diff --git a/backend/packages/harness/deerflow/runtime/journal.py b/backend/packages/harness/deerflow/runtime/journal.py
index 360d904bb..7f5a28957 100644
--- a/backend/packages/harness/deerflow/runtime/journal.py
+++ b/backend/packages/harness/deerflow/runtime/journal.py
@@ -263,7 +263,7 @@ class RunJournal(BaseCallbackHandler):
             self._put(
                 event_type="summary",
                 category="message",
-                content=data_dict.get("summary", ""),
+                content={"role": "system", "content": data_dict.get("summary", "")},
                 metadata={"replaced_count": data_dict.get("replaced_count", 0)},
             )
         else:
diff --git a/backend/tests/test_run_journal.py b/backend/tests/test_run_journal.py
index 3b9cdea78..1fc272ef7 100644
--- a/backend/tests/test_run_journal.py
+++ b/backend/tests/test_run_journal.py
@@ -214,6 +214,7 @@ class TestCustomEvents:
         messages = await store.list_messages("t1")
         assert len(messages) == 1
         assert messages[0]["event_type"] == "summary"
+        assert messages[0]["content"] == {"role": "system", "content": "Context was summarized."}
 
     @pytest.mark.anyio
     async def test_non_summarization_custom_event(self, journal_setup):