The metadata mirror stored one JSON document per package, so every
resolution parsed every version manifest of every packument it touched:
178MB of JSON for the 1246-package benchmark fixture, of which ~1% (the
picked versions) was ever read. loadMeta was 23% of resolution CPU after
pnpm/pnpm#13504.
The Rust CLI already shipped an indexed mirror layout (headers record,
index record with per-version byte spans, concatenated raw version
fragments); the TypeScript CLI treated those mirrors as cache misses,
so the two stacks thrashed a shared cache. Both CLIs now read and write
the same layout under the format id pnpm-meta-v1, and the metadata
cache directories move from v11 to v12 so a pnpm version that predates
the layout never opens the files at all. The offline legacy-mirror hint
now looks under v11, and pnpm cache prune removes the v11 roots. NDJSON
remains the layout for filterMetadata documents and is still read as a
fallback.
Loading an indexed mirror parses only the two leading records and
builds versions as enumerable parse-once getters over byte spans, so a
manifest keeps one identity across filtered views and hook mutations.
Corruption is treated like an unreadable mirror in both stacks: a
fragment that does not parse throws a typed error, offline resolution
fails with NO_OFFLINE_META, the disk fast paths fall through to the
network (only for errors attributable to the disk copy), and a 304 over
a damaged file escalates to a cache-bypassing refetch that rewrites the
mirror — otherwise the intact etag would keep 304-validating a poisoned
file forever. The declared headers length is bounded, the encoded
mirror form is memoized per fetch result so workspace projects sharing
one in-flight fetch do not each serialize a copy, and cache view reads
through the shared loader in both CLIs.
Resolution of the 1246-package fixture is 16% faster on a warm mirror
(3.82s -> 3.21s, interleaved paired runs, offline); the resulting
lockfile is byte-identical across old-format, new-format, and
mixed-format configurations.
---------
Co-authored-by: Zoltan Kochan <z@kochan.io>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
