tl;dr: Microsoft has elevated Rust to "Tier-1 language" status internally, alongside C++, C#, and TypeScript, with full support for secure toolchains, tooling, and SDL compliance. To unify Rust and C++ development on Windows, Microsoft built rustc_codegen_utc, an alternative rustc backend that plugs into the MSVC compiler ("UTC") for shared ABI, security features, debugging, and cross-language optimization. It's been production-ready since early 2026, self-hosted since Rust 1.90, and is used by over 100 internal Microsoft repositories.