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