diff --git a/backend/packages/harness/deerflow/agents/middlewares/summarization_middleware.py b/backend/packages/harness/deerflow/agents/middlewares/summarization_middleware.py
index b2f11b446..39e7f70b2 100644
--- a/backend/packages/harness/deerflow/agents/middlewares/summarization_middleware.py
+++ b/backend/packages/harness/deerflow/agents/middlewares/summarization_middleware.py
@@ -194,7 +194,7 @@ class DeerFlowSummarizationMiddleware(SummarizationMiddleware):
         formatted = get_buffer_string(trimmed)
 
         try:
-            response = self.model.invoke(
+            response = self.model.with_config(callbacks=[]).invoke(
                 self.summary_prompt.format(messages=formatted).rstrip(),
                 config={
                     "metadata": {"lc_source": "summarization"},
@@ -223,7 +223,7 @@ class DeerFlowSummarizationMiddleware(SummarizationMiddleware):
         formatted = get_buffer_string(trimmed)
 
         try:
-            response = await self.model.ainvoke(
+            response = await self.model.with_config(callbacks=[]).ainvoke(
                 self.summary_prompt.format(messages=formatted).rstrip(),
                 config={
                     "metadata": {"lc_source": "summarization"},
@@ -235,9 +235,11 @@ class DeerFlowSummarizationMiddleware(SummarizationMiddleware):
             return f"Error generating summary: {e!s}"
 
     def _extract_summary_text(self, response: Any) -> str:
-        summary_text = getattr(response, "content", None)
+        # Prefer .text which normalizes list content blocks (e.g. [{"type": "text", "text": "..."}]).
+        # Fall back to .content for non-LangChain responses.
+        summary_text = getattr(response, "text", None)
         if summary_text is None:
-            summary_text = getattr(response, "text", "")
+            summary_text = getattr(response, "content", "")
         return summary_text.strip() if isinstance(summary_text, str) else str(summary_text).strip()
 
     @override
diff --git a/backend/tests/test_summarization_middleware.py b/backend/tests/test_summarization_middleware.py
index 58f372488..0a5a80160 100644
--- a/backend/tests/test_summarization_middleware.py
+++ b/backend/tests/test_summarization_middleware.py
@@ -57,6 +57,7 @@ def _middleware(
 ) -> DeerFlowSummarizationMiddleware:
     model = MagicMock()
     model.invoke.return_value = AIMessage(content="compressed summary")
+    model.with_config.return_value.invoke.return_value = AIMessage(content="compressed summary")
     return DeerFlowSummarizationMiddleware(
         model=model,
         trigger=trigger,
@@ -660,14 +661,16 @@ def test_build_new_messages_sets_hide_from_ui() -> None:
 
 
 def test_create_summary_suppresses_callbacks() -> None:
-    """_create_summary must pass callbacks=[] to prevent the internal LLM call
-    from producing visible streaming events in the frontend (issue #2804)."""
+    """_create_summary must bind callbacks=[] on the model AND pass callbacks=[]
+    in the invoke config to suppress inherited LangGraph stream callbacks."""
     middleware = _middleware()
 
     middleware._create_summary(_messages())
 
-    middleware.model.invoke.assert_called_once()
-    call_config = middleware.model.invoke.call_args.kwargs.get("config") or middleware.model.invoke.call_args[1].get("config")
+    middleware.model.with_config.assert_called_once_with(callbacks=[])
+    bound = middleware.model.with_config.return_value
+    bound.invoke.assert_called_once()
+    call_config = bound.invoke.call_args.kwargs.get("config") or bound.invoke.call_args[1].get("config")
     assert call_config is not None
     assert call_config.get("callbacks") == []
     assert call_config.get("metadata", {}).get("lc_source") == "summarization"
@@ -675,15 +678,17 @@ def test_create_summary_suppresses_callbacks() -> None:
 
 @pytest.mark.anyio
 async def test_acreate_summary_suppresses_callbacks() -> None:
-    """_acreate_summary must pass callbacks=[] to prevent the internal LLM call
-    from producing visible streaming events in the frontend (issue #2804)."""
+    """_acreate_summary must bind callbacks=[] on the model AND pass callbacks=[]
+    in the ainvoke config to suppress inherited LangGraph stream callbacks."""
     middleware = _middleware()
-    middleware.model.ainvoke = mock.AsyncMock(return_value=AIMessage(content="async summary"))
+    middleware.model.with_config.return_value.ainvoke = mock.AsyncMock(return_value=AIMessage(content="async summary"))
 
     await middleware._acreate_summary(_messages())
 
-    middleware.model.ainvoke.assert_called_once()
-    call_config = middleware.model.ainvoke.call_args.kwargs.get("config") or middleware.model.ainvoke.call_args[1].get("config")
+    middleware.model.with_config.assert_called_once_with(callbacks=[])
+    bound = middleware.model.with_config.return_value
+    bound.ainvoke.assert_called_once()
+    call_config = bound.ainvoke.call_args.kwargs.get("config") or bound.ainvoke.call_args[1].get("config")
     assert call_config is not None
     assert call_config.get("callbacks") == []
     assert call_config.get("metadata", {}).get("lc_source") == "summarization"
@@ -718,3 +723,17 @@ def test_memory_flush_hook_passes_runtime_user_id(monkeypatch: pytest.MonkeyPatc
 
     queue.add_nowait.assert_called_once()
     assert queue.add_nowait.call_args.kwargs["user_id"] == "alice"
+
+
+def test_extract_summary_text_normalizes_list_content_blocks() -> None:
+    """AIMessage.content can be a list of content blocks; _extract_summary_text
+    must normalize to plain text via the .text property instead of producing
+    a Python repr like [{'type': 'text', 'text': 'summary'}]."""
+    middleware = _middleware()
+
+    response = AIMessage(content=[{"type": "text", "text": "A summary of the chat."}])
+    assert middleware._extract_summary_text(response) == "A summary of the chat."
+
+    # Plain string content still works
+    response_str = AIMessage(content="Plain summary")
+    assert middleware._extract_summary_text(response_str) == "Plain summary"