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Large Language ModelsAI Business & IndustrySimon Willison's WeblogPublished: Sep 22, 2026, 10:01 JST

TypeSafe AI's Jev: decision model at $0.042 per million tokens

TypeSafe AI's Jev: decision model at $0.042 per million tokens

3 Key Points

  1. What happened

    TypeSafe AI unveiled Jev, a "System One" model that takes text and returns floating point numbers for yes/no, choice, and score questions, priced at $0.042 per million input tokens with free output.

  2. Why it matters

    Jev's typed probabilistic outputs and low price make it suited to classification tasks like spam detection and ranking, but its opaque numbers may conceal bias, the article notes.

  3. What to watch

    The article warns that Jev's floating point outputs could hide unseen bias, making structured evals essential; meanwhile, community projects like Kev are already recreating Jev-class models using Qwen 3.5.

WHO IT HITSDevelopers building classification, spam detection, or search reranking pipelines may find Jev's cheap input-only pricing attractive, though teams ranking people, such as in hiring, face hard-to-audit bias risks in its opaque scores.

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Context & Analysis

TypeSafe AI's Jev arrives as a deliberate break from the text-in, text-out LLM pattern. Instead of generating prose, it accepts a "state" object—a string, array, or name-value pairs describing a record—and returns typed probabilistic outputs: a confidence score for a statement, a probability distribution across choices, or a number along a provided scale. The company frames it as a "frontier-intelligence function call," and prices it unconventionally: input only, at $0.042 per million tokens, with output free.

The appeal is speed and cost for classification-shaped work. The article points to spam detection, labeling, prioritization, ranking, and search reranking as natural fits, where many questions can be evaluated in parallel against a single document. But the design also strips away even the illusion of explanation that text-generating LLMs offer. As the article puts it, if Jev marks something as spam, the only thing you get back is a floating point number, leaving which content signals drove the decision unclear.

That opacity is why the article singles out bias as a first-order concern, floating the example of ranking job applicants, where an unexplained score could conceal unseen bias that is experimentally tricky to pick apart. One informal experiment scoring Bay Area cities on "Good city?" ranked Cupertino top and East Palo Alto bottom—a result the author flags with a "Huh." The stakes, then, may hinge less on Jev's speed than on whether its cheapness (hundreds or thousands of experimental prompts for a few cents) makes rigorous evals practical enough to expose what its numbers are actually measuring.

FAQ
How much does Jev cost?
Jev charges only for input, at $0.042 per million tokens, with output free—cheaper than OpenAI's GPT-5 Nano at $0.05/million.
What kinds of questions can Jev answer?
Jev supports yes/no ("Noul"), choice, and score questions, returning confidence scores or probability distributions.
Can Jev be recreated with open weight models?
Yes, projects like Kev use Qwen 3.5 to produce 0.8B, 4B, and 9B models, with a JevBench benchmark comparing "Jev-class decision models".
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