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System One

Workflow control

Decide where a piece of work goes next and whether your code is allowed to act on it without a person.

4 use cases

Workflow controlIntermediate

Confidence-gated actions with System One models

Jev returns a confidence value from 0 to 1 alongside every Choice and Score answer. Your code treats it as a separate axis: act automatically when it's high, confirm or flag when it's middling, hand the decision to a person when it's low. Riskier actions get higher bars.

ChoiceScore
Workflow controlIntermediate

Intent and model routing with System One models

One Jev call reads an incoming request and returns its intent as a label plus a difficulty rating on a scale you wrote. Your router reads both numbers and picks the handler: deterministic code, a cheap model, an expensive one, or a human queue.

ChoiceScore
Workflow controlStarter

Support inbox triage with System One models

Send a support ticket to Jev once with every question attached. Category comes back as a selected label, severity and frustration as numbers on scales you wrote, refund intent as a probability. Your code reads those values and decides what happens to the ticket.

ChoiceScoreNoul
Workflow controlAdvanced

Typed tool dispatch with System One models

Ask Jev one Choice question over your tool names and one per closed-set argument, so every value that comes back is a value the function already accepts. Nouls decide whether an optional argument was mentioned at all. Your code assembles the call and runs it.

ChoiceNoul

Examples in this category

All examples

Things people have built and written that match one of the use cases above.

Article

[AINews] Jev: a System One Model that only decides/classifies/routes/scores

AI News daily roundup leading with the Jev launch, summarising RLCD and TypeSafe's 20-200x speed and 40-400x cost claims. Frames Jev as part of a broader move toward task-specialised models.

Project

Ran Jev against an existing classifier eval that previously used Gemini 2.5 Flash Lite

Vercel CTO reports Jev saturated an existing classifier eval that had used Gemini 2.5 Flash Lite and ran about 6x faster. Original post; TypeSafe's quote-tweet is a separate item.

Discussion

Introducing System One Models and Jev (Hacker News launch thread)

The 1,863-point, 490-comment launch thread. Top comments argue the frontier-model framing is misleading, dispute the cannot-hallucinate claim on the grounds that type safety is not factual correctness, and note grammar-constrained decoding on ordinary LLMs already covers much of the interface.

Alternative

DSPy: programming, not prompting, language models

Declares typed input/output Signatures for LLM modules and optimizes the underlying prompts and weights against a metric. Its Signature abstraction is the closest widely-used open equivalent of Jev's typed-question interface. Star count is GitHub's rounded display figure.

Alternative

SetFit: efficient few-shot text classification

Fine-tunes Sentence Transformer embeddings plus a lightweight head for high-accuracy classification from a handful of labeled examples, with no prompting. The standard cheap alternative to an LLM classification call when the label set is fixed. Star count is GitHub's rounded display figure.

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