When to use Jev
Use Jev when a knowledgeable person could answer in a few seconds from text you already have. Skip it when the work is exact compute, long reasoning, generation, or a regulated attestation.
Independent operate page. Official: System One vs tasks that need extended reasoning. docs.typesafe.ai.
Independent angle (cover, do not clone)
Win delta (jev-vs-llms): hybrid decide-then-draft; cost/latency honesty; when not to use System One — Kahneman framing lives on the explainer, production “when” lives here.
Use Jev
- Intent / queue / tool / model routing
- Policy and injection screens (not a WAF)
- Completeness / consistency flags on text packets
- Composite Scores you weight in code
- Confidence-gated auto vs review
Do not use Jev
- Math, counts, date order (jaggedness)
- Image/audio/video as raw input
- Being the agent, the ESP, the bidder, or the KYC vendor
- On-device offline
- “Write the email”
Compose with LLMs
Decide (Jev) → draft (LLM) → optional second Jev screen on the draft. Label every latency and dollar figure as vendor unless you measured it.
A one-line test
“Could a sharp teammate answer this in a few seconds from this text, and can our code act on a label?” If yes, Jev is in-scope. If you need a proof, a picture, a generated paragraph, or a legal attestation, it is not.
What this page does not claim
- Not a complete use-case map — see TypeSafe’s use-case page and our /usecases.
FAQ
System Two work? Keep it in tools and checkers. See System One vs Two.
Healthcare / hiring / credit? Assume no unless counsel designs a narrow admin hop. See those comparison pages.
Disclaimer
This is an independent unofficial site and is not affiliated with TypeSafe AI; official documentation is available at https://docs.typesafe.ai. Never treat jev.pro as TypeSafe official documentation. We do not sell, issue, or proxy API keys.
Open-cluster pages are independent field-guide notes. Replicas and third-party interfaces mentioned anywhere on jev.pro are not Jev and not endorsed. Hub: Open. Siblings: why use jev, system one vs system two, vs prompt only systems. Canonical: https://docs.typesafe.ai.
Sources
Public TypeSafe or adjacent documentation only. No private claims.