cargo-bench-regression

name	cargo-bench-regression
description	Run criterion cold_start bench, diff against baseline, surface >5% regressions. Use when user asks "bench", "perf check", "regression check", "cargo bench".
disable-model-invocation	true

cargo-bench-regression

Runs cargo bench --bench cold_start against the saved baseline and reports regressions >5%.

Steps

1. Verify baseline exists at target/criterion/cold_start/base/. If missing, run cargo bench --bench cold_start -- --save-baseline base first and stop (no diff to make).
2. Run cargo bench --bench cold_start -- --baseline base.
3. Parse criterion output for change: lines.
4. Report:
   • PASS: all changes within ±5%
   • REGRESS: list any benchmark with >5% slower
   • IMPROVE: list any benchmark with >5% faster
5. If REGRESS, suggest user investigate before merge.

Baseline management

• cargo bench --bench cold_start -- --save-baseline base — overwrite baseline (use after intentional perf change)
• cargo bench --bench cold_start -- --save-baseline before-X — named baseline for A/B
• See docs/benchmarks.md for canonical numbers.

Notes

• Criterion stores results in target/criterion/. Not committed.
• Bench harness is custom (harness = false in Cargo.toml) — see benches/cold_start.rs.