fix: stabilize ai design history switching

tests/unit/image-workspace-route.test.ts

@@ -51,6 +51,14 @@ function createRequest(method: string, body?: unknown): IncomingMessage {
   return request;
 }
 
+function deferred<T>(): { promise: Promise<T>; resolve(value: T): void } {
+  let resolve!: (value: T) => void;
+  const promise = new Promise<T>((accept) => {
+    resolve = accept;
+  });
+  return { promise, resolve };
+}
+
 class MediaResponse extends Writable {
   statusCode = 0;
   readonly chunks: Buffer[] = [];
@@ -224,6 +232,21 @@ describe('AI design Main route boundary', () => {
       data: { conversationId: 'conversation/one' },
     });
 
+    const olderConversationResponse = createResponse();
+    await handleImageWorkspaceRoutes(
+      createRequest('GET'),
+      olderConversationResponse.res,
+      new URL(
+        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace%2Fone/conversations/conversation%2Fone?before=opaque-cursor',
+      ),
+      ctx,
+    );
+    expect(workspace.getConversation).toHaveBeenLastCalledWith(
+      'workspace/one',
+      'conversation/one',
+      'opaque-cursor',
+    );
+
     const updateQuoteResponse = createResponse();
     await handleImageWorkspaceRoutes(
       createRequest('PATCH', {
@@ -637,4 +660,33 @@ describe('AI design Main route boundary', () => {
     ].join('\n'));
     expect(close).toHaveBeenCalledOnce();
   });
+
+  it('closes an event subscription that finishes opening after the renderer disconnects', async () => {
+    const opening = deferred<{
+      events: AsyncIterable<never>;
+      close(): void;
+    }>();
+    const close = vi.fn();
+    const openWorkspaceEvents = vi.fn().mockReturnValue(opening.promise);
+    const response = new MediaResponse();
+    const handled = handleImageWorkspaceRoutes(
+      createRequest('GET'),
+      response as unknown as ServerResponse,
+      new URL(
+        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace%2Fone/conversations/conversation%2Fone/events',
+      ),
+      { imageWorkspace: { openWorkspaceEvents } } as unknown as HostApiContext,
+    );
+
+    await vi.waitFor(() => expect(openWorkspaceEvents).toHaveBeenCalledOnce());
+    response.emit('close');
+    opening.resolve({
+      events: (async function* () {})(),
+      close,
+    });
+
+    await expect(handled).resolves.toBe(true);
+    expect(close).toHaveBeenCalledOnce();
+    expect(response.statusCode).toBe(0);
+  });
 });