adjusted session management

app.py

@@ -76,7 +76,7 @@ async def retrieve_food_data(query):
 async def stream_completion(message_history):
     msg = cl.Message(content="")
     await msg.send()
-    
+
     try:
         stream = await client.chat.completions.create(
             messages=message_history,
@@ -85,14 +85,11 @@ async def stream_completion(message_history):
             temperature=0
         )
         
-        response_content = ""
         async for part in stream:
             token = part.choices[0].delta.content or ""
             await msg.stream_token(token)
-            response_content += token
         
-        message_history.append({"role": "assistant", "content": response_content})
-        await msg.update()
+        await msg.send()
     except Exception as e:
         logging.error(f"Error during stream completion: {e}")