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+# Phase 5: JamTrack Implementation - Context
+
+**Gathered:** 2026-01-14
+**Status:** Ready for planning
+
+<vision>
+## How This Should Work
+
+Users should be able to open a JamTrack and experience smooth, predictable playback. The experience should feel familiar to users who've used the Backing Track player from Phase 3 - same control patterns, same responsiveness, same reliability.
+
+The key difference is JamTracks need to download and sync before playing. This download experience should be clear and reassuring - users see exactly what's happening (progress percentage, current step) and understand why they're waiting. No confusion, no "is it stuck?" moments.
+
+Once synced, the JamTrack plays like any other media file. Users can play/pause/seek smoothly. They can also switch between different mixdowns:
+- **Master mixdown** - the final polished mix
+- **Existing custom mixes** - user-created mixdowns they or others have saved
+- **Individual stems** - single instrument tracks
+
+The mixdown switching should feel natural - select a different mix, audio changes. No complexity, just "here are your options, pick one."
+
+</vision>
+
+<essential>
+## What Must Be Nailed
+
+All three pillars are equally important:
+
+- **Clear download/sync experience** - Users see progress (percentage, steps), understand the sync state machine (checking → downloading → keying → ready), and get clear feedback at every stage
+- **Reliable playback** - Once synced, playback just works. Play/pause/seek respond instantly. No race conditions, no double-click workarounds, no mysterious pauses.
+- **Smooth mixdown selection** - Users can browse available mixdowns and switch between them without friction. Master, custom mixes, and stems all accessible and working.
+
+</essential>
+
+<boundaries>
+## What's Out of Scope
+
+- **Custom mix creation** - Phase 5 focuses on **playing** existing custom mixes, not creating new ones. The UI to adjust individual stem volumes and save custom mixdowns is deferred to a future phase.
+- **Stem editing** - Users can select individual stems to play, but can't edit stem properties (volume, pan, effects)
+- **JMEP customization** - JMEP (Jam Enhancement Package) files are loaded automatically if present, but users can't customize tempo/pitch modifications
+- **Advanced playback features** - Loop functionality, A-B repeat, playback speed adjustment - deferred
+- **Offline mode** - JamTracks must sync with server before playback, no offline-first capability
+
+</boundaries>
+
+<specifics>
+## Specific Ideas
+
+**Match Backing Track player feel:**
+- Users who learned the Backing Track player should feel at home
+- Same control layout (play/pause/stop buttons, seek slider, time display)
+- Same responsive behavior (immediate feedback, no lag)
+- Same error handling approach (clear messages, recovery actions)
+- Apply the same performance optimizations (visibility-aware polling, React optimizations)
+
+**Extend with JamTrack-specific features:**
+- Download progress UI (progress bar, step indicator, cancel button)
+- Sync state visualization (idle → checking → downloading → keying → synchronized → error)
+- Mixdown picker (dropdown or modal showing master/custom/stem hierarchy)
+- Handle both modal and popup modes (like Backing Track)
+
+**Quality bar from Phase 3:**
+- No race conditions (or document known limitations)
+- Comprehensive error handling (network, file, playback errors)
+- Clean console output (no diagnostic logging in production)
+- Cleanup on unmount (prevent stale state bugs)
+
+</specifics>
+
+<notes>
+## Additional Context
+
+**From Phase 4 design work:**
+- Architecture already designed: JKSessionJamTrackPlayer component with 10 sub-components
+- Redux state structure defined: jamTrackState (playback), downloadState (sync machine), availableMixdowns (mixdown cache)
+- 6 async thunks mapped out: loadJamTrack, downloadJamTrack, checkJamTrackSync, loadJMEP, seekJamTrack, closeJamTrack
+- Known bug to fix: existing loadJamTrack thunk uses wrong ID format (jamTrack.id instead of fqId)
+- Complexity estimate: 2.5-3x Phase 3 Backing Track effort
+- High risks identified: download/sync state machine complexity, native client race conditions
+
+**Phase 4 preliminary roadmap suggested 9 plans:**
+1. Redux infrastructure & bug fixes
+2. Async thunks & WebSocket handlers
+3. Player core structure
+4. Playback controls
+5. Mixdown selection
+6. Download/sync UI
+7. Modal updates
+8. Error handling & edge cases
+9. Performance optimization & final UAT
+
+**User confirmed:**
+- Phase 5 scope = download + play existing JamTracks + select existing mixdowns
+- Custom mix **creation** deferred to future phase
+- All three pillars equally important (download UX, playback reliability, mixdown selection)
+- Should match Backing Track player feel and quality
+
+</notes>
+
+---
+
+*Phase: 05-jamtrack-implementation*
+*Context gathered: 2026-01-14*