JEV GUIDE

What is Jev? A practical guide to decision models

Start with the answer your application needs: new text, or a decision that selects the next operation. This guide helps you find a small, useful place to try Jev.

Jev Gallery · Reviewed 2026-10-15

Separate the decision from the response

TypeSafe describes Jev as a System One model. It evaluates state using typed questions: Choice for a set of options, Score for a rubric, and Noul for the probability of a condition.

For an editor receiving “Export creates an empty file,” an application could judge whether a concrete failure is described, then open a bug-report form. A template or text model can handle the explanation shown to the user.

Source: TypeSafe · Introduction ↗

Find a project with the same shape

jev-ultrafast explores browser action selection. typesafe-mcp exposes decisions as a tool for coding assistants. Winnow filters tool output before it enters context. These are three different integration points: actions, tools and context.

Use the linked case pages to inspect each project’s inputs, decisions, execution and limitations. Match the smallest component to your problem before adopting a whole repository.

Design a small first experiment

Write down the trigger, required fields, allowed answers and action taken by the code. Prefer a reversible step, such as moving feedback into a review queue.

Pick one outcome to improve, such as time spent sorting feedback.
Include clear, ambiguous and incomplete examples with expected handling.
Record model decisions alongside existing rules before changing user outcomes.
Review mistakes before allowing any input class to route automatically.

Check whether a model is needed

Try ordinary code first for numerical comparisons, format validation or fixed-field matching. If the deliverable is an explanation, article or program, plan the generation and execution steps separately.

Source review is not a runtime acceptance test. Check dependencies, versions and failure handling in each case; one author’s speed demonstration does not establish performance for your application.

October 2026 version note

An experimental image and Box path is now documented. Box requires 1.14 and the image flag; older text examples are not image-localization examples. Follow the version update below for aliases, dependencies and formats. Existing text examples retain their original purpose.

Source: TypeSafe · Box ↗