Jev glossary
Core ConceptsSystem One model
System One
The class of AI models built to make fast, structured decisions software can use directly, named after Kahneman's fast-thinking System 1.
- Category
- Core Concepts
- Also known as
- System One model
- Reading time
- 1 min
- Related terms
- 5
- Directory entries
- 4
- Docs
- docs.typesafe.ai
- Added
- 2026-09-24
Definition
A System One model understands natural-language input like an LLM, but returns typed decisions and probabilities rather than generated text. You define the possible answers through the Choice, Score, and Noul primitives, and the model never invents a value outside them.
The name comes from Daniel Kahneman's Thinking, Fast and Slow: System 1 thinking is fast and intuitive, System 2 slower and more deliberate. System One models emphasize fast, focused judgments inside a larger code-owned workflow.
Tagscorearchitecture
Related terms
Definitions that connect to this one.
JevTypeSafe AI's flagship AI model and the first System One model: typed decisions and calibrated probabilities instead of generated text.Core ConceptsAI primitiveOne of TypeSafe's small, typed building blocks (Choice, Score, Noul) that pair a question with a typed answer you compose in code.Core ConceptsTyped decisionA model output that conforms to a software type your code expects, rather than free-form text that has to be parsed.Core ConceptsSystem Two taskWork that needs extended, multi-step reasoning; the docs treat it as a signal to decompose rather than a job for Jev.Core ConceptsAI-powered softwareThe architecture TypeSafe recommends: code owns the workflow and the model appears only where programmable common sense is needed.Core Concepts
From the Jev directory
Directory entries that go deeper on this term.
The idea behind Jev: models that return typed decisions and probabilities instead of generated text, named after Kahneman's fast-thinking System 1, with confidence to route around uncertainty.
Jev Guides & ArticlesDocs#official#docs#architecture
Official
The canonical introduction: Jev is TypeSafe's flagship model and the first System One model. Send state and typed questions, get structured answers your code can use directly.
Jev Guides & ArticlesDocs#docs#official#primitives
Official
The launch story: why TypeSafe built decision models, the side-by-side demo, the Doom and Wikiracing bots, and the published workflow evals.
Jev Guides & ArticlesArticle#official#announcement#benchmarks
Official
TypeSafe AI's official launch post: the company is out of stealth and developers can get access to Jev from the website, alongside the founder's launch thread.
Jev Guides & ArticlesPost#official#x#launch
Official
From the Jev AI model community
Posts from builders shipping with Jev right now.