feat(FN-4943): complete Step 2 — mirror stop flush behavior in useQuickChat

Fusion-Task-Id: FN-4943
Fusion-Task-Lineage: 67dd5c2b-0b44-43dd-a016-0bff858ec4b9

packages/dashboard/app/hooks/__tests__/useQuickChat.test.ts

@@ -569,6 +569,68 @@ describe("useQuickChat", () => {
       expect(result.current.isStreaming).toBe(false);
       expect(result.current.streamingText).toBe("");
       expect(result.current.streamingThinking).toBe("");
+      expect(mockStreamChatResponse).toHaveBeenCalledTimes(1);
+    });
+  });
+
+  it("stopStreaming sends queued pendingMessage after cancelling the stream", async () => {
+    const existingSession = makeSession({ id: "session-existing", agentId: "agent-001" });
+    const closeFn = vi.fn();
+
+    mockFetchResumeChatSession.mockResolvedValueOnce({ session: existingSession });
+    mockFetchChatMessages.mockResolvedValue({ messages: [] });
+    mockStreamChatResponse.mockReturnValue({ close: closeFn, isConnected: () => true });
+
+    const { result } = renderHook(() => useQuickChat("proj-123"));
+
+    await act(async () => {
+      await result.current.switchSession("agent-001");
+    });
+
+    act(() => {
+      result.current.sendMessage("Hello");
+    });
+
+    await waitFor(() => {
+      expect(result.current.isStreaming).toBe(true);
+    });
+
+    act(() => {
+      void result.current.sendMessage("Queued follow-up");
+      result.current.stopStreaming();
+    });
+
+    await waitFor(() => {
+      expect(closeFn).toHaveBeenCalled();
+      expect(mockStreamChatResponse).toHaveBeenCalledTimes(2);
+      expect(mockStreamChatResponse.mock.calls[1]?.[1]).toBe("Queued follow-up");
+      expect(result.current.pendingMessage).toBe("");
+    });
+  });
+
+  it("stopStreaming with no pendingMessage cancels stream without sending anything", async () => {
+    const existingSession = makeSession({ id: "session-existing", agentId: "agent-001" });
+    const closeFn = vi.fn();
+
+    mockFetchResumeChatSession.mockResolvedValueOnce({ session: existingSession });
+    mockFetchChatMessages.mockResolvedValue({ messages: [] });
+    mockStreamChatResponse.mockReturnValue({ close: closeFn, isConnected: () => true });
+
+    const { result } = renderHook(() => useQuickChat("proj-123"));
+
+    await act(async () => {
+      await result.current.switchSession("agent-001");
+    });
+
+    act(() => {
+      result.current.sendMessage("Hello");
+      result.current.stopStreaming();
+    });
+
+    await waitFor(() => {
+      expect(closeFn).toHaveBeenCalled();
+      expect(result.current.pendingMessage).toBe("");
+      expect(mockStreamChatResponse).toHaveBeenCalledTimes(1);
     });
   });
 

packages/dashboard/app/hooks/useQuickChat.ts

@@ -626,10 +626,12 @@ export function useQuickChat(
     });
 
     setIsStreaming(false);
+    isStreamingRef.current = false;
     setStreamingText("");
     setStreamingThinking("");
     setStreamingToolCalls([]);
-  }, [activeSession, projectId]);
+    void flushPendingMessage();
+  }, [activeSession, projectId, flushPendingMessage]);
 
   const sendMessageRef = useRef<(content: string, attachments?: File[]) => Promise<void>>(() => Promise.resolve());
   const visibilitySuspension = useTabVisibilitySuspension();