fix: minor issue fixes

tests/llm/handlers/test_llm_handlers.py

@@ -759,6 +759,66 @@ class TestHandleToolCalls:
         assistant_ids = {tc["id"] for tc in assistant_msg["tool_calls"]}
         assert tool_msg["tool_call_id"] in assistant_ids
 
+    def test_create_tool_message_failure_no_duplicate_assistant(self):
+        """A tool that succeeds but returns an unserializable result makes
+        create_tool_message raise *after* the success path appended the
+        assistant tool_calls message. The except branch must reuse that
+        message, not append a second one — exactly one assistant(tool_calls)
+        precedes the role:"tool" error, or the next completion 400s."""
+
+        class _SerializingHandler(ConcreteHandler):
+            def create_tool_message(
+                self, tool_call: ToolCall, result: Any
+            ) -> Dict:
+                # Mirror real handlers: JSON-encode non-str results, which
+                # raises on a value the encoder can't serialize. The error
+                # path passes a plain string, so only the success path trips.
+                import json as _json
+
+                content = (
+                    result
+                    if isinstance(result, str)
+                    else _json.dumps(result)
+                )
+                return {
+                    "role": "tool",
+                    "tool_call_id": tool_call.id,
+                    "content": content,
+                }
+
+        handler = _SerializingHandler()
+        agent = self._make_agent()
+        agent.tool_executor._name_to_tool = {}
+
+        # Tool runs fine but returns a value json.dumps can't encode.
+        def fake_execute(tools_dict, call):
+            yield {"type": "tool_call", "data": {"status": "pending"}}
+            return (object(), call.id)
+
+        agent._execute_tool_action = Mock(side_effect=fake_execute)
+
+        call = ToolCall(id="c1", name="action_1", arguments="{}")
+        gen = handler.handle_tool_calls(agent, [call], {"1": {"name": "t"}}, [])
+        try:
+            while True:
+                next(gen)
+        except StopIteration as e:
+            messages, _pending = e.value
+
+        # Exactly one assistant(tool_calls) for c1, then the tool error — the
+        # buggy path produced [assistant, assistant, tool].
+        assert [m["role"] for m in messages] == ["assistant", "tool"]
+        assistant_msgs = [
+            m for m in messages
+            if m.get("role") == "assistant"
+            and any(tc["id"] == "c1" for tc in m.get("tool_calls", []))
+        ]
+        assert len(assistant_msgs) == 1
+        tool_msg = messages[-1]
+        assert tool_msg["role"] == "tool"
+        assert tool_msg["tool_call_id"] == "c1"
+        assert "Error executing tool" in tool_msg["content"]
+
     def test_partial_batch_failure_answers_every_tool_call(self):
         """One tool raises, others succeed: every assistant tool_call must
         get a matching role:"tool" reply (OpenAI rejects unanswered ids)."""