diff --git a/src/chat/message_receive/chat_stream.py b/src/chat/message_receive/chat_stream.py
index ac2d7a94..850a5033 100644
--- a/src/chat/message_receive/chat_stream.py
+++ b/src/chat/message_receive/chat_stream.py
@@ -23,6 +23,7 @@ logger = get_logger("chat_stream")
 
 # LRU + TTL 配置
 MAX_LAST_MESSAGES_CACHE = 5000  # 最大缓存消息数
+LAST_MESSAGE_TTL = 1800  # 消息缓存时间
 
 
 class ChatMessageContext:
@@ -145,6 +146,8 @@ class ChatManager:
             # asyncio.create_task(self._initialize())
             # # 启动自动保存任务
             # asyncio.create_task(self._auto_save_task())
+            # # 启动 TTL 清理任务
+            asyncio.create_task(self._cleanup_expired_messages())
 
     async def _initialize(self):
         """异步初始化"""
@@ -164,6 +167,27 @@ class ChatManager:
             except Exception as e:
                 logger.error(f"聊天流自动保存失败: {str(e)}")
 
+    async def _cleanup_expired_messages(self):
+        """定期清理过期的 last_messages"""
+        while True:
+            await asyncio.sleep(300)  # 每5分钟清理一次
+            try:
+                current_time = time.time()
+                expired_keys = []
+                
+                for stream_id, timestamp in self.last_message_timestamps.items():
+                    if current_time - timestamp > LAST_MESSAGE_TTL:
+                        expired_keys.append(stream_id)
+                
+                for key in expired_keys:
+                    self.last_messages.pop(key, None)
+                    self.last_message_timestamps.pop(key, None)
+                
+                if expired_keys:
+                    logger.info(f"清理了 {len(expired_keys)} 条过期的 last_messages")
+            except Exception as e:
+                logger.error(f"清理过期消息失败: {str(e)}")
+
     def register_message(self, message: "MessageRecv"):
         """注册消息到聊天流"""
         stream_id = self._generate_stream_id(