Update app.py

app.py

@@ -302,7 +302,7 @@ def wechatai():
         user_message_content, from_user_name, to_user_name = getUserMessageContentFromXML(xml_str)
         
         if from_user_name not in user_sessions:
-            user_sessions[from_user_name] = {'model': 'gpt-3.5-turbo', 'messages': [], 'pending_response': []}
+            user_sessions[from_user_name] = {'model': 'gpt-4o-mini', 'messages': [], 'pending_response': []}
 
         session = user_sessions[from_user_name]