fix(agent-loop): recover malformed tool arguments

agent_loop.py

@@ -67,8 +67,22 @@ def agent_runner_loop(client, system_prompt, user_input, handler, tools_schema,
         _hook('llm_after', locals())
 
         if not response.tool_calls: tool_calls = [{'tool_name': 'no_tool', 'args': {}}]
-        else: tool_calls = [{'tool_name': tc.function.name, 'args': json.loads(tc.function.arguments), 'id': tc.id}
-                          for tc in response.tool_calls]
+        else:
+            tool_calls = []
+            for tc in response.tool_calls:
+                raw = tc.function.arguments
+                try:
+                    args = json.loads(raw)
+                    if not isinstance(args, dict):
+                        raise TypeError("tool arguments must be a JSON object")
+                except (json.JSONDecodeError, TypeError):
+                    raw_text = raw if isinstance(raw, str) else str(raw)
+                    raw_len = len(raw_text)
+                    raw_preview = raw_text[:800]
+                    if raw_len > len(raw_preview): raw_preview += f"... [truncated, total={raw_len} chars]"
+                    tool_calls.append({'tool_name': 'bad_json', 'args': {'msg': f"Tool {tc.function.name} arguments are invalid JSON or are not a JSON object: {raw_preview!r}. Retry with a valid JSON object."}, 'id': tc.id})
+                    continue
+                tool_calls.append({'tool_name': tc.function.name, 'args': args, 'id': tc.id})
 
         tool_results = []; next_prompts = set(); exit_reason = {}
         for ii, tc in enumerate(tool_calls):

tests/test_agent_loop_bad_json.py

@@ -0,0 +1,88 @@
+import unittest
+from types import SimpleNamespace
+
+from agent_loop import BaseHandler, exhaust, agent_runner_loop
+
+
+class StubClient:
+    def __init__(self, arguments):
+        self.arguments = arguments
+        self.last_tools = ""
+
+    def chat(self, messages, tools):
+        response = SimpleNamespace(
+            content="",
+            tool_calls=[SimpleNamespace(
+                id="call-1",
+                function=SimpleNamespace(name="file_read", arguments=self.arguments),
+            )],
+        )
+
+        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.next_prompts = []
+
+    def do_file_read(self, args, response):
+        if False:
+            yield None
+        return SimpleNamespace(data=None, next_prompt="ok", should_exit=False)
+
+    def turn_end_callback(self, response, tool_calls, tool_results, turn, next_prompt, exit_reason):
+        self.next_prompts.append(next_prompt)
+        return next_prompt
+
+
+class AgentLoopBadJsonTests(unittest.TestCase):
+    def _run(self, arguments):
+        handler = StubHandler()
+        result = exhaust(agent_runner_loop(
+            StubClient(arguments),
+            "system",
+            "user",
+            handler,
+            tools_schema=[],
+            max_turns=1,
+            verbose=False,
+        ))
+        return result, handler
+
+    def test_malformed_tool_arguments_are_returned_to_model_for_retry(self):
+        result, handler = self._run('{"path":')
+        self.assertEqual(result, {"result": "MAX_TURNS_EXCEEDED"})
+        self.assertEqual(len(handler.next_prompts), 1)
+        self.assertIn("file_read", handler.next_prompts[0])
+        self.assertIn("invalid JSON", handler.next_prompts[0])
+
+    def test_non_object_json_tool_arguments_are_returned_for_retry(self):
+        for arguments in ("null", "[]", '"path"', "1", "true"):
+            with self.subTest(arguments=arguments):
+                result, handler = self._run(arguments)
+                self.assertEqual(result, {"result": "MAX_TURNS_EXCEEDED"})
+                self.assertEqual(len(handler.next_prompts), 1)
+                self.assertIn("file_read", handler.next_prompts[0])
+                self.assertIn("JSON object", handler.next_prompts[0])
+
+    def test_malformed_argument_retry_preview_is_bounded(self):
+        arguments = '{"path":"' + ('x' * 20_000)
+        result, handler = self._run(arguments)
+
+        self.assertEqual(result, {"result": "MAX_TURNS_EXCEEDED"})
+        self.assertEqual(len(handler.next_prompts), 1)
+        prompt = handler.next_prompts[0]
+        self.assertLess(len(prompt), 2_000)
+        self.assertIn("truncated", prompt.lower())
+        self.assertIn(str(len(arguments)), prompt)
+
+
+if __name__ == "__main__":
+    unittest.main()