Worked on the jxxghp/MoviePilot repository to deliver a configuration-driven feature for managing default subtitles. Developed a backend solution in Python that automatically appends a ".default" suffix to designated subtitle files, enabling the application to consistently select default subtitles for English, Simplified Chinese, and Traditional Chinese. Leveraged configuration management techniques by introducing the DEFAULT_SUB setting, allowing flexible control over subtitle preferences. This approach improved the multilingual playback experience by ensuring reliable default subtitle selection. Maintained clear traceability through commit-level documentation, supporting future audits and rollbacks. The work focused on backend development and configuration management, emphasizing maintainability and user experience.