Upgrading an ObjectStack metadata project across a protocol major

preflight → mechanical chain → semantic residue → acceptance report

⛔ The boundary — read this before the first command

Never hand-write a rewrite the chain already applies. If a key was renamed, the conversion table knows the rename; running the chain attributes each rewrite to a hop and proves the result is schema-valid. A hand-edit does neither, and it silently diverges the moment the chain gains an entry.

Never add a tolerant read to make old metadata load. No ?? alias, no "accept both spellings" branch, no coercion in the project's own code. A key was retired because nothing enforced it or because exactly one spelling survives; re-admitting the old one at the consumer is how the defect the retirement closed comes back inside the customer's repo, where no gate can see it.