Update app.py

app.py

@@ -12,6 +12,10 @@ import chainlit as cl
 
 @cl.on_chat_start
 def query_llm():
+    openai_api_key = os.getenv("OPENAI_API_KEY")
+    if not openai_api_key:
+        raise ValueError("OPENAI_API_KEY environment variable not set")
+        
     llm = ChatOpenAI(model="gpt-4o",
                      temperature=0.3)
     conversation_memory = ConversationBufferMemory(memory_key="chat_history",