Migrate SessionContext to pure Zustand, eliminate hybrid overhead

Problem: SessionContext used useSyncedSessionState which synced every state
update from React useState to Zustand, creating double overhead and complexity.

Solution: Complete migration to pure Zustand architecture:

- session-store.ts is now the single source of truth
  - Moved ALL state directly into Zustand (no React useState)
  - Added per-session state: messages, agents, commands, permissions, etc.
  - Added Zustand actions for all state updates (setMessages, setAgents, etc.)
  - Exported all types (MessageEntry, Agent, Command, etc.)

- session-context.tsx is now a pure WebSocket message handler
  - Removed useSyncedSessionState hook entirely
  - Removed all useState calls for session state
  - Removed sync machinery (syncSessionField, syncSessionPartial)
  - WebSocket handlers now call Zustand setters directly
  - Context only provides imperative APIs (ws, audioPlayer, actions)
  - No state values in context

Architecture change:
  Before: WebSocket → React useState → sync → Zustand (double overhead)
  After:  WebSocket → Zustand directly (single source of truth)

Benefits:
- Eliminated double overhead from React → Zustand syncing
- Single state update per WebSocket message
- Better re-render optimization via Zustand selectors
- Cleaner separation: SessionProvider = message handler, SessionStore = state
- Reduced complexity: removed 400+ lines of hybrid sync code

Backward compatibility:
- useDaemonSession() already reads from Zustand, no changes needed
- Type exports re-exported from session-store for compatibility
- Components work exactly the same

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

packages/app/src/stores/session-store.ts

@@ -1,31 +1,275 @@
 import { create } from "zustand";
 import { subscribeWithSelector } from "zustand/middleware";
-import type { SessionContextValue } from "@/contexts/session-context";
+import type { UseWebSocketReturn } from "@/hooks/use-websocket";
+import type { useAudioPlayer } from "@/hooks/use-audio-player";
 import type { AgentDirectoryEntry } from "@/types/agent-directory";
+import type { StreamItem } from "@/types/stream";
+import type { PendingPermission } from "@/types/shared";
+import type {
+  AgentLifecycleStatus,
+} from "@server/server/agent/agent-manager";
+import type {
+  AgentPermissionResponse,
+  AgentSessionConfig,
+  AgentProvider,
+  AgentMode,
+  AgentCapabilityFlags,
+  AgentModelDefinition,
+  AgentUsage,
+  AgentPersistenceHandle,
+} from "@server/server/agent/agent-sdk-types";
+import type { GitSetupOptions } from "@server/server/messages";
 import { isPerfLoggingEnabled, measurePayload, perfLog } from "@/utils/perf";
 
-export type SessionData = SessionContextValue;
+// Re-export types that were in session-context
+export type MessageEntry =
+  | {
+      type: "user";
+      id: string;
+      timestamp: number;
+      message: string;
+    }
+  | {
+      type: "assistant";
+      id: string;
+      timestamp: number;
+      message: string;
+    }
+  | {
+      type: "activity";
+      id: string;
+      timestamp: number;
+      activityType: "system" | "info" | "success" | "error";
+      message: string;
+      metadata?: Record<string, unknown>;
+    }
+  | {
+      type: "artifact";
+      id: string;
+      timestamp: number;
+      artifactId: string;
+      artifactType: string;
+      title: string;
+    }
+  | {
+      type: "tool_call";
+      id: string;
+      timestamp: number;
+      toolName: string;
+      args: any;
+      result?: any;
+      error?: any;
+      status: "executing" | "completed" | "failed";
+    };
 
+export type DraftInput = {
+  text: string;
+  images: Array<{ uri: string; mimeType: string }>;
+};
+
+export type ProviderModelState = {
+  models: AgentModelDefinition[] | null;
+  fetchedAt: Date | null;
+  error: string | null;
+  isLoading: boolean;
+};
+
+export interface Agent {
+  serverId: string;
+  id: string;
+  provider: AgentProvider;
+  status: AgentLifecycleStatus;
+  createdAt: Date;
+  updatedAt: Date;
+  lastUserMessageAt: Date | null;
+  lastActivityAt: Date;
+  sessionId: string | null;
+  capabilities: AgentCapabilityFlags;
+  currentModeId: string | null;
+  availableModes: AgentMode[];
+  pendingPermissions: any[];
+  persistence: AgentPersistenceHandle | null;
+  lastUsage?: AgentUsage;
+  lastError?: string | null;
+  title: string | null;
+  cwd: string;
+  model: string | null;
+}
+
+export interface Command {
+  id: string;
+  name: string;
+  workingDirectory: string;
+  currentCommand: string;
+  isDead: boolean;
+  exitCode: number | null;
+}
+
+export type ExplorerEntryKind = "file" | "directory";
+export type ExplorerFileKind = "text" | "image" | "binary";
+export type ExplorerEncoding = "utf-8" | "base64" | "none";
+
+export interface ExplorerEntry {
+  name: string;
+  path: string;
+  kind: ExplorerEntryKind;
+  size: number;
+  modifiedAt: string;
+}
+
+export interface ExplorerFile {
+  path: string;
+  kind: ExplorerFileKind;
+  encoding: ExplorerEncoding;
+  content?: string;
+  mimeType?: string;
+  size: number;
+  modifiedAt: string;
+}
+
+interface ExplorerDirectory {
+  path: string;
+  entries: ExplorerEntry[];
+}
+
+interface ExplorerRequestState {
+  path: string;
+  mode: "list" | "file";
+}
+
+export interface AgentFileExplorerState {
+  directories: Map<string, ExplorerDirectory>;
+  files: Map<string, ExplorerFile>;
+  isLoading: boolean;
+  lastError: string | null;
+  pendingRequest: ExplorerRequestState | null;
+  currentPath: string;
+  history: string[];
+  lastVisitedPath: string;
+}
+
+// Per-session state
+export interface SessionState {
+  serverId: string;
+
+  // WebSocket (immutable reference)
+  ws: UseWebSocketReturn | null;
+
+  // Audio player (immutable reference)
+  audioPlayer: ReturnType<typeof useAudioPlayer> | null;
+
+  // Hydration status
+  hasHydratedAgents: boolean;
+
+  // Audio state
+  isPlayingAudio: boolean;
+
+  // Focus
+  focusedAgentId: string | null;
+
+  // Messages
+  messages: MessageEntry[];
+  currentAssistantMessage: string;
+
+  // Stream state
+  agentStreamState: Map<string, StreamItem[]>;
+
+  // Initializing agents
+  initializingAgents: Map<string, boolean>;
+
+  // Agents and commands
+  agents: Map<string, Agent>;
+  commands: Map<string, Command>;
+
+  // Permissions
+  pendingPermissions: Map<string, PendingPermission>;
+
+  // Git diffs
+  gitDiffs: Map<string, string>;
+
+  // File explorer
+  fileExplorer: Map<string, AgentFileExplorerState>;
+
+  // Provider models
+  providerModels: Map<AgentProvider, ProviderModelState>;
+
+  // Draft inputs (non-serializable, stored in Map)
+  draftInputs: Map<string, DraftInput>;
+
+  // Queued messages
+  queuedMessages: Map<string, Array<{ id: string; text: string; images?: Array<{ uri: string; mimeType: string }> }>>;
+}
+
+// Global store state
 interface SessionStoreState {
-  sessions: Record<string, SessionData>;
+  sessions: Record<string, SessionState>;
   agentDirectory: Record<string, AgentDirectoryEntry[]>;
 }
 
-interface SessionStore extends SessionStoreState {
+// Action types
-  setSession: (serverId: string, data: SessionData) => void;
+interface SessionStoreActions {
-  updateSession: (serverId: string, partial: Partial<SessionData>) => void;
+  // Session management
+  initializeSession: (serverId: string, ws: UseWebSocketReturn, audioPlayer: ReturnType<typeof useAudioPlayer>) => void;
   clearSession: (serverId: string) => void;
-  getSession: (serverId: string) => SessionData | undefined;
+  getSession: (serverId: string) => SessionState | undefined;
+
+  // Audio state
+  setIsPlayingAudio: (serverId: string, playing: boolean) => void;
+
+  // Focus
+  setFocusedAgentId: (serverId: string, agentId: string | null) => void;
+
+  // Messages
+  setMessages: (serverId: string, messages: MessageEntry[] | ((prev: MessageEntry[]) => MessageEntry[])) => void;
+  setCurrentAssistantMessage: (serverId: string, message: string | ((prev: string) => string)) => void;
+
+  // Stream state
+  setAgentStreamState: (serverId: string, state: Map<string, StreamItem[]> | ((prev: Map<string, StreamItem[]>) => Map<string, StreamItem[]>)) => void;
+
+  // Initializing agents
+  setInitializingAgents: (serverId: string, state: Map<string, boolean> | ((prev: Map<string, boolean>) => Map<string, boolean>)) => void;
+
+  // Agents
+  setAgents: (serverId: string, agents: Map<string, Agent> | ((prev: Map<string, Agent>) => Map<string, Agent>)) => void;
+
+  // Commands
+  setCommands: (serverId: string, commands: Map<string, Command> | ((prev: Map<string, Command>) => Map<string, Command>)) => void;
+
+  // Permissions
+  setPendingPermissions: (serverId: string, perms: Map<string, PendingPermission> | ((prev: Map<string, PendingPermission>) => Map<string, PendingPermission>)) => void;
+
+  // Git diffs
+  setGitDiffs: (serverId: string, diffs: Map<string, string> | ((prev: Map<string, string>) => Map<string, string>)) => void;
+
+  // File explorer
+  setFileExplorer: (serverId: string, state: Map<string, AgentFileExplorerState> | ((prev: Map<string, AgentFileExplorerState>) => Map<string, AgentFileExplorerState>)) => void;
+
+  // Provider models
+  setProviderModels: (serverId: string, models: Map<AgentProvider, ProviderModelState> | ((prev: Map<AgentProvider, ProviderModelState>) => Map<AgentProvider, ProviderModelState>)) => void;
+
+  // Draft inputs
+  getDraftInput: (serverId: string, agentId: string) => DraftInput | undefined;
+  saveDraftInput: (serverId: string, agentId: string, draft: DraftInput) => void;
+
+  // Queued messages
+  setQueuedMessages: (serverId: string, value: Map<string, Array<{ id: string; text: string; images?: Array<{ uri: string; mimeType: string }> }>> | ((prev: Map<string, Array<{ id: string; text: string; images?: Array<{ uri: string; mimeType: string }> }>>) => Map<string, Array<{ id: string; text: string; images?: Array<{ uri: string; mimeType: string }> }>>)) => void;
+
+  // Hydration
+  setHasHydratedAgents: (serverId: string, hydrated: boolean) => void;
+
+  // Agent directory
   setAgentDirectory: (serverId: string, agents: AgentDirectoryEntry[]) => void;
   clearAgentDirectory: (serverId: string) => void;
   getAgentDirectory: (serverId: string) => AgentDirectoryEntry[] | undefined;
 }
 
+type SessionStore = SessionStoreState & SessionStoreActions;
+
 const SESSION_STORE_LOG_TAG = "[SessionStore]";
 let sessionStoreUpdateCount = 0;
 
 function logSessionStoreUpdate(
-  type: "setSession" | "updateSession" | "clearSession" | "setAgentDirectory" | "clearAgentDirectory",
+  type: string,
   serverId: string,
   payload?: unknown
 ) {
@@ -44,23 +288,6 @@ function logSessionStoreUpdate(
   });
 }
 
-const shallowEqual = (left: SessionData, right: SessionData): boolean => {
-  if (left === right) {
-    return true;
-  }
-  const leftEntries = Object.entries(left);
-  const rightEntries = Object.entries(right);
-  if (leftEntries.length !== rightEntries.length) {
-    return false;
-  }
-  for (const [key, value] of leftEntries) {
-    if (right[key as keyof SessionData] !== value) {
-      return false;
-    }
-  }
-  return true;
-};
-
 function areAgentDirectoriesEqual(left: AgentDirectoryEntry[] | undefined, right: AgentDirectoryEntry[]): boolean {
   if (!left) {
     return false;
@@ -85,52 +312,52 @@ function areAgentDirectoriesEqual(left: AgentDirectoryEntry[] | undefined, right
   });
 }
 
+// Helper to create initial session state
+function createInitialSessionState(serverId: string, ws: UseWebSocketReturn, audioPlayer: ReturnType<typeof useAudioPlayer>): SessionState {
+  return {
+    serverId,
+    ws,
+    audioPlayer,
+    hasHydratedAgents: false,
+    isPlayingAudio: false,
+    focusedAgentId: null,
+    messages: [],
+    currentAssistantMessage: "",
+    agentStreamState: new Map(),
+    initializingAgents: new Map(),
+    agents: new Map(),
+    commands: new Map(),
+    pendingPermissions: new Map(),
+    gitDiffs: new Map(),
+    fileExplorer: new Map(),
+    providerModels: new Map(),
+    draftInputs: new Map(),
+    queuedMessages: new Map(),
+  };
+}
+
 export const useSessionStore = create<SessionStore>()(
   subscribeWithSelector((set, get) => ({
     sessions: {},
     agentDirectory: {},
-    setSession: (serverId, data) => {
+
+    // Session management
+    initializeSession: (serverId, ws, audioPlayer) => {
       set((prev) => {
-        if (prev.sessions[serverId] === data) {
+        if (prev.sessions[serverId]) {
           return prev;
         }
-        logSessionStoreUpdate("setSession", serverId, data);
+        logSessionStoreUpdate("initializeSession", serverId);
         return {
           ...prev,
           sessions: {
             ...prev.sessions,
-            [serverId]: data,
+            [serverId]: createInitialSessionState(serverId, ws, audioPlayer),
           },
         };
       });
     },
-    updateSession: (serverId, partial) => {
-      set((prev) => {
-        const existing = prev.sessions[serverId];
-        const next: SessionData | undefined = existing
-          ? { ...existing, ...partial, serverId }
-          : partial.serverId
-            ? ({ ...(partial as SessionData), serverId })
-            : undefined;
 
-        if (!next) {
-          return prev;
-        }
-
-        if (existing && shallowEqual(existing, next)) {
-          return prev;
-        }
-
-        logSessionStoreUpdate("updateSession", serverId, partial);
-        return {
-          ...prev,
-          sessions: {
-            ...prev.sessions,
-            [serverId]: next,
-          },
-        };
-      });
-    },
     clearSession: (serverId) => {
       set((prev) => {
         if (!(serverId in prev.sessions)) {
@@ -142,9 +369,335 @@ export const useSessionStore = create<SessionStore>()(
         return { ...prev, sessions: nextSessions };
       });
     },
+
     getSession: (serverId) => {
       return get().sessions[serverId];
     },
+
+    // Audio state
+    setIsPlayingAudio: (serverId, playing) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session || session.isPlayingAudio === playing) {
+          return prev;
+        }
+        logSessionStoreUpdate("setIsPlayingAudio", serverId, { playing });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, isPlayingAudio: playing },
+          },
+        };
+      });
+    },
+
+    // Focus
+    setFocusedAgentId: (serverId, agentId) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session || session.focusedAgentId === agentId) {
+          return prev;
+        }
+        logSessionStoreUpdate("setFocusedAgentId", serverId, { agentId });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, focusedAgentId: agentId },
+          },
+        };
+      });
+    },
+
+    // Messages
+    setMessages: (serverId, messages) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextMessages = typeof messages === "function" ? messages(session.messages) : messages;
+        if (session.messages === nextMessages) {
+          return prev;
+        }
+        logSessionStoreUpdate("setMessages", serverId, { count: nextMessages.length });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, messages: nextMessages },
+          },
+        };
+      });
+    },
+
+    setCurrentAssistantMessage: (serverId, message) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextMessage = typeof message === "function" ? message(session.currentAssistantMessage) : message;
+        if (session.currentAssistantMessage === nextMessage) {
+          return prev;
+        }
+        logSessionStoreUpdate("setCurrentAssistantMessage", serverId, { length: nextMessage.length });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, currentAssistantMessage: nextMessage },
+          },
+        };
+      });
+    },
+
+    // Stream state
+    setAgentStreamState: (serverId, state) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextState = typeof state === "function" ? state(session.agentStreamState) : state;
+        if (session.agentStreamState === nextState) {
+          return prev;
+        }
+        logSessionStoreUpdate("setAgentStreamState", serverId, { agentCount: nextState.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, agentStreamState: nextState },
+          },
+        };
+      });
+    },
+
+    // Initializing agents
+    setInitializingAgents: (serverId, state) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextState = typeof state === "function" ? state(session.initializingAgents) : state;
+        if (session.initializingAgents === nextState) {
+          return prev;
+        }
+        logSessionStoreUpdate("setInitializingAgents", serverId, { count: nextState.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, initializingAgents: nextState },
+          },
+        };
+      });
+    },
+
+    // Agents
+    setAgents: (serverId, agents) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextAgents = typeof agents === "function" ? agents(session.agents) : agents;
+        if (session.agents === nextAgents) {
+          return prev;
+        }
+        logSessionStoreUpdate("setAgents", serverId, { count: nextAgents.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, agents: nextAgents },
+          },
+        };
+      });
+    },
+
+    // Commands
+    setCommands: (serverId, commands) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextCommands = typeof commands === "function" ? commands(session.commands) : commands;
+        if (session.commands === nextCommands) {
+          return prev;
+        }
+        logSessionStoreUpdate("setCommands", serverId, { count: nextCommands.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, commands: nextCommands },
+          },
+        };
+      });
+    },
+
+    // Permissions
+    setPendingPermissions: (serverId, perms) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextPerms = typeof perms === "function" ? perms(session.pendingPermissions) : perms;
+        if (session.pendingPermissions === nextPerms) {
+          return prev;
+        }
+        logSessionStoreUpdate("setPendingPermissions", serverId, { count: nextPerms.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, pendingPermissions: nextPerms },
+          },
+        };
+      });
+    },
+
+    // Git diffs
+    setGitDiffs: (serverId, diffs) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextDiffs = typeof diffs === "function" ? diffs(session.gitDiffs) : diffs;
+        if (session.gitDiffs === nextDiffs) {
+          return prev;
+        }
+        logSessionStoreUpdate("setGitDiffs", serverId, { count: nextDiffs.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, gitDiffs: nextDiffs },
+          },
+        };
+      });
+    },
+
+    // File explorer
+    setFileExplorer: (serverId, state) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextState = typeof state === "function" ? state(session.fileExplorer) : state;
+        if (session.fileExplorer === nextState) {
+          return prev;
+        }
+        logSessionStoreUpdate("setFileExplorer", serverId, { agentCount: nextState.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, fileExplorer: nextState },
+          },
+        };
+      });
+    },
+
+    // Provider models
+    setProviderModels: (serverId, models) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextModels = typeof models === "function" ? models(session.providerModels) : models;
+        if (session.providerModels === nextModels) {
+          return prev;
+        }
+        logSessionStoreUpdate("setProviderModels", serverId, { providerCount: nextModels.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, providerModels: nextModels },
+          },
+        };
+      });
+    },
+
+    // Draft inputs
+    getDraftInput: (serverId, agentId) => {
+      const session = get().sessions[serverId];
+      if (!session) {
+        return undefined;
+      }
+      return session.draftInputs.get(agentId);
+    },
+
+    saveDraftInput: (serverId, agentId, draft) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextDraftInputs = new Map(session.draftInputs);
+        nextDraftInputs.set(agentId, draft);
+        logSessionStoreUpdate("saveDraftInput", serverId, { agentId });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, draftInputs: nextDraftInputs },
+          },
+        };
+      });
+    },
+
+    // Queued messages
+    setQueuedMessages: (serverId, value) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session) {
+          return prev;
+        }
+        const nextValue = typeof value === "function" ? value(session.queuedMessages) : value;
+        if (session.queuedMessages === nextValue) {
+          return prev;
+        }
+        logSessionStoreUpdate("setQueuedMessages", serverId, { agentCount: nextValue.size });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, queuedMessages: nextValue },
+          },
+        };
+      });
+    },
+
+    // Hydration
+    setHasHydratedAgents: (serverId, hydrated) => {
+      set((prev) => {
+        const session = prev.sessions[serverId];
+        if (!session || session.hasHydratedAgents === hydrated) {
+          return prev;
+        }
+        logSessionStoreUpdate("setHasHydratedAgents", serverId, { hydrated });
+        return {
+          ...prev,
+          sessions: {
+            ...prev.sessions,
+            [serverId]: { ...session, hasHydratedAgents: hydrated },
+          },
+        };
+      });
+    },
+
+    // Agent directory
     setAgentDirectory: (serverId, agents) => {
       set((prev) => {
         const existing = prev.agentDirectory[serverId];
@@ -161,6 +714,7 @@ export const useSessionStore = create<SessionStore>()(
         };
       });
     },
+
     clearAgentDirectory: (serverId) => {
       set((prev) => {
         if (!(serverId in prev.agentDirectory)) {
@@ -172,6 +726,7 @@ export const useSessionStore = create<SessionStore>()(
         return { ...prev, agentDirectory: nextDirectory };
       });
     },
+
     getAgentDirectory: (serverId) => {
       return get().agentDirectory[serverId];
     },