Jev is TypeSafe’s System One model: it takes application state, answers explicit narrow questions with a typed result and a confidence, and hands the answer back to code that stays in charge of what happens next.
Official Documentation
The shape of an integration
01Unstructured stateWhatever your application already has: a message, a diff, an event, a screen, a row.
02Narrow independent questionsDecomposed so each one can be answered on its own, and many can be asked at once.
03Choice · Score · NoulThe typed primitives. A bounded option, a calibrated number, or a probability.
04Probabilities and confidenceOrdinary values your code can threshold, log, compare, and regression-test.
05Deterministic application codePolicy, side effects, retries, and anything that has to be reproducible.
The interesting consequence is the last row. Because the model returns a value rather than prose, the decision boundary between the model and your program is explicit — which is what makes the rest of this atlas possible to reason about.
Jev is
A fast, narrow judgment layer that application code calls like any other function.
Typed output, so there is no free-form response to parse or repair.
Cheap enough per call that judging every item in a stream becomes affordable.
A source of probabilities that deterministic code composes into policy.
Jev is not
Not a chat interface. There is no conversation, persona, or message history to manage.
Not a code generator. It answers questions; it does not write your implementation.
Not autonomous control flow. It never decides what runs next — your code does.
Not a replacement for deterministic rules. Anything that must be exact stays in code.
Not a correctness guarantee. A typed answer constrains the shape of a decision, not its truth.
What is actually established
This atlas separates what has been demonstrated from what TypeSafe says about its own product. Both matter; they are not the same kind of statement.
Demonstrated · 3
Jev exposes constrained decision primitives for Boolean probability, choice distributions, and ordered scores.
Typed output removes free-form parsing but does not make wrong decisions impossible.
Developers have published small Jev integrations and demonstrations.
Vendor claim · 2
TypeSafe reports Jev as materially faster than LLM workflows on its own evaluations.
TypeSafe reports a low input-token price and no metered output-token charge for Jev.