Jev AI: the unofficial handbook

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What is Jev?The decision model that returns choices, scores and yes/no probabilities instead of text.

Your first Jev callFive minutes from API key to a working request in curl, Python or JavaScript.

Jev API pricing$0.042 per million input tokens, free output, and what real requests cost.

Errors and fixesEvery error code we reproduced, from 401 to max_tokens_exceeded.

Jev at a glance

Item	As of September 19, 2026
What it is	A “System One” model from TypeSafe AI that answers typed questions about text
Current version	Jev 1.13 (jev-1.13.0); jev-latest and jev-preview point to it
Question types	Noul (yes/no), Choice (one of up to 255 options), Score (your own scale)
Price	$0.042 per million input tokens; output is free
Speed	253 to 378 ms per small request in our tests (median 284 ms)
Input limit	About 32,000 tokens for the state plus the longest question
Access	Early access with a waitlist; also on Vercel, OpenRouter and Cloudflare

Popular questions

• Is Jev an LLM? What is known about how it works.
• Is Jev free? The free options and their catches.
• Why is there a waitlist? And how to use Jev while you wait.
• Can Jev hallucinate? What “can’t hallucinate” really covers.
• Is Jev open source? Weights, papers and local alternatives.
• Can Jev generate text? Why not, and how to pair it with an LLM.
• Why is it called Jev? The Jevons paradox behind the name.
• All questions

Four ways to call Jev

Channel	Model name	Before your first call
TypeSafe API	jev-1.13.0	Account approved from the waitlist
OpenRouter	typesafe/jev-1.13	Prepaid credits
Vercel AI Gateway	typesafe-ai/jev	A card on the Vercel team
Cloudflare Workers AI	typesafe/jev	A Cloudflare account

The differences that break code, such as the yes/no type being called boolean on Vercel and noul everywhere else, are in Jev channels compared.

What’s new

• Sep 19, 2026: Cloudflare adds Jev to Workers AI as typesafe/jev. We add first-hand error reference pages after testing every error code on the official API.
• Sep 18, 2026: OpenRouter lists typesafe/jev-1.13. The Python SDK reaches 0.7.0.
• Sep 15, 2026: TypeSafe launches Jev in early access. Vercel AI Gateway lists it the same day, free under a promotion that ends Sep 25, 2026.

Full history: Jev changelog.

Where to find things in TypeSafe’s docs

TypeSafe’s official documentation at docs.typesafe.ai is the primary source for everything on this site. If you are looking for a specific official page:

You want	Official location
The HTTP API reference	docs.typesafe.ai, “API reference”
Prices, limits and model aliases	docs.typesafe.ai, “Models”
How to write questions	docs.typesafe.ai, “Primitives (Questions)”
Known weaknesses of Jev 1.13	docs.typesafe.ai, “Jev 1.13 jaggedness”
Worked examples	docs.typesafe.ai, “Cookbooks”
Service status	status.typesafe.ai
API keys and the Playground	console.typesafe.ai

This site adds what the official docs do not cover: the resale channels, real error messages and where they differ from the docs, measured latency and cost, and plain answers to the questions developers keep asking.

About this site

Jev AI Guide is an independent handbook written by developers who use Jev. It is not affiliated with TypeSafe AI. Every page lists its sources and the date its facts were last checked. How we check what we publish.