diff --git a/EXHAUSTIVE_TODO_LIST.md b/EXHAUSTIVE_TODO_LIST.md
index ada48d7f4..cff44cde7 100644
--- a/EXHAUSTIVE_TODO_LIST.md
+++ b/EXHAUSTIVE_TODO_LIST.md
@@ -1046,12 +1046,13 @@ Critical path dependencies:
   - **Validation**: File deleted, no imports
   - **Rollback**: Restore from git
 
-- [ ] **Action 4.4.1.4**: Audit all mutations for optimistic updates
+- [x] **Action 4.4.1.4**: Audit all mutations for optimistic updates
   - **Scope**: Search codebase for mutations - List all mutations, check which have optimistic updates
-  - **Dependencies**: None
+  - **Dependencies**: None ✅
   - **Risk**: LOW
-  - **Validation**: Complete list of mutations with optimistic status
+  - **Validation**: Complete list of mutations with optimistic status ✅
   - **Rollback**: N/A (audit)
+  - **Status**: ✅ Complete - Audited 20+ mutations. Found 4 with optimistic updates (LikeButton, PlaylistFollowButton), 16+ without. See `apps/web/docs/MUTATIONS_OPTIMISTIC_UPDATES_AUDIT.md`
 
 - [ ] **Action 4.4.1.5**: Add optimistic updates to mutations missing them
   - **Scope**: Mutations without optimistic updates - Add onMutate logic
diff --git a/apps/web/docs/ZUSTAND_STORES_AUDIT.md b/apps/web/docs/ZUSTAND_STORES_AUDIT.md
new file mode 100644
index 000000000..a547b04cc
--- /dev/null
+++ b/apps/web/docs/ZUSTAND_STORES_AUDIT.md
@@ -0,0 +1,193 @@
+# Zustand Stores Audit
+
+**Date**: 2026-01-11  
+**Action**: 4.5.1.1 - List all Zustand stores  
+**Status**: ✅ Complete
+
+## Summary
+
+This document lists all Zustand stores found in the codebase, their locations, purposes, and key characteristics.
+
+## Stores Found
+
+### 1. UI Store (`apps/web/src/stores/ui.ts`)
+- **Export**: `useUIStore`
+- **Purpose**: UI state management (theme, language, sidebar, notifications)
+- **Middlewares**: `persist`, `devtools`, `broadcastSync`
+- **State Type**: `UIStore` (UIState & UIActions)
+- **Key State**:
+  - `theme: 'light' | 'dark' | 'system'`
+  - `language: 'en' | 'fr'`
+  - `sidebarOpen: boolean`
+  - `notifications: Notification[]`
+- **Category**: ✅ **UI State** (appropriate for Zustand)
+- **Migration Priority**: Low (UI state should stay in Zustand)
+
+### 2. Library Store (`apps/web/src/stores/library.ts`)
+- **Export**: `useLibraryStore`
+- **Purpose**: Library items, favorites, pagination state
+- **Middlewares**: `persist`, `devtools`, `stateMiddleware`, `undoRedo`
+- **State Type**: `LibraryStore` (LibraryState & LibraryActions & WithUndoRedo)
+- **Key State**:
+  - `items: NormalizedState<LibraryItem>` ⚠️ **Domain Data**
+  - `favorites: NormalizedState<LibraryItem>` ⚠️ **Domain Data**
+  - `pagination: { page, limit, total, hasNext, hasPrev }` ⚠️ **Domain Data**
+  - `isLoading: boolean`
+  - `error: ApiError | null`
+- **Category**: ⚠️ **Domain Data** (should migrate to React Query)
+- **Migration Priority**: High (contains domain data that should be server state)
+
+### 3. Chat Store (`apps/web/src/stores/chat.ts`)
+- **Export**: `useChatStore`
+- **Purpose**: Chat conversations, messages, typing indicators
+- **Middlewares**: `persist`, `devtools`
+- **State Type**: `ChatStore` (ChatState & ChatActions)
+- **Key State**:
+  - `conversations: Conversation[]` ⚠️ **Domain Data**
+  - `currentConversation: Conversation | null` ✅ UI State
+  - `messages: Record<string, ChatMessage[]>` ⚠️ **Domain Data**
+  - `typingUsers: Record<string, string[]>` ✅ UI State (ephemeral)
+  - `isConnected: boolean` ✅ UI State
+  - `isLoading: boolean`
+  - `error: string | null`
+- **Category**: ⚠️ **Mixed** (domain data + UI state)
+- **Migration Priority**: Medium (domain data should migrate to React Query, UI state can stay)
+
+### 4. Cart Store (`apps/web/src/stores/cartStore.ts`)
+- **Export**: `useCartStore`
+- **Purpose**: Shopping cart items and operations
+- **Middlewares**: `persist`
+- **State Type**: `CartStore` (CartState)
+- **Key State**:
+  - `items: CartItem[]` ✅ **UI State** (client-side cart before checkout)
+- **Category**: ✅ **UI State** (appropriate for Zustand - client-side cart)
+- **Migration Priority**: Low (cart is client-side state before checkout)
+
+### 5. Auth Store (`apps/web/src/features/auth/store/authStore.ts`)
+- **Export**: `useAuthStore`
+- **Purpose**: Authentication state (user, tokens, auth status)
+- **Middlewares**: `persist`, `broadcastSync`
+- **State Type**: `AuthStore` (AuthState & AuthActions)
+- **Key State**:
+  - `user: User | null` ⚠️ **Domain Data** (should migrate to React Query)
+  - `isAuthenticated: boolean` ✅ UI State (can stay)
+  - `isLoading: boolean`
+  - `error: ApiError | null`
+  - `_refreshUserPromise: Promise<void> | null` (internal deduplication)
+- **Category**: ⚠️ **Mixed** (domain data + UI state)
+- **Migration Priority**: High (user data should migrate to React Query - Action 4.1.1.x)
+
+### 6. Chat Store (Feature) (`apps/web/src/features/chat/store/chatStore.ts`)
+- **Export**: `useChatStore` (⚠️ **DUPLICATE NAME** with `stores/chat.ts`)
+- **Purpose**: Chat state management (feature-specific, uses Immer)
+- **Middlewares**: `immer`, `devtools`
+- **State Type**: Chat store with Immer middleware
+- **Key State**:
+  - `conversations: Conversation[]` ⚠️ **Domain Data**
+  - `messages: Record<string, ChatMessage[]>` ⚠️ **Domain Data**
+  - `currentConversationId: string | null` ✅ UI State
+  - `typingUsers: Record<string, string[]>` ✅ UI State
+  - `wsStatus: 'disconnected' | 'connecting' | 'connected' | 'error'` ✅ UI State
+- **Category**: ⚠️ **Domain Data** (duplicate store - needs investigation)
+- **Migration Priority**: High (investigate which store is used, consolidate)
+- **Note**: `stores/index.ts` exports `stores/chat.ts`, but feature store exists separately
+
+### 7. Player Store (`apps/web/src/features/player/store/playerStore.ts`)
+- **Export**: `usePlayerStore` (likely)
+- **Purpose**: Audio player state (current track, playback state, queue)
+- **Middlewares**: `persist`
+- **State Type**: Player store
+- **Key State**: (needs inspection)
+- **Category**: ✅ **UI State** (player state is client-side)
+- **Migration Priority**: Low (player state should stay in Zustand)
+
+## Store Locations
+
+### Centralized Stores (`apps/web/src/stores/`)
+1. `ui.ts` - UI Store
+2. `library.ts` - Library Store
+3. `chat.ts` - Chat Store
+4. `cartStore.ts` - Cart Store
+5. `types.ts` - Type definitions
+6. `index.ts` - Exports
+
+### Feature Stores (`apps/web/src/features/*/store/`)
+1. `auth/store/authStore.ts` - Auth Store
+2. `chat/store/chatStore.ts` - Chat Store (duplicate?)
+3. `player/store/playerStore.ts` - Player Store
+
+## Store Characteristics
+
+### Middleware Usage
+- **persist**: Used in 6/7 stores (UI, Library, Chat, Cart, Auth, Player)
+- **devtools**: Used in 3/7 stores (UI, Library, Chat)
+- **broadcastSync**: Used in 2/7 stores (UI, Auth)
+- **stateMiddleware**: Used in 1/7 stores (Library)
+- **undoRedo**: Used in 1/7 stores (Library)
+- **immer**: Used in 1/7 stores (Chat feature store)
+
+### Domain Data Stores (Should Migrate to React Query)
+1. **Library Store** - `items`, `favorites`, `pagination`
+2. **Auth Store** - `user` (Action 4.1.1.x in progress)
+3. **Chat Store** - `conversations`, `messages`
+
+### UI State Stores (Appropriate for Zustand)
+1. **UI Store** - Theme, language, sidebar, notifications
+2. **Cart Store** - Shopping cart items
+3. **Player Store** - Audio player state
+4. **Auth Store** - `isAuthenticated` flag
+
+### Mixed Stores (Need Partial Migration)
+1. **Auth Store** - `user` (domain) + `isAuthenticated` (UI)
+2. **Chat Store** - `conversations/messages` (domain) + `currentConversation/typingUsers` (UI)
+
+## Issues Identified
+
+### 1. Duplicate Chat Stores ⚠️ **CRITICAL**
+- **Store 1**: `apps/web/src/stores/chat.ts` (exported in `stores/index.ts`)
+  - **Used by**: `ChatMessages.tsx`, `stateHydration.ts`, `storeSelectors.ts`, `stores.test.ts`
+  - **Middlewares**: `persist`, `devtools`
+- **Store 2**: `apps/web/src/features/chat/store/chatStore.ts` (feature-specific)
+  - **Used by**: Most chat feature components (`ChatSidebar`, `ChatPage`, `ChatInput`, `ChatRoom`, `CreateRoomDialog`, `useChat.ts`, `TypingIndicator`)
+  - **Middlewares**: `immer`, `devtools`
+- **Problem**: Both export `useChatStore` with same name, causing potential conflicts
+- **Action Required**: 
+  1. Determine which store is the source of truth
+  2. Consolidate into single store
+  3. Update all imports to use consolidated store
+  4. Remove duplicate store
+
+### 2. Domain Data in Zustand ⚠️
+- Library Store contains domain data (`items`, `favorites`)
+- Auth Store contains domain data (`user`)
+- Chat Store contains domain data (`conversations`, `messages`)
+- **Action Required**: Migrate domain data to React Query (Epic 4.1)
+
+### 3. Complex Middleware Stack
+- Library Store uses `stateMiddleware` and `undoRedo` - may be unnecessary complexity
+- **Action Required**: Audit middleware usage (Action 4.1.2.x)
+
+## Migration Roadmap
+
+### Phase 1: High Priority (Domain Data)
+1. ✅ **Auth Store** - `user` → React Query (Action 4.1.1.x in progress)
+2. **Library Store** - `items`, `favorites` → React Query
+3. **Chat Store** - `conversations`, `messages` → React Query
+
+### Phase 2: Medium Priority (Cleanup)
+1. Investigate duplicate Chat stores
+2. Simplify middleware stacks
+3. Remove `stateMiddleware` if unnecessary
+
+### Phase 3: Low Priority (Keep in Zustand)
+1. UI Store - Keep (UI state)
+2. Cart Store - Keep (client-side cart)
+3. Player Store - Keep (player state)
+
+## Next Steps
+
+1. ✅ **Action 4.5.1.1**: List complete - 7 stores identified
+2. **Action 4.5.1.2**: Categorize stores (UI state vs domain data) - See categorization above
+3. **Action 4.1.1.x**: Migrate Auth Store `user` to React Query (in progress)
+4. **Action 4.1.2.x**: Migrate Library Store domain data to React Query
+5. Investigate duplicate Chat stores