Pnpm 12 rewrote the package manager in rust and kept every pnpm 11 flag, command, and lockfile.…
pnpm 12 rewrote the package manager in rust and kept every pnpm 11 flag, command, and lockfile. faster cold installs, smaller tlb misses. the part nobody is quoting is the part that should scare every js framework maintainer: a drop-in rewrite only works when the prior api was already overfit.
the next rust port is bun, and it will not be compatible.
Context
The pnpm post What's different in pnpm 12 says pnpm 12 is a rewrite in Rust, is stable, and apart from the differences it lists keeps the commands, flags, settings and lockfile format of pnpm 11. The 12.0 release post adds that peers resolve 2 to 3 times faster and cyclic workspaces use about 25% less memory.
The pnpm benchmarks page, with data fetched on 2 October 2026, lists fresh-clone installs with nothing cached (npm 12.2.0, pnpm 11 v11.28.2, pnpm 12 v12.8.2): alotta-files 7.34s for pnpm 11 against 4.34s for pnpm 12, and alotta-packages 21.5s against 13.5s.
Faster cold installs is supported as a vendor-reported benchmark for those two fixtures and versions, with a data snapshot of 2 October 2026, not independent and not specific to other projects. The page compares versions, so it does not show that the Rust rewrite caused the gain, and the snapshot date is later than the note, so it is not proof of what existed on 6 September 2026. Every flag and lockfile is overstated: the pnpm post lists differences, such as frozen-lockfile false no longer being supported and lockfile changes for git specifiers and cyclic graphs. Smaller TLB misses are unverified, with no inspected evidence. That a drop-in rewrite only works when the old API was overfit, and that the next Rust port is Bun and will not be compatible, are the author's opinion and prediction; no evidence about a Bun rewrite was inspected.
Watch next
- Cold-install measurements that isolate the rewrite from other changes.
Sources
- What's different in pnpm 12pnpm.io
- pnpm 12.0 release postpnpm.io
- pnpm benchmarkspnpm.io
Provenance
The note above is reproduced unedited from the original post, first published on Threads on 6 September 2026 at 05:03 IST. Sources are the papers and datasets the note draws on.
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