During a two-month period, Xes enhanced developer tooling and performance across several Facebook repositories. In facebook/buck2-prelude, Xes introduced OS-aware test path handling for Rustdoc by implementing a --remap-path-prefix option, which normalizes test paths and improves cross-platform test reliability. This C++ and Rust-based solution reduced flaky failures and streamlined CI workflows by producing cleaner, portable test artifacts. Additionally, Xes upgraded the simd-json library to version 0.15.0 in both facebook/ocamlrep and facebook/dotslash, coordinating cross-repo changes to enable future JSON parsing and serialization performance improvements. The work demonstrated depth in build systems, library management, and performance optimization.