fix: manage WebRTC pipeline shutdown

backend/services/conversation_history.py

@@ -169,6 +169,21 @@ class ConversationRecorder:
                 logger.error(f"保存对话文本失败，不影响本次通话: {exc}")
 
     async def finish(self, *, status: str = "completed") -> None:
+        """Finish the session even if the owning pipeline is being cancelled."""
+        finish_task = asyncio.create_task(
+            self._finish(status=status),
+            name=f"conversation-recorder-finish:{self.session_id}",
+        )
+        try:
+            await asyncio.shield(finish_task)
+        except asyncio.CancelledError:
+            # Shield prevents an interrupted pipeline cleanup from abandoning a
+            # checked-out asyncpg connection. Preserve cancellation only after
+            # the short database cleanup has returned the connection.
+            await asyncio.shield(finish_task)
+            raise
+
+    async def _finish(self, *, status: str) -> None:
         async with self._lock:
             try:
                 async with SessionLocal() as db: