Ask a question.Read a probability.
Jev Studio is where you word the questions your code asks Jev, watch their probabilities move, prove them on labeled examples, and take calibrated decisions into production.
What is Jev Studio?
Jev Studio is a web workbench for Jev, the decision model by TypeSafe AI. Jev reads a text and answers typed questions (yes or no, pick one, or a position on a scale) with calibrated probabilities instead of generated words. Jev Studio is where you word those questions, prove them on labeled examples, and take them into code.
What is Jev?
Jev (typesafe-ai/jev) is a System One decision model. It answers a fixed set of typed questions about one text in a single pass and returns a probability and a confidence for each answer. It writes no free text and gives no reasoning, and it is billed on input tokens only.
TypeSafe documentationHow it works: the calibration loop
Four steps take a question from a hunch to a decision your code can trust.
- 01
Word the question
Write the text Jev should read and ask it yes or no, pick one of your options, or place it on ordered levels. Everything saves as you type.
- 02
Watch the number move
Every ask shows the probability, how decided the answer is, and how far it moved since the last wording. Drag a yes-or-no threshold on the answer itself.
- 03
Prove it on examples
Add texts with the answer each should get. Jev Studio shows how many a question gets right, which it misses, and the threshold that separates them best. Compare two wordings side by side.
- 04
Take it to code
Copy the request, decision code with your thresholds, and your labeled examples as test cases. What the studio shows is what your code decides.
Watch Jev answer
Three texts, three questions each, one of every type. Pick a text or let it play.
We waited forty minutes for a table we had booked, and the risotto arrived lukewarm. That said, our waiter was genuinely lovely and comped the dessert without us asking. Not sure we will be back.
375 ms for all three questions, 454 input tokens
Recorded answers from jev-1.13.0 on 2026-09-29. This page never calls Jev.
Should the owner answer this review personally within a day?
Yes or no0.82Yesat threshold 0.60What is the overall sentiment of this review?
Pick one0.88mixed- mixed 0.88
- negative 0.12
- positive 0.00
How many stars would the author most likely give?
Scale2 stars1.26 / 4
Jev or a prompted LLM as a classifier?
Both can label a text. They differ in what they hand your code.
| Aspect | Jev | Prompted LLM |
|---|---|---|
| What comes back | Jev:A calibrated probability per answer | Prompted LLM:Generated text you parse |
| Question types | Jev:Yes or no, pick one, ordered scale | Prompted LLM:Anything the prompt describes |
| Where the decision lives | Jev:An explicit threshold in your code | Prompted LLM:Implicit in the prompt wording |
| Billing | Jev:Input tokens only | Prompted LLM:Input and output tokens |
| Best for | Jev:Branching code on options you know in advance | Prompted LLM:Writing text and open-ended reasoning |
Measured, not promised
Measurements from Jev Studio and its harness, September 2026.
- for one question, asked through the deployed studio (29 Sep 2026)
- 476 ms
- to evaluate a set of five labeled reviews, four calls in parallel (29 Sep 2026)
- 656 ms
- routing decisions matched human labels in a pilot of the owner's agent harness (20 Sep 2026)
- 24 of 24
- per million input tokens, TypeSafe list price (20 Sep 2026)
- $0.042
Questions
Who can use Jev Studio?
Jev Studio is invitation only. The admin creates a one-time link that works for seven days; the invited person signs in with GitHub or sets an email and password. Each person sees only their own studies.
Which question types does Jev answer?
Three: yes or no (noul), which returns one probability; pick one (choice), which returns a probability for each option; and scale (score), which returns a position on ordered levels.
How do I choose a threshold?
Label a few examples with the answer each should get and evaluate the set. For yes-or-no questions Jev Studio suggests the threshold that gets the most examples right and stays farthest from every one of them, so small wording changes do not flip answers.
What does asking Jev cost?
Jev is billed on input tokens only; the list price was 0.042 dollars per million input tokens in September 2026. A single question over a short review cost about a thousandth of a cent. Jev Studio adds a daily limit per person.
Where are texts and studies stored?
Studies live on the server that runs Jev Studio, on a private machine in Germany. The texts and questions of each ask are sent to TypeSafe, a US processor, to be answered.
Does Jev replace a language model?
No. Jev decides between options you know in advance; a language model writes text and explores open questions. Use Jev where your code branches, and a language model where text is the output.
Ask a question.Read a probability.