fix(loop-detection): keep tool-call pairing on warn injection (#2724) (#2725)

* fix(loop-detection): keep tool-call pairing on warn injection (#2724)

* make format

* fix(loop-detection): avoid IMMessage leak to downstream consumer

* fix(channels): filter loop warning text from IM replies

backend/tests/test_channels.py

@@ -372,6 +372,37 @@ class TestExtractResponseText:
         # Should return "" (no text in current turn), NOT "Hi there!" from previous turn
         assert _extract_response_text(result) == ""
 
+    def test_does_not_publish_loop_warning_on_tool_calling_ai_message(self):
+        """Loop-detection warning text on a tool-calling AI message is middleware-authored."""
+        from app.channels.manager import _extract_response_text
+
+        result = {
+            "messages": [
+                {"type": "human", "content": "search the repo"},
+                {
+                    "type": "ai",
+                    "content": "[LOOP DETECTED] You are repeating the same tool calls.",
+                    "tool_calls": [{"name": "grep", "args": {"pattern": "TODO"}, "id": "call_1"}],
+                },
+            ]
+        }
+        assert _extract_response_text(result) == ""
+
+    def test_preserves_visible_text_when_stripping_loop_warning(self):
+        from app.channels.manager import _extract_response_text
+
+        result = {
+            "messages": [
+                {"type": "human", "content": "prepare the report"},
+                {
+                    "type": "ai",
+                    "content": "Here is the report.\n\n[LOOP DETECTED] You are repeating the same tool calls.",
+                    "tool_calls": [{"name": "present_files", "args": {"filepaths": ["/mnt/user-data/outputs/report.md"]}, "id": "call_1"}],
+                },
+            ]
+        }
+        assert _extract_response_text(result) == "Here is the report."
+
 
 # ---------------------------------------------------------------------------
 # ChannelManager tests

backend/tests/test_loop_detection_middleware.py

@@ -3,7 +3,7 @@
 import copy
 from unittest.mock import MagicMock
 
-from langchain_core.messages import AIMessage, HumanMessage, SystemMessage
+from langchain_core.messages import AIMessage, SystemMessage
 
 from deerflow.agents.middlewares.loop_detection_middleware import (
     _HARD_STOP_MSG,
@@ -146,14 +146,42 @@ class TestLoopDetection:
         for _ in range(2):
             mw._apply(_make_state(tool_calls=call), runtime)
 
-        # Third identical call triggers warning
+        # Third identical call triggers warning. The warning is appended to
+        # the AIMessage content (tool_calls preserved) — never inserted as a
+        # separate HumanMessage between the AIMessage(tool_calls) and its
+        # ToolMessage responses, which would break OpenAI/Moonshot strict
+        # tool-call pairing validation.
         result = mw._apply(_make_state(tool_calls=call), runtime)
         assert result is not None
         msgs = result["messages"]
         assert len(msgs) == 1
-        assert isinstance(msgs[0], HumanMessage)
+        assert isinstance(msgs[0], AIMessage)
+        assert len(msgs[0].tool_calls) == len(call)
+        assert msgs[0].tool_calls[0]["id"] == call[0]["id"]
         assert "LOOP DETECTED" in msgs[0].content
 
+    def test_warn_does_not_break_tool_call_pairing(self):
+        """Regression: the warn branch must NOT inject a non-tool message
+        after an AIMessage(tool_calls=...). Moonshot/OpenAI reject the next
+        request with 'tool_call_ids did not have response messages' if any
+        non-tool message is wedged between the AIMessage and its ToolMessage
+        responses. See #2029.
+        """
+        mw = LoopDetectionMiddleware(warn_threshold=3, hard_limit=10)
+        runtime = _make_runtime()
+        call = [_bash_call("ls")]
+
+        for _ in range(2):
+            mw._apply(_make_state(tool_calls=call), runtime)
+
+        result = mw._apply(_make_state(tool_calls=call), runtime)
+        assert result is not None
+        msgs = result["messages"]
+        assert len(msgs) == 1
+        assert isinstance(msgs[0], AIMessage)
+        assert len(msgs[0].tool_calls) == len(call)
+        assert msgs[0].tool_calls[0]["id"] == call[0]["id"]
+
     def test_warn_only_injected_once(self):
         """Warning for the same hash should only be injected once per thread."""
         mw = LoopDetectionMiddleware(warn_threshold=3, hard_limit=10)
@@ -483,7 +511,11 @@ class TestToolFrequencyDetection:
         result = mw._apply(_make_state(tool_calls=[self._read_call("/file_4.py")]), runtime)
         assert result is not None
         msg = result["messages"][0]
-        assert isinstance(msg, HumanMessage)
+        # Warning is appended to the AIMessage content; tool_calls preserved
+        # so the tools node still runs and Moonshot/OpenAI tool-call pairing
+        # validation does not break.
+        assert isinstance(msg, AIMessage)
+        assert msg.tool_calls
         assert "read_file" in msg.content
         assert "LOOP DETECTED" in msg.content