---
phase: 20-vumeter-fixes
plan: 01
subsystem: audio
tags: [react, hooks, memory-leak, vu-meter, mixer, state-management]

# Dependency graph
requires:
  - phase: 19-audit-and-discovery
    provides: Memory leak audit identifying unbounded vuStates growth (VUMTR-02, VUMTR-03)
provides:
  - removeVuState function for cleaning up VU meter state
  - Automatic VU state cleanup when mixers are removed
  - Bounded vuStates object that doesn't grow indefinitely
affects: [21-chat-fixes, memory-leak-verification]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Ref-based state tracking for cleanup detection (previousMixerIdsRef pattern)"
    - "useEffect cleanup pattern for derived state objects"

key-files:
  created: []
  modified:
    - jam-ui/src/hooks/useVuHelpers.js
    - jam-ui/src/hooks/useMixerHelper.js

key-decisions:
  - "Use Set comparison for efficient mixer removal detection"
  - "Track previous mixer IDs with ref to avoid re-render triggers"
  - "Only run cleanup when mixers are ready (isReadyRedux guard)"

patterns-established:
  - "removeVuState: Cleanup callback for removing specific mixer VU state"
  - "previousMixerIdsRef: Ref-based tracking for detecting state removals"

# Metrics
duration: 2min
completed: 2026-02-08
---

# Phase 20 Plan 01: VU Meter State Cleanup Summary

**VU meter state cleanup preventing unbounded vuStates growth through removeVuState callback and automatic mixer lifecycle integration**

## Performance

- **Duration:** 2 min
- **Started:** 2026-02-08T13:56:17Z
- **Completed:** 2026-02-08T13:58:17Z
- **Tasks:** 3
- **Files modified:** 2

## Accomplishments
- Added removeVuState callback function to useVuHelpers for targeted state cleanup
- Integrated VU state cleanup with mixer lifecycle in useMixerHelper
- Prevented unbounded vuStates growth as tracks join/leave sessions

## Task Commits

Each task was committed atomically:

1. **Task 1: Add removeVuState function to useVuHelpers.js** - `3624c09` (feat)
2. **Task 2: Verify removeVuState is exposed through VuContext** - (verification only, no commit)
3. **Task 3: Integrate removeVuState with mixer lifecycle** - `6a7ee47` (feat)

## Files Created/Modified
- `jam-ui/src/hooks/useVuHelpers.js` - Added removeVuState callback for cleaning up individual mixer VU state
- `jam-ui/src/hooks/useMixerHelper.js` - Added cleanup effect detecting removed mixers and calling removeVuState
- `jam-ui/src/context/VuContext.js` - (No changes needed - automatically exposes removeVuState via existing pattern)

## Decisions Made

**Use Set comparison for mixer removal detection**
- Efficiently compares current vs previous mixer IDs using Set.has()
- Iterates only through previous mixers to find removals

**Track previous mixer IDs with ref**
- Uses useRef to avoid causing re-renders from tracking state
- Stores Set of mixer IDs between useEffect invocations

**Guard cleanup with isReadyRedux check**
- Only runs cleanup logic when mixers are fully initialized
- Prevents false positives during initial mount

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None - implementation followed plan specifications without obstacles.

## Next Phase Readiness

**Ready for Phase 21 (Chat Fixes):**
- VU meter state cleanup complete (VUMTR-02, VUMTR-03 resolved)
- vuStates object now bounded as tracks join/leave
- Pattern established can be applied to chat messages (CHAT-01)

**Manual verification available:**
- Join session, add/remove tracks, inspect vuStates in React DevTools
- Verify vuStates keys match current active mixers only

**Verification note:** Build verification encountered Node.js 23/OpenSSL compatibility issue with webpack (pre-existing, not related to changes). Syntax validation passed successfully.

---
*Phase: 20-vumeter-fixes*
*Completed: 2026-02-08*
