batch3 T5: frontend foundation — Pane types, panes API, user-events WS

- Mirror Pane/PaneState/UserStream types
- api.panes.* CRUD methods
- sessionEvents adds session_updated, session_loaded, open_file_in_browser
- useUserEvents hook: single app-level WS to /api/ws/user with reconnect
- useSidebar handles session_updated (in-place patch + re-sort) and
  session_loaded (active-project highlight gap fix); open_file_in_browser
  is a deliberate no-op here, consumed by Workspace later
- App.tsx mounts useUserEvents once

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/App.tsx

@@ -4,21 +4,29 @@ import { Home } from '@/pages/Home';
 import { Project } from '@/pages/Project';
 import { Session } from '@/pages/Session';
 import { Toaster } from '@/components/ui/sonner';
+import { useUserEvents } from '@/hooks/useUserEvents';
+
+function AppShell() {
+  useUserEvents();
+  return (
+    <div className="dark h-screen flex bg-background text-foreground">
+      <ProjectSidebar />
+      <main className="flex-1 flex flex-col min-w-0">
+        <Routes>
+          <Route path="/" element={<Home />} />
+          <Route path="/project/:id" element={<Project />} />
+          <Route path="/session/:id" element={<Session />} />
+        </Routes>
+      </main>
+      <Toaster position="bottom-right" />
+    </div>
+  );
+}
 
 export default function App() {
   return (
     <BrowserRouter>
-      <div className="dark h-screen flex bg-background text-foreground">
-        <ProjectSidebar />
-        <main className="flex-1 flex flex-col min-w-0">
-          <Routes>
-            <Route path="/" element={<Home />} />
-            <Route path="/project/:id" element={<Project />} />
-            <Route path="/session/:id" element={<Session />} />
-          </Routes>
-        </main>
-        <Toaster position="bottom-right" />
-      </div>
+      <AppShell />
     </BrowserRouter>
   );
 }

apps/web/src/api/client.ts

@@ -7,6 +7,9 @@ import type {
   SidebarResponse,
   ListDirResult,
   ViewFileResult,
+  Pane,
+  PaneCreateRequest,
+  PaneUpdateRequest,
 } from './types';
 
 export class ApiError extends Error {
@@ -113,4 +116,23 @@ export const api = {
   sidebar: {
     get: () => request<SidebarResponse>('/api/sidebar'),
   },
+
+  panes: {
+    getForSession: (sessionId: string) =>
+      request<{ panes: Pane[] }>(`/api/sessions/${sessionId}/panes`),
+    create: (sessionId: string, body: PaneCreateRequest) =>
+      request<Pane>(`/api/sessions/${sessionId}/panes`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify(body),
+      }),
+    update: (id: string, body: PaneUpdateRequest) =>
+      request<Pane>(`/api/panes/${id}`, {
+        method: 'PATCH',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify(body),
+      }),
+    remove: (id: string) =>
+      request<void>(`/api/panes/${id}`, { method: 'DELETE' }),
+  },
 };

apps/web/src/api/types.ts

@@ -64,6 +64,7 @@ export interface SidebarSession {
   name: string;
   model: string;
   updated_at: string;
+  project_id: string;
 }
 
 export interface SidebarProject {
@@ -96,6 +97,36 @@ export interface ViewFileResult {
   bytes_returned: number;
 }
 
+export type PaneKind = 'chat' | 'file_browser';
+
+export interface FileBrowserPaneState {
+  open_file?: string | null;
+  filter?: string;
+  expanded_dirs?: string[];
+}
+export type ChatPaneState = Record<string, never>;
+export type PaneState = ChatPaneState | FileBrowserPaneState;
+
+interface PaneBase {
+  id: string;
+  session_id: string;
+  position: number;
+  created_at: string;
+}
+export type Pane = PaneBase & (
+  | { kind: 'chat'; state: ChatPaneState }
+  | { kind: 'file_browser'; state: FileBrowserPaneState }
+);
+
+export interface PaneCreateRequest {
+  kind: PaneKind;
+  position?: number;
+}
+export interface PaneUpdateRequest {
+  state?: PaneState;
+  position?: number;
+}
+
 export type WsFrame =
   | { type: 'snapshot'; messages: Message[] }
   | { type: 'message_started'; message_id: string; role: MessageRole }

apps/web/src/hooks/sessionEvents.ts

@@ -32,12 +32,34 @@ export interface SessionDeletedEvent {
   project_id: string;
 }
 
+export interface SessionUpdatedEvent {
+  type: 'session_updated';
+  session_id: string;
+  project_id: string;
+  name: string;
+  updated_at: string;
+}
+
+export interface SessionLoadedEvent {
+  type: 'session_loaded';
+  session_id: string;
+  project_id: string;
+}
+
+export interface OpenFileInBrowserEvent {
+  type: 'open_file_in_browser';
+  path: string; // project-relative
+}
+
 export type SessionEvent =
   | SessionRenamedEvent
   | ProjectCreatedEvent
   | ProjectDeletedEvent
   | SessionCreatedEvent
-  | SessionDeletedEvent;
+  | SessionDeletedEvent
+  | SessionUpdatedEvent
+  | SessionLoadedEvent
+  | OpenFileInBrowserEvent;
 type Listener = (event: SessionEvent) => void;
 
 const listeners = new Set<Listener>();

apps/web/src/hooks/useSidebar.ts

@@ -13,6 +13,7 @@ let sharedError: string | null = null;
 let sharedLoading: boolean = true;
 let initialized = false;
 let fetchInFlight: Promise<void> | null = null;
+let activeSessionProjectId: string | null = null;
 const subscribers = new Set<() => void>();
 
 function notify(): void {
@@ -74,6 +75,7 @@ function applyEvent(prev: SidebarResponse, event: import('./sessionEvents').Sess
           name: event.session.name,
           model: event.session.model,
           updated_at: event.session.updated_at,
+          project_id: event.project_id,
         };
         return {
           ...p,
@@ -113,7 +115,30 @@ function applyEvent(prev: SidebarResponse, event: import('./sessionEvents').Sess
       });
       return changed ? { ...prev, projects } : prev;
     }
-    default:
+    case 'session_updated': {
+      let changed = false;
+      const projects = prev.projects.map((p) => {
+        if (p.id !== event.project_id) return p;
+        let projectChanged = false;
+        const recent = p.recent_sessions.map((s) => {
+          if (s.id !== event.session_id) return s;
+          projectChanged = true;
+          return { ...s, name: event.name, updated_at: event.updated_at };
+        });
+        if (!projectChanged) return p;
+        changed = true;
+        const sorted = [...recent].sort(
+          (a, b) => new Date(b.updated_at).getTime() - new Date(a.updated_at).getTime()
+        );
+        return { ...p, recent_sessions: sorted };
+      });
+      return changed ? { ...prev, projects } : prev;
+    }
+    case 'session_loaded':
+      // activeSessionProjectId is updated in the subscribe callback; no data change here.
+      return prev;
+    case 'open_file_in_browser':
+      // Consumed by Workspace (T7); no sidebar state change needed.
       return prev;
   }
 }
@@ -122,6 +147,13 @@ function applyEvent(prev: SidebarResponse, event: import('./sessionEvents').Sess
 // before the initial fetch resolves are dropped; the eventual fetch
 // result is the source of truth.
 sessionEvents.subscribe((event) => {
+  // session_loaded updates activeSessionProjectId regardless of whether
+  // sharedData is populated yet — notify so subscribers can re-read.
+  if (event.type === 'session_loaded') {
+    activeSessionProjectId = event.project_id;
+    notify();
+    return;
+  }
   if (!sharedData) return;
   const next = applyEvent(sharedData, event);
   if (next === sharedData) return;
@@ -133,10 +165,11 @@ interface Snapshot {
   data: SidebarResponse | null;
   error: string | null;
   loading: boolean;
+  activeSessionProjectId: string | null;
 }
 
 function snapshot(): Snapshot {
-  return { data: sharedData, error: sharedError, loading: sharedLoading };
+  return { data: sharedData, error: sharedError, loading: sharedLoading, activeSessionProjectId };
 }
 
 export function useSidebar(): {
@@ -144,6 +177,7 @@ export function useSidebar(): {
   error: string | null;
   loading: boolean;
   retry: () => void;
+  activeSessionProjectId: string | null;
 } {
   const [state, setState] = useState<Snapshot>(snapshot);
 
@@ -165,5 +199,5 @@ export function useSidebar(): {
     void load();
   };
 
-  return { data: state.data, error: state.error, loading: state.loading, retry };
+  return { data: state.data, error: state.error, loading: state.loading, retry, activeSessionProjectId: state.activeSessionProjectId };
 }

apps/web/src/hooks/useUserEvents.ts

@@ -0,0 +1,58 @@
+import { useEffect } from 'react';
+import { sessionEvents } from './sessionEvents';
+
+const RECONNECT_INITIAL_MS = 1000;
+const RECONNECT_MAX_MS = 30000;
+
+export function useUserEvents(): void {
+  useEffect(() => {
+    let ws: WebSocket | null = null;
+    let reconnectTimer: ReturnType<typeof setTimeout> | null = null;
+    let reconnectDelay = RECONNECT_INITIAL_MS;
+    let unmounted = false;
+
+    const connect = () => {
+      if (unmounted) return;
+      const url = new URL('/api/ws/user', window.location.href);
+      url.protocol = url.protocol === 'https:' ? 'wss:' : 'ws:';
+      ws = new WebSocket(url.toString());
+
+      ws.onopen = () => {
+        reconnectDelay = RECONNECT_INITIAL_MS;
+      };
+
+      ws.onmessage = (ev) => {
+        try {
+          const frame = JSON.parse(ev.data);
+          // The server emits frames whose `type` matches SessionEvent union members
+          // (project_created, project_deleted, session_created, session_deleted, session_updated).
+          // Pass through onto the bus.
+          sessionEvents.emit(frame);
+        } catch (err) {
+          console.warn('useUserEvents: failed to parse frame', err);
+        }
+      };
+
+      ws.onclose = () => {
+        if (unmounted) return;
+        reconnectTimer = setTimeout(() => {
+          reconnectDelay = Math.min(reconnectDelay * 2, RECONNECT_MAX_MS);
+          connect();
+        }, reconnectDelay);
+      };
+
+      ws.onerror = () => {
+        // close handler will trigger reconnect
+        try { ws?.close(); } catch {}
+      };
+    };
+
+    connect();
+
+    return () => {
+      unmounted = true;
+      if (reconnectTimer) clearTimeout(reconnectTimer);
+      if (ws) try { ws.close(); } catch {}
+    };
+  }, []);
+}