12. Versioning

The file format version is 6, stored in the header's version token and the footer's version field. Readers MUST reject every other value (unsupported_version). A change that an unmodified version-6 reader would misread requires version 7. There is no in-place compatibility path between file versions.

Each kind versions independently through v (§4.2).

• Adding an OPTIONAL member keeps v; older readers preserve it in extra.
• Removing a member, making one REQUIRED, or changing a member's type or meaning raises v. Older readers then keep the record opaque (§4.4), and it still round-trips through them.
• Adding a kind needs no version change; older readers keep it opaque.

This document is revision 6.0. A revision that only clarifies or adds OPTIONAL members, kinds or error kinds is 6.x. Report keys and error kind strings version together: adding one is a minor change with new conformance cases; removing one is a major change.