Schema Compatibility Shadow Policy

This unpublished crate compares the frozen V1 schema lane with the Rust-SSOT V2 lane. A matching report is evidence about their shared domain, not evidence that V1 can represent the complete V2 contract.

Corpus completion criterion

The schema shadow corpus is complete enough for a cutover decision only when all of the following are true:

1. Both effective lanes accept every fixture in the declared overlap corpus.
2. Every comparison has ShadowVerdict::Matched and no findings.
3. ShadowCoverage::unimplemented() is empty.
4. ShadowCoverage::not_representable() is exactly the frozen set below.
5. Every non-representable dimension has independent V2 acceptance coverage.

Any additional blind spot blocks cutover. A rejection in both lanes is not a match and cannot satisfy this criterion.

The frozen V1-inexpressible set is:

• FunctionBodiesAndAnnotations
• StructFields
• SourceCommentsAndSpans
• OmittedVersusExplicitIdentity
• IndependentAnnotationIdentityAndRemoval
• SubAnnotations
• ExtensionsAndCapabilities
• ResolverGraphsAndOrigins
• CardinalityOutsideV1U32

Changing this set requires evidence that the frozen V1 representation actually gained or lost the relevant information. It must not be changed merely to make is_cutover_evidence() return true.