Books an update could write a newer format for open on their old format and are asked at every open; anything needing a new feature is refused until the owner agrees with the passphrase, after a verified backup that includes the keys. New books start on the current format. Each projection schema has its own database file, so an older version still opens the books until the owner agrees. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj