# Kache: Zero-copy, compiler cache for Rust > Source: > Published: 2026-10-01 18:08:16+00:00 Kache is a compiler cache for Rust, C/C++, and CUDA. It keys every compiler invocation by the content of its inputs, so a crate built once is restored instead of rebuilt in your next worktree, branch, or CI run. Outputs live in a local content-addressed store and can be shared through S3-compatible or filesystem remotes. Linux, macOS, and Windows are supported and release-tested. Built by [Kunobi](https://kunobi.ninja/?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=brand). [Benchmarks](https://kunobi.ninja/docs/kache/benchmarks?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=nav_benchmarks) · [Kache vs sccache](https://kunobi.ninja/docs/kache/getting-started/comparison?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=nav_comparison) · [CI setup](https://kunobi.ninja/docs/kache/remote-cache/ci?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=nav_ci) [See how Kache shares build outputs across worktrees →](https://kunobi.ninja/product/kache?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=hero_details) ``` cargo install kache kache init ``` Your Cargo commands do not change. `kache init` sets `rustc-wrapper` in Cargo's config. On Unix it also adds the `[env]` keys for build-script C and C++. Run `kache init --check` to preview the changes, or `kache init --no-service` to skip the OS service. `cargo install` needs Rust 1.95 or newer. Prebuilt packages exist for Homebrew, APT, AUR, winget, Scoop, Chocolatey, mise, and Nix. Release builds cover x86_64 and ARM on Linux, macOS, and Windows. See [Install Kache](https://kunobi.ninja/docs/kache/getting-started/installation) for each channel. After `kache init`, [build the same revision in two temporary worktrees](https://kunobi.ninja/docs/kache/getting-started/quick-start?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=first_reuse). Each gets its own target directory, so your existing build outputs stay in place. The second tree's report lists the hits and a bypass reason for every unit that still compiled. Kache has three parts: a compiler wrapper, a local store, and an optional daemon. - The wrapper parses each `rustc` ,`rustdoc` ,`cc` ,`c++` , or`nvcc` invocation, hashes the inputs that change the output, and normalizes the machine-local paths that do not. Two worktrees of the same revision produce the same key. - Wrappers that reach the same key at the same time join one flight, so the compiler runs once per key on a machine, however many Cargo processes ask for it. - The store keeps outputs as content-addressed blobs. Identical bytes are stored once. Restores use copy-on-write clones where the filesystem supports them, so a second worktree costs little disk. - The daemon serves remote lookups after a local miss and uploads new entries in the background. Hits, misses, and passthroughs are reported per unit, and `kache why-miss` explains what changed. [Read the architecture →](https://kunobi.ninja/docs/kache/how-it-works/architecture) | Workload | Status | Notes | |---|---|---| | Rust libraries and build scripts | Supported | Run `kache init` . Build-script runs are cached on Linux and macOS | | Rust executables | Supported on Linux and macOS | Disabled by default on Windows | | C and C++ object files | Supported | GCC, Clang, Apple Clang, and clang-cl. Build scripts via `kache init` ; other builds via shims or`CC` /`CXX` | | CUDA object files | Supported | Single-source `nvcc -c` and`-dc` via`CUDACXX="kache nvcc"` or a CMake launcher | | Rust documentation | Unix | `cargo doc` with`RUSTC_BOOTSTRAP=1` and`-Z rustdoc-depinfo -Z rustdoc-mergeable-info` . Windows has no compiler shims, so`cargo doc` is not cached there | | Local storage | Built in | Content-addressed store with garbage collection | | S3-compatible remote storage | Built in | Includes AWS S3, MinIO, and Cloudflare R2 | | Google Cloud Storage | Built in | Application Default Credentials, including GKE workload identity | | Filesystem remote storage | Built in | Useful for shared disks and CI volumes | In a Firefox 151 benchmark with Kache 0.7.0 on macOS/APFS, the second worktree added about 3 GB of new data. [Read the measurements and methodology →](https://kunobi.ninja/blog/kache-storage-worktrees?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=storage_report) For a comparison with sccache, read [Kache or sccache?](https://kunobi.ninja/docs/kache/getting-started/comparison). The scheduled [benchmark workflow](https://github.com/kunobi-ninja/kache/actions/workflows/bench.yml) runs real cold and warm builds of Firefox, LLVM, SurrealDB, Lance, OpenDAL, cuda-oxide, and eza on Linux. Separate workflows build Firefox on Windows every night and compare Firefox with sccache once a week. It also measures how much of a Firefox build survives a source update. Each run checks its own measurement validity and uploads reports, traces, and logs for 30 days. Treat timing or hit-rate numbers as evidence only when the individual job succeeds and its benchmark verdict is `ok`. [See the benchmark setup and report guide →](https://kunobi.ninja/docs/kache/benchmarks?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=benchmark_guide) The official action installs Kache and wires it into the build: ``` - uses: kunobi-ninja/kache-action@v1 - run: cargo build --locked ``` See the [CI guide](https://kunobi.ninja/docs/kache/remote-cache/ci) for GitHub Actions and shell-based CI examples. On Unix, `kache init` creates compiler-name shims and offers to add their directory to `PATH` in your zsh, bash, or fish startup file. Make, CMake, autotools, and Arch PKGBUILDs that call `gcc` by name then go through Kache, with no `CC=` edit or shell wrapper. For managed dotfiles or another shell, set it up by hand: ``` kache install-shims export PATH="$HOME/.local/lib/kache/shims:$PATH" ``` APT and AUR packages install `/usr/lib/kache`. Nix packages include the same symlinks in `${kache}/shims` and `${kache}/lib/kache`; see the [Nix configuration example](https://kunobi.ninja/docs/kache/getting-started/installation#nix). For `makepkg`, put the same assignment in `~/.makepkg.conf`. Wrap extra names already on `PATH` with `kache install-shims --from-path`. Kache inspects the real compiler invocation. Unsupported or unsafe invocations pass through. See [C and C++](https://kunobi.ninja/docs/kache/getting-started/c-cpp). The default local cache is: - Linux: `$XDG_CACHE_HOME/kache` or`~/.cache/kache` - macOS: `~/Library/Caches/kache` - Windows: `%LOCALAPPDATA%\kache` Open the configuration editor with `kache config`, or edit the TOML file directly. A minimal S3-compatible remote looks like this: ``` [cache.remote] type = "s3" bucket = "my-build-cache" region = "us-east-1" ``` Credentials come from the standard AWS environment variables or credential chain. See [S3 setup](https://kunobi.ninja/docs/kache/remote-cache/s3-setup) and [filesystem setup](https://kunobi.ninja/docs/kache/remote-cache/filesystem-setup). ``` kache monitor # live build and cache activity kache stats # hit rate, time saved, cache size kache stats --last-build # hits, misses, and bypass reasons of the latest build kache stats --full --redact # full report without cache keys and paths, for sharing kache diff # compare the two newest sessions of one root kache doctor # setup and integrity checks kache install-shims # Unix compiler-name PATH farm kache why-miss # explain the latest miss kache list # inspect cached entries kache gc # enforce cache limits kache targets # target dirs, what each frees, deleted worktrees kache clean --orphans --yes # remove the targets of deleted worktrees kache sync # pull from and push to the configured remote kache daemon status # inspect the background service ``` Run `kache help ` for exact flags. The [command reference](https://kunobi.ninja/docs/kache/commands/reference) covers every top-level command. To pass one build through without changing the setup, run it with `KACHE_DISABLED=1`. For Kubernetes and GitOps, [Kunobi Desktop](https://kunobi.ninja/product/desktop?utm_source=github&utm_medium=readme&utm_campaign=kache&utm_content=desktop) lets you inspect clusters and manage Flux and Argo CD. - [Open a bug report](https://github.com/kunobi-ninja/kache/issues/new?template=bug_report.md) when Kache behaves differently from the documentation. - [Request a feature](https://github.com/kunobi-ninja/kache/issues/new?template=feature_request.md) for a missing compiler, remote backend, or build workflow. ``` git clone https://github.com/kunobi-ninja/kache.git cd kache cargo test --workspace --all-features ``` See [CONTRIBUTING.md](https://github.com/kunobi-ninja/kache/blob/main/.github/CONTRIBUTING.md) before opening a pull request. Kache is licensed under the [Apache License 2.0](https://github.com/kunobi-ninja/kache/blob/main/LICENSE).