typesafe-ai/jev, and what Parlour uses it for
Jev is the evaluation model Parlour runs on. It answers nine typed questions per character per beat in one call, is billed on input tokens only, and costs roughly three cents for a five-minute party.
- Model id
- typesafe-ai/jev (override with PARLOUR_MODEL)
- Called through
- experimental_evaluate from the ai package
- Per call
- nine questions, ~3,000 input tokens
- Billing
- input only
- A party
- ~250–300 calls, about 3–4¢
Jev is reached through the Vercel AI Gateway with the AI SDK's experimental_evaluate. One call hands it a JSON state object describing what a single character can see right now, plus the nine questions, and gets nine scored answers back.
What it is asked, and what it is never asked
It is asked what a person does. It is never asked what happened. It does not narrate, does not move anyone, never sees the resolution rules, and has no memory between calls beyond what the state object puts in front of it. The whole of what happens is lib/sim/engine.ts.
That division is why the simulation can be honest about itself. Because the model only ever supplies judgement, the screen can show you the judgement and the rule separately, and can say in amber when a rule overrules the judgement.
Swapping it out is not a config change
A chat model cannot stand in. It would not answer this shape: nine simultaneous typed questions with calibrated mass on every option. You could fake the answers with structured output, but then you get a self-report of confidence where you needed a measurement, and every threshold in the engine sits on that measurement.
With no key at all the rooms still run, on the house brain: a deterministic heuristic that answers the same nine questions and synthesises its own distributions.
Read next
What an evaluation model is
An evaluation model takes one shared state and a set of typed questions, and answers all of them in a single request. Each answer comes back as a full probability distribution instead of a sentence.
The nine-question pack
Every character answers the same nine questions every beat, in one evaluation call: action, target, mask, hunger, threat, betrayal, two questions the room cares about, and what they have left afterwards.
Running it through the Vercel AI Gateway
Parlour reaches Jev through the Vercel AI Gateway with one server-side key, and reads live per-token prices from the Gateway's model catalogue, so the cost counter on screen is a real number and not a constant.
The house brain: running with no model at all
The house brain is a deterministic personality heuristic that answers the same nine questions and synthesises its own distributions, so the simulation stays watchable, and tunable, with no API key and no network.
What a live LLM simulation actually costs
A Parlour party runs five or six minutes on roughly 250–300 evaluation calls of about 3,000 input tokens each, which is three to four cents. Every watcher of a room shares one party, so the bill does not grow with the audience.