create-rationale-contract

When to use this skill

After a Finding's protected property has been reviewed and confirmed by a human (not just proposed by the deterministic scan), capture it as a durable rationale contract so the next agent or reviewer does not have to re-trace the same history.

Workflow

1. Confirm the finding has moved from proposed to confirmed state (see .kiro/steering/evidence-policy.md) with a human actor recorded.
2. Create a new file at .whyguard/decisions/<short-slug>.yml following this shape:

   id: <short-slug>
   version: 1
   status: active
   scope:
     files:
       - <path/to/file.ts>
     symbols:
       - <symbolName>
   reason: >
     <one or two sentences describing the real-world incident or requirement>
   must_preserve:
     - <explicit behavioral property, phrased as an invariant>
   evidence:
     - type: issue
       id: "<number>"
     - type: pull_request
       id: "<number>"
   required_tests:
     - <path/to/regression-test>
   expires_when:
     - <condition under which this decision no longer applies>
   owners:
     - <team-or-individual>
   

3. Do not mark status: active unless a human has actually confirmed the property; if in doubt, leave it as a draft and ask.
4. Link the contract's id back to the originating finding for traceability.
5. If a decision is later superseded, set status: replaced or status: expired — do not delete the file; history matters as much for decisions as for code.

Anti-patterns to avoid

• Auto-generating a rationale contract straight from an unconfirmed proposed finding.
• Writing a vague must_preserve statement (e.g., "keep it safe") instead of a checkable invariant (e.g., "one idempotency key creates at most one order").
• Omitting evidence — a contract without evidence IDs cannot be audited later.