Worked on enhancing parser reliability and UI stability across swiftlang/swift-syntax, swiftlang/swift, and airbnb/lottie-ios repositories. Developed parser support for #warning and #error directives within switch-case positions, aligning Swift’s syntax handling with compiler expectations and improving AST generation. Addressed a regression in LottieAnimationView to ensure animation layout changes remain synchronized during in-flight animations. Introduced regression tests to preserve leading comments during function-to-computed-property refactoring, and expanded test coverage for pound directive handling. Leveraged Swift, syntax tree manipulation, and testing to deliver cross-repo improvements that reduce regression risk and improve long-term maintainability of Swift tooling and iOS animation components.