building-with-jev

# Building with Jev Jev reads one `state`, answers every question in the request independently and in parallel, and returns a probability distribution over answers you defined. A head cannot read another head's answer: parallel heads share evidence, not reasoning. For one state, maximize independent heads that can change a decision or action, subject to their token cost and the 64,000-token request budget; omit noise heads. Code owns control flow, arithmetic, policy, and every serial dependency; Jev owns the snap judgment. It does not reason in steps, count, do arithmetic, or generate text. Use this skill to design the questions, fit the state, compose answers in code, wire the call into a hook or script, and fix a call that answers wrong. **Before writing or changing any Jev request, apply [Jev production rules](../../shared-patterns/jev-production-lessons.md) and tick its pre-ship checklist.** It sets request size (2.5–4k tokens via Gateway until measured), per-run budget (~50k tokens), screen-then-detail above ~50 items, sending each stage at once with an instance cap of `floor(0.25 × 250,000 / tokens_per_request)`, retries by status code, eval pacing, caching, logging, and the order to measure failures. The rest of this skill is the method for designing questions; those rules govern how requests are sent. Its four facts come first: use Vercel AI Gateway; too much context is the most common failure, so split an oversized request into as many small requests as it takes (t...