Define what cannot drift
List the facts that break immersion if they change: ages, relationships, timelines, magic or technology rules, and point-of-view constraints. Put those in the Story Bible before long drafting sessions.
Add a short voice note — sentence length, humor level, sensory focus — so assistance mirrors how you want the book to sound.
Update as you discover
Discovery writing is welcome. When a new detail becomes canon, update the bible the same day. Stale bibles are the main reason AI drafts contradict earlier chapters.
After each major outline change, skim character goals and obstacles. Continuity is a maintenance habit, not a one-time form.