Mutation Adequacy Skill

Overview

The mutation-adequacy review dimension is the adequacy backstop for the relaxed verification mix (verification ladder slice 3, R5). When the planner ships the cheaper testing strategy — strict types + inline invariants + one PBT + one acceptance test instead of granular per-behavior red-green — mutation adequacy is the machine guard against the vacuous tests (and vacuous PBT properties) that omission could otherwise admit. It scores whether the test suite actually kills injected mutants: the strongest signal that tests fail for the right reason.

This dimension gates the HIGH risk tier only, at the /review boundary only — it is the review-phase counterpart to the delegation-time check_test_adequacy (R3) gate. The coupling to the high tier is policy data in review-contract.ts (the dimension name = this skill's folder name); you never decide tier membership in this skill. The gate is a required review dimension of the high tier — a structural participation fact, distinct from severity (below). The action table registers it as [MUTATION_GATE_NAME]: adaptLadderGate(handleMutationAdequacy), and the severity wrapper withGateSeverity reads its gate name and dimension from the gate metadata of its registration.