Nancy Hung focused on backend development and error handling for the mosaicml/composer repository, addressing a critical bug related to private link access. She enhanced the system’s response to access-denied scenarios by implementing logic in Python that raises PermissionError for 401 and 403 HTTP responses, unwraps internal errors, and inspects error details for permission-related messages. This approach improved the clarity and actionability of error messages when users encounter denied access to private objects. Her work reduced support and investigation time, increased reliability in private data workflows, and demonstrated depth in backend engineering and robust error handling within a production codebase.