Charlie Yan enhanced observability and diagnosability for the facebook/buck2-prelude repository by developing enriched logging for buckconfig operations. He implemented instrumented logging that captures return values and call stacks, providing detailed operational metrics for buckconfig read operations and mode-switch changes. Using Starlark and focusing on build system configuration and developer tooling, Charlie introduced configurable flags to control metrics collection, allowing targeted data gathering without affecting runtime performance. This work improved the linkage between code changes and business value by enabling data-driven performance tuning and faster issue resolution, reflecting a thoughtful approach to maintainability and operational insight within the build system.