Cache Playwright browser downloads in CI - #3
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The e2e job downloaded roughly 350 MB of browser builds on every push and pull request. `cache: pnpm` does not cover them: the browsers live in ~/.cache/ms-playwright, outside the pnpm store. The `playwright install` command is left exactly as it was. It skips browser revisions already present, so a warm cache makes it cheap, and it must keep running to install the apt system libraries the cache does not cover -- conditionalising it on a cache hit would break e2e precisely when the cache works. Keyed on the lockfile hash rather than an extracted Playwright version: a silent parse failure after a future lockfile format change would pin one entry forever and serve wrong-version browsers. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01SRgQmnzeh3vsVKudXWs3RV
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The
e2ejob downloads roughly 350 MB of browser builds on every push and pull request, entirely uncached.cache: pnpmdoesn't cover them — the browsers live in~/.cache/ms-playwright, outside the pnpm store.The install command is deliberately unchanged
playwright installstays exactly as it was. It skips browser revisions already present, so a warm cache makes it cheap — and it must keep running to install the apt system libraries, which the cache does not cover. Conditionalising it on a cache hit would break E2E precisely when the cache works.Key design
Keyed on the
pnpm-lock.yamlhash, exact-match, norestore-keys.Version-keying was considered and rejected: extraction from the lockfile is feasible, but a silent parse failure after a future pnpm format change would yield a constant key and serve wrong-version browsers forever. Lockfile churn busts the hash key often enough (~25–40% of commits across these repos) that it still hits on most runs, at zero staleness risk.
Where a repo has two jobs installing different browser sets, they get different keys. Sharing would be a bug: keys are immutable, so whichever job saved first would claim the key, and a job needing more browsers would restore a partial cache, re-download the rest, then fail to re-save — a permanently partial entry paying restore cost forever.
Measured on the canary
Validated on
RISCfuture/tim.codesbefore rollout. The cached entry is 467 MiB — larger than estimated, and entirely separate from the 141 MiB pnpm store, confirming the premise. E2E went 2m13s → 1m39s (26% faster) on the warm run, with the hit confirmed in the log.Note
actionlintandyamllintclean. This PR's own run is a guaranteed cache miss.🤖 Generated with Claude Code
https://claude.ai/code/session_01SRgQmnzeh3vsVKudXWs3RV