Worked on the google/mozc repository to enhance UI reliability within Emacs by addressing a bug affecting candidate overlay visibility when the tab-line feature is enabled. Focused on Emacs Lisp development, the solution involved adjusting y-coordinate calculations to account for tab-line height, ensuring overlays remained visible and correctly positioned across multiple Emacs versions. This fix improved user experience consistency and reduced confusion for Emacs users interacting with overlays in tab-line contexts. The work demonstrated attention to UI/UX design principles and adherence to maintainer guidance, harmonizing overlay behavior with established UI conventions while maintaining cross-version compatibility and robust bug resolution practices.