Jev unlocks SO many awesome new ideas. I built a macOS app that monitors my Downloads folder along with a customisable set of rules. Is the downloaded file an invoice? Move it to a special folder with the correct filename. No other LLM calls involved - just Jev!
Core Concepts
Typed decision
A model output that conforms to a software type your code expects, rather than free-form text that has to be parsed.
- Category
- Core Concepts
- Also known as
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- Related terms
- 4
- Directory entries
- 2
- Docs
- docs.typesafe.ai
- Added
- 2026-09-24
Definition
System One is type-safe by construction: decisions and probabilities conform to the structured types and JSON schema your code expects. The model returns a distribution over the options you supplied, never a value outside the schema.
Typed decisions are what make Jev composable. They can be compared, thresholded, sorted, stored, and fed into further logic — or into a classical ML model — without the parsing layer that text generation requires.
Tagscorearchitecture
Related terms
Definitions that connect to this one.
System OneThe class of AI models built to make fast, structured decisions software can use directly, named after Kahneman's fast-thinking System 1.Core ConceptsAnswerThe structured result returned under a question's ID: a choice, a score, or a probability of yes, plus distributions and confidence.Core ConceptsAI-powered softwareThe architecture TypeSafe recommends: code owns the workflow and the model appears only where programmable common sense is needed.Core ConceptsComposable AITypeSafe's manifesto position: intelligence as a dependable primitive that software branches on, rather than an assistant that keeps humans in the loop.Core Concepts
From the directory
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.
Sites & GuidesDocs#official#docs#architecture
Official
Design AI-powered software by keeping code in control and giving System One narrow, structured decisions to make.
Practices & PatternsDocs#official#patterns#architecture
Official
From the community
Posts from builders shipping with Jev right now.
A Downloads folder that sorts itself
Which outreach signals book demos
JEV is insanely fast. We gave it a massive dataset based on thousands of outreach messages and asked: Which intent signals generated the most booked demos? 40 seconds later, we had the answer. Cost: less than $0.20. JEV can also rank leads, measure prospect-message fit, and Show more
Website to App turns any URL into a native app
Introducing Jev for 'Website to App' Turn any website into a native mobile app. Just paste a URL. jev-1.13.0 decides how to build the original website as a *native* mobile app, then shipper submits to the app stores for you. We’ve been using this internally a ton for Show more
@CompleteSkeptic
After co-inventing ChatGPT, I kept asking myself: why have superhuman chat models not led to AGI? I’ve spent the last 2 years in stealth building a new way to train models (RLCD), and a new type of frontier AI model that we are releasing today: Jev • 20-200x faster • 40-400x
The compaction plugin, in Spanish
Este tipo de herramientas empieza a hacer que el contexto de los agentes parezca menos una ventana limitada y más una memoria que se administra dinámicamente. [fast-jev-compaction] No resume, hace que Jev analice cada tool call y su resultado para decidir qué sigue siendo Show more
A computer assistant that listens
building a computer assistant with Jev local whisper listens to everything I say which then gets classified by Jev to determine what actions to take it uses a small Swift app to provide the full accessibility tree to Jev (i.e. tell its what's on my screen, what can be clicked, Show more
A job crawler that reads careers pages with Jev
I rebuilt my job crawler with Jev. The task: start at a company's official homepage, find Careers, and identify jobs that match my profile. Before, with an LLM: ~5 minutes. After, with Jev: just over 20 seconds in my test. Every company organizes its website differently. Jev Show more