[systemfsoftware-maker]

What changed

stryker plan --target-seconds N [--max-shards K] [--projects <dir>...] [--out <file>] [--full] discovers each project's mutants without running tests, decides reuse against that project's incremental report, costs every scheduled mutant, and packs mutants across shards with longest-processing-time (LPT) list scheduling. It emits a versioned ShardPlan (project mutant lists, predicted seconds, GitHub Actions matrix) on the new plan stream event, deterministic for the same inputs. ShardPlan is a new minor contract of @systemfsoftware/stryker-js-cli-contract.

This branch also closes the flaky property the plan's full turbo test run exposed:

• ∀c_Mutants_≡LptKeepsTheBusiestShardWithinFourThirdsOfAveragePlusLargestItem falsified at seed 6: three mutants costing 3.4927206787701224e293 ms, 1.7976931348623123e308 ms and 1.8961673493674487e-132 ms with maxShards: 1 sum to Infinity; PlannedShard.make refuses a non-finite predictedSeconds, so planShards threw Error: Schema validation failed instead of returning a plan.
• costMs is now bounded to Number.MAX_SAFE_INTEGER ms, so any shard total over a realizable mutant list stays a finite double and every accepted command has a representable plan. The LPT bound itself is untouched; the in-source refusal law pins the boundary with the falsifying cost.

origin/main's worker line already declares stream schema version 4.0, so this branch raises StreamSchemaVersion to 5.0 and regenerates packages/stryker-js-cli-contract/contract/stream.schema.json; the wire fixtures move with it.

Borrowed

• cargo-mutants: a mutation run shards over mutant ids, not packages
• LPT list scheduling (Graham 1969): sort by cost descending, place each mutant on the least-loaded shard, which keeps the busiest shard within avg + (1 - 1/m) * largest
• Bazel: deterministic action output — the same inputs produce byte-identical plan JSON, so shards are reproducible and cache-friendly

Rejected

• index slicing (mutants[i::n] or chunked id lists): blind to the cost model, it parks the expensive mutants on one shard and makes the wall clock the max instead of the mean

Failing before (recorded)

1. The reported property, reproduced deterministically with the same generator and predicate (seed 6, runs 100) and shrunk to:

PlanShardsCommand {
  targetSeconds: 5e-324,
  maxShards: 1,
  mutants: [
    { project: "", id: "0000000000000000", costMs: 3.4927206787701224e+293 },
    { project: " ", id: "3bd10c5abb0509cc", costMs: 1.7976931348623123e+308 },
    { project: "", id: "5f6489e791d67f96", costMs: 1.8961673493674487e-132 },
  ],
}

planShards threw Error: Schema validation failed on it (Infinity shard total -> predictedSeconds rejected).

2. The new in-source refusal law ∀c_CostMsRefusal_≡RepresentableCostMs failed against the unbounded schema:

FAIL  src/plan-shards.workflow.ts > ∀c_CostMsRefusal_≡RepresentableCostMs
PropertyRefuted: ∀c_CostMsRefusal_≡RepresentableCostMs: the property was falsified. Property falsified after 1 run(s) and 1 shrink(s)
  Shrunk input: [0]
  Failure: returned false
  Replay: [0,"1718690611394657",0,0,[0],"ReturnedFalse"]

Gates (this worktree, rebased onto origin/main 5289c07)

command	result
stryker-js vitest run src/plan-shards.workflow.ts src/__tests__/plan-shards.workflow.property.test.ts	11 passed (6 generated codec laws + refusal law + 4 properties)
stryker-js vitest run tests/plan.integration.test.ts (after build)	1 passed
stryker-js vitest run tests/run-event-stream.integration.test.ts tests/framework-stream.integration.test.ts	11 passed
cli-contract vitest run tests/run-event-wire-line.integration.test.ts	5 passed
seed scan (3000 seeds x 100 runs, recorded predicate)	no falsification; the recorded command refused
derived-arbitrary audit (2000 draws)	every costMs <= 2^53-1
pnpm build (cli-contract, stryker-js; includes typecheck)	pass
pnpm lint (both packages), pnpm lint:tsgo	0 errors
pnpm format:check, pnpm guard:projects	pass
scripts/guards/check-contract-versions.ts	compared 4 contract documents, pass
scripts/guards/check-verdict-semantics.ts	declaration: unchanged

Mutation runs are never executed locally (engine refusal); the plan unit suites use fake/small fixtures.

[kiro-systemf]

Reviewed by Kiro: SOTA-ENGINE track 2: stryker plan packs mutants into deterministic LPT shards from the recorded cost model; getOrThrowWith only in an integration test. No threshold, exclude or scope change. All checks green on this head; merges cleanly after #183.