diff --git a/backend/packages/harness/deerflow/runtime/AGENTS.md b/backend/packages/harness/deerflow/runtime/AGENTS.md
index baccfa8ea6..dc491e0806 100644
--- a/backend/packages/harness/deerflow/runtime/AGENTS.md
+++ b/backend/packages/harness/deerflow/runtime/AGENTS.md
@@ -100,7 +100,10 @@ producers (currently slash-skill activation via `asyncio.to_thread`) schedule
 journal mutation directly onto its owning event loop; they never mutate or
 flush `RunJournal._buffer` from the worker thread. The task-tool subagent proxy
 rejects a loop that differs from the journal owner, so its close fence always
-drains the only scheduling hop.
+drains the only scheduling hop. `flush()` yields to the loop once before
+draining: since Python 3.13 an awaited executor future can complete without a
+loop iteration, so a hop queued by a worker that already returned may still be
+pending when flush starts.
 The persisted projection accepts
 only framework-defined error/action values and strict booleans (using null for
 invalid values) from the producer-supplied tool stamp; tool content, args,
diff --git a/backend/packages/harness/deerflow/runtime/journal.py b/backend/packages/harness/deerflow/runtime/journal.py
index ae5076d7ea..9fbae74a53 100644
--- a/backend/packages/harness/deerflow/runtime/journal.py
+++ b/backend/packages/harness/deerflow/runtime/journal.py
@@ -1352,6 +1352,15 @@ class RunJournal(BaseCallbackHandler):
 
     async def flush(self) -> None:
         """Force flush remaining buffer. Called in worker's finally block."""
+        if self._closed:
+            return
+        # Events recorded from worker threads reach this loop through
+        # call_soon_threadsafe (see record_middleware). Since Python 3.13 an
+        # awaited run_in_executor()/to_thread() may complete without yielding
+        # to the loop when the worker finished before its future was chained,
+        # so such callbacks can still be queued when flush() starts. Yield once
+        # so they land in the buffer instead of being dropped after detach.
+        await asyncio.sleep(0)
         if self._closed:
             return
         self._explicit_flush_in_progress = True