GoKawiilNew Relax JIT runtime lets Rust programs run while compiling
A new project called Relax introduces a JIT compiler and runtime for Rust that executes Cargo packages directly from source without invoking rustc, LLVM or a linker. It compiles functions on first call, optimizes hot paths during execution, and can patch code edits into a running process without restarting it. The tool is described as experimental and intended for development iteration rather than release builds.
GoKawiil's interpretation of the reporting above, not reported fact.
By skipping the traditional build-then-run cycle, Relax could meaningfully speed up edit-test loops for Rust developers, especially on large projects where full rebuilds take minutes. The tradeoff is runtime performance: the project's own benchmarks show code running 12-25% slower than optimized rustc builds, suggesting it's positioned as a development aid rather than a production compiler replacement. Its narrow platform support (Linux x86-64 and macOS arm64 tested) indicates it remains early-stage.
- Relax compiles and runs Rust functions on demand, avoiding rustc, LLVM and linker steps entirely during development.
- It can patch live edits into a running process, preserving program state instead of restarting.
- Optimized code produced by Relax runs 12% slower on x86-64 and 24% slower on AArch64 compared to rustc's --release builds.
Source: makepad.github.io, 2026-11-11
Published there as: “Relax: JIT compiler for Rust to reduce build times”
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