Ultra fast Rust compile for coding agents.
Rebuilding every step of the Rust build toolchain from scratch to be faster, more parallelizable, and more cacheable.
Website · Install · Use · Remote builds · Goal · Findings · Changelog
justrust is rebuilding every step of the Rust build toolchain from scratch, with a goal of 100–1,000× faster builds through more parallelism, finer-grained caching, and less redundant work.
The released client makes the edit, check, and test loop faster locally or with our remote build service while the new toolchain takes shape.
Your coding agents spend valuable time waiting for Rust checks, builds, and tests. Running those operations locally can slow down your machine, drive up CPU usage, temperature, and RAM consumption, and fill your disk with build artifacts. Our remote service offloads compilation, test execution, and build artifact storage to our machines, freeing up yours.
Each build command also returns actionable diagnostics, showing agents where time went, why crates rebuilt, and which bottlenecks to address, so they can proactively optimize builds within your codebase.
curl -fsSL https://jcode.sh/rust.sh | sh
justrust agentsLinux and macOS, x86_64 and aarch64. Installs to ~/.local/bin and starts
sign-in. justrust agents configures your coding agents (manual setup).
From source: cargo install justrust --locked (Rust 1.91+).
Prebuilt installs update automatically. Opt out with justrust update off;
disable anonymous telemetry with justrust telemetry off.
Send feedback with justrust feedback "Your suggestion".
justrust check -p my-crate
justrust test -p my-crate --lib some_module::
justrust buildcheck, test, build, clippy, and run take cargo's arguments and
return its exit code. Errors and failing tests stay in full, followed by
a concise result and timing report. Use justrust log for the full output
and justrust show for the timing breakdown.
Other cargo commands (cargo fmt, cargo add, cargo tree) stay plain cargo.
justrust login # approve in the browser
justrust upgrade # activate a remote build plan
justrust checkSigned in, check, clippy, and test use hosted build machines by default
on Linux. Choose --local, --remote, or --auto (remote only when predicted
faster). If hosted builds are unavailable, justrust falls back to local builds.
Local builds are free. Hosted plans start at $20/month for 5,000 builds,
with the first month free and a card required. See pricing.
For agents without a browser, justrust login --no-wait prints a sign-in link.
For CI, set JCODE_API_KEY from your account.
More setup details: remote builds.
The shortest possible path from a source edit to a trustworthy test result.
justrust is rebuilding every step of the Rust build stack from scratch: project discovery, dependency handling, compilation, code generation, linking, and test execution. Each step is designed to be faster, more parallelizable, and more cacheable, backed by shared artifact caches and our own build infrastructure. We optimize the whole loop, not just individual compiler stages. Our target is 100–1,000× faster builds, to be demonstrated with representative end-to-end measurements as the new toolchain matures.
The goal is for agents to spend their time editing and reasoning, not waiting for builds. We are rewriting the internals from scratch, rather than embedding Cargo, rustc, or their vendored implementations, while preserving build correctness and useful diagnostics. We use the standard Rust toolchain to build the new implementation and keep utility dependencies minimal. External correctness is the compatibility contract: Rust semantics, existing projects, build scripts, proc macros, platform ABIs, and trustworthy build and test results.
Compiler design, implementation plans, and feature contracts live in docs/compiler/.
The new compiler is one demand-driven graph, not a pipeline of phases. File discovery, parsing, name resolution, type and borrow checking, lowering, code generation, linking and tests are all designed as nodes that produce and consume immutable, typed facts. A node runs as soon as the facts it reads exist, not when a global phase ends, so code generation for one function can overlap checking of an unrelated one. A node that is missing an input suspends only the branch that needs it, never a worker thread. Success is released only after every required check passes.
Nodes are keyed per file, per item, or per generic instance, so equivalent work shares one node and is computed once within a build. Because every compiler fact lives in the graph, with no side tables or global state (enforced by GRAPH-INTEGRITY.md), the same identities are meant to become the units for incremental rebuilds, persistent and remote caching, and scheduling across cores and machines. Today reuse is within a single build only, a few stages (parsing, resolution) are still whole-program nodes being split, and cross-build persistence and shared caches are planned, not built. See ARCHITECTURE.md and ENGINE.md for details.
See CONTRIBUTING.md. The compiler is source-available under FSL-1.1-ALv2: use it for anything except a competing product or service, and each release becomes Apache 2.0 after two years. Contributions are accepted under Apache 2.0. Third-party sources keep their original licenses. See LICENSING.md.