Worked on the mozilla/gecko-dev repository to enhance scrolling behavior and test coverage, focusing on cross-browser consistency and regression prevention. Addressed a bug affecting right-to-left (RTL) layouts by removing an unnecessary layout-completion condition, which corrected scrolling for height-0 elements and included a dedicated test to verify the fix. Developed comprehensive tests for overscroll-behavior, ensuring that the 'none' value is respected across all scrollable containers, including those with hidden and auto overflow. Utilized CSS, JavaScript, and web platform testing techniques to deliver targeted improvements that stabilize user experience and strengthen the reliability of scrolling features across platforms.