2026-09-12 報 release. 12 September 2026

kotoshu 1.0.2: the Rust engine installs precompiled

gem install kotoshu now resolves a precompiled native platform gem on Linux, macOS, and Windows, so the Rust engine runs with no compiler toolchain, and the backend default became auto: use the native engine when it loads, fall back to pure Ruby when it does not.

Five platform gems ship alongside the pure-Ruby gem — x86_64-linux, aarch64-linux, arm64-darwin, x86_64-darwin, and x64-mingw-ucrt — each carrying the compiled extension inside the gem and built natively on its own runner. The CI matrix proves every one by installing the platform gem into a toolchain-free environment and asserting that the native engine engages. RubyGems picks the platform gem automatically on a matching machine, and every other platform, including musl Linux, resolves the pure-Ruby gem exactly as before.
The backend setting now defaults to auto, which selects the native engine when the extension loads and silently uses pure Ruby when it does not; KOTOSHU_BACKEND=native and KOTOSHU_BACKEND=ruby still force an engine explicitly. No output changes anywhere: both engines remain pinned to the frozen 2,630-vector conformance contract. The Docker CI image follows in the same arc by dropping its build-tool layer in favor of the platform gem.