Jev AIDeveloper Platform

What is Jev AI?

Jev AI is TypeSafe's System One decision model: you send state plus typed questions, and get Choice, Score, or Noul answers with calibrated confidence — probabilities and labels your code can branch on, not chat prose. This website is an independent third-party host (not the official TypeSafe product): try the playground free, then ship with prepaid jv_live_ keys against /api/v1/decide.

TypeSafe introduces Jev as a System One model aimed at structured decisions — labels and probabilities software can act on — rather than open-ended chat generation.

Deeper explainer: System One model · FAQ · API docs

Frequently asked questions about Jev AI

What is Jev AI?

Jev AI is TypeSafe’s System One decision model. It returns typed Choice, Score, and Noul answers your code can branch on — not chat prose. This site is an independent hosted API and playground, not the official TypeSafe product.

Can I try Jev free?

Yes. The homepage playground and /tools/ offer 5 free anonymous real-API runs with no signup. The Image / Box beta preview and games like 2048 and Snake can preview decisions with zero prepaid tokens — Image / Box remain dreamer-ready, not for production.

How does Jev API pricing work here?

Prepaid input-token packs start from $5. Output tokens are free on this host’s metering. See /pricing/ for pack sizes and rate bands — figures come from production billing config.

How do I get a Jev API key?

Sign in on Account, create a jv_live_ secret, store it as an environment variable, then call POST /api/v1/decide. Full steps: /jev-api-key/. Never put the key in a public frontend bundle.

Can I run Jev locally or download weights?

No. Jev is API-only today — there are no public downloadable weights for self-host. Inference runs in the cloud. Use this host’s decide API or an official TypeSafe channel when you have access.

What are Choice, Score, and Noul?

Choice picks one label from a closed set. Score places the state on an ordered scale. Noul returns a calibrated yes/no probability. Together they replace free-form chat strings for agent routing and gates.

Is this the official TypeSafe AI site?

No. jevtypesafe.org is an unofficial community host with its own accounts, prepaid balance, and jv_live_ keys. We are not affiliated with TypeSafe AI. Upstream keys stay on our servers.

This is an unofficial community resource. We are not affiliated with TypeSafe AI.

Full FAQ → · What is Jev AI (deep) →

When should you use Jev?

Why use Jev instead of a chat LLM?

Jev is the System One decision model introduced by TypeSafe AI. It is designed for AI agent pipelines where predictable, consistent decisions matter more than creative text generation. The core design philosophy is simple: Decisions not strings.

This unofficial host issues instant jv_live_ keys and meters prepaid capacity for /api/v1/decide, /api/v1/batch/decide, a free /api/v1/gate, and ready-made product paths — so you can ship agent routing without waiting on the official TypeSafe waitlist. Upstream keys stay on our servers.

Source reference: TypeSafe AI official announcement blog post.

System One vs System Two

The System One / System Two naming comes from behavioral psychology. In agent engineering terms, the split maps cleanly to two different jobs inside one pipeline. See the glossary for short definitions.

• System One (Jev): Fast, deterministic, consistent classification and decision making. Low variation, ideal for automated agent workflows.
• System Two (Generative LLM): Slow, flexible reasoning, text creation, open-ended conversation. Good for writing and complex reasoning.

Production stacks rarely pick only one. Most teams put Jev at the decision edge, then call a generative model only when the chosen path needs prose, tool planning, or deeper reasoning. Read the comparison page for a feature-by-feature breakdown.