Update app.py

app.py

@@ -6,7 +6,7 @@ from langchain_openai import ChatOpenAI
 from langchain_core.pydantic_v1 import BaseModel, Field
 from langgraph.graph import MessageGraph, END
 from langgraph.checkpoint.sqlite import SqliteSaver
-from langchain_core.messages import HumanMessage
+from langchain_core.messages import HumanMessage, AIMessage
 from typing import List
 import os
 import uuid
@@ -127,7 +127,7 @@ with container:
             submit_button = st.form_submit_button(label='Send')
     
         if submit_button and user_input:
-                for output in graph.stream([HumanMessage(content=user_input), st.session_state['past']], config=config):
+                for output in graph.stream([HumanMessage(content=user_input), AIMessage(content=st.session_state['past'])], config=config):
                   if "__end__" in output:
                       continue
                   # stream() yields dictionaries with output keyed by node name