Matthias contributed to GeyserMC/Geyser by addressing a Velocity ping version reporting issue, explicitly setting Minecraft and protocol versions to improve server ping accuracy and plugin compatibility. This backend work, implemented in Java with a focus on proxy management, reduced misreporting and enhanced operator experience in Velocity-enabled environments. In the keiyoushi/extensions-source repository, Matthias developed a MangaDex Extension feature that prioritizes alternate titles by language, refining title selection logic for better localization and user alignment. Using Kotlin and internationalization techniques, he refactored variable names and translations, resulting in clearer code and more consistent, personalized title presentation across languages.