fix(agent): add model request timeouts and empty-response fallback

src/backends/native/agent.test.ts

@@ -110,6 +110,43 @@ describe('NativeAgent', () => {
     const history = agent.getHistory();
     expect(history[history.length - 1]).toEqual({ role: 'assistant', content: 'Operation cancelled by user.' });
   });
+
+  it('returns fallback text when model response is empty', async () => {
+    const mockClient: ModelClient = {
+      chat: vi.fn().mockResolvedValue({
+        content: '',
+        stopReason: 'end_turn',
+        usage: { inputTokens: 10, outputTokens: 5 },
+      }),
+    };
+
+    const agent = new NativeAgent({
+      modelClient: mockClient,
+      systemPrompt: 'You are helpful.',
+    });
+
+    const response = await agent.process('Hi');
+    expect(response).toBe('I could not generate a response for that. Please try again.');
+    const history = agent.getHistory();
+    expect(history[history.length - 1]).toEqual({
+      role: 'assistant',
+      content: 'I could not generate a response for that. Please try again.',
+    });
+  });
+
+  it('times out single-turn model calls', async () => {
+    const mockClient: ModelClient = {
+      chat: vi.fn().mockImplementation(() => new Promise<ChatResponse>(() => {})),
+    };
+
+    const agent = new NativeAgent({
+      modelClient: mockClient,
+      systemPrompt: 'You are helpful.',
+      modelTimeoutMs: 10,
+    });
+
+    await expect(agent.process('Hi')).rejects.toThrow('Model request timed out after 10ms');
+  });
 });
 
 // Simple test tool
@@ -611,4 +648,65 @@ describe('NativeAgent tool loop', () => {
     expect(response).toBe('Got both results');
     expect(mockClient.chat).toHaveBeenCalledTimes(2);
   });
+
+  it('returns fallback text when tool loop final response is empty', async () => {
+    const mockClient: ModelClient = {
+      chat: vi
+        .fn()
+        .mockResolvedValueOnce({
+          content: '',
+          stopReason: 'tool_use',
+          usage: { inputTokens: 10, outputTokens: 5 },
+          toolCalls: [{ id: 'call_1', name: 'test.echo', args: { text: 'hello' } }],
+        })
+        .mockResolvedValueOnce({
+          content: '',
+          stopReason: 'end_turn',
+          usage: { inputTokens: 12, outputTokens: 4 },
+        }),
+    };
+
+    const registry = new ToolRegistry();
+    registry.register(echoTool);
+    const hooks = new HookEngine({ confirm: [], log: [], silent: [] });
+    const executor = new ToolExecutor(registry, hooks);
+
+    const agent = new NativeAgent({
+      modelClient: mockClient,
+      systemPrompt: 'You are helpful.',
+      toolRegistry: registry,
+      toolExecutor: executor,
+    });
+
+    const response = await agent.process('echo hello');
+    expect(response).toBe('I could not generate a response for that. Please try again.');
+    const history = agent.getHistory();
+    expect(history[history.length - 1]).toEqual({
+      role: 'assistant',
+      content: 'I could not generate a response for that. Please try again.',
+    });
+  });
+
+  it('times out tool-loop model calls and returns an error message', async () => {
+    const mockClient: ModelClient = {
+      chat: vi.fn().mockImplementation(() => new Promise<ChatResponse>(() => {})),
+    };
+
+    const registry = new ToolRegistry();
+    registry.register(echoTool);
+    const hooks = new HookEngine({ confirm: [], log: [], silent: [] });
+    const executor = new ToolExecutor(registry, hooks);
+
+    const agent = new NativeAgent({
+      modelClient: mockClient,
+      systemPrompt: 'You are helpful.',
+      toolRegistry: registry,
+      toolExecutor: executor,
+      modelTimeoutMs: 10,
+    });
+
+    const response = await agent.process('echo hello');
+    expect(response).toContain('Error in tool loop');
+    expect(response).toContain('Model request timed out after 10ms');
+  });
 });