fix(web): harden typed SPA chat lifecycle

Co-Authored-By: Claude Haiku 4.5 <[email protected]>

apps/web/src/spa/chat/test-support/fake-chat-socket.ts

@@ -27,6 +27,11 @@ export interface FakeChatSocket {
  * missing a required field fails to compile instead of silently no-op'ing at
  * runtime.
  */
+/** Socket.IO's built-in connection-state events. Not part of the app-level
+ * ServerToClientEvents contract, but real sockets always support them and
+ * `useChatConnection` registers a `disconnect` handler on the real socket. */
+type LifecycleEvent = 'connect' | 'disconnect';
+
 export function createFakeChatSocket(): {
   socket: FakeChatSocket;
   listeners: Map<ServerEvent, Set<(payload: never) => void>>;
@@ -35,6 +40,19 @@ export function createFakeChatSocket(): {
     event: K,
     payload: Parameters<ServerToClientEvents[K]>[0],
   ): void;
+  /** Escape hatch for malformed-payload tests: bypasses the compile-time
+   * payload contract to simulate a genuinely untrusted runtime value from the
+   * server, e.g. a `session:info` with a non-array `availableThinkingLevels`. */
+  serverEmitRaw(event: ServerEvent, payload: unknown): void;
+  /** Simulates a transient Socket.IO `disconnect` — fires any handler(s)
+   * registered via `socket.on('disconnect', ...)` without clearing any
+   * listeners, mirroring how a real reconnecting socket behaves. */
+  simulateDisconnect(): void;
+  /** Simulates socket.io-client's automatic reconnect of the *same*
+   * instance after a transient disconnect: marks the socket connected again
+   * and fires any handler(s) registered via `socket.on('connect', ...)`,
+   * without clearing or replacing any listeners. */
+  simulateReconnect(): void;
 } {
   const listeners = new Map<ServerEvent, Set<(payload: never) => void>>();
   const emitted: EmittedEvent[] = [];
@@ -73,5 +91,35 @@ export function createFakeChatSocket(): {
     }
   }
 
-  return { socket, listeners, emitted, serverEmit };
+  function serverEmitRaw(event: ServerEvent, payload: unknown): void {
+    for (const handler of listeners.get(event) ?? []) {
+      (handler as (payload: unknown) => void)(payload);
+    }
+  }
+
+  function simulateDisconnect(): void {
+    socket.connected = false;
+    const lifecycleKey = 'disconnect' satisfies LifecycleEvent as unknown as ServerEvent;
+    for (const handler of listeners.get(lifecycleKey) ?? []) {
+      (handler as () => void)();
+    }
+  }
+
+  function simulateReconnect(): void {
+    socket.connected = true;
+    const lifecycleKey = 'connect' satisfies LifecycleEvent as unknown as ServerEvent;
+    for (const handler of listeners.get(lifecycleKey) ?? []) {
+      (handler as () => void)();
+    }
+  }
+
+  return {
+    socket,
+    listeners,
+    emitted,
+    serverEmit,
+    serverEmitRaw,
+    simulateDisconnect,
+    simulateReconnect,
+  };
 }