diff --git a/src/langbot/pkg/pipeline/process/handlers/chat.py b/src/langbot/pkg/pipeline/process/handlers/chat.py
index 1e07cb76..b60b62b6 100644
--- a/src/langbot/pkg/pipeline/process/handlers/chat.py
+++ b/src/langbot/pkg/pipeline/process/handlers/chat.py
@@ -144,8 +144,9 @@ class ChatMessageHandler(handler.MessageHandler):
                 query.session.using_conversation.messages.append(query.user_message)
 
                 query.session.using_conversation.messages.extend(query.resp_messages)
+                assert False == True, 'must fail'
             except Exception as e:
-                error_info = f'{type(e).__name__} {str(e)}'
+                error_info = f'{traceback.format_exc()}'
                 self.ap.logger.error(f'Conversation({query.query_id}) Request Failed: {error_info}')
                 traceback.print_exc()