task: sets primary llm in user session

src/app.py

@@ -1,20 +1,11 @@
 import chainlit as cl
-from langchain_openai import AsyncChatOpenAI
+from langchain_openai import ChatOpenAI
 from langchain_core.messages import HumanMessage, SystemMessage
 from chains.design_rag import DesignRAG
 
 # Initialize components
 design_rag = DesignRAG()
 
-llm = AsyncChatOpenAI(
-    model="gpt-4o-mini",
-    temperature=0,
-    streaming=True,
-    callbacks=[cl.LangchainCallbackHandler()]
-)
-
-conversation_history = []
-
 # System message focused on design analysis
 SYSTEM_MESSAGE = """You are a helpful design assistant that finds and explains design examples.
 For every user message, analyze their design preferences and requirements, considering:
@@ -28,6 +19,16 @@ First briefly explain how you understand their requirements, then show the close
 
 @cl.on_chat_start
 async def init():
+    # Initialize LLM with callback handler inside the Chainlit context
+    llm = ChatOpenAI(
+        model="gpt-4o-mini",
+        temperature=0,
+        streaming=True,
+        callbacks=[cl.LangchainCallbackHandler()]
+    )
+    
+    # Store the LLM in the user session
+    cl.user_session.set("llm", llm)
     
     # init conversation history for each user
     cl.user_session.set("conversation_history", [
@@ -39,6 +40,9 @@ async def init():
 
 @cl.on_message
 async def main(message: cl.Message):
+    # Get the LLM from the user session
+    llm = cl.user_session.get("llm")
+    
     conversation_history = cl.user_session.get("conversation_history")
     # Add user message to history
     conversation_history.append(HumanMessage(content=message.content))