---
phase: 30-component-memoization
plan: 01
subsystem: session-ui
tags: [react, performance, memo, re-render-optimization]
requires:
  - 29-context-optimization
provides:
  - memoized-container-components
  - complete-memoization-chain
affects:
  - 30-02
tech-stack:
  added: []
  patterns:
    - React.memo for container components
    - displayName for DevTools visibility
key-files:
  created: []
  modified:
    - jam-ui/src/components/client/JKSessionAudioInputs.js
    - jam-ui/src/components/client/JKSessionRemoteTracks.js
decisions:
  - key: container-component-memoization
    decision: Wrap JKSessionAudioInputs and JKSessionRemoteTracks with React.memo
    rationale: Completes the memoization chain from Phase 29, prevents cascade re-renders from parent
    alternatives: ["PureComponent (class-based)", "manual shouldComponentUpdate"]
    impact: Containers skip re-renders when props are shallowly equal
  - key: default-comparison
    decision: Use default shallow comparison in React.memo
    rationale: Props are already stable from Phase 29 context optimization
    alternatives: ["custom comparison function"]
    impact: Simpler code, relies on upstream prop stability
metrics:
  duration: 76 seconds
  completed: 2026-03-05
---

# Phase 30 Plan 01: Memoize Container Components Summary

**One-liner:** Wrapped JKSessionAudioInputs and JKSessionRemoteTracks with React.memo to prevent unnecessary re-renders when parent re-renders with unchanged props.

## What Was Built

### Component Memoization
Wrapped two container components with React.memo following the Phase 29 pattern:

1. **JKSessionAudioInputs**
   - Added `memo` to React imports
   - Wrapped with `memo(function JKSessionAudioInputs(...))`
   - Added displayName for React DevTools visibility
   - Prevents re-renders when myTracks, chat, mixerHelper, isRemote, mixType unchanged

2. **JKSessionRemoteTracks**
   - Added `memo` to React imports (alongside existing useMemo)
   - Wrapped with `memo(function JKSessionRemoteTracks(...))`
   - Added displayName for React DevTools visibility
   - Prevents re-renders when mixerHelper and sessionModel unchanged

### Memoization Chain
Completes the optimization chain started in Phase 29:
- **Phase 29:** Stabilized context values and hook functions with useCallback/useMemo
- **Phase 30-01:** Memoized container components that receive those stable props
- **Existing:** Child components (JKSessionMyTrack, SessionTrackVU, SessionTrackGain) already memoized

Result: Parent re-renders no longer cascade through these components when props haven't changed.

## Technical Decisions

### Pattern Consistency
Used the same memo pattern established in Phase 29:
```javascript
const ComponentName = memo(function ComponentName({ props }) {
  // implementation
});
ComponentName.displayName = 'ComponentName';
```

### No Custom Comparison
Did not add custom comparison functions because:
- Props are already stable from Phase 29 context optimization
- Default shallow comparison is sufficient
- Simpler code, easier to maintain
- Custom comparisons can mask upstream prop stability issues

## Files Modified

### jam-ui/src/components/client/JKSessionAudioInputs.js
- Added `memo` to React imports
- Wrapped component with `memo(function JKSessionAudioInputs)`
- Added displayName for DevTools
- Commit: `4dea95e85`

### jam-ui/src/components/client/JKSessionRemoteTracks.js
- Added `memo` to React imports (with useMemo)
- Wrapped component with `memo(function JKSessionRemoteTracks)`
- Added displayName for DevTools
- Commit: `a26f75591`

## Deviations from Plan

None - plan executed exactly as written.

## Testing Notes

### Automated Verification
- Syntax checks passed for both files
- Pattern verification confirmed memo wrappers present
- displayName properties added correctly

### Manual Verification Available
Users can verify with React DevTools:
1. Open session screen in browser
2. Open React DevTools Profiler tab
3. Record while triggering parent re-render
4. Check that JKSessionAudioInputs and JKSessionRemoteTracks show "Did not render" when props unchanged

## Integration Points

### Upstream Dependencies
- Relies on Phase 29 context optimization for stable props
- mixerHelper from SessionMixerContext (memoized in 29-01)
- sessionModel passed from parent (stable reference)

### Downstream Impact
- Phase 30-02 can build on this foundation
- Future phases benefit from complete memoization chain
- Performance gains compound across optimization phases

## Performance Impact

### Re-render Prevention
Before: JKSessionAudioInputs and JKSessionRemoteTracks re-rendered on every parent re-render
After: Components skip re-renders when props are shallowly equal

### Expected Benefit
- Reduces wasted renders in session screen
- Prevents unnecessary VU meter and track component updates
- Complements Phase 28 VU store and Phase 29 context optimizations

## Next Phase Readiness

**Ready for Phase 30-02** ✅

No blockers identified. Component memoization chain is complete:
- Context values stable (Phase 29)
- Container components memoized (Phase 30-01)
- Child components already memoized (previous work)

## Lessons Learned

### Memoization Effectiveness
React.memo only works when props are stable. Phase 29's context optimization was essential prerequisite.

### Pattern Benefits
- Named function expressions provide better stack traces
- displayName improves debugging in React DevTools
- Consistent pattern across codebase aids comprehension

### Dependency Chain
Performance optimizations often require coordinated changes:
1. Stabilize data sources (Phase 28: VU store)
2. Stabilize prop values (Phase 29: context memoization)
3. Prevent re-renders (Phase 30: component memoization)

## Commits

| Hash      | Type     | Description                                      |
|-----------|----------|--------------------------------------------------|
| 4dea95e85 | refactor | wrap JKSessionAudioInputs with React.memo        |
| a26f75591 | refactor | wrap JKSessionRemoteTracks with React.memo       |

**Total commits:** 2
**Total files modified:** 2
**Execution time:** 76 seconds
