Computer-implemented methods and computer-readable storage media are disclosed relating to displaying server errors on the client computing system that caused the failed request. A client listener application configured to execute on a client computing system. The client listener application is further configured to exchange data over a network with a server system, and provide metadata to the server system identifying the client computing system in association with a client request for execution of code on the server system. The client listener program is configured to receive an assert message indicating an error resulting from the execution of the code on the server and signal receipt of the assert message over a user interface. The client listener program is further configured to provide an opportunity for a user to respond to the assert message via the user interface by choosing to ignore the assert message or to analyze the error.