#Jev

A decision catalog with numbers, not adjectives: ten tasks that run on a frontier LLM today and fit Jev's three primitives. One million calls in each case costs $46,200 on the LLM and $523 on Jev. It has the payload for each case, the cascade pattern, how to measure the migration in shadow mode without labeling anything, and the four tasks where Jev is the wrong choice.

TypeSafe launched Jev, the first System One model: it doesn't complete text, it takes your program's state and returns a typed decision in a single parallel pass. No parser, no retries, no broken JSON. In this post: what Jev actually is, why it can't hallucinate (and why that doesn't mean it can't be wrong), the real math on $0.042 per million tokens with free output, the three primitives with running Python code, and the 5 traps the docs themselves admit to.