# Phase 3 Plan 2: Error Handling & Resilience Summary

**Added production-ready error handling, loading states, and resilience to backing track player**

## Accomplishments

- Implemented error state management with user-facing messages
- Added loading states and disabled controls during transitions
- Handled edge cases: invalid files, network issues, null jamClient
- Added proper cleanup on component unmount
- No uncaught exceptions in any scenario

## Files Created/Modified

- `jam-ui/src/components/client/JKSessionBackingTrackPlayer.js` - Error handling, loading states, edge cases

## Commits

- `acbddd35e` - feat(03-02): add comprehensive error handling with user feedback
- `9c0455dc6` - feat(03-02): add loading states and disabled UI
- `31bc9ea2a` - feat(03-02): handle file and network edge cases

## Decisions Made

- **Error display approach**: Banner/alert above controls with dismiss and retry buttons
  - Color coding: red for critical errors (file/network), yellow for warnings (playback/general)
  - Retry button for network/file errors only
  - Applied to both popup and modal versions

- **Loading indicator style**: "Loading track..." text during duration fetch, "..." suffix on buttons during operations

- **Debounce strategy**: `isOperating` flag prevents rapid clicks on play/stop buttons
  - Reset in finally block to ensure cleanup
  - Seek slider not blocked (allows immediate UI updates)

## Error Types Implemented

1. **file** - Failed to load track duration, invalid files (red)
2. **network** - Lost connection after 3 consecutive polling failures (red)
3. **playback** - Failed playback operations (yellow)
4. **general** - Audio engine not available (yellow)

## Edge Cases Handled

1. **Invalid/missing file**: Validates duration (rejects 0 or NaN), warns about suspicious values
2. **Network disconnection**: Tracks consecutive polling errors, stops after 3 failures
3. **jamClient null**: Guards in all handlers with early return
4. **Stale state**: Cleanup on unmount stops playback
5. **Invalid state recovery**: Polling syncs UI to jamClient state
6. **Graceful degradation**: Error states show but player stays open
7. **File format validation**: Warns about durations <1s or >10h

## Issues Encountered

None - all implementations worked as expected.

## Next Phase Readiness

Ready for Plan 03-03 (Performance Optimization & Final UAT). Player is now resilient and production-ready for error scenarios.
