Perf regression: hatch/hosted wall +21% (9c43dfc9..17793173) #1471

[agent] Bench: hatch/hosted and hatch/rescan have regressed by 10% or more in three consecutive daily runs (10-09, 10-12, 10-13). Today's run confirmed it on the same machine. This is slow drift across about 220 commits, not one step.

• Base: 9c43dfc9 (main on 2026-10-06). Head: 15c2c839 (main on 2026-10-13). The daily A/B (17793173 → 15c2c839) is flat (+4.7% and -5.1%, both ≈), so nothing landed in the last day.
• Range: 9c43dfc9..17793173. One bisect point, f3c6313a, measured hatch/hosted at +11.0% [-4.8, +23.8] over the base. That puts about half the cost in 9c43dfc9..f3c6313a, where the candidates are Fix Hatch environments being invisible to stale-install checks and VEX (#335) #700 (Hatch envs in stale-install checks and VEX), Fix vendored uv/Hatch re-vendor to a newer patch (#742, #650) #943 (uv/Hatch re-vendor), Pick pure pypi lock wheels through one shared portability rule (#1150) #1151 and Fix PyPI package specs ignoring PEP 503 spellings (#910) #911. The other half is in f3c6313a..17793173, where the candidates are Fix Hatch-derived pylock.toml lock-only rewrite (#479) #1336 (Hatch-derived pylock rewrite) and the shared hosted-engine changes. No single culprit was found within the 3-build budget.
• Hot spot (callgrind, head, hatch/hosted): utils::hatch::rewrite → utils::hatch::plan takes 40% of Ir inside rewriter_groups. utils::purl_key::PurlKey::new / canonical_base_purl takes 13%, and python_crawler::list_dist_info_packages_sync takes 12%, mostly in canonicalize_pypi_name. The plan step re-canonicalizes purls per environment pin, which looks like the per-pin cost that grew.

Repro:

export CARGO_PROFILE_PERF_INHERITS=release CARGO_PROFILE_PERF_LTO=thin CARGO_PROFILE_PERF_STRIP=none
git worktree add /tmp/base 9c43dfc9 && (cd /tmp/base && CARGO_TARGET_DIR=/tmp/tb cargo build --locked --profile perf -p socket-patch-cli)
cargo build --locked --profile perf -p socket-patch-cli -p socket-patch-bench
target/perf/socket-patch-bench compare --base /tmp/tb/perf/socket-patch --head target/perf/socket-patch -f '^hatch/' --runs 20

Runner: 4 vCPU, Intel(R) Xeon(R) Processor @ 2.10GHz (cloud sandbox), run 2026-10-13.

Generated by Claude Code