Clef is a decision model from Cloudflare, post-trained from Alibaba's Qwen3.8-27B with a joint schema head that reads the whole input once and scores every option of every question together. You send a state (text or any JSON value) and named questions, and it returns typed answers: the probability that a statement is true, a choice among options you define, or a position on your own rubric, each with a full probability distribution. It generates no text, so answers cannot fall outside the options given. Clef speaks the same request and response format as TypeSafe's System One API, so code written for Jev can switch models by changing the model name. Several questions can be asked about one state in a single request. Use it for decisions composed in code where accuracy matters more than the last few milliseconds: ticket and invoice routing, intent detection, tool selection, guardrail checks and rubric scoring in place of an LLM judge. Clef-flash is the smaller, faster sibling. Weights are published by Cloudflare under Apache-2.0 at https://huggingface.co/Cloudflare/clef.
Call Clef on Opper through the System One evaluation API. Sign up without a credit card. Get started
Clef runs on 1 route through the Opper gateway. Compare residency, zero data retention and training posture at a glance, with full data-handling detail per route below. In the EU it is served by Opper (Dublin). See every model hosted in the EU.
| Provider | Region | Zero data retention | Training | Input | Output | Cache read |
|---|---|---|---|---|---|---|
| EU | No | $0.24 | $0 | Input price |
Live routes and prices as JSON: api.opper.ai/v3/models?q=opper%2Fclef
Clef runs on a single route through the Opper gateway today, so its availability is that provider's availability.
Name a second model in the same request and the gateway tries it on retriable errors, so a busy hour never has to reach your users. Set up a fallback chain.
Measured over the last 30 days from each provider's official status feed via StatusGator. Refreshed hourly. See uptime for every provider Opper monitors.
Each route hosting Clef has its own privacy posture, residency, and GDPR terms. Postures are maintained by Opper with a last-verification timestamp.
Zero data retention: nothing is logged, held for abuse monitoring or used for training. No training on customer data. EU; DPA available.
Call Clef through the Opper gateway with one API key. Evaluate state against typed questions using TypeSafe’s System One API for yes/no decisions, classification, and rubric scoring.
See the Opper evaluation guide and the TypeSafe API reference for question types and response formats.
Clef is a premium model on Opper. Sign up needs no credit card: you get an API key straight away and the free models work in the playground and the API. Add a card to use premium models, pay-as-you-go with no minimum.
Copy this and paste it into a coding agent like Claude Code, Cursor or Codex and it'll wire up Opper for you.
curl https://api.opper.ai/v3/compat/v1/systemone \-H "Authorization: Bearer $OPPER_API_KEY" \-H "Content-Type: application/json" \-d '{"model": "opper/clef","state": "The customer cannot sign in and needs help immediately.","questions": {"is_urgent": {"type": "noul","instructions": "Does the customer need urgent help?"}}}'
Pick your tool to see how to run it on Clef through Opper.
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