fix: stabilize ai design history switching

tests/unit/works-square-design-workspace.test.ts

@@ -464,6 +464,41 @@ describe('Works Square AI design adapter', () => {
     );
   });
 
+  it('passes the opaque older-history cursor through and preserves server message ids', async () => {
+    const pagedConversation = {
+      ...serverConversation,
+      messages: [{
+        ...serverConversation.messages[0],
+        message_id: 'persisted-turn-one:assistant',
+      }],
+      message_page: {
+        has_older: true,
+        next_before: 'opaque-older-page',
+      },
+    };
+    const fetchMock = vi.fn<typeof fetch>().mockResolvedValue(jsonResponse(pagedConversation));
+    const adapter = new WorksSquareDesignWorkspace({
+      apiBaseUrl: 'https://square.example',
+      fetchImpl: fetchMock,
+    });
+
+    const result = await adapter.getConversation(
+      'workspace-one',
+      'conversation-one',
+      'opaque-older-page',
+    );
+
+    expect(fetchMock).toHaveBeenCalledWith(
+      'https://square.example/api/design/workspaces/workspace-one/conversations/conversation-one?before=opaque-older-page',
+      expect.objectContaining({ headers: expect.any(Object) }),
+    );
+    expect(result.messages[0]?.id).toBe('persisted-turn-one:assistant');
+    expect(result.messagePage).toEqual({
+      hasOlder: true,
+      nextBefore: 'opaque-older-page',
+    });
+  });
+
   it('normalizes a missing Brief medium to null and rejects invalid non-null values', async () => {
     const { medium: _medium, ...legacyBrief } = serverConversation.brief;
     const legacyConversation = {
@@ -1148,6 +1183,46 @@ describe('Works Square AI design adapter', () => {
     }
   });
 
+  it('fails a WebSocket event stream that never opens instead of leaving it pending', async () => {
+    vi.useFakeTimers();
+    const { sockets, webSocketFactory } = scriptedSockets([{ open: false }]);
+    const fetchMock = vi.fn<typeof fetch>(async (input) => {
+      const url = String(input);
+      if (url.endsWith('/conversations/conversation-one')) {
+        return jsonResponse({ ...serverConversation, agent_session_id: 'session-open-timeout' });
+      }
+      if (url.endsWith('/stream-tickets')) {
+        return jsonResponse({
+          stream_url: '/api/agents/sessions/session-open-timeout/ws?ticket=ticket-open-timeout',
+        });
+      }
+      throw new Error(`Unexpected request: ${url}`);
+    });
+    const adapter = new WorksSquareDesignWorkspace({
+      apiBaseUrl: 'https://square.example',
+      fetchImpl: fetchMock,
+      webSocketFactory,
+    });
+
+    try {
+      const opening = adapter.openWorkspaceEvents({
+        workspaceId: 'workspace-one',
+        conversationId: 'conversation-one',
+      });
+      const openingAssertion = expect(opening).rejects.toMatchObject({
+        status: 504,
+        code: 'DESIGN_EVENT_STREAM_TIMEOUT',
+      });
+      await vi.advanceTimersByTimeAsync(10_000);
+
+      await openingAssertion;
+      expect(sockets).toHaveLength(1);
+      expect(sockets[0].readyState).toBe(3);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
   it('maps a failed Run received from the connected WebSocket without polling', async () => {
     const { webSocketFactory } = scriptedSockets([{
       open: true,