Relax: Rust without the wait

Relax, a Rust live compiler and JIT runtime built in Rust, launched as a tool that runs Cargo packages directly from source without rustc, LLVM, or a linker, compiling functions on first call and patching edits into running processes. The project claims a large 3D game reaches its first frame in 11 seconds from a clean checkout on an M4 MacBook versus roughly 3 minutes with cargo and rustc, and a small app starts in 3.7 seconds cold and 0.41 seconds warm. Relax ships as a single 438k-line Rust library with zero crates.io dependencies and supports x86-64 and AArch64 code generation, tested on Linux x86-64 and macOS arm64 but not Windows. The tradeoff is performance: optimized code runs at 1.12× rustc's release time on x64 and 1.24× on arm64 across 21 workloads, while the compiler and its caches add 120–190 MB of code cache for a hello-world package. Relax is positioned for the edit-run loop rather than release builds, with known gaps including incomplete crate support and live patching limited to function bodies, so watch whether the team closes the check-speed and compatibility gaps and whether developers adopt it alongside cargo.