Worked on modernizing lexer infrastructure across the facebook/ocamlrep, facebook/relay, and facebook/buck2 repositories by upgrading the Logos library to version 0.15. Focused on improving token handling, error reporting, and pattern matching to support more robust parsing and future feature development. Adapted the lexer in buck2 to accommodate API changes, shifting from Option<Token> to Result<Token, ()>, and updated whitespace and escaped newline handling using Rust attributes. Leveraged skills in Rust, dependency management, and compiler design to ensure cross-repository compatibility, minimize disruption, and lay the groundwork for enhanced reliability and maintainability in token parsing and error handling.