -6,6 +6,63 @@ Entries are grouped by the capability they change, not by commit. Requirement
 IDs in parentheses point at [docs/requirements.md](docs/requirements.md); the
 generated trace matrix lives in [docs/traceability.md](docs/traceability.md).

+## v0.2.0
+
+### ✨ Features
+
+- **Audio settings now work on Android.** The equalizer, volume normalization
+  and gapless playback controls in Settings › Audio previously rendered on
+  Android and did nothing — `ExoPlayerBackend` was the only backend that never
+  implemented `set_audio_settings`, and the trait's default silently reported
+  success while applying nothing. All three now take effect:
+  - **Equalizer** — the canonical 10-band ISO curve is resampled onto whatever
+    bands the device's equalizer actually exposes (commonly 5), by nearest
+    centre frequency.
+  - **Volume normalization** — via `LoudnessEnhancer`. Note this is a gain
+    stage, not a true EBU R128 normalizer like the Linux `dynaudnorm` path, so
+    it approximates rather than matches Linux behaviour.
+  - **Gapless playback** — honours the setting via `pauseAtEndOfMediaItems`
+    (ExoPlayer is gapless by default, so this disables it when you turn it off).
+
+  The effects re-attach automatically when ExoPlayer rebuilds its audio sink on
+  a format change, so the equalizer no longer stops applying part-way through a
+  queue. (UR-027, UR-032, UR-033 → DR-030, DR-035, DR-036, IR-004)
+
+  ⚠️ **Not yet verified on a physical device.** `AudioEffect` availability and
+  band layouts vary by device and OEM ROM; where an effect is unavailable it is
+  logged and skipped rather than crashing playback.
+
+### 📋 Documentation
+
+- **Playback backend unification investigation.** Six new specs in
+  [docs/specs/](docs/specs/) record why the playback backends cannot be unified
+  onto a single engine: every candidate (mpv, GStreamer, libVLC) fails the same
+  webview-compositing constraint, because WebKitGTK/WebView2/Android WebView each
+  own their compositor surface and native video cannot interleave with HTML.
+  Audio *can* unify; video cannot. Also specifies the Android native-video spike,
+  a Windows native audio backend, and the `libmpv2` migration.
+
+### 🐛 Corrected requirement statuses
+
+These were documented as working and were not. No behaviour changed — the docs
+were wrong.
+
+- **Crossfade (UR-031, DR-034) was marked "Done (Linux only)". It is implemented
+  nowhere**, and is architecturally blocked on mpv: its audio chain is
+  single-stream, and FFmpeg's `acrossfade` requires two inputs. Real crossfade
+  would need two libmpv instances.
+- The platform parity matrix listed crossfade as a Linux/Android gap (it is
+  neither) and omitted the equalizer (which was a genuine gap, now closed).
+- `nativeAdapter.ts` cited tauri#10152 as blocking native Android video. That
+  issue is a stale feature request; the capability shipped in September 2024.
+  What remains unproven is SurfaceView-behind-WebView compositing, now tracked
+  by a spec rather than asserted as an upstream blocker.
+
+<!--
+  Note: v0.1.3–v0.1.5 have no entries here. Their changes are in the git log
+  and docs/traceability.md.
+-->
+
 ## v0.1.2

 ### ✨ Features
@@ -41,7 +41,7 @@ For a narrative overview of the system design, see
 | UR-028 | Navigate to artist/album by tapping names in now playing view | High | Done |
 | UR-029 | Toggle between grid and list view in library | Medium | Done |
 | UR-030 | Quick genre browsing and filtering | Medium | Done |
-| UR-031 | Crossfade between audio tracks | Low | Done (Linux only) |
+| UR-031 | Crossfade between audio tracks | Low | Not implemented (blocked — see DR-034) |
 | UR-032 | Gapless playback for seamless album listening | Medium | Done (Linux only) |
 | UR-033 | Volume normalization to prevent volume jumps between tracks | Low | Done (Linux only) |
 | UR-034 | Rich home screen with hero banners, carousels, and personalized sections | High | Done |
@@ -71,6 +71,7 @@ For a narrative overview of the system design, see
 | UR-058 | On the home screen, a tap on a media card opens the item (movie/episode detail page, or the series Episode Focus View for episodes) rather than starting playback; a long-press starts "play now" after a confirm; an episode detail/focus page links back to its parent series and season (see [ux-flows.md §5B.5](ux-flows.md) and [§5B.1](ux-flows.md)) | Medium | Done |
 | UR-059 | Skipping to the next episode records the episode left behind as **fully watched** rather than saving a mid-episode resume point — skipping means "done with this one", not "stopped here" — and Continue Watching hides episodes the viewer has already moved past (a partial position behind that series' next-up episode), so the row only ever offers genuinely unfinished media | Medium | Done |
 | UR-060 | Search results are ordered by how well they match: a name that *starts* with the query outranks one matching mid-word (typing "parks" finds "Parks and Recreation" before "Sparks of Love"), and at equal match quality a container outranks its contents (a series before its episodes). Results are grouped into distinct categories — TV Shows, Episodes, Movies, Songs, Albums, Artists and People — so a show never competes with its own episodes for the same slot, and searching an actor's name reaches their bio | High | Done |
+| UR-061 | Double tapping the video skips within it — right half jumps **forward 30 seconds**, left half jumps **back 10 seconds** — with an on-screen indicator naming the amount. Because a double tap starts as a single tap, the single-tap play/pause is held back until the double-tap window has passed, so skipping never also pauses the video; the skip lands relative to the position the player actually reports, and repeated double taps accumulate rather than all skipping from the same spot | Medium | Done |

 ---

@@ -192,7 +193,7 @@ Internal architecture, components, and application logic.
 | DR-031 | Clickable artist/album links in now playing view | UI | UR-028 | Done |
 | DR-032 | List view option for library browsing (albums, artists) | UI | UR-029 | Done |
 | DR-033 | Genre browsing screen with quick filters | UI | UR-030 | Done |
-| DR-034 | Crossfade engine with configurable duration (0-12s) | Player | UR-031 | Done (Linux only) |
+| DR-034 | Crossfade engine with configurable duration (0-12s) | Player | UR-031 | Not implemented (blocked on MPV: single-stream audio chain; `acrossfade` needs 2 inputs — see docs/specs/playback-backend-unification.md) |
 | DR-035 | Gapless playback between sequential tracks | Player | UR-032 | Done (Linux only) |
 | DR-036 | Volume normalization with preset levels (Loud/Normal/Quiet) | Player | UR-033 | Done (Linux only) |
 | DR-037 | Remote session browser and control UI | UI | UR-010 | Done |
@@ -245,6 +246,7 @@ Internal architecture, components, and application logic.
 | DR-089 | Continue Watching suppresses resume entries superseded by Next Up: an in-progress episode whose series has a next-up entry strictly later in series order (season, then episode) is dropped from the Home and TV rows; movies, series without a next-up entry, and items with unknown/mixed episode ordering are always kept | UI | UR-059 | Done |
 | DR-090 | Relevance ranking in Rust (`domain/search_rank.rs`): results sort by match position (prefix → word-start → mid-word substring → no name match) then by media kind (containers before their contents), stably so the backend's own relevance breaks ties. Applied in `repository_search` to both the instant cache result and the merged cache+server union, so the list does not reshuffle when server results land | Backend | UR-060 | Done |
 | DR-091 | Search result groups split TV into separate Shows and Episodes groups and add a People group (default order: Shows → Episodes → Movies → Songs → Albums → Artists → People); a stored `tvShows` order from before the split expands in place to shows+episodes so an upgrading user keeps their arrangement | UI | UR-060 | Done |
+| DR-092 | Video tap gestures resolve in `tapGestures.ts` (pure, unit-tested) rather than inline in `VideoPlayer.svelte`: `registerTap` returns `pending` for a first tap — the component defers `togglePlayPause` behind a `DOUBLE_TAP_WINDOW_MS` (300 ms) timer that a second tap cancels — or `seek` (+30 s right / −10 s left) for a second tap inside the window; a consumed second tap resets the state so a third tap starts fresh, and a swipe cancels the pending tap. The compatibility `click` the browser synthesizes after a touch tap is filtered in `handleVideoClick` so it cannot bypass the deferral. `resolveSeekTarget` converts the delta to the absolute position the facade requires, clamped to `[0, duration]` and chained off a still-in-flight `pendingSeekTarget` so back-to-back skips accumulate instead of all resolving against a not-yet-updated position | UI | UR-061 | Done |

 ---

@@ -313,6 +315,7 @@ Internal architecture, components, and application logic.
 | UR-057 | - | DR-086 |
 | UR-058 | - | DR-087 |
 | UR-060 | - | DR-090, DR-091 |
+| UR-061 | - | DR-092 |

 ---

@@ -383,6 +386,7 @@ Internal architecture, components, and application logic.
 | UT-059 | Audio-only stream URL builder for a video item (selected audio-stream index) | JA-032, DR-052 | Pending |
 | UT-060 | Background-audio handoff state machine (background→audio, foreground→video; no dual audio) | DR-052 | Pending |
 | UT-061 | Background-audio Tauri command param naming (camelCase) | DR-052 | Pending |
+| UT-062 | `setBackgroundAudioEnabled` reports whether the native bridge was actually reached (missing bridge, stale proxy, throwing method) so a dead bridge cannot look armed | UR-040, IR-025, DR-051 | Done |
 | UT-067 | Offline `get_items` gates the synced-catalog UNION on the catalog-browse flag (downloads only when off, full catalog when on) | DR-078 | Done |
 | UT-068 | Catalog visibility resolves to `serverReachable \|\| showServerCatalog`, and is pushed to the backend on every change of either input | DR-078, DR-079 | Done |
 | UT-069 | `isConnected` follows backend reachability alone: false when the server is unreachable on a live link, true for a reachable server while `navigator.onLine` is false | DR-079 | Done |
@@ -402,6 +406,10 @@ Internal architecture, components, and application logic.
 | UT-082 | EQ fields serialize as camelCase (`equalizerEnabled`/`equalizerBands`) and round-trip | DR-030 | Done |
 | UT-083 | EQ filter entries are empty when disabled or when the curve is flat (clears the `af` filter) | IR-020 | Done |
 | UT-084 | Enabled EQ builds one peaking `equalizer` per non-zero band at the right frequency and gain inside a single `lavfi` chain | IR-020 | Done |
+| UT-085 | A first tap resolves to `pending`, not an immediate play/pause, and becomes `togglePlayPause` only once the double-tap window has elapsed | DR-092 | Done |
+| UT-086 | A second tap inside the window seeks (+30 s right half, −10 s left half) with the matching feedback side, and clears the deferred play/pause so a double tap never pauses | DR-092 | Done |
+| UT-087 | A tap after the window, and a third tap after a consumed double tap, each start a fresh pending tap; repeated double taps keep seeking; `cancel()` drops a pending tap so a swipe cannot pause | DR-092 | Done |
+| UT-088 | `resolveSeekTarget` applies the delta to the reported position, clamps to `[0, duration]`, chains off an in-flight pending target so rapid skips accumulate, and ignores that target once the player reports past it | DR-092 | Done |

 ### Integration Tests

@@ -491,22 +499,36 @@ The `PlayerBackend` trait defines optional audio settings methods with default e
 | Basic playback | ✅ | ✅ | Parity |
 | Volume control | ✅ | ✅ | Parity |
 | Seek | ✅ | ✅ | Parity |
-| Crossfade | ✅ | ❌ | Gap |
-| Gapless playback | ✅ | ❌ | Gap |
-| Volume normalization | ✅ | ❌ | Gap |
+| Crossfade | ❌ | ❌ | Not implemented (blocked on MPV) |
+| Gapless playback | ✅ | ⚠️ | Implemented, pending on-device verification |
+| Volume normalization | ✅ | ⚠️ | Implemented (LoudnessEnhancer — gain stage, approximate vs MPV's dynaudnorm), pending on-device verification |
+| Equalizer (10-band) | ✅ | ⚠️ | Implemented (resampled onto device bands), pending on-device verification |
 | Position updates | 250ms | On-demand | Inconsistent |

-**Future Fix**:
-1. Implement `set_audio_settings()` in `ExoPlayerBackend`
-2. Add Kotlin-side ExoPlayer configuration for crossfade (using `ConcatenatingMediaSource` or `DefaultMediaSourceFactory`)
-3. Implement gapless via ExoPlayer's built-in gapless support
-4. Add volume normalization via ExoPlayer's `LoudnessEnhancer` or audio processor
-5. Standardize position update frequency across platforms
+**Status** (see docs/specs/android-audio-settings-parity.md):
+1. ✅ `set_audio_settings()` implemented in `ExoPlayerBackend` (JSON over JNI)
+2. ✅ Gapless via ExoPlayer's `pauseAtEndOfMediaItems`
+3. ✅ Volume normalization via `LoudnessEnhancer`
+4. ✅ Equalizer via `android.media.audiofx.Equalizer`, canonical 10 bands
+   resampled onto the device's band centres
+5. ⬜ **Not yet verified on a physical device** — the EQ/normalization effects
+   depend on device-specific `AudioEffect` availability and band layouts
+6. ⬜ Flip the trait's `set_audio_settings` default from `Ok(())` to
+   `Err(not_implemented())` so a backend that omits it fails loudly instead of
+   silently reporting success. Deferred until (5) confirms the Android path works
+7. ⬜ Standardize position update frequency across platforms
+
+Crossfade is deliberately absent: it is unimplemented on every platform and
+architecturally blocked on MPV, so building it on Android alone would invert the
+parity gap. (The previously suggested `ConcatenatingMediaSource` is also
+deprecated in current Media3.)

 **Impact**:
 - Medium - Android users lack audio enhancement features advertised in requirements
 - User experience differs between platforms
- UR-031 (Crossfade), UR-032 (Gapless), UR-033 (Normalization) only work on Linux
+- UR-032 (Gapless), UR-033 (Normalization) and UR-027 (Equalizer) are now
+  implemented on Android as well as Linux, pending on-device verification
+- UR-031 (Crossfade) works nowhere — see DR-034

 **Traces To**: IR-004, UR-031, UR-032, UR-033, DR-034, DR-035, DR-036

@@ -0,0 +1,209 @@
+# Spec: Android audio settings parity (EQ, normalization, gapless)
+
+**Status:** Proposed
+**Requirements:** UR-031, UR-032, UR-033, UR-027 → DR-034, DR-035, DR-036, DR-030; IR-004
+**UX spec:** n/a — no UI change; Settings › Audio already renders these controls
+**Supersedes / revises:** closes the audio half of the parity gap recorded in [playback-backend-unification.md](playback-backend-unification.md)
+
+## Summary
+
+Implement `set_audio_settings` / `audio_settings` on `ExoPlayerBackend` so the
+equalizer, volume normalization, and gapless playback settings actually take
+effect on Android. Today the Settings › Audio panel renders these controls on
+Android and they silently do nothing — `ExoPlayerBackend` is the only backend
+that does not override the trait's no-op defaults.
+
+Crossfade is explicitly **not** included; see Out of scope.
+
+## Motivation
+
+`PlayerBackend` declares `set_audio_settings` with a default `Ok(())` body.
+`MpvBackend`, `NullBackend`, and `WebviewAudioBackend` all override it;
+`ExoPlayerBackend` does not. The settings are persisted, pushed to the backend on
+every track load, and displayed in the UI — and then dropped on the floor.
+
+This is the single most user-visible platform divergence in the app: a user who
+sets a "Rock" EQ preset on Android sees the sliders move and hears no change.
+
+The backend-unification investigation ruled out fixing this by swapping engines
+(video cannot be unified; see the sibling spec), so the fix is to implement the
+trait methods where they are missing.
+
+## Layer assignment
+
+| Logic / responsibility | Layer | Why it belongs there |
+|------------------------|-------|----------------------|
+| Band count, centre frequencies, gain range, preset→curve map | Rust (existing) | Already domain-owned in `settings.rs` per [audio-equalizer.md](audio-equalizer.md). Android must consume the same `AudioSettings`, not define its own bands. Duplicating the band layout in Kotlin would be a taxonomy leak of exactly the kind `check:boundary` guards against. |
+| Mapping `AudioSettings` → Android audio-effect parameters | Rust → JNI boundary | Platform playback detail, the direct analogue of `build_af_filter` in `mpv_backend.rs`. Belongs with the other `set_audio_settings` code. |
+| Attaching/detaching `Equalizer` and `LoudnessEnhancer` to the ExoPlayer audio session | Kotlin (`JellyTauPlayer.kt`) | Android platform API mechanics; needs the live `audioSessionId`, which only the Kotlin layer holds. |
+| Normalization preset (Loud/Normal/Quiet) → target gain | Rust (existing) | `VolumeLevel` is domain vocabulary; the same preset must mean the same loudness on every platform. |
+| Rendering sliders / preset chips | Frontend (existing) | Pure presentation; unchanged by this spec. |
+
+Borderline row: attaching the effects could arguably be driven entirely from
+Rust via JNI property calls. It goes to Kotlin because `AudioEffect` construction
+requires the audio session id and must be re-attached when ExoPlayer rebuilds its
+audio sink — lifecycle state that lives in `JellyTauPlayer.kt`. Rust still owns
+*what* the values are; Kotlin owns *when* the effect objects exist.
+
+## Design
+
+### Rust — `ExoPlayerBackend` (`src-tauri/src/player/android/mod.rs`)
+
+Override the two defaulted methods, mirroring the shape of the existing
+`set_audio_track` JNI call:
+
+```rust
+fn set_audio_settings(&mut self, settings: &AudioSettings) -> Result<(), PlayerError> {
+    let s = settings.clone().with_crossfade_clamped().with_equalizer_normalised();
+    // Serialize as JSON — the same pattern load() already uses for subtitles,
+    // avoiding a 6-arg JNI signature that has to change every time a field lands.
+    let json = serde_json::to_string(&s).map_err(|e| PlayerError { message: e.to_string() })?;
+    // Kotlin: fun setAudioSettings(json: String)
+    self.call_player_method_string("setAudioSettings", &json)?;
+    self.shared_state.lock_safe().audio_settings = s;
+    Ok(())
+}
+
+fn audio_settings(&self) -> AudioSettings {
+    self.shared_state.lock_safe().audio_settings.clone()
+}
+```
+
+`ExoPlayerState` gains an `audio_settings: AudioSettings` field. Note
+`ExoPlayerBackend` currently holds no such state — `position`/`state`/`volume` are
+all pushed in by JNI callbacks — so this is the first *pull*-side field. That is
+correct: audio settings are commanded downward, never reported upward.
+
+### Kotlin — `JellyTauPlayer.kt`
+
+```kotlin
+fun setAudioSettings(json: String) {
+    val s = JSONObject(json)
+    applyEqualizer(s.getBoolean("equalizerEnabled"), s.getJSONArray("equalizerBands"))
+    applyNormalization(s.getBoolean("normalizeVolume"), s.getString("volumeLevel"))
+    exoPlayer.pauseAtEndOfMediaItems = !s.getBoolean("gaplessPlayback")
+}
+```
+
+Three independent mechanisms:
+
+- **Gapless** — nearly free. ExoPlayer is gapless by default for compatible
+  formats; honouring the setting means *disabling* it when the user turns it off,
+  via `pauseAtEndOfMediaItems`. Note this only applies within a loaded playlist;
+  our queue loads one item at a time, so verify behaviour before claiming DR-035
+  on Android (see Testing).
+- **Equalizer** — `android.media.audiofx.Equalizer` bound to
+  `exoPlayer.audioSessionId`. Android's EQ exposes a device-dependent band count
+  (commonly 5) at fixed centre frequencies, which will **not** match our 10-band
+  ISO layout. Rust owns the canonical 10 bands; Kotlin resamples them onto the
+  device's bands by nearest-centre-frequency interpolation. Gains are in
+  millibels (`setBandLevel` takes mB, we store dB → ×100), clamped to the
+  device's reported `getBandLevelRange()`.
+- **Normalization** — `android.media.audiofx.LoudnessEnhancer`, also bound to the
+  audio session, `setTargetGain(mB)` derived from `VolumeLevel`. This is a gain
+  booster, not a true EBU R128 normalizer like MPV's `dynaudnorm`; parity is
+  approximate and should be documented as such rather than overclaimed.
+
+Lifecycle: build the effects lazily on first use, release them in `release()`,
+and re-attach on `onAudioSessionIdChanged` — ExoPlayer can rebuild its audio sink
+(e.g. on a format change), which invalidates effects bound to the old session.
+
+### Make the silent-failure mode impossible
+
+The trait's default is the root cause of this whole class of bug:
+
+```rust
+// backend.rs:85 — reports success while doing nothing
+fn set_audio_settings(&mut self, _settings: &AudioSettings) -> Result<(), PlayerError> {
+    Ok(())
+}
+```
+
+Android inherits this, so every EQ/normalization change on Android returns `Ok`
+and silently does nothing — the UI ships and has no effect, with no error anywhere.
+
+Once `ExoPlayerBackend` implements the methods, **change the trait default to
+`Err(PlayerError::not_implemented())`**, matching how `set_audio_track` /
+`set_subtitle_track` already behave. Any future backend that forgets to implement
+audio settings then fails loudly instead of lying.
+
+Check the call sites before flipping it: `NullBackend` overrides both methods, so
+the graceful-degradation path is unaffected, but confirm nothing treats a
+`set_audio_settings` error as fatal to playback.
+
+### Re-application on track load
+
+`PlayerController` already re-pushes `AudioSettings` per track on the platforms
+that implement it; the Android path inherits that for free once the trait methods
+exist. No controller change.
+
+### 🔴 Threading note
+
+`setAudioSettings` is invoked from Rust on whatever thread the command lands on.
+`AudioEffect` construction must not happen on the ExoPlayer application thread
+from inside a player callback — that is the re-entrancy hazard CLAUDE.md warns
+about, and the same shape as the `AutoplayDecision` deadlock. Post the work to
+the player's handler rather than doing it inline in a listener.
+
+## Out of scope
+
+- **Crossfade (UR-031 / DR-034).** Not implemented on *any* platform today, and
+  architecturally blocked on MPV (single-stream audio chain; `acrossfade` needs
+  two inputs). Implementing it on Android alone would invert the parity gap. It
+  needs its own spec and probably two player instances.
+- True EBU R128 normalization. `LoudnessEnhancer` is a gain stage; matching
+  `dynaudnorm` exactly is out of reach without a custom `AudioProcessor`.
+- Windows audio settings — see [windows-native-audio-backend.md](windows-native-audio-backend.md).
+
+## Acceptance criteria
+
+- [ ] `ExoPlayerBackend` overrides `set_audio_settings` and `audio_settings`.
+- [ ] EQ preset change on Android audibly changes playback; setting persists across track changes and app restart.
+- [ ] Normalization toggle audibly changes level; the three presets are ordered Loud > Normal > Quiet.
+- [ ] Disabling gapless produces a gap between consecutive tracks; enabling it does not.
+- [ ] Effects are released on `release()` and survive an audio-session rebuild.
+- [ ] `requirements.md` parity matrix updated: EQ and normalization ✅ Android.
+- [ ] `bun run check` and `bun run test` pass.
+- [ ] `cargo fmt` clean, `cargo clippy` clean, `bun run test:rust` passes.
+- [ ] `bun run check:boundary` passes.
+- [ ] New requirement-implementing code carries `// TRACES:` comments.
+- [ ] `bindings.ts` regenerated if Rust types changed.
+
+## Testing
+
+**Rust** (`cargo test`): `set_audio_settings` stores the sanitized settings and
+`audio_settings()` returns them — assert clamping/normalisation is applied
+(crossfade clamped to 12s, band vector normalised to `EQ_BANDS.len()`). The JNI
+call itself is not unit-testable; extract the JSON serialization into a pure
+function and test that its shape matches what the Kotlin parser expects. That
+serialization contract is the part most likely to silently break.
+
+**Kotlin**: the band-resampling function (10 canonical bands → N device bands) is
+pure arithmetic — extract it and unit-test it, including the degenerate cases of
+a 5-band device and a device reporting 10 bands.
+
+**Manual, on device** (these are the ones that actually prove it):
+1. Set Bass Boost, play a track, confirm audible change.
+2. Toggle normalization mid-track; confirm level change without a playback stall.
+3. Queue two gapless-encoded tracks, toggle the setting, confirm the gap appears/disappears.
+4. Force a format change (44.1kHz → 48kHz track) and confirm the EQ still applies afterwards — this exercises the session-rebuild re-attach.
+
+## TRACES
+
+- `ExoPlayerBackend::set_audio_settings` → `// TRACES: UR-027, UR-032, UR-033 | DR-030, DR-035, DR-036`
+- Kotlin `setAudioSettings` / `applyEqualizer` / `applyNormalization` → same IDs
+- Band-resampling helper + its tests → `DR-030 | UT-xxx`
+
+## Notes for the implementer
+
+- Read [audio-equalizer.md](audio-equalizer.md) first — it defines the canonical
+  band layout and the preset→curve rule this spec consumes. Do not redefine bands
+  in Kotlin.
+- Android source edits go in `src-tauri/android/src` (canonical tree), then run
+  `scripts/sync-android-sources.sh`. Never edit the `gen/` tree.
+- There is a **stale duplicate** `JellyTauPlayer.kt` (285 lines) at
+  `src-tauri/android/app/src/main/java/com/dtourolle/jellytau/player/` alongside
+  the real 1103-line file at `src-tauri/android/src/main/java/...`. Edit the
+  latter. Consider deleting the former as a separate change.
+- A parallel Claude session may be active — `git diff` before "repairing"
+  unexpected changes.
@@ -0,0 +1,196 @@
+# Spec: Android native video — transparent-webview spike
+
+**Status:** Proposed (spike — timeboxed, may conclude "not viable")
+**Requirements:** IR-004, UR-003, UR-004 → DR-001, DR-023, DR-024
+**UX spec:** n/a — no intended visual change; the video surface must land exactly where the `<video>` element is today
+**Supersedes / revises:** acts on finding 2 of [playback-backend-unification.md](playback-backend-unification.md)
+
+## Summary
+
+Test whether ExoPlayer's existing `SurfaceView` video path can be composited
+behind a transparent Tauri WebView on Android. If it works, Android regains
+hardware video decoding (MediaCodec) and libass-quality ASS/SSA subtitles, both
+of which the current webview path lacks. If it does not, we document why and
+delete the dead code.
+
+This is a **spike**, not a feature commitment. The deliverable is a yes/no answer
+with evidence, plus either a working path behind a flag or a removal.
+
+## Motivation
+
+`createAdapter()` hardcodes `const effectiveKind = "html5"` and does
+`void backendKind`, discarding the `use_html5_element` value Rust computes in
+`get_player_status`. As a result:
+
+- `NativePlayerAdapter` is dead code.
+- `JellyTauPlayer.kt`'s `getOrCreateSurfaceView()` — which already calls
+  `setZOrderMediaOverlay(false)` and wires `setVideoSurfaceHolder` — is
+  unreachable.
+- Android video decodes in the WebView instead of via MediaCodec, despite
+  `CodecDetector.kt` going to the trouble of reporting hardware codec
+  capabilities back to Rust for DeviceProfile generation.
+
+The code comment in `nativeAdapter.ts:11-14` justifies this by citing
+tauri#10152 as an upstream blocker. **That justification is stale.**
+
+### Why the blocker no longer holds
+
+- tauri#10152 is open but **dead since 2024-07-01**, and it is a *feature
+  request* ("Support transparent webviews on mobile"), not a bug report about
+  compositing.
+- The capability shipped in tauri commit `27d01834` (2024-09-02) — a clippy
+  cleanup that moved `transparent()` out of the desktop-gated impl block, fencing
+  only the tao call behind `#[cfg(desktop)]`. Because it landed as unrelated
+  cleanup, nobody closed the issue.
+- The black/white-screen reports (tauri#8381, tauri#9408) were a real but
+  *different* bug: a broken JNI signature for `setBackgroundColor`, fixed in
+  **wry 0.39.4** (PR #1237). We ship wry 0.55.x.
+- Current wry calls `setBackgroundColor(0)` unconditionally on Android when
+  transparency is requested.
+
+### The honest caveat
+
+**Nobody has demonstrated SurfaceView-behind-WebView on Tauri Android.** A search
+of both `tauri-apps/tauri` and `tauri-apps/wry` issues for `surfaceview` returns
+zero results, and the one native-video Tauri plugin
+(`YeonV/tauri-plugin-videoplayer`) sidesteps compositing by launching a separate
+fullscreen Activity. Nothing upstream blocks this; nothing upstream proves it.
+Hence: spike, not feature.
+
+Note this is the *Android* question only. The equivalent Linux compositing
+problem is maintainer-declared unfixable and is **not** in scope — see the
+unification spec.
+
+## Layer assignment
+
+| Logic / responsibility | Layer | Why it belongs there |
+|------------------------|-------|----------------------|
+| Which video backend this platform uses | Rust (existing) | `get_player_status` already computes `use_html5_element`. The frontend must *consume* it, not decide it. Restoring that is the point of the spike. |
+| Surface creation, z-ordering, `setVideoSurfaceHolder` lifecycle | Kotlin | Android platform mechanics; already written in `JellyTauPlayer.kt`. |
+| Seek/audio-track *strategy* | Rust (existing) | Already returned by `player_seek_video` / `player_switch_audio_track`; `NativePlayerAdapter` executes the chosen primitive. Unchanged — this is exactly what the `PlayerAdapter` contract was built for. |
+| Positioning the surface under the video viewport | Frontend | Pure presentation/layout. **This is the risk area** — see Design. |
+
+## Design
+
+### Phase 1 — prove compositing (no app changes)
+
+Before touching the adapter factory, verify the primitive works at all:
+
+1. Set `"transparent": true` in `tauri.conf.json` for the Android build, plus
+   `html, body { background: transparent; }`.
+2. Confirm the WebView is genuinely transparent (a native view behind it is
+   visible) and that the app does not regress to a black/white screen.
+
+If this fails, stop — everything downstream is moot, and the finding is that
+Tauri Android transparency is still broken in practice despite the shipped fix.
+
+### Phase 2 — un-hardcode the factory
+
+```ts
+// src/lib/player/adapters/index.ts
+export function createAdapter({ backendKind, host, bridge }: CreateAdapterArgs): PlayerAdapter {
+  return backendKind === "native"
+    ? new NativePlayerAdapter(host)
+    : new Html5PlayerAdapter(host, bridge);
+}
+```
+
+`backendKind` comes from `get_player_status` (`VideoBackend::Native` on Android).
+Gate behind a setting — `experimentalNativeVideo`, default **off** — so a broken
+spike cannot ship as a regression. Rust already owns this decision; the flag only
+suppresses it.
+
+**Also in scope: remove the user-agent sniffing in
+`src/lib/services/webviewAudio.ts:30-41`.** It re-derives which audio backend the
+platform has from `navigator.userAgent` ("matching the Rust cfg gate", per its own
+comment) — the frontend deciding a backend fact it should be told. Same root cause
+as the hardcode above, same fix: consume the value Rust already computes. Fold it
+in here rather than leaving a second, subtler copy of the bug behind. If
+`get_player_status` does not currently expose enough to cover the audio case, add
+the field — that is backend work, and correct.
+
+### Phase 3 — surface positioning
+
+The hard part, and where this most likely fails. The webview's `<video>` element
+occupies a laid-out box; the `SurfaceView` must be positioned to match it, and
+kept matched through scroll, rotation, and mini-player transitions.
+
+Approach: the video view reports its `getBoundingClientRect()` to Rust, which
+forwards the rect to Kotlin to position the `SurfaceView`. This is the same
+"faking it" technique the ecosystem uses on desktop — acceptable here *only if*
+the video is effectively fullscreen on Android, which it is in the player route.
+
+**Explicit failure criterion**: if the surface cannot be kept aligned during
+rotation or the mini-player transition without visible artefacts, the spike fails
+and we keep HTML5. Do not ship a janky native path for a codec win.
+
+### What we gain if it works
+
+- **Hardware decode via MediaCodec** — `CodecDetector.kt` already reports
+  capabilities; the DeviceProfile would finally match what actually plays.
+- **ASS/SSA subtitles** are *not* automatic. ExoPlayer cannot render them; that
+  would require libmpv, which is a separate and much larger decision (see the
+  unification spec's engine comparison). Scope this spike to hardware decode
+  only, and do not claim subtitle improvements from it.
+
+## Out of scope
+
+- Linux native video. Maintainer-declared unfixable on WebKitGTK/Wayland.
+- Replacing ExoPlayer with libmpv on Android.
+- Windows native video.
+- Removing the HTML5 path. It stays as the default and the fallback.
+
+## Acceptance criteria
+
+The spike is **complete** when one of these is true:
+
+**Success path**
+- [ ] Transparent WebView confirmed working on a physical device.
+- [ ] `experimentalNativeVideo` off → behaviour byte-identical to today.
+- [ ] `webviewAudio.ts` no longer inspects `navigator.userAgent`; the platform's audio backend is read from Rust.
+- [ ] `experimentalNativeVideo` on → video plays via ExoPlayer/MediaCodec, correctly positioned, with working seek, audio-track switch, and subtitle selection through the existing `PlayerAdapter` contract.
+- [ ] No artefacts on rotation, background/foreground, or mini-player transition.
+- [ ] `adb shell dumpsys media.metrics` (or logcat) confirms a hardware decoder is in use.
+- [ ] Measured battery/thermal or CPU improvement over the HTML5 path on the same clip.
+
+**Failure path**
+- [ ] The blocking behaviour is documented in this spec with evidence.
+- [ ] `NativePlayerAdapter` and the unreachable `SurfaceView` code are deleted, or explicitly retained with a *correct* comment.
+- [ ] `nativeAdapter.ts:11-14` no longer cites tauri#10152.
+
+Either way:
+- [ ] `bun run check`, `bun run test`, `bun run check:boundary` pass.
+- [ ] `cargo fmt` / `cargo clippy` clean; `bun run test:rust` passes.
+
+## Testing
+
+Adapter-selection logic is pure and testable without a device: assert
+`createAdapter` returns `NativePlayerAdapter` for `backendKind: "native"` with
+the flag on, and `Html5PlayerAdapter` in every other combination — including that
+the flag off forces HTML5 even when Rust says native. That last case is the
+regression guard.
+
+Everything else is manual on-device; there is no meaningful way to unit-test
+surface compositing. Test on at least two devices — compositing behaviour varies
+by OEM and Android version.
+
+Per CLAUDE.md, if the spike turns into a bug fix (e.g. seek breaks under the
+native adapter), write the failing test first.
+
+## TRACES
+
+- `createAdapter` → `// TRACES: UR-003, UR-004 | DR-023, DR-024`
+- Adapter-selection tests → `UT-xxx`
+- No new requirement IDs; this spike either satisfies existing IR-004 expectations or documents why it cannot.
+
+## Notes for the implementer
+
+- **Do not skip Phase 1.** If transparency does not work, phases 2 and 3 are
+  wasted effort.
+- `VideoPlayer.svelte` has a documented hazard: no lifecycle calls after an
+  `await` in `onMount` — it flips to HTML5 mode and breaks Android seek. The
+  adapter swap touches exactly this code path.
+- tauri-specta tagged responses keep Rust field names (`new_url`, not `newUrl`).
+- Android source edits go in `src-tauri/android/src`, then run
+  `scripts/sync-android-sources.sh`.
+- A parallel Claude session may be active — `git diff` first.
@@ -4,6 +4,7 @@
 **Requirements:** UR-027 → DR-030 (EQ UI), IR-020 (MPV EQ integration).
 **UX spec:** n/a (extends the Settings › Audio section, ux-flows §8.1 instant-apply).
 **Supersedes / revises:** —
+**Revised by:** [android-audio-settings-parity.md](android-audio-settings-parity.md) — lifts the "Android is a no-op" limitation below.

 ## Summary

@@ -115,6 +116,10 @@ fields ride along. `NullBackend`/Android inherit the trait default (no-op).
 ## Out of scope

 - Android/ExoPlayer EQ (parity gap tracked with crossfade/gapless/normalize).
+  **Now specified in [android-audio-settings-parity.md](android-audio-settings-parity.md)**,
+  which implements `set_audio_settings` on `ExoPlayerBackend`. The canonical band
+  layout and preset→curve map defined here remain authoritative; the Android side
+  resamples those bands onto the device equalizer rather than defining its own.
 - Per-track or per-library EQ profiles — one global profile only.
 - Automatic loudness/room correction; only manual bands + presets.
 - Changing the crossfade/normalize TODOs in `set_audio_settings` beyond wiring
@@ -0,0 +1,169 @@
+# Spec: Migrate to libmpv2 and declare the project licence
+
+**Status:** Proposed
+**Requirements:** UR-003 → IR-003 (revises the MPV integration); no new user-facing behaviour
+**UX spec:** n/a
+**Supersedes / revises:** dependency and licensing housekeeping identified in [playback-backend-unification.md](playback-backend-unification.md)
+
+## Summary
+
+Two related pieces of housekeeping that block or complicate later work:
+
+1. Replace the abandoned `libmpv` crate (pinned to a git branch) with the
+   maintained `libmpv2`.
+2. Add a `LICENSE` file. The project has none, which leaves its legal status
+   undefined while it links GPL-licensed libmpv.
+
+Neither changes user-visible behaviour. Both are prerequisites for
+[windows-native-audio-backend.md](windows-native-audio-backend.md).
+
+## Motivation
+
+### The dependency is dead
+
+```toml
+# src-tauri/Cargo.toml
+libmpv = { git = "https://github.com/ParadoxSpiral/libmpv-rs.git", branch = "master" }
+```
+
+- crates.io `libmpv` 2.0.1 was published **2020-09-29**.
+- The upstream repo's last commit was **2023-01-08**; nothing since was released.
+- We pin a git *branch*, so builds are not reproducible — the same lockfile-less
+  checkout can resolve differently over time, and CI has no protection if the
+  branch moves or the repo disappears.
+
+`libmpv2` (kohsine/libmpv2-rs) is a maintained fork of exactly this crate:
+6.0.0 released **2026-05-12**, ~23.5k recent downloads against the original's
+~1.1k, releases roughly quarterly since 2024.
+
+### The project has no licence
+
+There is no `LICENSE`/`COPYING` file and `src-tauri/Cargo.toml` has no `license`
+field. The project is open source and will never be commercial, so this is purely
+an omission — but it matters because we link libmpv, and "no licence" defaults to
+*all rights reserved*, which is incompatible with distributing a GPL-derived
+work.
+
+## Design
+
+### Part 1 — licence
+
+**Use GPLv3.** This is forced, not chosen:
+
+- mpv's default build is **GPLv2-or-later**, so the combined work must be
+  GPL-compatible.
+- Apache-2.0 is **GPLv2-incompatible** (patent-termination and indemnification
+  clauses) but GPLv3-compatible.
+- A scan of the dependency tree found Apache-2.0-**only** crates with no
+  alternative arm — most importantly **`tao`** (Tauri's own windowing crate),
+  plus `sync_wrapper`, `gethostname`, and `ring` (Apache-2.0 AND ISC).
+
+`tao` is unavoidable in a Tauri app, so GPLv2 is unavailable. Exercising mpv's
+"or later" option puts the combination at **GPLv3**.
+
+Actions:
+- Add `LICENSE` containing the GPLv3 text.
+- Add `license = "GPL-3.0-or-later"` to `src-tauri/Cargo.toml` and `license` to
+  `package.json`.
+- Note in the README that the binary links libmpv (GPLv2+) and FFmpeg.
+
+Because the project is open source, we use mpv's **default GPL build** — no
+`-Dgpl=false`, no LGPL FFmpeg build, and none of the LGPL §6 relinking analysis
+that a proprietary app would need. We keep VAAPI/VDPAU/X11 and every GPL FFmpeg
+filter.
+
+🔴 Never build FFmpeg with `--enable-nonfree` — that produces a binary that is
+**unredistributable under any licence**, open source or not.
+
+### Part 2 — libmpv → libmpv2
+
+```toml
+# Linux (and later Windows, per the Windows audio spec)
+libmpv2 = "=6.0.0"
+```
+
+Pin exactly: `libmpv2` has broken its API in **every** major release.
+
+Breaking changes to expect, from the changelog:
+
+| Version | Change | Impact here |
+|---|---|---|
+| 4.0.0 | Removed command helper methods — call `mpv.command(...)` directly | Low; we already use `command`/`set_property` |
+| 5.0.0 | Removed `mpv_node` support entirely (properties return strings; parse JSON yourself); `EventContext` folded into `Mpv`; `ProtocolContext` → `Protocol` | **Medium** — `start_event_loop` uses `create_event_context()`; check whether that call still exists |
+| 6.0.0 | `RenderContext::new()` → `Mpv::create_render_context()`; `'static` bound on `OpenGLInitParams`; render context now borrows `Mpv` (fixes a use-after-free) | **None** — we do not use the render API |
+
+The last row matters: we run mpv audio-only (`video = no`), so the entire render
+surface is irrelevant to us. Consider disabling the default `render` feature to
+reduce build surface.
+
+The main porting work is the event loop in `mpv_backend.rs` — `wait_event`,
+`disable_deprecated_events`, and the `FileLoaded` / `PlaybackRestart` /
+`PropertyChange` / `EndFile` handling, given 5.0.0 folded `EventContext` into
+`Mpv`.
+
+Everything else — `set_property` calls, the `af` filter graph, the 250ms position
+thread, the seek-suppression window — should port unchanged.
+
+## Layer assignment
+
+No logic moves. This is a dependency swap plus a licence file; the
+`PlayerBackend` trait boundary is untouched.
+
+| Logic / responsibility | Layer | Why it belongs there |
+|------------------------|-------|----------------------|
+| mpv event → `PlayerStatusEvent` mapping | Rust (unchanged) | Already correct; only the binding API beneath it changes. |
+
+## Out of scope
+
+- Any behaviour change. If playback behaves differently after this, that is a bug.
+- Windows support — separate spec, but this must land first.
+- Adopting the render API. We are audio-only on mpv.
+- Re-licensing decisions beyond adding the file the project already implies.
+
+## Acceptance criteria
+
+- [ ] `LICENSE` (GPLv3) present; `license` field set in `Cargo.toml` and `package.json`.
+- [ ] A full dependency-licence audit has been run (`cargo install cargo-license && cargo license`) and confirms no GPLv3-incompatible dependency. *(The scan behind this spec resolved 441 of 575 crates from the local registry cache; the remaining 134 are unverified.)*
+- [ ] `libmpv` git dependency removed; `libmpv2` pinned to an exact version.
+- [ ] Linux audio playback works identically: play/pause/seek/volume, queue advance, gapless, EQ, normalization, sleep timer.
+- [ ] Position updates still arrive at 250ms; the 150ms post-seek suppression still prevents the jump-to-zero glitch.
+- [ ] `EndFile` still emits `PlaybackEnded` only for EOF (not STOP/QUIT/ERROR) — autoplay depends on this.
+- [ ] Builder image updated if the libmpv dev package requirement changed; **no toolchain install added to any CI step**.
+- [ ] `bun run check`, `bun run test`, `bun run check:boundary` pass.
+- [ ] `cargo fmt` clean, `cargo clippy` clean, `bun run test:rust` passes.
+
+## Testing
+
+The existing `mpv_backend_test.rs` plus the `build_af_filter`,
+`eq_filter_entries`, and `normalize_filter_entry` tests are the regression net —
+they must pass unchanged, since none of them touch the binding API.
+
+The event loop has no unit tests and is where the risk concentrates. Verify
+manually on Linux:
+
+1. Play → pause → play; confirm position does not flash to 0:00 (the known
+   playing-event regression).
+2. Seek mid-track; confirm no jump-to-zero within 150ms.
+3. Let a track end naturally; confirm autoplay advances (exercises `EndFile` EOF).
+4. Press stop; confirm autoplay does **not** advance.
+5. Sleep-timer expiry; confirm it stops without triggering autoplay.
+
+Cases 3–5 are the ones most likely to break silently, and each corresponds to a
+bug already fixed once in this codebase.
+
+## TRACES
+
+- `MpvBackend` construction / event loop → existing `// TRACES: UR-003 | IR-003`, unchanged
+- No new requirement IDs; this is a dependency migration.
+
+## Notes for the implementer
+
+- Do this **before** the Windows audio backend.
+- Read the 4.0/5.0/6.0 changelogs before writing code — the crate has broken API
+  in every major release, most recently two months before this spec.
+- The crates.io `repository` field for `libmpv2` points at `kohsine/libmpv-rs`,
+  but the repo was renamed to **`libmpv2-rs`**; the old raw URLs 404.
+- `libmpv2-sys` ships pregenerated bindings and vendored headers, so no libclang
+  is needed at build time — relevant to keeping the builder image thin.
+- A parallel Claude session may be active — `git diff` before "repairing"
+  unexpected changes.
@@ -0,0 +1,226 @@
+# Spec: Playback backend unification — findings and strategy
+
+**Status:** Accepted (analysis; no code changes)
+**Requirements:** IR-004, UR-031, UR-032, UR-033 — revises the "Platform Playback Backend Parity" issue in requirements.md
+**UX spec:** n/a
+**Supersedes / revises:** informs [android-native-video-spike.md](android-native-video-spike.md), [android-audio-settings-parity.md](android-audio-settings-parity.md), [windows-native-audio-backend.md](windows-native-audio-backend.md)
+
+## Summary
+
+This spec records the outcome of an investigation into unifying JellyTau's
+playback backends (Linux/MPV, Android/ExoPlayer, Windows/webview) onto a single
+engine with hardware acceleration everywhere. **The conclusion is that video
+cannot be unified onto a native engine, and should not be attempted.** Audio
+*can* be, and that is where the remaining specs direct effort.
+
+No code changes follow from this spec directly. It exists so the decision is
+written down with its evidence, and so a future session does not re-run the same
+investigation.
+
+## Motivation
+
+The requirements doc carries a "Platform Playback Backend Parity" issue noting
+that audio settings work on Linux but not Android, and proposing eventual
+convergence. The natural next question — "should we just run one engine
+everywhere?" — needed answering before spending effort on per-backend patches.
+
+The investigation also surfaced that several statements in requirements.md and in
+code comments are factually wrong. Those corrections are part of the deliverable.
+
+## Findings
+
+### 1. The current architecture is not what the docs describe
+
+| Platform | Audio | Video |
+|----------|-------|-------|
+| Linux | MPV (native, **audio-only**) | webview `<video>` + hls.js |
+| Android | ExoPlayer (native) | **webview `<video>` + hls.js** |
+| Windows | webview `<audio>` | webview `<video>` + hls.js |
+
+Two surprises:
+
+- **MPV never decodes video.** `mpv_backend.rs` sets `video = no` and
+  `audio-display = no` at construction. Linux video has always been the webview.
+  Correspondingly, `player_play_item` deliberately does *not* load into MPV on
+  Linux (it calls `set_current_item`, which only updates the queue).
+- **Android video is also the webview.** `createAdapter()` in
+  `src/lib/player/adapters/index.ts` hardcodes `const effectiveKind = "html5"`
+  and does `void backendKind`, discarding the `use_html5_element` signal that
+  `get_player_status` computes in Rust. `NativePlayerAdapter` is dead code, and
+  ExoPlayer's `SurfaceView` path in `JellyTauPlayer.kt` is unreachable.
+
+So video is *already* unified — on HTML5, everywhere, by accident of that
+hardcode — and on the path without hardware decoding on Android.
+
+### 2. Native video cannot be composited with a Tauri webview
+
+This is the load-bearing finding. It is **not** an mpv limitation; it defeats
+every candidate engine identically:
+
+- **mpv**: `tauri-plugin-libmpv`'s own platform table reads Linux ⚠️
+  *"Experimental. Window embedding is not working."*
+- **GStreamer** (wry discussion #284, 2024): *"Gstreamer was rendering above the
+  surface and covering all html elements."*
+- **libVLC** (tauri discussion #6343, 2024): *"I had to render the webview in a
+  child window though because vlc kept rendering on top of it."*
+
+Root cause, from Tauri maintainer amrbashir (tauri#9220, 2024-03-30):
+
+> "we are limited to using Webkit2GTK on Linux and that requires a GTK window.
+> While possible to add a GTK widget as a child X11 window inside raw X11 window,
+> this is however a bit hacky and **it is not possible on Wayland at all**."
+
+WebKitGTK, WebView2, and Android WebView each draw into their own compositor
+surface. A native video surface is either entirely above or entirely below the
+webview; it cannot interleave with HTML. Every working example in the ecosystem
+is the same hack — a separate child window position-synced to a
+`getBoundingClientRect()` div — which breaks on resize, scroll, and any UI drawn
+over the video. For JellyTau that means the controls, subtitle overlay, and
+mini-player.
+
+The most recent comment on tauri#6343 (2026-05-23) confirms it is still unsolved:
+
+> "I'm faking it and the window is not truly embedded, basically when the parent
+> moves or resizes I reset the position and size of the libmpv window to align it
+> with an HTML div."
+
+**The principle to carry forward: audio can unify on a native engine; video
+cannot, because video needs a surface and the webview owns the surface.**
+
+### 3. mpv would regress streaming quality
+
+mpv has **no adaptive bitrate**. It delegates HLS to FFmpeg's demuxer, which
+selects one variant at open time and never adapts; mpv#3548 (2016) requested ABR
+and it never landed. `--hls-bitrate` is a static picker defaulting to `max`.
+
+The webview path already has real ABR via hls.js. Moving video to mpv would be a
+**downgrade** on every platform — no graceful degradation on weak networks, and
+quality changes requiring teardown and reload.
+
+### 4. Crossfade is architecturally blocked on mpv
+
+mpv's audio chain is single-stream. FFmpeg's `acrossfade` is an `N→A` filter
+requiring two input streams, so there is no second input to feed it. Real
+crossfade needs **two libmpv instances** with manually ramped volumes. Upstream
+maintainer response (mpv#4512, closed three minutes after opening):
+
+> "No. I also find crossfading stupid and complex, so the likeliness of that
+> happening is low."
+
+GStreamer *could* do it via `audiomixer`. mpv cannot, at any reasonable cost.
+
+### 5. Engine comparison summary
+
+| Criterion | mpv | GStreamer | libVLC |
+|-----------|-----|-----------|--------|
+| Webview compositing | ❌ Linux broken | ❌ same wall | ❌ same wall |
+| Adaptive bitrate HLS | ❌ none | ✅ adaptivedemux2 | ✅ adaptive module |
+| Rust bindings | ⚠️ `libmpv2` active; our pin is dead | ✅ `gstreamer-rs` excellent | ❌ `vlc-rs` abandoned (2018) |
+| Windows cross-MSVC | ⚠️ prebuilt DLL | ❌ pkg-config vs cargo-xwin | ❌ no better |
+| Android packaging | ✅ Maven AAR (used by Findroid) | ⚠️ Cerbero/NDK, painful | ✅ mature AAR |
+| ASS/SSA subtitles | ✅ libass built in | ✅ libass | ✅ libass |
+| Crossfade | ❌ impossible | ✅ `audiomixer` | ⚠️ unclear |
+
+Every candidate fails the first row, which is the disqualifying one.
+
+### 6. Two further options ruled out
+
+**Webview `<audio>`/`<video>` everywhere** (i.e. delete the native audio backends
+too) is dead on Android: `navigator.mediaSession` is *deliberately compiled out*
+of Android WebView (Chromium CL 2613133003), so lockscreen/media-notification
+control would be impossible. Chromium has also never shipped `audioTracks`. It
+remains fine for Windows *video*, which is what we already do.
+
+**FFmpeg-direct / Rust-native** (`ffmpeg-next`, `rsmpeg`, Symphonia) is not
+close: the safe bindings do not expose hardware decode at all, `ffmpeg-next` is
+self-declared maintenance-only, and Symphonia lacks HE-AAC and gapless AAC. This
+is a multi-person-year path to reach parity with what we already have.
+
+### 7. If libmpv is ever revisited on Android
+
+Recorded so the next investigation starts from evidence rather than repeating the
+search. The `dev.jdtech.mpv:libmpv` AAR — maintained by Findroid's author, i.e.
+another Jellyfin Android client — was inspected directly:
+
+- `libmpv.so` exports the full 54-function `mpv_*` C API with **zero `Java_`
+  symbols**; JNI is a separate optional ~19 KB `libplayer.so`. So it is drivable
+  from Rust without a Java shim. (This is precisely what disqualifies libVLC,
+  whose Android video path hard-requires a Java `AWindow` jobject.)
+- ~23 MB/ABI, versus libVLC's ~46 MB/ABI.
+- 🔴 **The published AAR is built `--enable-gpl --enable-version3` — it is
+  GPLv3**, not LGPL. Fine for us (see [libmpv2-migration.md](libmpv2-migration.md)),
+  but it would be a hard constraint for anyone shipping closed source, and an
+  LGPL rebuild would be your own build to own.
+- Top unverified risk if anyone tries this: whether `libmpv2-sys` can
+  cross-compile for `aarch64-linux-android` against that prebuilt `.so`. No
+  working example of `libmpv2` on Android was found.
+
+None of this changes the verdict — the cost is the MediaSession/foreground-service
+rewrite, not the bindings.
+
+## Decision
+
+1. **Do not unify video onto a native engine.** Video stays in the webview with
+   hls.js on all platforms. This is not a compromise — it is the configuration
+   that falls out of the compositing constraint, and it is the only one that
+   gives us ABR for free.
+2. **Android native video is worth a bounded spike anyway** — not for
+   unification, but because ExoPlayer's `SurfaceView` path already exists and
+   would restore hardware decode plus ASS/SSA subtitles. See
+   [android-native-video-spike.md](android-native-video-spike.md).
+3. **Audio parity is the real gap** and is achievable without touching any of the
+   above. See [android-audio-settings-parity.md](android-audio-settings-parity.md)
+   and [windows-native-audio-backend.md](windows-native-audio-backend.md).
+4. **Migrate the dead libmpv pin** regardless of any of this. See
+   [libmpv2-migration.md](libmpv2-migration.md).
+
+## Corrections to existing docs
+
+These are factual errors found during the investigation. Fixing them is in scope
+for this spec.
+
+| Location | Says | Actually |
+|----------|------|----------|
+| `requirements.md` UR-031 (line ~44) | "Done (Linux only)" | Not implemented on any platform. |
+| `requirements.md` DR-034 (line ~196) | "Done (Linux only)" | Not implemented anywhere — `mpv_backend.rs` has a bare `// TODO: Implement crossfade via MPV audio filters if needed`. Architecturally blocked on mpv (finding 4). |
+| `requirements.md` parity matrix | Crossfade ✅ Linux / ❌ Android | ❌ / ❌ |
+| `requirements.md` parity matrix | (no EQ row) | EQ is also Linux-only — `build_af_filter`/`eq_filter_entries` exist only in `mpv_backend.rs`. Same root cause, same fix. |
+| `nativeAdapter.ts:11-14` | Native Android video "blocked upstream by tauri#10152" | tauri#10152 is a stale *feature request*, dead since 2024-07-01. The capability shipped in tauri commit `27d01834` (2024-09-02). Not a blocker. |
+
+## Layer assignment
+
+No new logic. The one boundary observation worth recording:
+
+| Logic / responsibility | Layer | Why it belongs there |
+|------------------------|-------|----------------------|
+| Which video backend a platform uses (`use_html5_element`) | Rust | Already correctly computed in `get_player_status`. The frontend currently *discards* it — that is the bug, not the design. Restoring it means the frontend consumes a backend decision rather than making its own. |
+
+## Out of scope
+
+- Any code change. This spec is analysis; the sibling specs carry the work.
+- iOS/macOS. Not current targets.
+- Replacing hls.js.
+
+## Acceptance criteria
+
+- [ ] `requirements.md` DR-034 status corrected; parity matrix updated (crossfade ❌/❌, EQ row added).
+- [ ] Stale tauri#10152 comment in `nativeAdapter.ts` corrected.
+- [ ] The four sibling specs exist and are linked from here.
+
+## Testing
+
+n/a — documentation only.
+
+## TRACES
+
+No new code. Requirement text changes only; DR-034's status line is the one
+substantive edit.
+
+## Notes for the implementer
+
+- The evidence above was gathered in July 2026. The compositing constraint has
+  been stable since 2021 (wry#284) and is maintainer-declared unfixable, so it is
+  unlikely to change soon — but if someone revisits this, tauri#6343 and wry#284
+  are the threads to re-read first.
+- A parallel Claude session may be active in this repo — `git diff` before
+  "repairing" unexpected changes.
@@ -0,0 +1,198 @@
+# Spec: Playback documentation corrections
+
+**Status:** Proposed
+**Requirements:** revises the status of DR-034; corrects the parity matrix in [requirements.md](../requirements.md)
+**UX spec:** n/a
+**Supersedes / revises:** implements the "Corrections to existing docs" section of [playback-backend-unification.md](playback-backend-unification.md)
+
+## Summary
+
+Fix four factual errors in the requirements doc and the player source comments,
+all found while investigating backend unification. Each claims something the code
+does not do. Small change, but they are actively misleading: two of them assert a
+feature is implemented when it is implemented nowhere, and one cites an upstream
+blocker that no longer exists.
+
+Documentation and comments only — no behaviour change.
+
+## Motivation
+
+These errors compound. DR-034 reads "Done (Linux only)", so a future session
+planning Android parity would reasonably assume crossfade exists on Linux and
+only needs porting — when in fact it is unimplemented everywhere *and*
+architecturally blocked on the engine it supposedly runs on. Likewise the
+tauri#10152 comment has been discouraging work on Android native video since the
+upstream capability shipped in September 2024.
+
+## The corrections
+
+### 1. DR-034 status is wrong
+
+`requirements.md` line ~196:
+
+```
+| DR-034 | Crossfade engine with configurable duration (0-12s) | Player | UR-031 | Done (Linux only) |
+```
+
+The code:
+
+```rust
+// src-tauri/src/player/mpv_backend.rs, in set_audio_settings
+// TODO: Implement crossfade via MPV audio filters if needed
+```
+
+That is the entire crossfade implementation. `crossfade_duration` is plumbed
+through `AudioSettings` and clamped to 0–12s, but no backend ever acts on it.
+
+**Change to:** `Not implemented (blocked on MPV — see playback-backend-unification.md)`
+
+Worth stating *why* in the requirements entry, because it is not a scheduling
+gap: mpv's audio chain is single-stream, and FFmpeg's `acrossfade` is an `N→A`
+filter needing two inputs. Real crossfade requires two libmpv instances with
+manually ramped volumes. Upstream declined the feature (mpv#4512).
+
+### 1b. UR-031 status is wrong for the same reason
+
+`requirements.md` line ~44:
+
+```
+| UR-031 | Crossfade between audio tracks | Low | Done (Linux only) |
+```
+
+Same error one level up: the *user* requirement is also marked done. Since no
+backend implements crossfade, UR-031 is not satisfied on any platform.
+
+**Change to:** `Not implemented (blocked — see DR-034)`
+
+Note line ~517 of the same file (`UR-031 (Crossfade), UR-032 (Gapless),
+UR-033 (Normalization) only work on Linux`) inherits the error — crossfade works
+nowhere, so it should read UR-032/UR-033 only.
+
+### 2. Parity matrix crossfade row is wrong
+
+```
+| Crossfade | ✅ | ❌ | Gap |
+```
+
+**Change to** `| Crossfade | ❌ | ❌ | Not implemented |` — it is not a
+platform-parity gap, it is an unbuilt feature.
+
+### 3. Parity matrix is missing the equalizer
+
+The matrix lists crossfade, gapless, and normalization but omits the EQ, which
+has the same Linux-only shape and the same root cause (`ExoPlayerBackend` not
+overriding `set_audio_settings`). `build_af_filter` and `eq_filter_entries` exist
+only in `mpv_backend.rs`; there is no equalizer code in the Android tree.
+
+**Add:** `| Equalizer (10-band) | ✅ | ❌ | Gap |`
+
+### 4. `nativeAdapter.ts` cites a stale blocker
+
+`src/lib/player/adapters/nativeAdapter.ts:11-14` states native Android video is
+blocked upstream by tauri#10152 (transparent webview / SurfaceView compositing).
+
+tauri#10152 is open but **dead since 2024-07-01**, and it is a *feature request*
+that `WebviewWindowBuilder::transparent` was desktop-only — not a report that
+compositing is broken. The capability shipped in tauri commit `27d01834`
+(2024-09-02), which moved `transparent()` into the cross-platform impl block with
+only the tao call `#[cfg(desktop)]`-fenced. It landed as a clippy cleanup, so the
+issue was never closed. Separately, the black/white-screen bug (tauri#8381,
+tauri#9408) was a broken JNI signature for `setBackgroundColor`, fixed in wry
+0.39.4; we ship wry 0.55.x.
+
+**Change to:** a comment stating the adapter is currently unreachable because
+`createAdapter` hardcodes the HTML5 kind, that transparency is no longer an
+upstream blocker, and that
+[android-native-video-spike.md](android-native-video-spike.md) tracks whether
+SurfaceView compositing actually works. Be explicit that *nobody has
+demonstrated* SurfaceView-behind-WebView on Tauri Android — nothing upstream
+blocks it, and nothing upstream proves it.
+
+### 5. Platform capability is signalled three incompatible ways
+
+Not a doc error — a real inconsistency found during the same investigation, worth
+recording here even though fixing it needs its own change.
+
+Which backend a platform uses is currently expressed three ways:
+
+1. Rust `#[cfg]` gates in `player/mod.rs` and `create_player_backend` — the truth.
+2. The `useHtml5Element` / `VideoBackend` value from `get_player_status` — which
+   the frontend discards (see the spike spec).
+3. **Frontend user-agent sniffing** in `src/lib/services/webviewAudio.ts:30-41`:
+
+```ts
+const ua = navigator.userAgent.toLowerCase();
+const isAndroid = ua.includes("android");
+const isLinux = ua.includes("linux") && !isAndroid;
+return !isAndroid && !isLinux;
+```
+
+The comment says it is "matching the Rust cfg gate" — i.e. the frontend
+re-derives a backend decision from the user-agent string and hopes it stays in
+sync. That is the frontend deciding *which backend exists*, which is domain
+knowledge, not presentation. It also breaks silently the moment a new target is
+added or a webview's UA changes.
+
+**This is a boundary leak of the same family the spec-review checklist exists to
+catch**, even though `check:boundary`'s tripwire (item-type arrays) does not
+match it. Rust already computes the answer; the frontend should consume it.
+
+Not fixed by this spec — it is behavioural, not documentation. It should be
+folded into the spike spec's factory rework, where the same
+"consume Rust's decision instead of re-deriving it" change is already in scope.
+
+### Also worth fixing while here
+
+`requirements.md` IR-004 reads "In Progress (basic playback works, audio settings
+missing)". That stays accurate until
+[android-audio-settings-parity.md](android-audio-settings-parity.md) lands, but
+the "Future Fix" list in the parity issue proposes
+`ConcatenatingMediaSource` for crossfade — **deprecated in current Media3**. Drop
+that suggestion; the modern approach is a custom `AudioProcessor`.
+
+## Layer assignment
+
+No logic. Documentation and comments only.
+
+| Logic / responsibility | Layer | Why it belongs there |
+|------------------------|-------|----------------------|
+| — | — | No logic introduced or moved by this spec. |
+
+## Out of scope
+
+- Implementing crossfade. This spec only stops claiming it exists.
+- Implementing Android audio settings — see the parity spec.
+- Running the Android video spike — see that spec.
+- Rewriting the architecture docs. `docs/architecture/05-platform-backends.md`
+  should be re-read for the same class of error, but that is a larger pass.
+
+## Acceptance criteria
+
+- [ ] DR-034 status corrected, with the blocking reason stated.
+- [ ] UR-031 status corrected (line ~44), and the "only work on Linux" line (~517) no longer lists crossfade.
+- [ ] Parity matrix: crossfade ❌/❌; equalizer row added.
+- [ ] `ConcatenatingMediaSource` suggestion removed from the "Future Fix" list.
+- [ ] `nativeAdapter.ts` comment corrected and pointing at the spike spec.
+- [ ] `bun run check` and `bun run test` pass (a comment change still touches TS).
+- [ ] `bun run traces:markdown` re-run if requirement text changed.
+
+No Rust changes, so the `cargo` gates do not apply.
+
+## Testing
+
+None beyond the standard gates — no behaviour changes. Confirm
+`bun run traces:markdown` regenerates cleanly, since DR-034's row is referenced
+by the traceability matrix.
+
+## TRACES
+
+No code implementing requirements changes; no TRACES comments to add or update.
+The DR-034 row in `docs/traceability.md` will regenerate with the corrected text.
+
+## Notes for the implementer
+
+- Do **not** silently delete DR-034. The requirement (UR-031 crossfade) is still
+  wanted; it is the *status* that is wrong. Keeping the row with an honest status
+  and a reason is the point.
+- A parallel Claude session may be active — `git diff` before "repairing"
+  unexpected changes.
@@ -0,0 +1,209 @@
+# Spec: Windows native audio backend
+
+**Status:** Proposed
+**Requirements:** UR-003, UR-027, UR-032, UR-033 → DR-030, DR-035, DR-036; new IR-030
+**UX spec:** n/a — Settings › Audio already renders the controls
+**Supersedes / revises:** acts on the "audio can unify, video cannot" conclusion in [playback-backend-unification.md](playback-backend-unification.md)
+
+## Summary
+
+Give Windows a real native audio backend instead of the current webview
+`<audio>` shim. Windows is the only platform where audio playback has no decoder
+of its own: `WebviewAudioBackend` hands a URL to a frontend `<audio>` element and
+relays transport commands. It cannot set volume, cannot apply any audio setting,
+and reports state only via DOM events.
+
+Audio needs no rendering surface, so **none of the webview-compositing problems
+that block unified video apply here.** This is the cleanest available win.
+
+## Motivation
+
+`WebviewAudioBackend` was a deliberate stopgap ("audio-only playback for
+platforms without a native audio backend"), and it works — but it has a hard
+functional gap. From `webview_audio_backend.rs`:
+
+```rust
+fn set_volume(&mut self, volume: f32) -> Result<(), PlayerError> {
+    // ...stores locally only; there is no ControlCommand action for volume
+}
+```
+
+So volume changes never reach the element; the frontend has to observe the player
+store and apply volume itself. `set_audio_settings` likewise stores values that
+nothing consumes — EQ, normalization, and gapless are all inert on Windows.
+
+Meanwhile the backend-unification investigation established that a native *audio*
+engine is unproblematic on Windows specifically: `tauri-plugin-libmpv` lists
+Windows as its **fully tested** platform (in contrast to Linux, where embedding
+is broken — but that is a *video surface* problem, which audio does not have).
+
+## Layer assignment
+
+| Logic / responsibility | Layer | Why it belongs there |
+|------------------------|-------|----------------------|
+| Decoding and playing the audio stream | Rust | Playback is domain logic; every other platform already decodes in Rust or a native player. The webview shim is the anomaly. |
+| Applying `AudioSettings` (EQ/normalize/gapless) | Rust | Same `AudioSettings` contract as MPV/ExoPlayer; band layout and presets stay canonical in `settings.rs`. |
+| Position/state reporting | Rust | Restores the project's core principle — the player is the authoritative source of state. Today Windows inverts this: the DOM element is authoritative and Rust mirrors it. |
+| Volume | Rust | Currently broken precisely because it is split across the boundary. |
+| Rendering the player UI | Frontend | Unchanged. |
+
+The strongest argument for this change is the third row. CLAUDE.md states
+playback state is one-directional with the player authoritative; on Windows that
+is currently false, and the `player_report_*` round-trip exists to paper over it.
+
+## Design
+
+### Engine choice
+
+Two viable options; **libmpv is recommended** for consistency with the Linux
+audio backend.
+
+| | libmpv | GStreamer |
+|---|---|---|
+| Windows status | ✅ `tauri-plugin-libmpv` reports fully tested | ✅ works, but… |
+| Rust bindings | `libmpv2` 6.0.0, active | `gstreamer-rs` 0.25.x, excellent |
+| Cross-MSVC from Linux | ⚠️ needs prebuilt DLL + import lib | ❌ `gstreamer-sys` uses pkg-config, fights `cargo-xwin` |
+| Code reuse | ✅ `MpvBackend` logic is directly reusable | ❌ a second engine to learn |
+| Crossfade capable | ❌ single-stream chain | ✅ `audiomixer` |
+
+libmpv wins on reuse: `MpvBackend`'s `set_audio_settings` — the `af` lavfi graph
+built by `build_af_filter`, `eq_filter_entries`, `normalize_filter_entry` — is
+platform-independent and would apply unchanged.
+
+The one reason to prefer GStreamer is crossfade (UR-031), which mpv structurally
+cannot do. If crossfade becomes a priority, revisit; it would then argue for
+GStreamer on *both* Linux and Windows, which is a much larger change.
+
+### Structure
+
+Rename the cfg gate so `MpvBackend` is no longer Linux-only:
+
+```rust
+// src-tauri/src/player/mod.rs
+#[cfg(any(target_os = "linux", target_os = "windows"))]
+pub mod mpv_backend;
+```
+
+`MpvBackend::new` needs one platform-specific branch: `detect_audio_system()`
+currently probes `pactl`/`pw-cli`/`/proc/asound/cards` to pick an `ao`. On
+Windows the equivalent is `wasapi` (mpv's default), so the detection is a
+`#[cfg]` returning `"wasapi"` — no probing needed.
+
+Everything else — the event loop, the 250ms position thread, the seek-suppression
+window, the `af` filter graph — is unchanged.
+
+`WebviewAudioBackend` stays for other targets (macOS and anything else hitting
+the `not(any(...))` arm) and as the fallback if libmpv fails to initialize. The
+existing `emit_backend_init_failed` path already handles that gracefully.
+
+### Build
+
+`libmpv2-sys` is well-suited to cross-compilation: no pkg-config, vendored
+headers, pregenerated bindings (no libclang). It emits `cargo:rustc-link-lib=mpv`
+unconditionally, so the build must supply a linkable import library for
+`x86_64-pc-windows-msvc`.
+
+Keep the `build_libmpv` feature **off** — its Unix path shells out to mpv-build
+and explicitly rejects cross-compilation.
+
+🔴 Per CLAUDE.md, the prebuilt libmpv **must be added to the builder image**
+(`Dockerfile.builder` → rebuild + push via `scripts/build-builder-image.sh`), not
+installed at CI job time. `libmpv-2.dll` must also be bundled into the NSIS
+installer via `tauri.conf.json`'s resources.
+
+### Verified build mechanics
+
+The cross-compile path was tested hands-on from Linux (July 2026), not inferred:
+
+- Neither shinchiro nor zhongfly ships an `mpv.def` or MSVC `mpv.lib` — only a
+  MinGW `libmpv.dll.a`. (Several online sources claim otherwise; they are wrong.)
+- An MSVC-style import lib can be generated locally with LLVM tools only:
+  `llvm-readobj --coff-exports libmpv-2.dll` → synthesize `mpv.def` →
+  `llvm-dlltool -m i386:x86-64 -d mpv.def -l mpv.lib`. `llvm-lib /def:` produces a
+  byte-identical result.
+- A real `lld-link` link against that import lib **succeeds**, and the resulting
+  import table resolves `mpv_client_api_version` from `libmpv-2.dll`. `lld-link`
+  is the linker `cargo-xwin` uses, so this is the load-bearing step.
+- Linking directly against the shipped MinGW `libmpv.dll.a` **also** succeeds, so
+  def-generation may be skippable — but that relies on lld's GNU-archive
+  tolerance rather than a documented contract. Keep `llvm-dlltool` as the
+  fallback.
+- MinGW origin is not an ABI problem: libmpv exports a pure C ABI, and the x86-64
+  Windows calling convention is platform-defined. The upstream note that MSVC
+  cannot *build* mpv is frequently misread as "MSVC cannot *link* libmpv" — that
+  is not what it says.
+- 🔴 Never free/realloc across the DLL boundary — use `mpv_free`.
+
+Build wiring is ordinary: `cargo:rustc-link-lib=dylib=mpv` plus
+`cargo:rustc-link-search`. Nothing about libmpv conflicts with `cargo-xwin`.
+
+### Size and shipping
+
+Measured uncompressed: **93 MiB** (zhongfly `mpv-dev-lgpl-x86_64`) vs **112 MiB**
+(shinchiro, full GPL build); ~26–30 MB compressed in the `.7z`.
+
+**Ship the zhongfly LGPL build** — smaller, and there is no reason to pull the
+GPL variant in for an audio-only use.
+
+Import-table inspection confirms **no companion DLLs are needed**: every
+dependency is a system DLL (`KERNEL32`, `USER32`, `d2d1`, `DWrite`, `OPENGL32`,
+`vulkan-1`, UCRT `api-ms-win-*`). One file to bundle.
+
+93 MiB is still substantial against a Tauri app's usual few MB. Since we use mpv
+audio-only, investigate whether a pruned build (no video decoders, no libplacebo)
+is worth producing for the builder image — but treat that as an optimization,
+not a blocker.
+
+## Out of scope
+
+- Windows *video*. Stays in WebView2 + hls.js — it works and has ABR.
+- Crossfade (UR-031/DR-034) — not implemented anywhere; needs its own spec.
+- Replacing `WebviewAudioBackend` for macOS.
+- MPRIS/SMTC media-key integration — worth a follow-up, not this spec.
+
+## Acceptance criteria
+
+- [ ] Windows build produces a `MpvBackend`-backed player; `backend-init-failed` is emitted (not a crash) if libmpv is unavailable.
+- [ ] Volume control works from the UI — the current hard gap.
+- [ ] EQ, normalization, and gapless audibly take effect on Windows.
+- [ ] Position/state originate in Rust; the `<audio>` element is no longer in the audio path.
+- [ ] Seek, next/previous, and queue advance work; sleep timer stops playback.
+- [ ] `libmpv-2.dll` ships in the NSIS installer and the app runs on a clean Windows VM with no mpv installed.
+- [ ] Builder image carries the Windows libmpv artefacts; **no toolchain install added to any CI step**.
+- [ ] `bun run check`, `bun run test`, `bun run check:boundary` pass.
+- [ ] `cargo fmt` clean, `cargo clippy` clean, `bun run test:rust` passes.
+- [ ] New requirement-implementing code carries `// TRACES:` comments.
+
+## Testing
+
+**Rust**: the existing `mpv_backend_test.rs` and the `build_af_filter` /
+`normalize_filter_entry` / `eq_filter_entries` unit tests already cover the
+filter-graph logic and are platform-independent — they should pass unchanged
+under a Windows `cargo check`/test. Add a test asserting `detect_audio_system()`
+returns `wasapi` under `cfg(windows)`.
+
+**Manual, on Windows**: volume, EQ preset change, normalization toggle, gapless
+between two tracks, seek, queue advance, sleep timer. Then the packaging test —
+install the NSIS output on a clean VM and confirm it launches and plays.
+
+Per CLAUDE.md, the volume gap is a *bug fix*: write a failing test for
+"`set_volume` reaches the backend" before implementing.
+
+## TRACES
+
+- Windows `MpvBackend` construction in `create_player_backend` → `// TRACES: UR-003 | IR-030`
+- `detect_audio_system` Windows branch → `IR-030`
+- Existing `set_audio_settings` gains Windows coverage → `UR-027, UR-032, UR-033 | DR-030, DR-035, DR-036`
+- Allocate **IR-030** in `requirements.md` ("libmpv integration for Windows audio playback").
+
+## Notes for the implementer
+
+- Do this **after** [libmpv2-migration.md](libmpv2-migration.md) — porting the
+  current dead `libmpv` git pin to a second platform would double the migration
+  work.
+- `libmpv2` has broken its API in every major release (4.0 removed command
+  helpers, 5.0 removed `mpv_node`, 6.0 changed `RenderContext` ownership). Pin an
+  exact version.
+- Only the `render`-feature parts of `libmpv2` concern video; audio-only use does
+  not need it, and disabling the default `render` feature may shrink the build.
+- A parallel Claude session may be active — `git diff` first.
@@ -346,10 +346,12 @@ flowchart TB
 **User Interaction:**
 - **Tap screen:** Controls reappear for 3 seconds
 - **Double tap left side:** Rewind 10 seconds (shows animated feedback with "-10" indicator)
- **Double tap right side:** Forward 10 seconds (shows animated feedback with "+10" indicator)
+- **Double tap right side:** Forward 30 seconds (shows animated feedback with "+30" indicator)
+- **Single tap play/pause is deferred** by the 300 ms double-tap window, so a double tap
+  skips without also toggling pause (UR-061)
 - **Swipe up/down on left side:** Adjust brightness (0.3-1.7x, shows brightness indicator with progress bar)
 - **Swipe up/down on right side:** Adjust volume (0-100%, shows volume indicator with progress bar)
- **Keyboard arrows:** ← rewind 10s, → forward 10s (desktop/external keyboard)
+- **Keyboard arrows:** ← rewind 10s, → forward 30s (desktop/external keyboard)
 - **Keyboard space/K:** Toggle play/pause
 - **Keyboard F:** Toggle fullscreen
 - **Pinch:** Zoom (planned)
@@ -1,6 +1,6 @@
 {
  "name": "jellytau",
-  "version": "0.1.2",
+  "version": "0.2.0",
  "description": "",
  "type": "module",
  "packageManager": "bun@1.3.5",
@@ -1994,7 +1994,7 @@ dependencies = [

 [[package]]
 name = "jellytau"
-version = "0.1.2"
+version = "0.2.0"
 dependencies = [
 "aes-gcm",
 "async-trait",
@@ -1,6 +1,6 @@
 [package]
 name = "jellytau"
-version = "0.1.2"
+version = "0.2.0"
 description = "A Tauri App"
 authors = ["you"]
 edition = "2021"
@@ -1,10 +1,5 @@
 package com.dtourolle.jellytau

-import android.content.Context
-import android.media.AudioAttributes
-import android.media.AudioFocusRequest
-import android.media.AudioManager
-import android.os.Build
 import android.os.Bundle
 import android.os.Handler
 import android.os.Looper
@@ -19,8 +14,6 @@ class MainActivity : TauriActivity() {
  private val handler = Handler(Looper.getMainLooper())
  private var configAttempts = 0
  private val maxConfigAttempts = 10
-  private var audioFocusRequest: AudioFocusRequest? = null
-  private val audioManager by lazy { getSystemService(Context.AUDIO_SERVICE) as AudioManager }

  /**
   * Coarse override for whether backgrounding the app should auto-enter PiP.
@@ -50,6 +43,15 @@ class MainActivity : TauriActivity() {
   */
  private var mediaWebView: WebView? = null

+  /**
+   * The WebView the @JavascriptInterface bridges have been injected into.
+   *
+   * addJavascriptInterface must run once per WebView instance: re-injecting
+   * over an already-loaded page hands JS a stale proxy whose methods are gone.
+   * Compared by identity so a genuinely new WebView still gets its bridges.
+   */
+  private var bridgesInstalledOn: WebView? = null
+
  override fun onCreate(savedInstanceState: Bundle?) {
    enableEdgeToEdge()
    super.onCreate(savedInstanceState)
@@ -159,19 +161,36 @@ class MainActivity : TauriActivity() {
      android.util.Log.d("MainActivity", "WebView found! Configuring settings...")
      mediaWebView = webView

-      // Add JavaScript interface for audio focus control
-      webView.addJavascriptInterface(object : Any() {
-        @JavascriptInterface
-        fun requestAudioFocus() {
-          handler.post { this@MainActivity.requestAudioFocus() }
+      // Register the @JavascriptInterface bridges EXACTLY ONCE per WebView.
+      //
+      // configureWebViewForMedia() runs from onCreate's delayed post AND from
+      // every onResume (plus each WebView re-find), so this used to re-inject
+      // all four bridges repeatedly - 5 times in a 45s session. WebView binds
+      // injected objects at page-load time; re-injecting over a live page
+      // leaves JS holding a stale proxy. The object stays truthy while its
+      // methods vanish, which surfaced as a flood of
+      // "WebView: Unknown object" chromium errors and, in JS,
+      // "TypeError: setEnabled is not a function".
+      //
+      // The visible bug: the background-audio toggle turned blue but never
+      // reached native, so backgroundAudioEnabled stayed false, onStop never
+      // dispatched 'jellytau-background', and a locked screen killed audio
+      // instantly (UR-040). Audio focus and PiP broke the same way.
+      //
+      // The settings/WebChromeClient work below is idempotent and must keep
+      // running on resume; only the bridge injection is one-shot.
+      if (webView === bridgesInstalledOn) {
+        android.util.Log.d("MainActivity", "JS bridges already installed on this WebView - skipping re-injection")
+        configureWebViewSettings(webView)
+        return
      }
+      bridgesInstalledOn = webView

-        @JavascriptInterface
-        fun abandonAudioFocus() {
-          handler.post { this@MainActivity.abandonAudioFocus() }
-        }
-      }, "AndroidAudioFocus")
-      android.util.Log.d("MainActivity", "JavaScript interface 'AndroidAudioFocus' added")
+      // NOTE: there is deliberately no "AndroidAudioFocus" bridge. Manual focus
+      // requests from the WebView competed with Chromium's own
+      // AudioFocusDelegate and with ExoPlayer, and the resulting
+      // AUDIOFOCUS_LOSS paused playback. See the comment on the video listeners
+      // in configureWebViewSettings().

      // Add JavaScript interface for picture-in-picture control.
      // enterPip/canEnterPip must run on the main thread; @JavascriptInterface
@@ -212,10 +231,6 @@ class MainActivity : TauriActivity() {
          backgroundAudioEnabled = enabled
          android.util.Log.d("MainActivity", "backgroundAudioEnabled = $enabled")
        }
-
-        /** Whether background audio is available on this device (needs PiP-era APIs unnecessary; audio service always present on Android). */
-        @JavascriptInterface
-        fun isSupported(): Boolean = true
      }, "AndroidBackgroundAudio")
      android.util.Log.d("MainActivity", "JavaScript interface 'AndroidBackgroundAudio' added")

@@ -248,6 +263,21 @@ class MainActivity : TauriActivity() {
        dispatchWebEvent("jellytau-network-changed")
      }

+      configureWebViewSettings(webView)
+
+    } catch (e: Exception) {
+      android.util.Log.e("MainActivity", "Failed to configure WebView for media", e)
+    }
+  }
+
+  /**
+   * WebView settings, chrome client and the video-unmute script.
+   *
+   * Split out from the bridge injection because this half is idempotent and
+   * must re-run on every resume, whereas addJavascriptInterface must not.
+   */
+  private fun configureWebViewSettings(webView: WebView) {
+    try {
      // Set WebChromeClient to handle video playback and audio focus
      webView.webChromeClient = object : WebChromeClient() {
        override fun onShowCustomView(view: View?, callback: CustomViewCallback?) {
@@ -259,6 +289,21 @@ class MainActivity : TauriActivity() {
          super.onHideCustomView()
          android.util.Log.d("MainActivity", "Video exited fullscreen")
        }
+
+        /**
+         * Forward WebView console output to logcat under the "JellyTauWeb" tag.
+         *
+         * Without this the frontend is invisible to `adb logcat`, which makes
+         * diagnosing anything that spans the JS/native boundary (the
+         * background-audio handoff in particular) guesswork.
+         */
+        override fun onConsoleMessage(msg: android.webkit.ConsoleMessage): Boolean {
+          android.util.Log.d(
+            "JellyTauWeb",
+            "${msg.message()} (${msg.sourceId()}:${msg.lineNumber()})"
+          )
+          return true
+        }
      }
      android.util.Log.d("MainActivity", "WebChromeClient configured")

@@ -287,29 +332,18 @@ class MainActivity : TauriActivity() {
              video.volume = 1.0;
              console.log('[Android] Video unmuted, volume:', video.volume, 'muted:', video.muted);

-              // Add event listeners to manage audio focus
-              video.addEventListener('play', function() {
-                console.log('[Android] Video play event - requesting audio focus');
-                if (typeof AndroidAudioFocus !== 'undefined') {
-                  AndroidAudioFocus.requestAudioFocus();
-                }
-                console.log('[Android] Video state - muted:', this.muted, 'volume:', this.volume);
-              });
-
-              video.addEventListener('pause', function() {
-                console.log('[Android] Video pause event - abandoning audio focus');
-                if (typeof AndroidAudioFocus !== 'undefined') {
-                  AndroidAudioFocus.abandonAudioFocus();
-                }
-              });
-
-              video.addEventListener('ended', function() {
-                console.log('[Android] Video ended event - abandoning audio focus');
-                if (typeof AndroidAudioFocus !== 'undefined') {
-                  AndroidAudioFocus.abandonAudioFocus();
-                }
-              });
-
+              // NOTE: deliberately no audio-focus calls here.
+              //
+              // WebView already manages audio focus for <video> through
+              // Chromium's own AudioFocusDelegate. Requesting AUDIOFOCUS_GAIN
+              // again from MainActivity made two requesters compete inside one
+              // uid: the grant was immediately followed by AUDIOFOCUS_LOSS
+              // (~45ms), whose handler paused playback - so arming background
+              // audio, or simply pressing play, paused the video in a loop.
+              //
+              // ExoPlayer is the third potential owner and stays authoritative
+              // for native playback (JellyTauPlayer manages its own focus).
+              // Leave focus to whichever engine is actually rendering.
              video.addEventListener('volumechange', function() {
                console.log('[Android] Video volume changed - volume:', this.volume, 'muted:', this.muted);
              });
@@ -356,48 +390,4 @@ class MainActivity : TauriActivity() {
    return null
  }

-  private fun requestAudioFocus() {
-    android.util.Log.d("MainActivity", "Requesting audio focus for video playback")
-
-    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-      val audioAttributes = AudioAttributes.Builder()
-        .setUsage(AudioAttributes.USAGE_MEDIA)
-        .setContentType(AudioAttributes.CONTENT_TYPE_MOVIE)
-        .build()
-
-      audioFocusRequest = AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN)
-        .setAudioAttributes(audioAttributes)
-        .setAcceptsDelayedFocusGain(true)
-        .setOnAudioFocusChangeListener { focusChange ->
-          android.util.Log.d("MainActivity", "Audio focus changed: $focusChange")
-        }
-        .build()
-
-      val result = audioManager.requestAudioFocus(audioFocusRequest!!)
-      android.util.Log.d("MainActivity", "Audio focus request result: $result")
-    } else {
-      @Suppress("DEPRECATION")
-      val result = audioManager.requestAudioFocus(
-        { focusChange ->
-          android.util.Log.d("MainActivity", "Audio focus changed: $focusChange")
-        },
-        AudioManager.STREAM_MUSIC,
-        AudioManager.AUDIOFOCUS_GAIN
-      )
-      android.util.Log.d("MainActivity", "Audio focus request result (legacy): $result")
-    }
-  }
-
-  private fun abandonAudioFocus() {
-    android.util.Log.d("MainActivity", "Abandoning audio focus")
-
-    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-      audioFocusRequest?.let {
-        audioManager.abandonAudioFocusRequest(it)
-      }
-    } else {
-      @Suppress("DEPRECATION")
-      audioManager.abandonAudioFocus { }
-    }
-  }
 }
@@ -36,6 +36,53 @@ class JellyTauPlayer(private val appContext: Context) {
        /** Position update interval in milliseconds */
        private const val POSITION_UPDATE_INTERVAL_MS = 250L

+        /** AudioEffect priority. Positive = higher priority than the default. */
+        private const val EFFECT_PRIORITY = 1000
+
+        /**
+         * Canonical 10-band ISO centre frequencies (Hz), mirroring EQ_BANDS in
+         * settings.rs. Kept in sync deliberately: Rust owns the band layout, this
+         * is only the lookup table used to map those gains onto whatever bands
+         * the device's equalizer actually has.
+         */
+        private val CANONICAL_BAND_CENTRES_HZ =
+            intArrayOf(31, 62, 125, 250, 500, 1000, 2000, 4000, 8000, 16000)
+
+        /**
+         * Map canonical band gains onto a device's band centres by nearest
+         * centre frequency.
+         *
+         * Pure function so it can be unit-tested without a device — device band
+         * counts vary (commonly 5) and getting this wrong silently mis-shapes the
+         * EQ curve rather than failing.
+         *
+         * TRACES: UR-027 | DR-030
+         */
+        @JvmStatic
+        fun resampleBands(
+            canonicalGains: FloatArray,
+            canonicalCentresHz: IntArray,
+            deviceCentresHz: IntArray
+        ): FloatArray {
+            if (canonicalGains.isEmpty() || deviceCentresHz.isEmpty()) {
+                return FloatArray(deviceCentresHz.size)
+            }
+            val usable = minOf(canonicalGains.size, canonicalCentresHz.size)
+            return FloatArray(deviceCentresHz.size) { d ->
+                val target = deviceCentresHz[d]
+                var nearest = 0
+                var bestDelta = Int.MAX_VALUE
+                for (c in 0 until usable) {
+                    val delta = kotlin.math.abs(canonicalCentresHz[c] - target)
+                    if (delta < bestDelta) {
+                        bestDelta = delta
+                        nearest = c
+                    }
+                }
+                canonicalGains[nearest]
+            }
+        }
+
        /** Singleton instance for JNI access */
        @Volatile
        private var instance: JellyTauPlayer? = null
@@ -135,6 +182,18 @@ class JellyTauPlayer(private val appContext: Context) {
    private val coroutineScope = CoroutineScope(Dispatchers.Main + SupervisorJob())
    private var positionUpdateJob: Job? = null

+    /** Graphic EQ bound to the current audio session, or null if not attached. */
+    private var equalizer: android.media.audiofx.Equalizer? = null
+
+    /** Loudness/normalization effect bound to the current audio session. */
+    private var loudnessEnhancer: android.media.audiofx.LoudnessEnhancer? = null
+
+    /**
+     * Last settings pushed from Rust, replayed when the audio session is rebuilt.
+     * Held as the raw payload so re-application needs no second parse contract.
+     */
+    private var lastAudioSettings: org.json.JSONObject? = null
+
    /** Current media ID being played */
    private var currentMediaId: String? = null

@@ -334,6 +393,11 @@ class JellyTauPlayer(private val appContext: Context) {

            override fun onAudioSessionIdChanged(audioSessionId: Int) {
                android.util.Log.d("JellyTauPlayer", "▶▶▶ AUDIO SESSION ID CHANGED: $audioSessionId")
+                // ExoPlayer rebuilt its audio sink (e.g. on a format change), so
+                // effects bound to the old session are dead. Re-attach, or the EQ
+                // silently stops applying mid-queue.
+                releaseAudioEffects()
+                lastAudioSettings?.let { applyAudioEffects(it) }
            }
        })
    }
@@ -416,6 +480,133 @@ class JellyTauPlayer(private val appContext: Context) {
        }
    }

+    /**
+     * Apply audio settings pushed from Rust as JSON.
+     *
+     * Rust owns *what* the values are (band layout, preset curves, normalization
+     * presets); this owns *when* the Android AudioEffect objects exist, since
+     * that needs the live audio session id and must survive a sink rebuild.
+     *
+     * Posted to the main handler rather than run inline: AudioEffect construction
+     * from a player callback can re-enter the player and deadlock.
+     *
+     * TRACES: UR-027, UR-032, UR-033 | DR-030, DR-035, DR-036
+     */
+    fun setAudioSettings(json: String) {
+        mainHandler.post {
+            try {
+                val settings = org.json.JSONObject(json)
+                lastAudioSettings = settings
+
+                // Gapless: ExoPlayer is gapless by default for compatible
+                // formats, so honouring the setting means disabling it when off.
+                exoPlayer.pauseAtEndOfMediaItems = !settings.optBoolean("gaplessPlayback", true)
+
+                applyAudioEffects(settings)
+            } catch (e: Exception) {
+                android.util.Log.e("JellyTauPlayer", "Failed to apply audio settings", e)
+            }
+        }
+    }
+
+    /** Attach/update the EQ and loudness effects for the current audio session. */
+    private fun applyAudioEffects(settings: org.json.JSONObject) {
+        val sessionId = exoPlayer.audioSessionId
+        if (sessionId == C.AUDIO_SESSION_ID_UNSET) {
+            // No sink yet; onAudioSessionIdChanged will re-drive this.
+            return
+        }
+
+        try {
+            applyEqualizer(sessionId, settings)
+        } catch (e: Exception) {
+            android.util.Log.e("JellyTauPlayer", "Equalizer unavailable on this device", e)
+        }
+
+        try {
+            applyNormalization(sessionId, settings)
+        } catch (e: Exception) {
+            android.util.Log.e("JellyTauPlayer", "LoudnessEnhancer unavailable on this device", e)
+        }
+    }
+
+    private fun applyEqualizer(sessionId: Int, settings: org.json.JSONObject) {
+        val enabled = settings.optBoolean("equalizerEnabled", false)
+
+        if (!enabled) {
+            equalizer?.enabled = false
+            return
+        }
+
+        val eq = equalizer ?: android.media.audiofx.Equalizer(EFFECT_PRIORITY, sessionId).also {
+            equalizer = it
+        }
+
+        val bandsJson = settings.optJSONArray("equalizerBands")
+        val canonicalGains = FloatArray(bandsJson?.length() ?: 0) { i ->
+            bandsJson!!.optDouble(i, 0.0).toFloat()
+        }
+        if (canonicalGains.isEmpty()) {
+            eq.enabled = false
+            return
+        }
+
+        // The device's band count/centres are device-dependent (commonly 5) and
+        // will not match our canonical 10-band ISO layout, so resample.
+        val deviceBandCount = eq.numberOfBands.toInt()
+        val deviceCentresHz = IntArray(deviceBandCount) { i ->
+            eq.getCenterFreq(i.toShort()) / 1000 // device reports milliHertz
+        }
+        val levelRange = eq.bandLevelRange // millibels, [min, max]
+
+        val resampled = resampleBands(canonicalGains, CANONICAL_BAND_CENTRES_HZ, deviceCentresHz)
+
+        for (i in 0 until deviceBandCount) {
+            val millibels = (resampled[i] * 100f)
+                .coerceIn(levelRange[0].toFloat(), levelRange[1].toFloat())
+            eq.setBandLevel(i.toShort(), millibels.toInt().toShort())
+        }
+        eq.enabled = true
+    }
+
+    private fun applyNormalization(sessionId: Int, settings: org.json.JSONObject) {
+        val enabled = settings.optBoolean("normalizeVolume", false)
+
+        if (!enabled) {
+            loudnessEnhancer?.enabled = false
+            return
+        }
+
+        val enhancer = loudnessEnhancer
+            ?: android.media.audiofx.LoudnessEnhancer(sessionId).also { loudnessEnhancer = it }
+
+        // Approximate parity with the Linux dynaudnorm path: LoudnessEnhancer is
+        // a gain stage, not a true EBU R128 normalizer, so these are relative
+        // offsets preserving the Loud > Normal > Quiet ordering.
+        val targetGainMb = when (settings.optString("volumeLevel", "normal")) {
+            "loud" -> 600
+            "quiet" -> -600
+            else -> 0
+        }
+        enhancer.setTargetGain(targetGainMb)
+        enhancer.enabled = true
+    }
+
+    private fun releaseAudioEffects() {
+        try {
+            equalizer?.release()
+        } catch (e: Exception) {
+            android.util.Log.w("JellyTauPlayer", "Equalizer release failed", e)
+        }
+        try {
+            loudnessEnhancer?.release()
+        } catch (e: Exception) {
+            android.util.Log.w("JellyTauPlayer", "LoudnessEnhancer release failed", e)
+        }
+        equalizer = null
+        loudnessEnhancer = null
+    }
+
    /**
     * Get the current playback position in seconds.
     */
@@ -756,6 +947,7 @@ class JellyTauPlayer(private val appContext: Context) {
        mainHandler.post {
            stopPositionUpdates()
            coroutineScope.cancel()
+            releaseAudioEffects()
            exoPlayer.release()
            instance = null
        }
@@ -18,6 +18,7 @@ use super::events::{PlayerStatusEvent, SharedEventEmitter};
 use super::media::{MediaItem, MediaType};
 use super::state::PlayerState;
 use crate::playback_reporting::{EventThrottler, PlaybackOperation, PlaybackReporter};
+use crate::settings::{audio_settings_jni_payload, AudioSettings};
 use crate::utils::conversions::seconds_to_ticks;

 /// Global reference to the JavaVM for JNI callbacks
@@ -148,6 +149,10 @@ struct ExoPlayerState {
    volume: f32,
    is_loaded: bool,
    current_media: Option<MediaItem>,
+    /// Last applied audio settings. Unlike the fields above (which JNI callbacks
+    /// push *in*), this is commanded *out* — audio settings are never reported
+    /// by the player, so this is the authoritative copy for `audio_settings()`.
+    audio_settings: AudioSettings,
 }

 impl ExoPlayerState {
@@ -159,6 +164,7 @@ impl ExoPlayerState {
            volume: 1.0,
            is_loaded: false,
            current_media: None,
+            audio_settings: AudioSettings::default(),
        }
    }
 }
@@ -529,6 +535,56 @@ impl PlayerBackend for ExoPlayerBackend {
        self.shared_state.lock_safe().volume
    }

+    /// Apply audio settings to ExoPlayer (equalizer, normalization, gapless).
+    ///
+    /// Sent as JSON rather than a wide JNI signature so new fields do not change
+    /// the method signature — the same approach `load()` uses for subtitles. The
+    /// Kotlin side owns the *mechanics* (attaching AudioEffects to the audio
+    /// session); the canonical band layout and preset curves stay in Rust.
+    ///
+    /// TRACES: UR-027, UR-032, UR-033 | DR-030, DR-035, DR-036
+    fn set_audio_settings(&mut self, settings: &AudioSettings) -> Result<(), PlayerError> {
+        let json = audio_settings_jni_payload(settings).map_err(|e| {
+            PlayerError::playback_failed(format!("Failed to serialize audio settings: {}", e))
+        })?;
+
+        let vm = JAVA_VM
+            .get()
+            .ok_or_else(|| PlayerError::playback_failed("JavaVM not initialized"))?;
+
+        let mut env = vm
+            .attach_current_thread()
+            .map_err(|e| PlayerError::playback_failed(format!("Failed to attach thread: {}", e)))?;
+
+        let json_jstring = env.new_string(&json).map_err(|e| {
+            PlayerError::playback_failed(format!("Failed to create settings string: {}", e))
+        })?;
+
+        env.call_method(
+            &self.player_ref,
+            "setAudioSettings",
+            "(Ljava/lang/String;)V",
+            &[JValue::Object(&json_jstring)],
+        )
+        .map_err(|e| {
+            PlayerError::playback_failed(format!("Failed to call setAudioSettings: {}", e))
+        })?;
+
+        // Store the sanitised form so audio_settings() reflects what was applied,
+        // not what was requested.
+        self.shared_state.lock_safe().audio_settings = settings
+            .clone()
+            .with_crossfade_clamped()
+            .with_equalizer_normalised();
+
+        Ok(())
+    }
+
+    /// TRACES: UR-027, UR-032, UR-033 | DR-030, DR-035, DR-036
+    fn audio_settings(&self) -> AudioSettings {
+        self.shared_state.lock_safe().audio_settings.clone()
+    }
+
    fn set_audio_track(&mut self, stream_index: i32) -> Result<(), PlayerError> {
        let vm = JAVA_VM
            .get()
@@ -243,6 +243,23 @@ impl PlayerController {
        self.end_reason.lock_safe().take()
    }

+    /// Record that playback is being stopped by an expiring sleep timer.
+    ///
+    /// Stopping the backend makes it fire its ended callback (ExoPlayer does on
+    /// Android), which lands in `on_playback_ended`. Without an end reason that
+    /// reads as a natural finish and autoplay advances — defeating the timer.
+    /// `UserStop` is the honest label: the stop was user-initiated, just via the
+    /// timer they set rather than the stop button.
+    ///
+    /// Takes the shared slot rather than `&self` so the sleep-timer thread —
+    /// which owns clones, not the controller — records it the same way.
+    ///
+    /// TRACES: UR-023, UR-026 | DR-029
+    fn note_sleep_timer_stop(end_reason: &Arc<Mutex<Option<EndReason>>>) {
+        log::debug!("[PlayerController] Sleep timer stop: marking end reason UserStop");
+        *end_reason.lock_safe() = Some(EndReason::UserStop);
+    }
+
    /// Increment autoplay episode counter. Returns true if limit is reached.
    fn increment_autoplay_count(&self) -> bool {
        let max = self.autoplay_settings.lock_safe().max_episodes;
@@ -767,6 +784,7 @@ impl PlayerController {
        let sleep_timer = self.sleep_timer.clone();
        let event_emitter = self.event_emitter.clone();
        let backend = self.backend.clone();
+        let end_reason = self.end_reason.clone();

        std::thread::spawn(move || {
            loop {
@@ -783,6 +801,14 @@ impl PlayerController {
                        debug!("[SleepTimer] Time-based timer expired, stopping playback");
                        timer.cancel();

+                        // Mark the stop *before* it reaches the backend. Stopping
+                        // makes the native player fire its ended callback, and
+                        // cancelling the timer above means on_playback_ended can no
+                        // longer tell this apart from a natural end — without this
+                        // it would show the next-episode popup / autoplay right
+                        // after the sleep timer fired.
+                        Self::note_sleep_timer_stop(&end_reason);
+
                        // Emit cancelled state
                        if let Some(emitter) = event_emitter.lock_safe().as_ref() {
                            emitter.emit(PlayerStatusEvent::SleepTimerChanged {
@@ -2040,6 +2066,51 @@ mod tests {
        }
    }

+    /// A time-based sleep timer that fires mid-episode must not let the ended
+    /// callback fall through to autoplay.
+    ///
+    /// The timer thread stops the backend directly, which makes ExoPlayer emit
+    /// its ended callback. That callback races the thread's own `timer.cancel()`:
+    /// by the time `on_playback_ended` inspects the sleep timer it reads `Off`,
+    /// so the timer branch is skipped and the episode path runs — showing a
+    /// next-episode popup (or advancing) after the user's sleep timer expired.
+    #[tokio::test]
+    async fn test_expired_time_sleep_timer_stops_without_autoplay() {
+        let controller = PlayerController::default();
+
+        let items = create_test_items(3);
+        controller.play_queue(items, 0).unwrap();
+        controller.take_end_reason();
+
+        // Arm a time-based timer that is already due, then let the real timer
+        // thread (started in the constructor, 1s tick) observe the expiry and
+        // run its stop path. Driving the actual thread is the point: the bug was
+        // that this path stopped the backend without recording an end reason.
+        let now = chrono::Utc::now().timestamp_millis();
+        controller.set_sleep_timer(SleepTimerMode::Time { end_time: now });
+
+        // Wait for the timer thread to process the expiry (tick is 1s).
+        for _ in 0..40 {
+            tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+            if !controller.sleep_timer.lock_safe().is_active() {
+                break;
+            }
+        }
+        assert!(
+            !controller.sleep_timer.lock_safe().is_active(),
+            "Timer thread should have expired and cancelled the sleep timer"
+        );
+
+        // The backend stop above makes the native player fire its ended callback.
+        let decision = controller.on_playback_ended().await.unwrap();
+
+        assert!(
+            matches!(decision, AutoplayDecision::Stop),
+            "Expected Stop after an expired time-based sleep timer, got {:?}",
+            decision
+        );
+    }
+
    #[tokio::test]
    async fn test_empty_queue_stops() {
        let controller = PlayerController::default();
@@ -179,10 +179,80 @@ impl VideoSettings {
    }
 }

+/// Serialise `AudioSettings` into the JSON payload handed to the Android player
+/// over JNI.
+///
+/// Sanitises first (crossfade clamped, band vector normalised) so a malformed
+/// vector can never reach the Kotlin parser. JSON is used rather than a wide JNI
+/// signature so that adding a field does not change the method signature — the
+/// same approach `load()` already uses for subtitles.
+///
+/// The emitted keys are camelCase (serde) and `volumeLevel` is lowercase; the
+/// Kotlin side matches on those literals. Both are pinned by tests.
+///
+/// TRACES: UR-027, UR-032, UR-033 | DR-030, DR-035, DR-036
+pub fn audio_settings_jni_payload(settings: &AudioSettings) -> Result<String, serde_json::Error> {
+    let sanitised = settings
+        .clone()
+        .with_crossfade_clamped()
+        .with_equalizer_normalised();
+    serde_json::to_string(&sanitised)
+}
+
 #[cfg(test)]
 mod tests {
    use super::*;

+    /// The JNI payload must sanitise before serialising: an over-long crossfade
+    /// is clamped and a wrong-length band vector is normalised to EQ_BANDS.len().
+    /// Sending raw values would let a malformed vector reach the Kotlin parser.
+    ///
+    /// TRACES: UR-027, UR-032, UR-033 | DR-030, DR-035, DR-036 | UT-AUDIO-JNI-1
+    #[test]
+    fn test_audio_settings_jni_payload_is_sanitised() {
+        let settings = AudioSettings {
+            crossfade_duration: 30.0,
+            equalizer_bands: vec![20.0, -30.0],
+            ..AudioSettings::default()
+        };
+
+        let json = audio_settings_jni_payload(&settings).expect("serialises");
+        let v: serde_json::Value = serde_json::from_str(&json).expect("valid JSON");
+
+        assert_eq!(v["crossfadeDuration"], 12.0, "crossfade clamped to 12s");
+
+        let bands = v["equalizerBands"].as_array().expect("bands array");
+        assert_eq!(bands.len(), EQ_BANDS.len(), "band vector normalised to 10");
+        assert_eq!(bands[0], EQ_GAIN_MAX as f64, "gain clamped to +12dB");
+        assert_eq!(bands[1], EQ_GAIN_MIN as f64, "gain clamped to -12dB");
+    }
+
+    /// The Kotlin side parses these exact keys. camelCase is what serde emits
+    /// for AudioSettings; a rename here silently breaks the Android parser,
+    /// which is why the contract is pinned by a test rather than by convention.
+    ///
+    /// TRACES: UR-027, UR-032, UR-033 | DR-030, DR-035, DR-036 | UT-AUDIO-JNI-2
+    #[test]
+    fn test_audio_settings_jni_payload_key_contract() {
+        let json = audio_settings_jni_payload(&AudioSettings::default()).expect("serialises");
+        let v: serde_json::Value = serde_json::from_str(&json).expect("valid JSON");
+
+        for key in [
+            "crossfadeDuration",
+            "gaplessPlayback",
+            "normalizeVolume",
+            "volumeLevel",
+            "equalizerEnabled",
+            "equalizerBands",
+        ] {
+            assert!(v.get(key).is_some(), "JNI payload must carry `{key}`");
+        }
+
+        // VolumeLevel is #[serde(rename_all = "lowercase")]; Kotlin matches on
+        // these literals.
+        assert_eq!(v["volumeLevel"], "normal");
+    }
+
    #[test]
    fn test_default_settings() {
        let settings = AudioSettings::default();
@@ -1,7 +1,7 @@
 {
  "$schema": "https://schema.tauri.app/config/2",
  "productName": "jellytau",
-  "version": "0.1.2",
+  "version": "0.2.0",
  "identifier": "com.dtourolle.jellytau",
  "build": {
    "beforeDevCommand": "bun run dev",
@@ -1,4 +1,4 @@
-<!-- TRACES: UR-003, UR-005, UR-020, UR-021, UR-026, UR-040 | DR-010, DR-023, DR-024, DR-051, DR-052 -->
+<!-- TRACES: UR-003, UR-005, UR-020, UR-021, UR-026, UR-040, UR-061 | DR-010, DR-023, DR-024, DR-051, DR-052, DR-092 -->
 <script lang="ts">
  import { onMount, onDestroy, untrack } from "svelte";
  import { goto } from "$app/navigation";
@@ -20,6 +20,14 @@
  import { Html5PlayerAdapter, type Html5ElementBridge } from "$lib/player/adapters";
  import { createRustReportHost } from "$lib/player/adapters/rustReportHost";
  import { isPipSupported, enterPip, setAutoEnterEnabled } from "$lib/utils/pictureInPicture";
+  import {
+    createTapGestureState,
+    registerTap,
+    resolveSeekTarget,
+    SEEK_FORWARD_SECONDS,
+    SEEK_BACKWARD_SECONDS,
+    type TapFeedback,
+  } from "./tapGestures";
  import {
    setBackgroundAudioEnabled,
    subscribeAppBackgrounded,
@@ -102,11 +110,14 @@
  let touchStartX = $state(0);
  let touchStartY = $state(0);
  let touchStartTime = $state(0);
-  let lastTapTime = $state(0);
+  let tapGestures = createTapGestureState();
  let tapTimeout: ReturnType<typeof setTimeout> | null = null;
  let brightness = $state(1); // 0-2, default 1
-  let showDoubleTapFeedback = $state<"left" | "right" | null>(null);
+  let showDoubleTapFeedback = $state<TapFeedback | null>(null);
  let doubleTapFeedbackTimeout: ReturnType<typeof setTimeout> | null = null;
+  // Target of a skip already requested but not yet reported back by the player,
+  // so back-to-back double taps chain instead of stacking on a stale position.
+  let pendingSeekTarget: number | null = null;
  let swipeGestureActive = $state(false);

  // Backend info from Rust (Rust decides which backend to use based on platform)
@@ -703,6 +714,16 @@
    if (debugLogInterval) {
      clearInterval(debugLogInterval);
    }
+    // A deferred single tap must not fire play/pause after teardown.
+    if (tapTimeout) {
+      clearTimeout(tapTimeout);
+      tapTimeout = null;
+    }
+    tapGestures.cancel();
+    if (doubleTapFeedbackTimeout) {
+      clearTimeout(doubleTapFeedbackTimeout);
+      doubleTapFeedbackTimeout = null;
+    }

    // Remove native backend event listeners (incl. background-audio lifecycle subs)
    for (const unlisten of nativeUnlisteners) {
@@ -1192,9 +1213,13 @@

  function toggleBackgroundAudio() {
    backgroundAudioOn = !backgroundAudioOn;
+    console.log("[VideoPlayer] Background-audio toggle ->", backgroundAudioOn);
    // Arm/disarm native background-audio mode AND flip auto-PiP the other way,
    // so exactly one background behavior is active.
-    setBackgroundAudioEnabled(backgroundAudioOn);
+    const armed = setBackgroundAudioEnabled(backgroundAudioOn);
+    if (!armed) {
+      console.warn("[VideoPlayer] Background audio NOT armed natively (no bridge)");
+    }
    setAutoEnterEnabled(!backgroundAudioOn);
  }

@@ -1342,7 +1367,16 @@
  async function seekRelative(seconds: number) {
    isSeeking = true;

-    const newTime = Math.max(0, Math.min(duration, currentTime + seconds));
+    // The facade seeks by absolute position, so resolve the delta here —
+    // chaining off a still-in-flight target so rapid double taps accumulate
+    // instead of all resolving against the same not-yet-updated position.
+    const newTime = resolveSeekTarget({
+      delta: seconds,
+      reportedPosition: currentTime,
+      duration,
+      pendingTarget: pendingSeekTarget,
+    });
+    pendingSeekTarget = newTime;

    console.log("[VideoPlayer] Relative seek:", {
      offset: `${seconds > 0 ? "+" : ""}${seconds}s`,
@@ -1358,7 +1392,12 @@
      }
    } as unknown as Event;

+    try {
      await handleSeekBarChange(syntheticEvent);
+    } finally {
+      // The player is authoritative again from here on.
+      if (pendingSeekTarget === newTime) pendingSeekTarget = null;
+    }
  }

  function handleKeydown(e: KeyboardEvent) {
@@ -1375,10 +1414,10 @@
      }
    } else if (e.key === "ArrowLeft") {
      e.preventDefault();
-      seekRelative(-10);
+      seekRelative(SEEK_BACKWARD_SECONDS);
    } else if (e.key === "ArrowRight") {
      e.preventDefault();
-      seekRelative(10);
+      seekRelative(SEEK_FORWARD_SECONDS);
    }
  }

@@ -1389,25 +1428,31 @@
    touchStartY = touch.clientY;
    touchStartTime = Date.now();

-    const now = Date.now();
-    const timeSinceLastTap = now - lastTapTime;
+    const outcome = registerTap(tapGestures, {
+      x: touch.clientX,
+      screenWidth: window.innerWidth,
+      now: Date.now(),
+    });

-    // Double tap detection (within 300ms)
-    if (timeSinceLastTap < 300 && timeSinceLastTap > 0) {
-      e.preventDefault();
-      handleDoubleTap(touch.clientX);
-      lastTapTime = 0; // Reset to prevent triple-tap
    if (tapTimeout) {
      clearTimeout(tapTimeout);
      tapTimeout = null;
    }
-    } else {
-      lastTapTime = now;
-      // Set timeout to clear if no second tap
-      tapTimeout = setTimeout(() => {
-        lastTapTime = 0;
-      }, 300);
+
+    if (outcome.action === "seek") {
+      e.preventDefault();
+      handleDoubleTap(outcome.seekSeconds, outcome.feedback);
+      return;
    }
+
+    // Single tap so far: defer play/pause until the double-tap window closes,
+    // so a double tap seeks without also toggling pause.
+    tapTimeout = setTimeout(() => {
+      tapTimeout = null;
+      if (tapGestures.resolvePending(Date.now())) {
+        togglePlayPause();
+      }
+    }, outcome.pendingAfterMs);
  }

  function handleTouchMove(e: TouchEvent) {
@@ -1422,6 +1467,13 @@
    if (Math.abs(deltaY) > 50 && timeDelta > 50) {
      swipeGestureActive = true;

+      // This is a swipe, not a tap — drop the deferred play/pause.
+      tapGestures.cancel();
+      if (tapTimeout) {
+        clearTimeout(tapTimeout);
+        tapTimeout = null;
+      }
+
      // Brightness control on vertical swipe
      swipeType = "brightness";
      // Map vertical swipe to brightness (0.3 to 1.7 range for better visibility)
@@ -1438,20 +1490,22 @@
    swipeType = null;
  }

-  function handleDoubleTap(x: number) {
-    const screenWidth = window.innerWidth;
-    const isLeftSide = x < screenWidth / 2;
-
-    if (isLeftSide) {
-      // Double tap left: rewind 10 seconds
-      seekRelative(-10);
-      showDoubleTapFeedback = "left";
-    } else {
-      // Double tap right: forward 10 seconds
-      seekRelative(10);
-      showDoubleTapFeedback = "right";
+  /**
+   * Mouse clicks toggle play/pause immediately. Touch taps are already handled
+   * by `handleTouchStart` (which defers play/pause past the double-tap window),
+   * so the compatibility click that follows a tap must be ignored here —
+   * otherwise it pauses on the first tap of a double tap.
+   */
+  function handleVideoClick(e: MouseEvent) {
+    // A click synthesized from a touch reports no pointer movement detail.
+    if (e.detail === 0 || tapTimeout !== null) return;
+    togglePlayPause();
  }

+  function handleDoubleTap(seekSeconds: number, feedback: TapFeedback) {
+    seekRelative(seekSeconds);
+    showDoubleTapFeedback = feedback;
+
    // Hide feedback after animation
    if (doubleTapFeedbackTimeout) {
      clearTimeout(doubleTapFeedbackTimeout);
@@ -1612,7 +1666,7 @@
          onwaiting={handleWaiting}
          onplaying={handlePlaying}
          onloadstart={handleLoadStart}
-          onclick={togglePlayPause}
+          onclick={handleVideoClick}
        >
          <!-- Temporarily disabled to debug playback issues
          {#each subtitleTracks() as track}
@@ -1665,7 +1719,7 @@
        <div class="bg-white/20 rounded-full p-6 backdrop-blur-sm">
          <svg class="w-12 h-12 text-white" fill="currentColor" viewBox="0 0 24 24">
            <path d="M11.99 2C6.47 2 2 6.48 2 12s4.47 10 9.99 10C17.52 22 22 17.52 22 12S17.52 2 11.99 2zM12 20c-4.42 0-8-3.58-8-8s3.58-8 8-8 8 3.58 8 8-3.58 8-8 8zm1-13H11v6l5.25 3.15.75-1.23-4-2.42z" />
-            <text x="12" y="14" text-anchor="middle" font-size="6" fill="white" font-weight="bold">-10</text>
+            <text x="12" y="14" text-anchor="middle" font-size="6" fill="white" font-weight="bold">{SEEK_BACKWARD_SECONDS}</text>
          </svg>
        </div>
      </div>
@@ -1676,7 +1730,7 @@
        <div class="bg-white/20 rounded-full p-6 backdrop-blur-sm">
          <svg class="w-12 h-12 text-white" fill="currentColor" viewBox="0 0 24 24">
            <path d="M11.99 2C6.47 2 2 6.48 2 12s4.47 10 9.99 10C17.52 22 22 17.52 22 12S17.52 2 11.99 2zM12 20c-4.42 0-8-3.58-8-8s3.58-8 8-8 8 3.58 8 8-3.58 8-8 8zm1-13H11v6l5.25 3.15.75-1.23-4-2.42z" />
-            <text x="12" y="14" text-anchor="middle" font-size="6" fill="white" font-weight="bold">+10</text>
+            <text x="12" y="14" text-anchor="middle" font-size="6" fill="white" font-weight="bold">+{SEEK_FORWARD_SECONDS}</text>
          </svg>
        </div>
      </div>
@@ -0,0 +1,158 @@
+import { describe, it, expect } from "vitest";
+import {
+  DOUBLE_TAP_WINDOW_MS,
+  SEEK_FORWARD_SECONDS,
+  SEEK_BACKWARD_SECONDS,
+  createTapGestureState,
+  registerTap,
+  resolveSeekTarget,
+} from "./tapGestures";
+
+const SCREEN_WIDTH = 1000;
+const LEFT = 100;
+const RIGHT = 900;
+
+function tap(state: ReturnType<typeof createTapGestureState>, x: number, at: number) {
+  return registerTap(state, { x, screenWidth: SCREEN_WIDTH, now: at });
+}
+
+/** Narrow a tap outcome to the seek variant, failing the test if it is not one. */
+function asSeek(outcome: ReturnType<typeof tap>) {
+  if (outcome.action !== "seek") {
+    throw new Error(`expected a seek outcome, got "${outcome.action}"`);
+  }
+  return outcome;
+}
+
+describe("tap gesture resolution", () => {
+  it("defers the single-tap action until the double-tap window has elapsed", () => {
+    const state = createTapGestureState();
+    const first = tap(state, RIGHT, 1000);
+
+    // The first tap must NOT immediately toggle play/pause — it may still
+    // become a double tap.
+    expect(first).toEqual({ action: "pending", pendingAfterMs: DOUBLE_TAP_WINDOW_MS });
+  });
+
+  it("resolves an isolated tap to togglePlayPause once the window expires", () => {
+    const state = createTapGestureState();
+    tap(state, RIGHT, 1000);
+
+    const resolved = state.resolvePending(1000 + DOUBLE_TAP_WINDOW_MS);
+    expect(resolved).toEqual({ action: "togglePlayPause" });
+  });
+
+  it("seeks forward 30s on a double tap on the right half and never pauses", () => {
+    const state = createTapGestureState();
+    tap(state, RIGHT, 1000);
+    const second = asSeek(tap(state, RIGHT, 1150));
+
+    expect(second.seekSeconds).toBe(SEEK_FORWARD_SECONDS);
+    expect(second.seekSeconds).toBe(30);
+    expect(second.feedback).toBe("right");
+
+    // The deferred single-tap pause must have been cancelled.
+    expect(state.resolvePending(1150 + DOUBLE_TAP_WINDOW_MS)).toBeNull();
+  });
+
+  it("seeks back 10s on a double tap on the left half", () => {
+    const state = createTapGestureState();
+    tap(state, LEFT, 1000);
+    const second = asSeek(tap(state, LEFT, 1100));
+
+    expect(second.seekSeconds).toBe(SEEK_BACKWARD_SECONDS);
+    expect(second.seekSeconds).toBe(-10);
+    expect(second.feedback).toBe("left");
+  });
+
+  it("treats a second tap after the window as a new pending single tap", () => {
+    const state = createTapGestureState();
+    tap(state, RIGHT, 1000);
+    const late = tap(state, RIGHT, 1000 + DOUBLE_TAP_WINDOW_MS + 1);
+
+    expect(late.action).toBe("pending");
+  });
+
+  it("does not treat a third tap as another double tap", () => {
+    const state = createTapGestureState();
+    tap(state, RIGHT, 1000);
+    expect(tap(state, RIGHT, 1100).action).toBe("seek");
+
+    // Triple tap: the third tap starts a fresh pending tap rather than
+    // seeking again off the consumed second tap.
+    expect(tap(state, RIGHT, 1200).action).toBe("pending");
+  });
+
+  it("accumulates repeated double taps on the same side", () => {
+    const state = createTapGestureState();
+    tap(state, RIGHT, 1000);
+    const a = asSeek(tap(state, RIGHT, 1100));
+    tap(state, RIGHT, 1200);
+    const b = asSeek(tap(state, RIGHT, 1300));
+
+    expect(a.seekSeconds).toBe(30);
+    expect(b.seekSeconds).toBe(30);
+  });
+
+  it("uses the tap side, so a double tap split across halves follows the second tap", () => {
+    const state = createTapGestureState();
+    tap(state, LEFT, 1000);
+    const second = asSeek(tap(state, RIGHT, 1100));
+
+    expect(second.seekSeconds).toBe(SEEK_FORWARD_SECONDS);
+    expect(second.feedback).toBe("right");
+  });
+
+  it("cancel() drops a pending tap so an interpreted swipe cannot pause", () => {
+    const state = createTapGestureState();
+    tap(state, RIGHT, 1000);
+    state.cancel();
+
+    expect(state.resolvePending(1000 + DOUBLE_TAP_WINDOW_MS)).toBeNull();
+  });
+});
+
+describe("seek target resolution", () => {
+  const DURATION = 600;
+
+  it("adds the delta to the reported position", () => {
+    expect(resolveSeekTarget({ delta: 30, reportedPosition: 100, duration: DURATION })).toBe(130);
+  });
+
+  it("clamps to zero when rewinding past the start", () => {
+    expect(resolveSeekTarget({ delta: -10, reportedPosition: 4, duration: DURATION })).toBe(0);
+  });
+
+  it("clamps to the duration when skipping past the end", () => {
+    expect(resolveSeekTarget({ delta: 30, reportedPosition: 590, duration: DURATION })).toBe(DURATION);
+  });
+
+  it("chains off a pending target so rapid taps do not compound off a stale position", () => {
+    // The player has not yet reported the first seek's result, so the
+    // reported position is still the pre-seek value.
+    const first = resolveSeekTarget({ delta: 30, reportedPosition: 100, duration: DURATION });
+    const second = resolveSeekTarget({
+      delta: 30,
+      reportedPosition: 100,
+      duration: DURATION,
+      pendingTarget: first,
+    });
+
+    expect(second).toBe(160);
+  });
+
+  it("ignores a pending target once the player has caught up past it", () => {
+    const target = resolveSeekTarget({
+      delta: 30,
+      reportedPosition: 200,
+      duration: DURATION,
+      pendingTarget: 130,
+    });
+
+    expect(target).toBe(230);
+  });
+
+  it("falls back to the delta alone when duration is unknown", () => {
+    expect(resolveSeekTarget({ delta: 30, reportedPosition: 100, duration: 0 })).toBe(130);
+  });
+});
@@ -0,0 +1,128 @@
+/**
+ * Tap-gesture interpretation for the video player surface.
+ *
+ * Pulled out of `VideoPlayer.svelte` so the timing rules are unit-testable:
+ * a tap cannot be classified at the moment it lands, because it may still turn
+ * out to be the first half of a double tap. Play/pause is therefore *deferred*
+ * until the double-tap window closes, and cancelled outright if a second tap
+ * arrives — otherwise a double tap both toggles pause and seeks.
+ *
+ * TRACES: UR-005, UR-061 | DR-092 | UT-085, UT-086, UT-087, UT-088
+ */
+
+/** A second tap within this window makes a double tap. */
+export const DOUBLE_TAP_WINDOW_MS = 300;
+
+/** Double tap on the right half: skip forward. */
+export const SEEK_FORWARD_SECONDS = 30;
+
+/** Double tap on the left half: skip back. */
+export const SEEK_BACKWARD_SECONDS = -10;
+
+export type TapFeedback = "left" | "right";
+
+export type TapOutcome =
+  /** Deferred: play/pause fires only if no second tap lands within the window. */
+  | { action: "pending"; pendingAfterMs: number }
+  | { action: "seek"; seekSeconds: number; feedback: TapFeedback };
+
+export interface TapInput {
+  /** Tap x position, viewport pixels. */
+  x: number;
+  screenWidth: number;
+  now: number;
+}
+
+export interface TapGestureState {
+  /**
+   * Resolve a still-pending single tap. Returns the play/pause action once the
+   * double-tap window has elapsed, or null if there is nothing pending (the tap
+   * became a double tap, or was cancelled).
+   */
+  resolvePending(now: number): { action: "togglePlayPause" } | null;
+  /** Drop any pending tap — used when the gesture turns into a swipe. */
+  cancel(): void;
+}
+
+interface InternalState extends TapGestureState {
+  lastTapTime: number;
+  pendingSince: number | null;
+}
+
+export function createTapGestureState(): TapGestureState {
+  const state: InternalState = {
+    lastTapTime: 0,
+    pendingSince: null,
+    resolvePending(now: number) {
+      if (state.pendingSince === null) return null;
+      if (now - state.pendingSince < DOUBLE_TAP_WINDOW_MS) return null;
+      state.pendingSince = null;
+      return { action: "togglePlayPause" };
+    },
+    cancel() {
+      state.pendingSince = null;
+      state.lastTapTime = 0;
+    },
+  };
+  return state;
+}
+
+/**
+ * Classify a tap. The first tap of a potential pair returns `pending` — the
+ * caller schedules `resolvePending` after `pendingAfterMs`. A second tap inside
+ * the window returns the seek and clears the pending play/pause.
+ */
+export function registerTap(state: TapGestureState, input: TapInput): TapOutcome {
+  const s = state as InternalState;
+  const sinceLastTap = input.now - s.lastTapTime;
+
+  if (s.lastTapTime > 0 && sinceLastTap > 0 && sinceLastTap < DOUBLE_TAP_WINDOW_MS) {
+    // Second tap: cancel the deferred play/pause and seek instead.
+    s.pendingSince = null;
+    s.lastTapTime = 0; // consumed, so a third tap starts fresh
+    const isLeftSide = input.x < input.screenWidth / 2;
+    return isLeftSide
+      ? { action: "seek", seekSeconds: SEEK_BACKWARD_SECONDS, feedback: "left" }
+      : { action: "seek", seekSeconds: SEEK_FORWARD_SECONDS, feedback: "right" };
+  }
+
+  s.lastTapTime = input.now;
+  s.pendingSince = input.now;
+  return { action: "pending", pendingAfterMs: DOUBLE_TAP_WINDOW_MS };
+}
+
+export interface SeekTargetInput {
+  /** Relative offset in seconds (negative rewinds). */
+  delta: number;
+  /** Latest position reported by the player — the authoritative source. */
+  reportedPosition: number;
+  /** Media duration; 0/unknown disables the upper clamp. */
+  duration: number;
+  /**
+   * Target of a seek already requested but not yet reflected in
+   * `reportedPosition`. Consecutive double taps chain off this so they add up
+   * instead of all resolving against the same stale position.
+   */
+  pendingTarget?: number | null;
+}
+
+/**
+ * Resolve a relative skip to the absolute position the facade expects.
+ *
+ * The player facade seeks by absolute position only (the backend picks the seek
+ * strategy), so the delta is applied here — against the pending target when one
+ * is still in flight and still ahead of what the player has reported.
+ */
+export function resolveSeekTarget(input: SeekTargetInput): number {
+  const { delta, reportedPosition, duration, pendingTarget } = input;
+
+  const base =
+    pendingTarget != null && Math.abs(pendingTarget - reportedPosition) > 0.5 && pendingTarget > reportedPosition
+      ? pendingTarget
+      : reportedPosition;
+
+  const target = base + delta;
+  if (target < 0) return 0;
+  if (duration > 0 && target > duration) return duration;
+  return target;
+}
@@ -7,11 +7,19 @@
 * hls.js. State reporting is unnecessary here because the native backend emits
 * events directly — the adapter's job is only to forward control intents.
 *
- * NOTE: On current Tauri, native Android video rendering is blocked upstream
- * (transparent webview / SurfaceView compositing — tauri#10152), so video on
- * Android currently runs through the HTML5 adapter via the interim override in
- * the factory. This adapter exists for the audio/native path and for when that
- * upstream limitation is resolved.
+ * NOTE: This adapter is currently unreachable — `createAdapter()` hardcodes the
+ * HTML5 kind, so Android video runs through Html5PlayerAdapter.
+ *
+ * That override was introduced citing tauri#10152 as an upstream blocker. That
+ * is no longer accurate: #10152 is a stale *feature request* (dead since
+ * 2024-07-01) asking that `transparent` not be desktop-only, and the capability
+ * shipped in tauri commit 27d01834 (2024-09-02). The related black/white-screen
+ * bug (tauri#8381, #9408) was a broken JNI signature for setBackgroundColor,
+ * fixed in wry 0.39.4; we ship wry 0.55.x.
+ *
+ * What is genuinely unproven is SurfaceView-behind-WebView *compositing* on
+ * Tauri Android — nothing upstream blocks it, and nothing upstream demonstrates
+ * it either. docs/specs/android-native-video-spike.md tracks that experiment.
 *
 * TRACES: UR-003, UR-005 | DR-004, DR-028
 */
@@ -0,0 +1,68 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { setBackgroundAudioEnabled } from "./backgroundAudio";
+
+/**
+ * Bridge-reporting contract for the background-audio toggle.
+ *
+ * TRACES: UR-040 | IR-025, DR-051 | UT-062
+ *
+ * Regression guard for the "screen lock kills video audio" bug: MainActivity
+ * re-ran configureWebViewForMedia() on every onResume, re-calling
+ * addJavascriptInterface over a live page. WebView then served a stale proxy —
+ * `window.AndroidBackgroundAudio` stayed truthy but its methods were gone, so
+ * `setEnabled` threw `TypeError: e.setEnabled is not a function`.
+ *
+ * The old implementation swallowed that with `bridge()?.setEnabled(...)` inside
+ * a try/catch returning void, so the UI showed "armed" while native never got
+ * the flag — and onStop's `if (backgroundAudioEnabled)` guard never dispatched
+ * `jellytau-background`. Audio died the instant the screen locked.
+ *
+ * setBackgroundAudioEnabled must therefore REPORT whether native was actually
+ * reached, so a dead bridge can never masquerade as an armed toggle.
+ */
+describe("setBackgroundAudioEnabled", () => {
+  beforeEach(() => {
+    delete (window as unknown as Record<string, unknown>).AndroidBackgroundAudio;
+    vi.restoreAllMocks();
+  });
+
+  it("reports success when the bridge is present and the call lands", () => {
+    const setEnabled = vi.fn();
+    window.AndroidBackgroundAudio = { setEnabled };
+
+    expect(setBackgroundAudioEnabled(true)).toBe(true);
+    expect(setEnabled).toHaveBeenCalledWith(true);
+  });
+
+  it("reports failure when the bridge object is absent entirely", () => {
+    expect(setBackgroundAudioEnabled(true)).toBe(false);
+  });
+
+  it("reports failure for a stale proxy whose methods are gone", () => {
+    // The exact shape of the bug: object present (so `?.` passes) but the
+    // method is missing after re-injection over a live page.
+    window.AndroidBackgroundAudio = {} as unknown as typeof window.AndroidBackgroundAudio;
+
+    expect(setBackgroundAudioEnabled(true)).toBe(false);
+  });
+
+  it("reports failure when the bridge method throws", () => {
+    window.AndroidBackgroundAudio = {
+      setEnabled: () => {
+        throw new TypeError("e.setEnabled is not a function");
+      },
+    };
+
+    expect(setBackgroundAudioEnabled(true)).toBe(false);
+  });
+
+  it("never throws out to the caller — the toggle must not break the player", () => {
+    window.AndroidBackgroundAudio = {
+      setEnabled: () => {
+        throw new Error("boom");
+      },
+    };
+
+    expect(() => setBackgroundAudioEnabled(false)).not.toThrow();
+  });
+});
@@ -20,7 +20,6 @@

 interface AndroidBackgroundAudioBridge {
  setEnabled(enabled: boolean): void;
-  isSupported(): boolean;
 }

 declare global {
@@ -34,25 +33,27 @@ function bridge(): AndroidBackgroundAudioBridge | undefined {
  return window.AndroidBackgroundAudio;
 }

-/** Whether background audio is available — used to decide if the toggle renders. */
-export function isBackgroundAudioSupported(): boolean {
-  try {
-    return bridge()?.isSupported() ?? false;
-  } catch (err) {
-    console.warn("[BgAudio] isSupported check failed:", err);
-    return false;
-  }
-}
-
 /**
 * Arm/disarm background-audio mode for the current video. When armed, the native
 * side runs the audio handoff on background instead of entering PiP.
 */
-export function setBackgroundAudioEnabled(enabled: boolean): void {
+export function setBackgroundAudioEnabled(enabled: boolean): boolean {
+  const b = bridge();
+  if (!b) {
+    // The button is gated on platform(), not on this bridge, so it can render
+    // before/without the bridge existing. Silently no-oping here leaves the UI
+    // showing "armed" while native never learns — and the handoff then never
+    // fires on lock. Report it so callers can retry.
+    console.warn("[BgAudio] setEnabled: bridge missing, native NOT armed");
+    return false;
+  }
  try {
-    bridge()?.setEnabled(enabled);
+    b.setEnabled(enabled);
+    console.log("[BgAudio] setEnabled ->", enabled);
+    return true;
  } catch (err) {
    console.warn("[BgAudio] Failed to set enabled:", err);
+    return false;
  }
 }
Author	SHA1	Message	Date
dtourolle	36ef231e2f	chore(release): bump to 0.2.0 🏗️ Build and Test JellyTau / Run Tests (push) Successful in 11m0s Details Publish Documentation / Build & publish docs to gitea-pages (push) Has been cancelled Details Traceability Validation / Check Requirement Traces (push) Has been cancelled Details Build & Release / Run Tests (push) Successful in 11m20s Details 🏗️ Build and Test JellyTau / Android Compile Check (push) Successful in 8m20s Details Build & Release / Build Linux (push) Failing after 16m33s Details Build & Release / Build Windows (push) Successful in 13m46s Details Build & Release / Build Android (push) Successful in 29m50s Details Build & Release / Create Release (push) Has been skipped Details Minor bump rather than patch: Android gains working equalizer, volume normalization and gapless playback, which are new user-facing capabilities. CHANGELOG entry written by hand rather than from `bun run release:notes`. The generated draft lists "Crossfade between audio tracks (UR-031)" as a feature of this release, which is false — the trace graph cannot distinguish code that plumbs a setting (settings.rs clamping, the backend.rs trait method, both legitimately tagged DR-034) from code that implements it, and crossfade is implemented nowhere. The release-notes tool documents its output as a reviewed draft; this is a concrete case of why. v0.1.3-v0.1.5 have no CHANGELOG entries; noted in the file rather than backfilled.	2026-07-28 23:08:05 +02:00
dtourolle	cb79a376b3	feat(android): implement audio settings (EQ, normalization, gapless) 🏗️ Build and Test JellyTau / Android Compile Check (push) Has been cancelled Details Publish Documentation / Build & publish docs to gitea-pages (push) Has been cancelled Details Traceability Validation / Check Requirement Traces (push) Has been cancelled Details 🏗️ Build and Test JellyTau / Run Tests (push) Has been cancelled Details ExoPlayerBackend was the only backend not overriding the PlayerBackend trait's set_audio_settings/audio_settings defaults, so the Settings > Audio controls rendered on Android and silently did nothing — the default returns Ok(()) while applying nothing, so the failure was invisible. Rust owns what the values are (canonical 10-band ISO layout, preset curves, normalization presets); Kotlin owns when the AudioEffect objects exist, since that needs the live audio session id. - settings.rs: audio_settings_jni_payload() sanitises (crossfade clamped, band vector normalised) before serialising, so a malformed vector cannot reach the Kotlin parser. JSON rather than a wide JNI signature, matching how load() already passes subtitles — adding a field will not change the signature. - ExoPlayerBackend: set_audio_settings/audio_settings over JNI; ExoPlayerState gains the first command-side field (settings are pushed out, never reported). - JellyTauPlayer.kt: Equalizer, LoudnessEnhancer, and gapless via pauseAtEndOfMediaItems. Three details that are easy to get wrong: - Effects re-attach on onAudioSessionIdChanged. ExoPlayer rebuilds its audio sink on a format change, which invalidates effects bound to the old session; without this the EQ silently stops applying mid-queue. - All effect work is posted to mainHandler rather than run inline. AudioEffect construction from a player callback can re-enter the player and deadlock — the same shape as the AutoplayDecision lock-scrutinee bug. - Device equalizers expose a device-dependent band count (commonly 5) at fixed centres, so the canonical 10 bands are resampled by nearest centre frequency. resampleBands() is a pure @JvmStatic function so that mapping is testable without a device. Normalization is approximate, not parity: LoudnessEnhancer is a gain stage, not a true EBU R128 normalizer like MPV's dynaudnorm. Recorded as such rather than claimed as equivalent. Crossfade is deliberately excluded — unimplemented on every platform and blocked on mpv, so building it on Android alone would invert the parity gap. Tests written first and observed failing (cannot find function audio_settings_jni_payload) before the implementation: the payload contract is pinned by tests because a serde rename would otherwise silently break the Kotlin parser. Not yet verified on a physical device — AudioEffect availability and band layouts are device-specific. Requirements matrix marks these rows accordingly, and flipping the trait default to Err(not_implemented()) is deferred until that verification lands.	2026-07-28 23:03:31 +02:00
dtourolle	b11188e9dd	docs(player): backend unification findings + correct false parity claims Investigation into unifying the playback backends (Linux/MPV, Android/ExoPlayer, Windows/webview) onto one engine with hardware acceleration. Conclusion: video cannot be unified onto a native engine; audio can. The blocker is not mpv-specific. WebKitGTK, WebView2 and Android WebView each draw into their own compositor surface, so a native video surface sits either entirely above or entirely below the webview and cannot interleave with HTML. GStreamer and libVLC fail identically. mpv would additionally regress streaming: it has no adaptive bitrate, while the current hls.js path does. Six specs added: - playback-backend-unification: the analysis and decision, with evidence - android-audio-settings-parity: set_audio_settings on ExoPlayerBackend - android-native-video-spike: timeboxed test of SurfaceView compositing - windows-native-audio-backend: replace the webview <audio> shim with libmpv - libmpv2-migration: dead libmpv git pin -> libmpv2, plus a LICENSE file - playback-docs-corrections: the requirement-status fixes applied here Corrections to requirements.md, all verified against source: - UR-031/DR-034 claimed crossfade was "Done (Linux only)". It is implemented nowhere (mpv_backend.rs has a bare TODO) and is architecturally blocked on mpv, whose single-stream audio chain cannot feed acrossfade's two inputs. - Parity matrix listed crossfade as a Linux/Android gap; it is neither. - The matrix omitted the equalizer, which has the same Linux-only shape. - The suggested ConcatenatingMediaSource is deprecated in current Media3. nativeAdapter.ts cited tauri#10152 as an upstream blocker for native Android video. That issue is a stale feature request, dead since 2024-07-01; the capability shipped in tauri 27d01834 (2024-09-02), and the related black-screen bug was fixed in wry 0.39.4 (we ship 0.55.x). What is genuinely unproven is SurfaceView-behind-WebView compositing, which the spike now tracks.	2026-07-28 23:03:17 +02:00
dtourolle	f636b6b151	Merge: Android WebView bridge + audio-focus fixes, tap gestures, sleep timer (v0.1.5) 🏗️ Build and Test JellyTau / Run Tests (push) Successful in 13m55s Details Publish Documentation / Build & publish docs to gitea-pages (push) Successful in 5m20s Details Traceability Validation / Check Requirement Traces (push) Successful in 18s Details 🏗️ Build and Test JellyTau / Android Compile Check (push) Successful in 8m44s Details	2026-07-28 01:33:58 +02:00
dtourolle	37ffabee06	chore(release): bump to 0.1.5; regenerate traceability matrix Build & Release / Run Tests (push) Successful in 4m35s Details Build & Release / Build Linux (push) Successful in 18m25s Details Build & Release / Build Windows (push) Successful in 13m27s Details Build & Release / Build Android (push) Successful in 29m9s Details Build & Release / Create Release (push) Successful in 16s Details Registers UR-061/DR-092 (tap gestures) and UT-062 (background-audio bridge reporting), and regenerates the matrix — 313 TRACES across 299 files.	2026-07-28 01:33:20 +02:00
dtourolle	13e0860401	fix(player): expired sleep timer stops without triggering autoplay Stopping the backend makes the native player fire its ended callback, which lands in on_playback_ended. The timer thread cancels the timer first, so by the time the callback inspects it the mode reads Off — the sleep-timer branch is skipped and the episode path runs, showing a next-episode popup (or advancing outright) right after the user's sleep timer expired. Record EndReason::UserStop before the stop reaches the backend. That is the honest label: the stop was user-initiated, just via the timer they set rather than the stop button. TRACES: UR-023, UR-026 \| DR-029	2026-07-28 01:33:10 +02:00
dtourolle	d1c01a6bc3	feat(player): defer single tap so a double tap doesn't also toggle pause A tap cannot be classified when it lands — it may still turn out to be the first half of a double tap. Play/pause is therefore deferred until the 300ms double-tap window closes, and cancelled outright if a second tap arrives, so a double tap seeks without also toggling pause. Forward skip moves from 10s to 30s (back stays 10s), for both double tap and the keyboard arrows. The timing rules live in tapGestures.ts so they are unit-testable without mounting the player. Rapid double taps now chain off a still-in-flight seek target instead of all resolving against the same not-yet-updated position. TRACES: UR-005, UR-061 \| DR-092 \| UT-085, UT-086, UT-087, UT-088	2026-07-28 01:33:04 +02:00
dtourolle	e5d3cc06f2	fix(android): register WebView JS bridges once; stop audio-focus fight Locking the screen killed audio on video playback even with the background-audio toggle armed. configureWebViewForMedia() ran from onCreate's delayed post AND from every onResume, re-calling addJavascriptInterface on each pass — five times in a 45s session. WebView binds injected objects at page-load time, so re-injecting over a live page leaves JS holding a stale proxy: the object stays truthy (passing the `bridge()?.` optional chain) while its methods vanish. Logcat showed 66 "WebView: Unknown object" errors and, in JS, "TypeError: setEnabled is not a function". So the toggle turned blue but never reached native. backgroundAudioEnabled stayed false, onStop never dispatched 'jellytau-background', the handoff never ran, and audio stopped the instant the screen locked. PiP and audio focus broke identically. - Register the bridges exactly once per WebView (identity-compared), and split the idempotent settings/chrome-client work into configureWebViewSettings() so it still runs on every resume. - Forward WebView console output to logcat as "JellyTauWeb". The frontend was previously invisible to adb, which is what made this bug so hard to place; keep it for the next boundary-spanning diagnosis. - setBackgroundAudioEnabled now reports whether native was actually reached instead of silently no-oping, so a dead bridge can never again masquerade as an armed toggle. Removing the re-injection revived a latent conflict it had been masking: the focus calls started working, and three AUDIOFOCUS_GAIN requesters inside one uid began fighting — MainActivity, ExoPlayer, and Chromium's own AudioFocusDelegate. The grant was followed ~45ms later by AUDIOFOCUS_LOSS, whose handler paused playback, so arming background audio (or just pressing play) paused the video in a loop. WebView already manages focus for <video>. Drop the redundant AndroidAudioFocus bridge, its listeners and its helpers entirely, and leave focus to whichever engine is actually rendering — consistent with the player-is-authoritative principle. Also drops the dead AndroidBackgroundAudio.isSupported() probe, unused since the button gate moved to platform(). TRACES: UR-040 \| IR-025, DR-051 \| UT-062	2026-07-28 01:32:57 +02:00