fix(middleware): Handle invalid tool calls in dangling pairing middleware (#2890) (#2891)

backend/packages/harness/deerflow/agents/middlewares/dangling_tool_call_middleware.py

@@ -36,42 +36,73 @@ class DanglingToolCallMiddleware(AgentMiddleware[AgentState]):
 
     @staticmethod
     def _message_tool_calls(msg) -> list[dict]:
-        """Return normalized tool calls from structured fields or raw provider payloads."""
+        """Return normalized tool calls from structured fields or raw provider payloads.
+
+        LangChain stores malformed provider function calls in ``invalid_tool_calls``.
+        They do not execute, but provider adapters may still serialize enough of
+        the call id/name back into the next request that strict OpenAI-compatible
+        validators expect a matching ToolMessage. Treat them as dangling calls so
+        the next model request stays well-formed and the model sees a recoverable
+        tool error instead of another provider 400.
+        """
+        normalized: list[dict] = []
+
         tool_calls = getattr(msg, "tool_calls", None) or []
-        if tool_calls:
-            return list(tool_calls)
+        normalized.extend(list(tool_calls))
 
         raw_tool_calls = (getattr(msg, "additional_kwargs", None) or {}).get("tool_calls") or []
-        normalized: list[dict] = []
-        for raw_tc in raw_tool_calls:
-            if not isinstance(raw_tc, dict):
+        if not tool_calls:
+            for raw_tc in raw_tool_calls:
+                if not isinstance(raw_tc, dict):
+                    continue
+
+                function = raw_tc.get("function")
+                name = raw_tc.get("name")
+                if not name and isinstance(function, dict):
+                    name = function.get("name")
+
+                args = raw_tc.get("args", {})
+                if not args and isinstance(function, dict):
+                    raw_args = function.get("arguments")
+                    if isinstance(raw_args, str):
+                        try:
+                            parsed_args = json.loads(raw_args)
+                        except (TypeError, ValueError, json.JSONDecodeError):
+                            parsed_args = {}
+                        args = parsed_args if isinstance(parsed_args, dict) else {}
+
+                normalized.append(
+                    {
+                        "id": raw_tc.get("id"),
+                        "name": name or "unknown",
+                        "args": args if isinstance(args, dict) else {},
+                    }
+                )
+
+        for invalid_tc in getattr(msg, "invalid_tool_calls", None) or []:
+            if not isinstance(invalid_tc, dict):
                 continue
-
-            function = raw_tc.get("function")
-            name = raw_tc.get("name")
-            if not name and isinstance(function, dict):
-                name = function.get("name")
-
-            args = raw_tc.get("args", {})
-            if not args and isinstance(function, dict):
-                raw_args = function.get("arguments")
-                if isinstance(raw_args, str):
-                    try:
-                        parsed_args = json.loads(raw_args)
-                    except (TypeError, ValueError, json.JSONDecodeError):
-                        parsed_args = {}
-                    args = parsed_args if isinstance(parsed_args, dict) else {}
-
             normalized.append(
                 {
-                    "id": raw_tc.get("id"),
-                    "name": name or "unknown",
-                    "args": args if isinstance(args, dict) else {},
+                    "id": invalid_tc.get("id"),
+                    "name": invalid_tc.get("name") or "unknown",
+                    "args": {},
+                    "invalid": True,
+                    "error": invalid_tc.get("error"),
                 }
             )
 
         return normalized
 
+    @staticmethod
+    def _synthetic_tool_message_content(tool_call: dict) -> str:
+        if tool_call.get("invalid"):
+            error = tool_call.get("error")
+            if isinstance(error, str) and error:
+                return f"[Tool call could not be executed because its arguments were invalid: {error}]"
+            return "[Tool call could not be executed because its arguments were invalid.]"
+        return "[Tool call was interrupted and did not return a result.]"
+
     def _build_patched_messages(self, messages: list) -> list | None:
         """Return a new message list with patches inserted at the correct positions.
 
@@ -114,7 +145,7 @@ class DanglingToolCallMiddleware(AgentMiddleware[AgentState]):
                 if tc_id and tc_id not in existing_tool_msg_ids and tc_id not in patched_ids:
                     patched.append(
                         ToolMessage(
-                            content="[Tool call was interrupted and did not return a result.]",
+                            content=self._synthetic_tool_message_content(tc),
                             tool_call_id=tc_id,
                             name=tc.get("name", "unknown"),
                             status="error",

backend/tests/test_dangling_tool_call_middleware.py

@@ -14,6 +14,10 @@ def _ai_with_tool_calls(tool_calls):
     return AIMessage(content="", tool_calls=tool_calls)
 
 
+def _ai_with_invalid_tool_calls(invalid_tool_calls):
+    return AIMessage(content="", tool_calls=[], invalid_tool_calls=invalid_tool_calls)
+
+
 def _tool_msg(tool_call_id, name="test_tool"):
     return ToolMessage(content="result", tool_call_id=tool_call_id, name=name)
 
@@ -22,6 +26,16 @@ def _tc(name="bash", tc_id="call_1"):
     return {"name": name, "id": tc_id, "args": {}}
 
 
+def _invalid_tc(name="write_file", tc_id="write_file:36", error="Failed to parse tool arguments: malformed JSON"):
+    return {
+        "type": "invalid_tool_call",
+        "name": name,
+        "id": tc_id,
+        "args": '{"description":"write report","path":"/mnt/user-data/outputs/report.md","content":"bad {"json"}"}',
+        "error": error,
+    }
+
+
 class TestBuildPatchedMessagesNoPatch:
     def test_empty_messages(self):
         mw = DanglingToolCallMiddleware()
@@ -144,6 +158,42 @@ class TestBuildPatchedMessagesPatching:
         assert patched[1].name == "bash"
         assert patched[1].status == "error"
 
+    def test_invalid_tool_call_is_patched(self):
+        mw = DanglingToolCallMiddleware()
+        msgs = [_ai_with_invalid_tool_calls([_invalid_tc()])]
+        patched = mw._build_patched_messages(msgs)
+        assert patched is not None
+        assert len(patched) == 2
+        assert isinstance(patched[1], ToolMessage)
+        assert patched[1].tool_call_id == "write_file:36"
+        assert patched[1].name == "write_file"
+        assert patched[1].status == "error"
+        assert "arguments were invalid" in patched[1].content
+        assert "Failed to parse tool arguments" in patched[1].content
+
+    def test_valid_and_invalid_tool_calls_are_both_patched(self):
+        mw = DanglingToolCallMiddleware()
+        msgs = [
+            AIMessage(
+                content="",
+                tool_calls=[_tc("bash", "call_1")],
+                invalid_tool_calls=[_invalid_tc()],
+            )
+        ]
+        patched = mw._build_patched_messages(msgs)
+        assert patched is not None
+        tool_msgs = [m for m in patched if isinstance(m, ToolMessage)]
+        assert len(tool_msgs) == 2
+        assert {tm.tool_call_id for tm in tool_msgs} == {"call_1", "write_file:36"}
+
+    def test_invalid_tool_call_already_responded_is_not_patched(self):
+        mw = DanglingToolCallMiddleware()
+        msgs = [
+            _ai_with_invalid_tool_calls([_invalid_tc()]),
+            _tool_msg("write_file:36", "write_file"),
+        ]
+        assert mw._build_patched_messages(msgs) is None
+
 
 class TestWrapModelCall:
     def test_no_patch_passthrough(self):