Worked on enhancing build configuration flexibility in the facebook/buck2 and facebook/buck2-prelude repositories by introducing a customizable output directory for filegroup rules. Developed and implemented an 'out' attribute for filegroup rules using Starlark and Python, allowing users to specify custom artifact directories and reducing naming conflicts within macros. Focused on achieving cross-repository consistency, the changes streamlined artifact organization and improved macro-based filegroup usage. The technical approach involved extending rule attributes and ensuring default behaviors for backward compatibility. Emphasized design, implementation, and documentation, contributing to more maintainable build systems and simplifying artifact management across multiple repositories without introducing new bugs.