Browser tests need an archive that matches the installed Playwright runtime. The public extension reads the caller's declared browsers.json and selects archive versions from that manifest. Each platform has a caller-owned SHA-256 checksum; repository preparation verifies the download before exposing files.
The extension declares separate repositories for each platform and a hub with platform-selected edges. This keeps unrelated browser archives out of a build. An unsupported browser, duplicate declaration, missing platform set, or malformed manifest fails during preparation. A requested platform without a declaration has no compatible payload.
Payload files remain native runfiles under one Chromium installation directory. An INSTALLATION_COMPLETE marker names that installation. Runners own writable validation state and temporary directories; they do not mutate the archive or use a developer's browser cache. The native test resolves the selected executable from the declared payload and checks JavaScript-rendered DOM from the HTML fixture.
Only Chromium is supported. Linux hosts supply Chromium's operating-system libraries; those belong to the runner image rather than the browser archive.
Native verification invokes the declared Chromium executable against the HTML example, observes complete JavaScript-updated DOM, and deliberately requests bounded shutdown through the development-only graceproc dependency. The selected browser payload stays immutable; profile state belongs to each probe. This keeps browser acquisition independent of JavaScript build execution.