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TypeSafe Jev: a System One model that returns judgments, not text
· typesafe, jev, system-one, classification, api, topxai
What Jev (jev-1.13.0) is, how noul, choice and score work, what the official docs say it is bad at, what it costs, and how to call it through TopxAI.
TopxAI now relays TypeSafe's Jev at 7% above the official price. This article is for developers deciding whether Jev belongs in their stack. Everything below comes from TypeSafe's documentation as of 2026-09-18, with the page named where it matters.
Three steps to a working setup
If you only want it running first:
Sign in to TopxAI and create a key on the API keys page. Pick the "TypeSafe · Official line" group; the "Auto route" group works too, since Jev has a single line and lands on it automatically.
The key's detail panel shows a setup command. Paste it into a terminal. It installs TypeSafe's agent skill, points the official SDKs and the skill at https://ai.topxea.com, and sends one test request to confirm the key works:
curl -fsSL https://ai.topxea.com/install/typesafe.sh | sh -s -- --key sk-xxxx
From there, code against TypeSafe's own documentation: docs.typesafe.ai, the API reference at docs.typesafe.ai/api and models and prices at docs.typesafe.ai/models. The endpoint and request bodies are identical to the official ones; only the base URL and the key are TopxAI's.
The script is safe to run again (every file it touches is rewritten in place); add --no-skill or --no-verify to skip the skill install or the test request. The rest of this article explains what Jev is, what it is good at and what it is not.
What a System One model is
A chat model produces text for a person to read. When your code needs a decision, you end up prompting for JSON, parsing it, and hoping the schema holds. TypeSafe calls Jev "the first System One model": you send a state and a map of typed questions, and it returns typed values and probability distributions. In the docs' words, "No text generation, no parsing."
The name comes from Kahneman's fast, intuitive System 1. The intended unit of work is a snap judgment a knowledgeable person could make in a few seconds, such as "Does this message convey urgency?" The docs are explicit that "Analyze this message and determine the best course o
Models: jev-1.13.0 · Models & pricing
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