docs(32-02): complete mixer categorization optimization plan

Tasks completed: 3/3
- Task 1: Add mixer array comparison helper
- Task 2: Add prevCategoriesRef to track dispatched values
- Task 3: Add conditional dispatch to categorization

SUMMARY: .planning/phases/32-state-update-optimization/32-02-SUMMARY.md

.planning/STATE.md

@@ -10,11 +10,11 @@ See: .planning/PROJECT.md (updated 2026-03-03)
 ## Current Position
 
 Phase: 32 of 32 (State Update Optimization)
-Plan: Not started
-Status: Ready to plan
-Last activity: 2026-03-05 — Completed Phase 31 Selector Optimization
+Plan: 2 of 2 (Mixer Categorization Optimization)
+Status: In progress
+Last activity: 2026-03-05 — Completed 32-02-PLAN.md
 
-Progress: [████████░░] 80%
+Progress: [█████████░] 82%
 
 ## Performance Metrics
 
@@ -26,8 +26,8 @@ Progress: [████████░░] 80%
 **v1.7 Performance Optimization (In Progress):**
 - Phases: 5 (phases 28-32)
 - Phases completed: 4 (Phases 28, 29, 30, 31)
-- Requirements: 19 (13 complete)
-- Plans completed: 5
+- Requirements: 19 (15 complete)
+- Plans completed: 7
 
 ## Accumulated Context
 
@@ -54,6 +54,10 @@ Recent decisions (v1.7):
 - Default shallow comparison sufficient when props are stable from upstream - 30-01
 - Group selectors by usage pattern (core, track, lookup, metadata) - 31-01
 - shallowEqual with composed selectors for object return comparisons - 31-01
+- Single debounced track sync call prevents triple API calls on session join - 32-01
+- useCallback with stable dependency array for debounce instance prevents recreation - 32-01
+- Ref-based tracking for previous category values avoids circular updates - 32-02
+- ID-based array comparison faster than deep equality for mixer arrays - 32-02
 
 ### Investigation Findings (v1.7)
 
@@ -61,17 +65,19 @@ Recent decisions (v1.7):
 1. VU meter updates at 50-70/sec through Redux - FIXED (Phase 28)
 2. MixersContext creates new reference every render - FIXED (Phase 29)
 3. 18+ individual selectors in useMixerHelper - FIXED (Phase 31)
-4. Triple track sync calls on session join
-5. Debounce instance recreation on dependency change
+4. Triple track sync calls on session join - FIXED (Phase 32-01)
+5. Debounce instance recreation on dependency change - FIXED (Phase 32-01)
 6. Missing React.memo on child components - FIXED (Phase 30)
+7. Redundant mixer categorization dispatches - FIXED (Phase 32-02)
 
 **Hotspot files:**
 - `useMixerStore.js:178-185` - VU update dispatch - FIXED
 - `useVuHelpers.js:99-104` - setVuStates object creation - FIXED
 - `mixersSlice.js:145-165` - updateMixer creates new objects
-- `JKSessionScreen.js:463-475` - Triple track sync calls
-- `useSessionModel.js:605-614` - Debounced trackChanges
+- `JKSessionScreen.js:463-475` - Triple track sync calls - FIXED
+- `useSessionModel.js:605-614` - Debounced trackChanges - FIXED
 - `MixersContext.js:10` - Unmemoized context value - FIXED
+- `useMixerHelper.js:291-295` - Unconditional category dispatches - FIXED
 
 ### Deferred Issues
 
@@ -97,8 +103,9 @@ Recent decisions (v1.7):
 ## Session Continuity
 
 Last session: 2026-03-05
-Stopped at: Completed 31-01-PLAN.md (Selector Optimization)
+Stopped at: Completed 32-02-PLAN.md (Mixer Categorization Optimization)
 Resume file: None
 
 **Next steps:**
-1. `/gsd:plan-phase 32` — plan final verification/performance testing phase
+1. Continue Phase 32 execution or verify all performance optimizations complete
+2. Plan verification/performance testing if needed

.planning/phases/32-state-update-optimization/32-02-SUMMARY.md

@@ -0,0 +1,132 @@
+---
+phase: 32-state-update-optimization
+plan: 02
+subsystem: state-management
+tags: [redux, react, performance, selectors, memoization]
+
+# Dependency graph
+requires:
+  - phase: 31-selector-optimization
+    provides: Composed selectors with shallowEqual comparisons
+provides:
+  - Conditional dispatch with content comparison for mixer categorization
+  - mixerArraysEqual helper for ID-based array comparison
+  - prevCategoriesRef to track last dispatched category values
+affects: [33-performance-testing, mixer-ui-components]
+
+# Tech tracking
+tech-stack:
+  added: []
+  patterns:
+    - "Content comparison before Redux dispatch"
+    - "useRef for tracking previous dispatch values"
+    - "ID-based array equality checking"
+
+key-files:
+  created: []
+  modified:
+    - jam-ui/src/hooks/useMixerHelper.js
+
+key-decisions:
+  - "Use ref instead of selectors to track previous values (avoids circular updates)"
+  - "ID-based comparison via master.id + personal.id pairs (stable and fast)"
+  - "Console logs for debugging dispatch decisions (can be commented out in production)"
+
+patterns-established:
+  - "Conditional dispatch pattern: if (!arrayEqual(prev, next)) { dispatch(); prev = next; }"
+  - "Comparison by stable IDs rather than deep object comparison"
+  - "Ref-based tracking for values that shouldn't trigger re-renders"
+
+# Metrics
+duration: 2min
+completed: 2026-03-05
+---
+
+# Phase 32 Plan 02: Mixer Categorization Optimization Summary
+
+**Conditional Redux dispatches eliminate redundant category updates - only dispatch when mixer IDs actually change**
+
+## Performance
+
+- **Duration:** 2 min
+- **Started:** 2026-03-05T14:05:42Z
+- **Completed:** 2026-03-05T14:07:07Z
+- **Tasks:** 3
+- **Files modified:** 1
+
+## Accomplishments
+- Added mixerArraysEqual helper for efficient ID-based array comparison
+- Implemented prevCategoriesRef to track last dispatched category values
+- Replaced unconditional dispatches with conditional checks for all 5 categories
+- Prevents unnecessary re-renders when mixer objects change but categories stay the same
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Add mixer array comparison helper** - `10a1eb657` (feat)
+   - Added mixerArraysEqual function with ID-based comparison
+   - Compares by master.id + personal.id pair keys
+
+2. **Task 2: Add prevCategoriesRef to track dispatched values** - `f7f6f10d6` (feat)
+   - Added useRef with category tracking object
+   - Avoids circular updates by using ref instead of selectors
+
+3. **Task 3: Add conditional dispatch to categorization** - `d53603cd0` (feat)
+   - Wrapped all 5 category dispatches in mixerArraysEqual checks
+   - Updates prevCategoriesRef after each dispatch
+   - Added console logs for debugging
+
+## Files Created/Modified
+- `jam-ui/src/hooks/useMixerHelper.js` - Added content comparison before Redux dispatches
+
+## Decisions Made
+
+**1. Use ref instead of selectors for previous values**
+- Selectors would cause circular updates (selector reads state that dispatch updates)
+- Ref provides stable reference across renders without triggering re-renders
+- Stores last dispatched values for next comparison
+
+**2. ID-based comparison instead of deep equality**
+- Mixer objects have stable `id` fields
+- Deep comparison with JSON.stringify would be slow and fragile
+- Only care if the set of mixers changed, not individual properties
+- Master/personal pair creates unique identifier per mixer pair
+
+**3. Console logs for debugging**
+- Useful during development to verify dispatches being skipped
+- Can be commented out in production
+- Help confirm optimization is working as expected
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Issues Encountered
+
+**Pre-existing ESLint warnings**
+- File has 60 pre-existing ESLint warnings (unused imports, missing dependencies)
+- Not related to this change
+- All formatting errors fixed with prettier
+- New code follows existing patterns
+
+## Next Phase Readiness
+
+**Ready for performance testing (Phase 33):**
+- Mixer categorization now only dispatches when content changes
+- Expected reduction: 5 unnecessary dispatches per mixer update
+- Can measure with Redux DevTools dispatch count before/after
+
+**Impact on downstream components:**
+- Any components subscribed to category selectors will re-render less frequently
+- VU meter updates won't trigger category re-categorization dispatches
+- Should reduce overall render count significantly
+
+**Monitoring approach:**
+- Console logs show when dispatches are skipped
+- Redux DevTools can verify dispatch reduction
+- React DevTools Profiler can measure render time improvements
+
+---
+*Phase: 32-state-update-optimization*
+*Completed: 2026-03-05*