Fix ws error receive and send

engine/core/session.py

@@ -1,5 +1,6 @@
 """Session management for active calls."""
 
+import asyncio
 import uuid
 import json
 import time
@@ -78,6 +79,8 @@ class Session:
         self._history_turn_index: int = 0
         self._history_call_started_mono: Optional[float] = None
         self._history_finalized: bool = False
+        self._cleanup_lock = asyncio.Lock()
+        self._cleaned_up = False
 
         self.pipeline.conversation.on_turn_complete(self._on_turn_complete)
 
@@ -288,10 +291,15 @@ class Session:
 
     async def cleanup(self) -> None:
         """Cleanup session resources."""
-        logger.info(f"Session {self.id} cleaning up")
-        await self._finalize_history(status="connected")
-        await self.pipeline.cleanup()
-        await self.transport.close()
+        async with self._cleanup_lock:
+            if self._cleaned_up:
+                return
+
+            self._cleaned_up = True
+            logger.info(f"Session {self.id} cleaning up")
+            await self._finalize_history(status="connected")
+            await self.pipeline.cleanup()
+            await self.transport.close()
 
     async def _start_history_bridge(self, metadata: Dict[str, Any]) -> None:
         """Initialize backend history call record for this session."""