• Jev outputs only floating-point confidence scores, not text. No output tokens means input-only pricing: $0.042 per million input tokens, undercutting GPT-5 Nano's $0.05/million input rate.
• Jev supports three query types: yes/no ("Noul," named for the Bernoulli distribution per TypeSafe's CEO on Hacker News), multiple-choice with a probability distribution, and score questions along a numeric range.
• Questions run in parallel against one input document, so sending hundreds of questions takes about as long as sending one. One use case: scoring 100 BM25-retrieved candidates for relevance in a search reranker.
• Willison flags a bias risk: asking Jev to rate whether Bay Area cities are a 'Good city?' returned Cupertino highest and East Palo Alto lowest, with no explanation for the score - a concern for uses like ranking job applicants.
• Within a week of release, open-weight clones appeared, including 'Kev' (0.8B/4B/9B models built on Qwen 3.5) and a community benchmark called JevBench for comparing decision models.

• token — The chunk of text a model reads and writes in — roughly three-quarters of a word — and the unit AI usage is billed in.
• AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
• open weights — A model whose trained parameters are published for anyone to download and run — unlike API-only models you can access but never possess.
• benchmark — A standard public test set for comparing AI models — the shared scoreboards behind every "model X beats model Y" claim.

Jev returns typed probabilistic decisions (yes/no scores, ratings, category confidences) instead of text, priced only on input tokens at $0.042/M, giving agent builders a cheap, fast primitive for classification-style sub-tasks.

• articleIntroducing System One Models and Jevalbelfio
• articleLangChain Benchmarks a Non-Generative Model as an Agent-Eval JudgeLangChain
• articleTypeSafe AI's Jev now available on AI GatewayRohan Taneja

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