fix(web): harden typed SPA chat lifecycle

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

apps/web/src/lib/socket.spec.ts

@@ -10,30 +10,32 @@ vi.mock('socket.io-client', () => ({
 
 import { destroySocket, getSocket } from './socket';
 
+function createMockSocket(): {
+  on: ReturnType<typeof vi.fn>;
+  offAny: ReturnType<typeof vi.fn>;
+  disconnect: ReturnType<typeof vi.fn>;
+} {
+  const mockSocket = {
+    on: vi.fn(() => mockSocket),
+    offAny: vi.fn(() => mockSocket),
+    disconnect: vi.fn(() => mockSocket),
+  };
+  return mockSocket;
+}
+
 describe('chat socket', () => {
-  let disconnectHandler: (() => void) | undefined;
-
   beforeEach(() => {
-    disconnectHandler = undefined;
     ioMock.mockReset();
-
-    const mockSocket = {
-      on: vi.fn((event: string, handler: () => void) => {
-        if (event === 'disconnect') disconnectHandler = handler;
-        return mockSocket;
-      }),
-      offAny: vi.fn(() => mockSocket),
-      disconnect: vi.fn(() => mockSocket),
-    };
-
-    ioMock.mockReturnValue(mockSocket);
+    // A fresh object per io() call so identity assertions (same singleton vs.
+    // a genuinely new instance) are meaningful.
+    ioMock.mockImplementation(() => createMockSocket());
   });
 
   afterEach(() => {
     destroySocket();
   });
 
-  it('creates one same-origin /chat namespace socket until it disconnects', () => {
+  it('creates one same-origin /chat namespace socket', () => {
     const first = getSocket();
     const second = getSocket();
 
@@ -44,9 +46,28 @@ describe('chat socket', () => {
       autoConnect: false,
       transports: ['websocket', 'polling'],
     });
+  });
 
-    disconnectHandler?.();
-    getSocket();
+  it('keeps the same singleton instance across a transient disconnect', () => {
+    const first = getSocket();
+
+    // socket.ts must not react to a real socket's `disconnect` event by
+    // nulling the singleton — it registers no such handler at all now, so
+    // simply calling getSocket() again after a "disconnect" must still
+    // return the same instance.
+    const second = getSocket();
+
+    expect(second).toBe(first);
+    expect(ioMock).toHaveBeenCalledOnce();
+  });
+
+  it('only creates a new singleton after an explicit destroySocket()', () => {
+    const first = getSocket();
+
+    destroySocket();
+    const second = getSocket();
+
+    expect(second).not.toBe(first);
     expect(ioMock).toHaveBeenCalledTimes(2);
   });
 });