What is this?
Blaze is a tool that sits in front of cargo and makes incremental Rust rebuilds dramatically faster by compiling only the functions you changed and patching them into the already-built binary instead of relinking from scratch.
Blaze is a tool that sits in front of cargo and makes incremental Rust rebuilds dramatically faster by compiling only the functions you changed and patching them into the already-built binary instead of relinking from scratch.Is this a replacement for cargo or does it work alongside it?It is a wrapper CLI that passes every command straight through to cargo except incremental builds, which it intercepts and speeds up itself; you keep using the same workflow via 'cargo blaze'.
It is a wrapper CLI that passes every command straight through to cargo except incremental builds, which it intercepts and speeds up itself; you keep using the same workflow via 'cargo blaze'.How do I install and start using it?Install blaze for macOS on Apple Silicon or Linux, then in any Rust project run 'cargo blaze build' or 'cargo blaze run' instead of the plain cargo commands; the first build runs normal cargo while blaze loads, and later edits rebuild in milliseconds.
Install blaze for macOS on Apple Silicon or Linux, then in any Rust project run 'cargo blaze build' or 'cargo blaze run' instead of the plain cargo commands; the first build runs normal cargo while blaze loads, and later edits rebuild in milliseconds.Do I need Rust or rustup already installed?No — blaze downloads its own pinned Rust toolchain (about 100 to 135 MB) if you don't have Rust, or uses rustup's installation if you already have one.
No — blaze downloads its own pinned Rust toolchain (about 100 to 135 MB) if you don't have Rust, or uses rustup's installation if you already have one.Does it work on Windows?Not yet — blaze only speeds things up on macOS Apple Silicon and Linux; on Windows every build just falls back to plain cargo with no speedup.
Not yet — blaze only speeds things up on macOS Apple Silicon and Linux; on Windows every build just falls back to plain cargo with no speedup.Is it safe to rely on for production builds right now?Not fully — the project explicitly calls itself young and advises keeping 'cargo check' or your CI as the final word, since blaze output can occasionally differ from plain cargo.
Not fully — the project explicitly calls itself young and advises keeping 'cargo check' or your CI as the final word, since blaze output can occasionally differ from plain cargo.How much faster are builds with blaze compared to plain cargo?On average over real projects, edits rebuild about 10x faster on macOS arm64, 24x faster on Linux aarch64, and 11x faster on Linux x86-64; for example bun's 1.25M-line codebase drops from 9.11s to 451ms per rebuild.
On average over real projects, edits rebuild about 10x faster on macOS arm64, 24x faster on Linux aarch64, and 11x faster on Linux x86-64; for example bun's 1.25M-line codebase drops from 9.11s to 451ms per rebuild.What does it cost in memory and disk space?Blaze trades memory for speed by keeping your project compiled in memory, which costs a few GB even for a small project.
Blaze trades memory for speed by keeping your project compiled in memory, which costs a few GB even for a small project.Can a running program pick up code changes without restarting?Yes — if a program opts in, it can take newly compiled code while it keeps running, giving live edits in about 20ms from saving a file to the updated code actually running.
Yes — if a program opts in, it can take newly compiled code while it keeps running, giving live edits in about 20ms from saving a file to the updated code actually running.Why was the project renamed from ra-jit?Blaze was called ra-jit until 2026-10-24; the old 'cargo ra-jit' command still works, but the project is now named blaze.
Blaze was called ra-jit until 2026-10-24; the old 'cargo ra-jit' command still works, but the project is now named blaze.Which topics is it in?cargo, llvm, jit, rust-lang, toolchain, nix, benchmarking, devtools, build-tool, low-level, systems-programming, compiler
cargo, llvm, jit, rust-lang, toolchain, nix, benchmarking, devtools, build-tool, low-level, systems-programming, compiler