Gunnlaugur worked on performance optimization for the oxc-project/oxc minifier, focusing on improving speed and maintainability when processing large JavaScript files with thousands of variable declarations. Using Rust, he refactored core algorithms to eliminate O(n^2) bottlenecks, introduced efficient reference handling, and optimized inlining decisions to achieve faster build times. His approach included implementing cache-based symbol mutation checks and streamlining single-use symbol substitution, resulting in linear scaling for substitution attempts. Gunnlaugur’s work was supported by comprehensive performance tests and documentation, demonstrating depth in algorithm design and performance engineering while preparing the codebase for future enhancements and real-world usage.