Closed answer space
Choice, Score, and Noul do not sample a paragraph. Jev Patterns declares the options. TypeSafe Jev fills a distribution over that set.
Independent library · jevpatterns.com
Jev Patterns: 12 TypeSafe Jev schemas you can copy.
Copy a paste-ready System One request, run it on your state, keep the threshold in your code. Not a chatbot. Not affiliated with TypeSafe AI.
Fixture · Support ticket routing
Open in Studio“Cannot log in. Reset email never arrives.” Closed options, not a drafted reply.
Demo fixture
418 in · 28 out
department
CHOICEaccount
confidence 81%
- account86%
- technical8%
- other3%
- billing2%
- sales1%
is_urgent
NOUL71%
Probability the statement is true. 50% means unsure, not medium.
How a call works
State in. Typed answers out. About 70–500ms.
01
State
A ticket, a chunk, a tool result, a form. Facts you already have — not a prompt to invent them.
02
Typed questions
Choice, Score, Noul. The answer space is closed before the call. Copy it from a Jev Patterns page.
03
Branch in code
Read the distribution. Auto-apply at high confidence. Ask a human in the middle. Keep the threshold in config.
Then calibrate on your labels. Run a fixture in Studio before you spend a key.
Three primitives
Every Jev Patterns schema is Choice, Score, or Noul
Choice
One label from a set you declared. The model fills a distribution. Your router reads the argmax and the peak.
Score
An ordered rubric. 0 Calm, 3 Outage. Do not round a Score into a boolean until the threshold says so.
Noul
Probability a statement is true. 0.5 is unsure, not medium. Gate on it; do not narrate it.
Probability you can branch on
Confidence is how peaked the distribution is. Put 0.75 in your router. Leave the fluent guess in the writer model.
Jev Patterns, not prompts
These schemas are starting points with paste-ready JSON. Calibrate on your labels. Keep policy in code.
What Jev Patterns is
TypeSafe Jev is a System One model: it takes state plus typed questions and returns Choice, Score, and Noul answers with calibrated probabilities. It does not generate text. Official launch was 15 September 2026. The public alias is jev-latest. Jev Patterns does not host that model. Jev Patterns collects the request shapes teams actually need — routing, agents, guardrails, moderation, growth, ops — so you are not inventing a schema from a chat transcript.
Search results for “ticket routing AI” and “JSON mode vs function calling” still assume a language model will emit an object you parse. That is a real stack. It is not this stack. Jev Patterns exists because the answer space should be closed before the call, and because confidence should be a peakedness number your if can see.
Use Jev Patterns when the next line of code is a switch. Use a writer model when the next line of code is a sentence. The TypeSafe Jev guide and the Jev vs ChatGPT page spell out that split. Jev Patterns will not put a chat bubble on a System One schema.
Catalog
Six Jev Patterns to start with
SupportCHOICENOUL
Support ticket routing
Send a ticket to the right department and flag whether it should jump the queue.
Open pattern
AgentsCHOICE
Agent tool selection
Given the current agent state, pick the next tool from a closed toolbox — including stop.
Open pattern
GuardrailsNOULCHOICE
LLM output guardrail
Decide whether a generated answer is grounded in the sources you actually retrieved.
Open pattern
OpsNOUL
Refund eligibility
Ask two Nouls: did they request a refund, and does the policy you passed in support one?
Open pattern
GuardrailsSCORE
RAG chunk relevance
Score each retrieved chunk on a 0–3 rubric before it is stuffed into the writer prompt.
Open pattern
GuardrailsCHOICE
Eval judge
Given a claim and a passage, choose supports, contradicts, or says nothing.
Open patternJev Patterns is not a chatbot
This is a category contrast, not a quality war. Use an LLM to write. Use Jev Patterns to judge, route, and gate. TypeSafe Jev returns typed decisions. Chat products return language.
| LLM string generation | Jev Patterns / System One |
|---|---|
| Samples tokens until stop. You parse the string. | Constrains the answer space by construction. No text to parse. |
| JSON mode still emits field values as language. | Choice / Score / Noul return distributions over the criteria you declared. |
| Confidence is a vibe in the prose. | Confidence is how peaked the distribution is. Branch on it. |
| Great at writing, summarizing, chatting. | Great at routing, scoring, and gating. About 70–500ms. No generation. |
How to use Jev Patterns
- Pick a schema from the Jev Patterns catalog that matches a switch in your code — not a paragraph you wish someone would write.
- Copy the request JSON. Point
stateat your ticket, chunk, form, or tool result. Keep the question keys stable so logs stay comparable. - POST to
https://api.typesafe.ai/v1/systemonewithmodel: "jev-latest", or run the fixture in the Jev playground first. - Put thresholds in config: auto-apply at high confidence, human review in the middle. Read confidence thresholds.
- Calibrate on your labels. Jev Patterns are starting points, not warranties.
Who Jev Patterns is for
Platform engineers wiring support queues. Agent authors who need a next tool enum instead of another parser. RAG owners who want a chunk Score before they spend a writer turn. Trust and safety teams who need parallel Nouls, not a chatbot that explains the violation. If you are looking for a ChatGPT clone, you are on the wrong site. See when not to use Jev.
Jev Patterns is published on jevpatterns.com. It is not a product of TypeSafe AI. Official documentation remains docs.typesafe.ai. Read about for the full disclaimer.
What you will not find on Jev Patterns
No accounts. No hosted quota. No chat widget. No purple gradient. No promise that a schema is calibrated on your labels. Jev Patterns is the missing catalog between a model launch and a production switch statement. If you need TypeSafe to sign a DPA, that is their site. If you need a department Choice that will not emit “finance,” that is this site.
Next
Go deeper than the homepage
Frequently asked questions
- What is Jev Patterns?
- Jev Patterns is an independent library of reusable decision schemas for TypeSafe Jev. Each Jev Patterns entry is a paste-ready System One request: state, typed questions, and the thresholds that belong in your code.
- What is TypeSafe Jev?
- TypeSafe Jev is a System One decision model. You send state and typed questions; it returns Choice, Score, and Noul answers with probabilities. It does not generate text. Official product: typesafe.ai.
- Is TypeSafe Jev a typeface?
- No. TypeSafe (sometimes searched as typeface or typespace) is the company. Jev is their System One decision model, not a font.
- What is Noul in Jev?
- Noul is TypeSafe Jev’s yes/no primitive: P(true) in [0, 1], not a boolean. Full guide: What is Noul in Jev on this site.
- Is there a Jev playground?
- Yes. Jev Studio on this site is a fixture playground: no account, no API key required. Paste a TypeSafe key only if you want a live call.
- How do I get a Jev API key?
- Sign in at console.typesafe.ai — TypeSafe dropped the waitlist on 20 September 2026. New users start with $5 credit, per TypeSafe. Gateways include OpenRouter, Vercel, Cloudflare, Netlify, Venice, and AI/ML API. See Where to call Jev.
- Is Jev Patterns a chatbot?
- No. Jev Patterns does not chat, write emails, or generate code. TypeSafe Jev returns Choice, Score, and Noul answers. Jev Patterns packages those primitives into schemas you copy.
- Is Jev Patterns affiliated with TypeSafe AI?
- No. Jev Patterns is independent and not affiliated with TypeSafe AI. Official product: typesafe.ai. Official docs: docs.typesafe.ai. If this site disagrees with the docs, the docs win.
- How do I use Jev Patterns with jev-latest?
- Copy the request JSON from a Jev Patterns page, POST it to https://api.typesafe.ai/v1/systemone with model jev-latest, and branch on the returned distributions. Or open the Jev playground and run the fixture first.
- What problems do Jev Patterns solve?
- Jev Patterns covers support ticket routing, urgency scoring, agent tool selection, guardrails, moderation, lead intent, refunds, duplicates, escalation, RAG chunk relevance, and eval judging — decisions software can take without parsing a paragraph.
- Do I need an API key to try Jev Patterns?
- No. The Jev playground draws fixture bars with no key. A TypeSafe key is optional and stored only in your browser. Live calls may fail CORS; Studio stays on the fixture.
Last reviewed 2 October 2026. Independent of TypeSafe AI.