Drift happens because each scene prompt describes the character fresh,
and "fresh" means "slightly different" every time. The fix is a story
bible that locks canon once and feeds it into every generation.

WHAT THE BIBLE LOCKS — checklist format, so nothing is left to re-guess
  CHARACTER
    Physical: exact hair, eyes, build, age, distinguishing marks
    Wardrobe rules: what they wear, what they NEVER wear
    Voice: how they speak, verbal tics
  WORLD
    Logic, rules, look — so environments stay canon too, not just faces
  PLOT
    Beat-by-beat, so scene prompts inherit story context

WHY A CHECKLIST, NOT A PARAGRAPH
A prose description gets paraphrased differently each time it's used. A
checklist of locked attributes gets inherited verbatim — "hair: shoulder
length, copper, center part" is either in the prompt exactly or it
isn't. That exactness is what stops the drift.

THE PART THAT ACTUALLY FIXES IT — automatic inheritance
The bible is wired to feed banana-pro-director and cinema-worldbuilder,
so scene prompts pull the character lock automatically. You're not
re-pasting the description into shot 47 and hoping — the character
attributes are inherited into every prompt by the tools that generate
them. That's the difference between a document you maintain and a lock
that enforces itself.

WHEN TO BUILD IT
At the START of a multi-shot project, before you generate anything. A
bible written after 20 shots means 20 shots to redo. Build it first,
generate against it, and shot 1 and shot 50 share a face.

Describe your main character and I'll draft the locked checklist the
scene prompts will inherit.