diff --git a/lang_agent/pipeline.py b/lang_agent/pipeline.py
index 0fabac4..4e4f004 100644
--- a/lang_agent/pipeline.py
+++ b/lang_agent/pipeline.py
@@ -1,5 +1,5 @@
 from dataclasses import dataclass, field
-from typing import Type
+from typing import Type, List
 import tyro
 import asyncio
 import websockets
@@ -8,6 +8,7 @@ from loguru import logger
 import os
 
 from langchain.chat_models import init_chat_model
+from langchain_core.messages import SystemMessage, HumanMessage
 from langgraph.prebuilt import create_react_agent
 from langgraph.checkpoint.memory import MemorySaver
         
@@ -72,7 +73,7 @@ class Pipeline:
         tools = self.tool_manager.get_tools()
         self.agent = create_react_agent(self.llm, tools, checkpointer=memory)
     
-    def respond(self, msg:str):
+    def respond(self, msg:str | List[SystemMessage, HumanMessage]):
         return self.agent.invoke(msg)
 
     async def handle_connection(self, websocket:ServerConnection):