diff --git a/agent_loop.py b/agent_loop.py
index a744f0d26..5c19d5fcf 100644
--- a/agent_loop.py
+++ b/agent_loop.py
@@ -24,6 +24,7 @@ def dispatch(self, tool_name, args, response, index=0, tool_num=1):
             _hook('tool_after', locals())
             return ret
         elif tool_name == 'bad_json': return StepOutcome(None, next_prompt=args.get('msg', 'bad_json'), should_exit=False)
+        elif tool_name == 'no_tool': return StepOutcome(response.content, next_prompt=None, should_exit=False)
         else:
             yield f"未知工具: {tool_name}\n"
             return StepOutcome(None, next_prompt=f"未知工具 {tool_name}", should_exit=False)
diff --git a/tests/test_agent_loop_no_tool.py b/tests/test_agent_loop_no_tool.py
new file mode 100644
index 000000000..92b036c5a
--- /dev/null
+++ b/tests/test_agent_loop_no_tool.py
@@ -0,0 +1,58 @@
+import unittest
+from types import SimpleNamespace
+
+from agent_loop import BaseHandler, exhaust, agent_runner_loop
+
+
+class StubClient:
+    def __init__(self):
+        self.last_tools = ""
+
+    def chat(self, messages, tools):
+        response = SimpleNamespace(content="final answer", tool_calls=[])
+
+        def gen():
+            if False:
+                yield None
+            return response
+
+        return gen()
+
+
+class StubHandler(BaseHandler):
+    def __init__(self):
+        self.parent = SimpleNamespace(task_dir=None)
+        self._done_hooks = []
+        self.turns = []
+
+    def turn_end_callback(self, response, tool_calls, tool_results, turn, next_prompt, exit_reason):
+        self.turns.append({
+            "tool_calls": tool_calls,
+            "next_prompt": next_prompt,
+            "exit_reason": exit_reason,
+        })
+        return next_prompt
+
+
+class AgentLoopNoToolTests(unittest.TestCase):
+    def test_direct_answer_completes_without_fake_unknown_tool_retry(self):
+        handler = StubHandler()
+        result = exhaust(agent_runner_loop(
+            StubClient(),
+            "system",
+            "user",
+            handler,
+            tools_schema=[],
+            max_turns=1,
+            verbose=False,
+        ))
+
+        self.assertEqual(result["result"], "CURRENT_TASK_DONE")
+        self.assertEqual(len(handler.turns), 1)
+        self.assertEqual(handler.turns[0]["tool_calls"][0]["tool_name"], "no_tool")
+        self.assertEqual(handler.turns[0]["next_prompt"], "")
+        self.assertNotIn("未知工具", handler.turns[0]["next_prompt"])
+
+
+if __name__ == "__main__":
+    unittest.main()