Backends & Resolution

shirabe drives any browser that speaks the Chrome DevTools Protocol — Google Chrome, Chromium, Microsoft Edge — through one CDP engine. Select one with SHIRABE_BACKEND:

Value	Backend
`chrome` (default in `auto`)	Google Chrome
`chromium`	Chromium
`edge`	Microsoft Edge
`auto` (default)	Try Chrome, then Chromium, then Edge

Resolution order

Whichever backend is chosen, shirabe resolves an executable in this order (mirroring ort's dependency model):

Backend-specific override — CHROME_PATH / CHROMIUM_PATH / EDGE_PATH. If set, the path is authoritative; a missing path is a hard error.
Build-time baked path — SHIRABE_BROWSER_PATH, emitted by build.rs when the `auto-fetch` feature downloads the pinned Chrome for Testing build into the shared cache during compilation.
System binary on $PATH plus a handful of well-known install locations (`/usr/bin/google-chrome`, `/Applications/Google Chrome.app/...`, `C:\Program Files\Google\Chrome\Application\chrome.exe`, …).
Runtime fetch (the runtime-fetch feature) — download the pinned Chrome for Testing build on first use into the cache.

Download knobs

The fetch step honours these environment variables, both at build time (build.rs) and at runtime:

Env	Purpose
`SHIRABE_CHROME_VERSION`	Override the pinned Chrome for Testing version.
`SHIRABE_CHROME_MIRROR`	Download from a mirror (e.g. a GFW-friendly one) instead of the default Google host.
`SHIRABE_CHROME_SHA256`	Optional hex checksum; the download is verified against it.
`SHIRABE_DOWNLOAD_PROXY`	Route the download through an `http://`, `https://` or `socks5://` proxy.
`SHIRABE_DOWNLOAD_TIMEOUT_SECS`	Per-request timeout (default 600).
`SHIRABE_SKIP_BROWSER_FETCH`	Skip both build-time and runtime downloads.

Because build.rs reads these too, a downstream crate can pin the whole toolchain in CI with one env: block.