Jev topics
Short, focused answers to the things people ask about Jev — the System One model from TypeSafe AI. Pick a topic, then try it live in the playground.
Jev vs ChatGPT and other LLMs
Jev vs ChatGPT is not a fair fight, because the two do different jobs: Jev vs ChatGPT is really typed decisions versus free-flowing text. Where an LLM writes, Jev returns a calibrated answer locked to a type you declare.
The Jev benchmark, in plain numbers
Every Jev benchmark you will see today is about speed, cost and calibration — not a public accuracy leaderboard. This page explains what the published figures actually mean and how to test them.
What is a System One model?
Jev is TypeSafe AI's first System One model, launched in September 2026. A System One model returns fast, calibrated decisions instead of text.
How the Jev architecture works
The Jev architecture is best understood from the outside in: Jev returns typed, calibrated decisions instead of text. This page describes the observable Jev architecture, since TypeSafe AI has not publicly disclosed the model's internal weights or parameter count.
RLCD: how Jev is trained
RLCD stands for Reinforcement Learning for Calibrated Decisions, the training method behind Jev. Instead of optimising for fluent writing, it optimises for calibration — so when Jev says 80%, it is right about 80% of the time.
What is a noul in Jev?
A noul is Jev's yes/no primitive. Instead of a bare true or false, it returns a single calibrated number from 0 to 1: the probability that the answer is yes.
Using Jev as a classifier
A Jev classifier picks exactly one of your labels and returns it with calibrated probabilities and a confidence value, so there is nothing to parse and no way to get an invalid class back.
Jev models and versions
The Jev models you call are the same System One engine behind one of two names: jev-latest, a moving pointer, or a pinned version like jev-1.13.0 that never shifts under you.
Running Jev locally
If you are searching for Jev local, the honest answer is that you cannot run Jev locally: it is a hosted API with no public weights, and there is no supported way to self-host the model.
How to get a Jev API key
Getting a Jev API key takes two minutes. You can join the official TypeSafe waitlist, or skip the line entirely with our hosted Jev API key that works the moment you sign in.
Diogo Almeida and Jev
Diogo Almeida is a former OpenAI researcher and a co-inventor of the RLHF work behind ChatGPT. Today Diogo Almeida is the mind behind Jev, TypeSafe AI's first System One model.