During April 2026, this developer enhanced build observability in the element-hq/synapse repository by delivering a Prometheus metric that reports the Rust compiler version used at build time. They implemented an end-to-end workflow that captures the rustc version during builds, exposes it through a Python-callable function from the Rust extension, and exports it via a new rustc_version metric endpoint. Using Python and Rust, they ensured the feature was fully integrated with changelog documentation, testing guidance, and project code style. This work enables teams to correlate build behavior with compiler versions, improving diagnosis and reducing mean time to resolution in CI/CD environments.