= Cutdown Cross-Implementation Validation Policy

== Decision

Reference parser conformance is the required release gate.

Cross-implementation runs beyond the reference parser are encouraged but not required for change effectiveness.

== Required Gate

- For a change to reach ``Effective``, the reference parser must pass the required conformance corpus for the target version.

Reference parser governance status and divergence rules are defined in ``./reference-parser-status-policy.md``.

== Optional Validation

- Additional parser implementations may run the same corpus and publish results.
- These results are advisory and do not block ``Effective`` transition.

== Transparency Rule

- If non-reference implementations are known to diverge, release notes should include compatibility notes.

== Related

- [``./conformance-policy.md``](/latest/policies/conformance-policy)
- [``./change-publication-policy.md``](/latest/policies/change-publication-policy)
- [``./reference-parser-status-policy.md``](/latest/policies/reference-parser-status-policy)