Learn about Jev
10 guides to the Jev decision model. Every one of them is grounded in something specific — this directory's own submissions, our production review pipeline, or the vendor's published numbers with the caveats attached. Nothing here is a rewritten press release.
Updated September 2026
New to Jev entirely? Start with What is Jev? for the background, then come back here for the parts that need a longer answer.
Fundamentals
What a decision model is, and how it differs from an LLM.
- Jev vs LLM: a decision model is not a smaller text modelWhy a decision model and a text model aren't substitutes, where the boundary sits, and the cost math.7 min read
- How Jev sorts a build into one of 21 use casesThe 21 criteria Jev classifies against, published in full, plus what the reviewer sees and how ambiguity is handled.6 min read
What people build
Real submissions from this directory, grouped by the use case Jev assigned them.
- What people actually build with Jev, by use caseAll 21 use cases with live counts from real submissions, plus what each one is actually for.6 min read
- Jev in the agent loop: routing, guardrails, contextRouting, tool-call guardrails and context compaction — the three places a decision model earns its keep inside an agent.7 min read
- Open-source Jev: what is actually open, and what is notThe model is hosted, the tooling is open — the exact split, plus every open-source Jev repo in the directory.5 min read
- Wiring Jev into Claude Code and Codex via MCPPutting a decision model behind a coding agent: what MCP buys you, what to gate, and what we have not verified.6 min read
- Using Jev as a judge for evalsGrading with a decision model instead of a prose-writing judge, and why calibrated confidence is the real prize.6 min read
Cost, scale & trust
What it costs, what the published numbers actually mean, and where Jev falls short.
- Jev pricing, and what a real build actually costsPer-decision cost, the free-output explanation, and the input-price discrepancy nobody else flags.6 min read
- Jev statistics: latency, cost, and this directory's own numbersPublished benchmarks with their caveat attached, plus live directory figures that update automatically.5 min read
- Is Jev reliable? The honest limitationsWhat the no-hallucination claim really covers, where the accuracy ceiling sits, and the failure mode we hit ourselves.7 min read
The directory itself
BuiltOnJev is an independent community project, not affiliated with TypeSafe AI. Where public sources disagree on a specification we show both figures rather than picking one.