EcosystemSystem One decision model
Decision model
A model that returns a typed decision — a choice, a score, or a probability — instead of generated text.
- Category
- Ecosystem
- Also known as
- System One decision model
- Related terms
- 4
- Directory entries
- 3
- Docs
- —
- Added
- 2026-10-11
Definition
Jev is the best-known decision model, but it is now one of several: Liquid AI's d1, Cloudflare's Clef, Perplexity's Decider, and open reproductions like Laya, Kev, and Bespoke Nimble all answer the same Choice, Score, and Noul shape with probabilities in place of prose.
The category is defined by its output rather than its architecture: the answer space is fixed before the call, so the model cannot emit an invalid type, and the response carries probabilities your code can threshold instead of text to parse.
Tagsecosystemmodels
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 ConceptsJevTypeSafe AI's flagship model and the first System One model: typed decisions and calibrated probabilities instead of generated text.Core ConceptsOpen weightsModel checkpoints published for anyone to download, run, and fine-tune, as opposed to a hosted closed API like Jev.EcosystemTyped decisionA model output that conforms to a software type your code expects, rather than free-form text that has to be parsed.Core Concepts
From the Jev directory
Liquid AI's 3.12B decision model built on LFM2.5-VL: state plus typed questions in one forward pass with zero output tokens, 48.57 on Decision Index 0.2.1 and 8 ms per decision on an RTX 4090.
Jev Models & Reimplementations#community#open-models#local
Community
8.9kGitHub stars
Apache-licensed, locally runnable Jev-style decision models (0.8B, 4B, 9B on Qwen3.5) with released weights, training code, a System One-compatible server, frozen eval suites, and a playground.
Jev Practices & Patterns#community#python#open-models
Community
jaredpalmer/kevPython
jaredpalmer/kevPython32.2kGitHub stars
Open multilingual System 1 decision models with published checkpoints for choice, score and noul questions, plus a router that dispatches each request to the right checkpoint in one forward pass.
Jev Repos & SDKs#community#python#open-models
Community
NandhaKishorM/layaPython
NandhaKishorM/layaPythonFrom the Jev community
Posts from builders shipping with Jev right now.