Four independent cuts into the 2-4 hour full run, none touching the contract
"a mutant must turn its guard red":
- guardNeedsBundle: rollup runs only for guards that open the built bundle
(demo/ smokes, golden captures, bundle:sync) — 68 of 253 registry entries.
Unit and backend guards never read dist/ as a build artifact (verified
against every test that mentions dist/**: they read the git checkout or
synthetic files), so 185 mutants skip the most expensive step entirely.
- seedTestBuild + incremental tsc: the mutant worktree starts from the main
tree's warm test-build/ and .tsbuildinfo; tsc compares file hashes, not
mtimes, so the fresh checkout stays warm and only the mutated delta is
recompiled. This also speeds up the long guards that run tsc themselves.
- --changed[=range]: run only mutants whose patch files are touched by the
diff (origin/dev..HEAD by default). An empty selection is an honest success
with an explicit message — the full registry remains the pre-release
contract, per the workflow comment.
- --shard=i/n: deterministic interleaved slices; the workflow runs a 4-way
matrix, and a warm test-build step feeds every shard. Interleaving spreads
the expensive browser mutants across shards instead of clumping them.
Measured per mutant on this machine: unit 12-13 s (was ~50-70 s), backend
6 s, browser 32 s (unchanged — the bundle is genuinely needed there). Full
run estimate drops to ~70 sequential minutes, ~20 on four shards.
Unit coverage: guard classification on real registry shapes, a floor on both
classes so the split cannot silently collapse, changed-selection semantics,
and shard completeness/disjointness with an anti-clumping bound.
Issue: #332
User-Visible: no
Codex
2c20f2dc35