Windows builds

Install Kache through a supported package manager or extract the Windows release ZIP. Keep kache.exe and kache-engine.exe from the same release in the same directory. A standalone client EXE is not a complete v2 installation.

kache init
kache doctor
kache doctor --probe
cargo build

Init configures the Cargo wrapper and can register a Task Scheduler daemon. Windows does not use the Unix compiler-name shim farm or Unix shell-startup edits. For PowerShell completions, generate the script with kache completions powershell and load it from your profile.

Rust libraries and executable outputs

Eligible Rust libraries use the artifact cache. Executable caching remains opt-in on Windows:

[cache]
cache_executables = true

For one PowerShell session, set $env:KACHE_CACHE_EXECUTABLES = "1" before the build. If you use the GitHub Action, configure its cache-executables input instead of relying on the CLI default.

V2 pairs a cached MSVC PE executable with the sibling PDB named by its debug record, checking that their identities agree. Missing/mismatched PDBs, unsupported debug layouts, FASTLINK dependencies, and incremental-link sidecars leave the compile uncached. A PE without a CodeView record needs no PDB. See Windows executable keys for the exact admission rules.

Rust links can key supported rust-lld toolchains, compiled resource inputs, and modeled runtime/default-library selections. This does not make direct cl.exe object compilation cacheable. On main, DLL caching also retains import libraries omitted from rustc's artifact notifications.

Long Rust commands can remain cacheable: RC2 moves Kache-injected arguments into a response file when they would overflow the Windows command line. Unsupported invocations still pass through.

Daemon execution

The frontend keeps native compiler processes, console access, and brokered restores under the client's token and job lifetime. The daemon coordinates the cache pipeline over an authenticated named pipe.

kache doctor reports daemon health separately from compiler-execution eligibility. A refused handoff can use the local engine before Commit. After Commit, a lost connection fails the invocation rather than rerunning it.

RC2 supports an explicit trust option for certain known process-identity token differences. It must be enabled in both configurations and requires a daemon restart. Other token checks still apply. Read Process restrictions before enabling it.

C/C++, CUDA, and documentation

• GCC, Clang, and eligible clang-cl object compiles can use explicit prefix wrapping or build-tool launcher settings. clang-cl debug objects stay machine-local. See C/C++.
• Single-source nvcc -c and separate-compilation object outputs can use the CUDA cache, including CMake's modeled host/compiler flags. Device and final links pass through. See CUDA.
• Windows cargo doc passes through. Unix rustdoc caching also has toolchain restrictions; it is not a general v2 promise for every documentation build.

On volumes without copy-on-write support, restores can copy bytes. Logical target sizes alone do not demonstrate shared disk blocks. See Storage and cleanup.