During June 2025, Marten van der Meulen enhanced the craftcms/cms repository by developing a robust upgrade to GraphQL error handling. He focused on extending the GQL service to support ClientAware errors, ensuring that client-safe exceptions are surfaced appropriately depending on whether the environment is in development or production mode. This approach improved error visibility and resilience for both end-users and developers, while maintaining consistency with the existing error-handling architecture for long-term maintainability. Marten utilized PHP and back end development skills, with a strong emphasis on error handling, delivering a focused and well-integrated feature that addressed nuanced error management requirements.