Sean McBroom refactored the subtitle parsing engine in the jellyfin/jellyfin-vue repository, focusing on improving performance and maintainability. He replaced custom SSA subtitle parsing logic in the frontend worker and player element store with the ass.js library, leveraging a robust external parser to handle subtitle processing. This transition eliminated redundant parsing paths, reducing CPU overhead and latency during subtitle rendering. Working primarily with JavaScript, TypeScript, and Vue.js, Sean’s approach simplified the codebase and reduced the risk of edge-case bugs. The refactor established clean integration points, supporting future enhancements and aligning with the project’s strategy to streamline frontend development.