In development ยท first playable targeted for Q1 2027
Worlds that remember.
Vivarium is a long-form AI roleplay and world-simulation app. Step into a living world as a character of your own. The people you meet keep their own schedules, beliefs and grudges. Skip ahead an hour, a day or a week, and the whole world catches up.
The AI controls expression.The application controls reality.
The AI narrates and gives every character a voice, but it never decides what is true. The world's state, the rules and every roll of the dice live in the application. Each turn runs in that order.
- You
You act
Say what your character does, in your own words. Persuade, sneak, bargain, fight, wait.
- The application
The world resolves
Your action is checked against the records and the dice are rolled. The outcome is written down.
- The AI
The narrator writes it
It is told what happened and gives every character a voice. Prose that contradicts the outcome is rejected.
The world's records
Places, items, time, and what every character knows, wants and thinks of you. Read before every turn, changed only by what the turn resolved, and kept with the cause of each change.
Four things that break a long AI roleplay, and what Vivarium does instead
- The story forgets.
- A long chat loses promises, secrets and old grudges as they scroll out of reach. Vivarium stores them as records: facts, memories per character, and threads left unresolved. You can open the memory inspector, read what the world remembers, and correct it.
- Memory that holds
- The scene drifts.
- Who is in the room, which door is locked, who is holding the letter. The application tracks places, presence and every item, and hands the narrator the scene as it stands before each turn.
- A world that moves when you move time
- Everyone agrees with you.
- Characters here have goals, fears and values with real weight. They can refuse, bargain, lie, hold something back or walk away. Asking nicely does not change what a character wants.
- Characters with minds of their own
- Nothing is at stake.
- A check is rolled against your character's skills and conditions before any prose is written. What you do to people is remembered by them, and by everyone who saw it or hears of it. The narrator cannot write its way around either.
- Dice and consequences
What that gets you
Every featureKnowledge kept apart from truth
Each character speaks only from what they know. They can be wrong, keep a secret, or repeat a lie they believe, and act on all of it.
Moments that are remembered
Insult someone, rescue them, betray them or apologise, and the application records the moment. It moves how they feel about you, and how everyone who saw it feels.
A turn you can take back
Every change is written down with its cause, so a turn can be retracted cleanly. The items, the injuries and the opinions return to where they were.
A world that catches up
Skip an hour or a week and the application works out the interval: who travelled, what changed, and what your character could plausibly have heard.
Your own worlds Subscription
Write places, people, items, lore, factions, routines, events and merchants, then play in them.
The model included Subscription
Choose the subscription with the model included and you need no provider account and no key. A monthly allowance comes with a meter you can see, and when it runs out play continues on a lighter model.
Everything above is built. Cards marked Subscription describe what the subscription adds; the rest is part of play on the free plan. The roadmap shows what is being built now.
Free to play, more with the subscription
There is a free plan and one subscription. The subscription comes two ways, which differ only in who provides the model, and you can switch between them in the app. Nothing is sold one piece at a time. No price is set yet, so none is given.
Free
The whole game at the table, on your own provider key.
- Decisions, checks, honest dice, travel and time.
- The living world when you skip time: schedules, factions, events, rumours, and word of what you did.
- Characters who remember, refuse and hold their own beliefs.
- Consequences, promises and standing, and a turn you can take back.
- Characters who age, change and raise children over a long story.
- The starter worlds, each with a full cast.
- Your own characters, and the character cards you already have.
- A few stories running at once.
- Download what you wrote, always.
Subscription
Everything on the free plan, still on your own provider key, and:
- Every premium world in the catalogue, with more added over time.
- World authoring: write your own worlds, or clone one and change it.
- Deep, permanent memory for very long stories.
- Many stories running at once.
Subscription with the model included
The same subscription, and Vivarium provides the model:
- No provider account and no key to set up.
- A monthly allowance, with a meter you can see.
- When the allowance runs out, play continues on a lighter model until the month resets.
- A second provider steps in if the first is down.
- Every turn names the model that wrote it.
If a subscription ends, nothing is deleted. What you wrote stays yours, and stories in premium worlds pause, stay readable, and resume where they were. The FAQ has the full answers.
From the devblog
All postsTen more phases, and a look at the screens
Fights, pronouns, characters you can keep, the first live playtest, and every screen laid out again. The site now has a Screens page, and the roadmap has a new order.
Six more phases done
The world has content, the table plays better, the catalogue is built, the subscription can include the model, and what you do now has consequences. The roadmap now shows everything left before launch.
The road to launch: four phases and one cut
Play quality, the world catalogue, launch readiness and hosting: the four phases left, and why sharing worlds between players is not in the first release.
Vivarium is built in the open, one milestone at a time. Subscribe with RSS to get new posts as they land, or write to hello@vivariumonline.com.