Mateusz Kaplon improved the reliability of OAuth2 configuration in the authelia/authelia repository by correcting a documentation error related to the Donetick integration. He identified and fixed the misnamed environment variable for the OAuth2 user info URL, ensuring that users configuring Donetick would avoid common misconfigurations. His work focused on configuration management and documentation, using Markdown to clearly communicate the necessary changes. By aligning the documentation with the actual code and configuration, Mateusz reduced the risk of support issues and improved onboarding for new users. The update enhanced maintainability and traceability within the project’s authentication setup.