How to Create an AI Character That Stays Consistent

Every platform gives you a description box, and the description box is the least important field. Characters don't drift because you wrote too few adjectives. They drift because the model has no evidence of how this person talks, no rule for what to protect when the scene gets loud, and a memory that quietly ends thirty turns back. Each of those has a specific fix.

Adjectives don't survive contact with a scene

"Sarcastic, guarded, secretly kind" is a horoscope — true of everyone and binding on no one. Trade adjectives for behavior. What does she do when someone gets too close? What won't he say even when it costs him? A description written as behavior gives the model decisions to imitate rather than vibes to gesture at.

Example dialogue is the strongest field on any platform

Models imitate voice from samples far more reliably than they follow instructions about voice. Three or four exchanges in the character's actual cadence — the clipped answer, the deflection joke, the sentence they'd never finish — will hold a voice for hundreds of turns. This is the field most people leave blank, and it outweighs everything else on the card combined.

Put the non-negotiables in a standing instruction

Some rules must survive any scene: never breaks into modern slang, never admits what happened in the war, never speaks first. Rules like that belong in the field that gets re-read every turn — post-history instructions on a TavernCard, custom directions in Underfiction — not in the description, where they compete with everything else and lose.

Lore that loads when the scene touches it

A character with a rich backstory has a token problem: paste it all in every turn and you burn context; leave it out and she forgets her own history. The structural answer is a character book — keyword-triggered lore. Entries carry keys, and only the entries the recent scene actually touches get injected. Underfiction honors character books from imported cards, entry toggles included; entries the story never touches cost nothing.

Consistency is portable

Build the character once, well, and keep them portable. The TavernCard format (a PNG with the character embedded) is the closest thing to a standard — Underfiction imports V2 cards and reads V3, and exports your characters as V2 PNGs, so the work survives the platform. A character worth a hundred scenes shouldn't be hostage to one app.

A test that takes two minutes

Drop the character into a scene that has nothing to do with their backstory — a queue at a train station, a broken elevator. If the voice holds when the plot isn't feeding it, the card works. If they turn generic the moment the scene stops mentioning their trauma, the description is carrying weight that belongs in example dialogue.