Luka Rajic contributed to both Homebrew/brew and SerenityOS/serenity, focusing on practical system-level improvements. For Homebrew/brew, Luka developed a disk-space visibility feature that allows users to view the storage used by each installed formula or cask through a new command-line flag, implementing supporting data structures and formatted output in C++ and Shell. In SerenityOS/serenity, Luka addressed kernel process lifecycle reliability by fixing a bug that ensured proper cleanup of kernel stacks when processes terminate, modifying process state handling within the scheduler. Luka’s work demonstrated depth in system programming and kernel development, emphasizing maintainability and user-oriented enhancements.