Version layers
Do not use one version as a substitute for another. A newer record can still follow the same schema; a recalculation under a new policy must retain its own provenance.
Breaking changes
Changing a field’s meaning, type, requiredness, units, sign convention, or calculation requires contract review and versioned client communication. Endpoint removal, changed authorization behavior, and changed idempotency or pagination semantics also require compatibility review. New optional fields can be additive when existing meanings remain intact. Enum additions must be announced. Retain raw provider statuses and handle normalizedunknown values where the resource defines them.