fix(app): handle nullable detail consumers

apps/next/tests/unit/thread-message-route.test.ts

@@ -0,0 +1,50 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+import { POST } from '../../src/app/api/threads/[threadId]/message/route';
+
+const { mockAuthToken, mockFetchMutation, mockFetchQuery, mockProxyWorker } =
+  vi.hoisted(() => ({
+    mockAuthToken: vi.fn(),
+    mockFetchMutation: vi.fn(),
+    mockFetchQuery: vi.fn(),
+    mockProxyWorker: vi.fn(),
+  }));
+
+vi.mock('@convex-dev/auth/nextjs/server', () => ({
+  convexAuthNextjsToken: mockAuthToken,
+}));
+
+vi.mock('convex/nextjs', () => ({
+  fetchMutation: mockFetchMutation,
+  fetchQuery: mockFetchQuery,
+}));
+
+vi.mock('@/lib/agent-worker-proxy', () => ({
+  proxyWorker: mockProxyWorker,
+}));
+
+describe('thread message route', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockAuthToken.mockResolvedValue('token');
+  });
+
+  it('returns 404 when the thread detail query returns null', async () => {
+    mockFetchQuery.mockResolvedValue(null);
+
+    const response = await POST(
+      new Request('http://localhost/api/threads/thread-1/message', {
+        method: 'POST',
+        body: JSON.stringify({ content: 'Hello' }),
+      }),
+      { params: Promise.resolve({ threadId: 'thread-1' }) },
+    );
+
+    expect(response.status).toBe(404);
+    await expect(response.json()).resolves.toEqual({
+      error: 'Thread not found.',
+    });
+    expect(mockFetchMutation).not.toHaveBeenCalled();
+    expect(mockProxyWorker).not.toHaveBeenCalled();
+  });
+});