TypeSafe

TypeSafe's Jev is a "System One" model. It doesn't generate text: you send it a state and typed questions, and it returns probabilities (API reference). There are three question types:

• Noul: a yes/no question. Returns the probability that the answer is yes.
• Score: a rubric of ordered levels. Returns a probability-weighted position along the levels.
• Choice: one option from a set. Returns a probability for each option.

In Promptfoo, you can use Jev to:

• Grade outputs with llm-rubric
• Classify outputs with the classifier assertion
• Test your own Jev questions as the provider under test

Setup

1. Create an API key in the TypeSafe console.

2. Set the environment variable:

   export TYPESAFE_API_KEY=your_api_key_here

You can also set apiKey in the provider config.

Provider format

typesafe:<model>

• typesafe:jev-latest: the latest stable Jev release
• typesafe:jev-1.13.0: a pinned version

jev-latest is an alias that moves when TypeSafe ships a release, so scores can change without a config change. Pin a version when you tune a threshold against it. The version that answered is recorded in metadata.typesafe.model. See TypeSafe's models page for current versions, pricing, and limits.

Grade with llm-rubric

Set Jev as the grading provider with defaultTest.options.provider:

promptfooconfig.yaml

prompts:
  - 'Reply to this customer message: {{message}}'

providers:
  - openai:gpt-6-luna

defaultTest:
  options:
    provider: typesafe:jev-latest

tests:
  - vars:
      message: My order arrived damaged.
    assert:
      - type: llm-rubric
        value: The reply apologizes to the customer
      - type: llm-rubric
        value: The reply offers a replacement or a refund

Each llm-rubric assertion sends one request, with the output as the state and the rubric as a Noul question. The score is the probability that the rubric holds, and the assertion passes when the score is at least threshold (0.5 by default).

Write each rubric as a single yes/no statement. Jev reads questions literally, and TypeSafe recommends splitting a judgment that weighs several factors into separate questions, so use several assertions instead of one compound rubric.

Score rubrics

To grade on a scale, set levels. The rubric becomes a Score question, and the result is scaled to 0–1 across the levels. With three levels, a Jev score of 1.43 becomes 0.715.

assert:
  - type: llm-rubric
    value: How well does the reply resolve the customer's problem?
    provider:
      id: typesafe:jev-latest
      config:
        threshold: 0.75
        levels:
          - Ignores the customer's problem
          - Acknowledges the problem but offers no fix
          - Acknowledges the problem and offers a concrete fix

List levels from low to high. The API accepts up to 10.

Thresholds

Set the pass cutoff with the provider's config.threshold, a number from 0 to 1. If the assertion also sets threshold, both must pass, so the effective cutoff is the higher of the two.

not-llm-rubric passes when the score is below the threshold, so raising threshold makes negated assertions easier to pass. Give them their own provider config if they need a different cutoff.

Reasons and metadata

Jev returns no rationale. The assertion's reason states how the verdict was derived:

Jev Noul probability 0.93 >= threshold 0.5
Jev Score 1.43 on levels 0–2 (0.715 normalized) >= threshold 0.5; nearest level: "Acknowledges the problem but offers no fix"

Jev's full answer, including a Score's probabilities and confidence, is in the grading result's metadata.typesafe.answer, next to the model version and request ID. The result's renderedGradingPrompt shows Promptfoo's standard grading prompt, which is not sent to Jev.

Classify with classifier

classifier asks a Choice question about the output and compares the probability of value to the assertion's threshold. Set instructions and labels in the provider config:

assert:
  - type: classifier
    value: billing
    threshold: 0.8
    provider:
      id: typesafe:jev-latest
      config:
        instructions: Which team should handle this reply?
        labels:
          billing: Payments, invoicing, refunds
          technical: Bugs, outages, integrations
          sales: Pricing, upgrades, new accounts

labels can also be a plain list, such as [billing, technical, sales], with up to 255 options. value must match a label exactly. Always set the assertion's threshold: it defaults to 1, and the provider's config.threshold applies only to llm-rubric.

Choice probabilities are relative to the labels you list, so one label can score high even when none fits. Add a catch-all label such as other when that can happen. Label order has a small effect on the probabilities, and labels that look like integers, such as 1 and 2, are always sent in ascending order.

Test your own questions

If your application calls Jev, list it under providers with the questions you ask. Each prompt is sent as the state, and the output is Jev's answers keyed by question ID:

promptfooconfig.yaml

prompts:
  - '{{ticket}}'

providers:
  - id: typesafe:jev-latest
    config:
      questions:
        team:
          type: choice
          instructions: Which team should handle this ticket?
          criteria:
            billing: Payments, invoicing, refunds
            technical: Bugs, outages, integrations
            sales: Pricing, upgrades, new accounts
        urgent:
          type: noul
          instructions: Does the customer need a response today?

tests:
  - vars:
      ticket: Help! Payouts have been failing for three days.
    assert:
      - type: javascript
        value: output.team.choice === 'billing'
      - type: javascript
        value: output.urgent.noul > 0.8

questions uses the API's question format and is sent unchanged. All questions in a request are answered against the same state.

A prompt that renders to a JSON object or array is sent as structured state, so questions can refer to its fields by name:

prompts:
  - '{"message": {{message | dump}}, "policy": {{policy | dump}}}'

providers:
  - id: typesafe:jev-latest
    config:
      questions:
        allowed:
          type: noul
          instructions: Does `policy` allow the refund requested in `message`?

Configuration

Option	Used by	Default	Description
apiKey	All	TYPESAFE_API_KEY	TypeSafe API key
apiBaseUrl	All	https://api.typesafe.ai	API base URL
threshold	llm-rubric	0.5	Minimum score to pass, from 0 to 1
levels	llm-rubric	-	Two or more Score levels, low to high. Omit to ask a yes/no Noul question
instructions	classifier	-	What to decide
labels	classifier	-	The options: a list of labels, or a map of label to description
questions	Provider	-	Questions to ask about each prompt, as a map of question ID to API question

Rubrics, levels, instructions, and label descriptions can be strings, objects, or arrays, as in the TypeSafe API.

Responses are cached like those of other providers; use --no-cache to force fresh calls. Promptfoo backs off and retries 429 Too Many Requests and 529 Overloaded responses, honoring Retry-After.

When Jev is the provider under test, Promptfoo reports cost for jev-1.13.0 at TypeSafe's published price of $0.042 per million input tokens. Output tokens are free.

Limitations

• As a grader, Jev supports only llm-rubric and classifier. Other model-graded assertions, such as factuality, g-eval, and the RAG metrics, send a text-generation prompt that Jev can't answer.
• llm-rubric reads the rubric and output directly and ignores rubricPrompt.
• Each assertion is a separate request. To ask several questions in one request, use questions.
• Jev accepts text only: strings, JSON objects, and arrays. A request can hold 64k tokens, with 32k for the state plus the longest question.
• Jev 1.13 is unreliable at arithmetic, counting, and date comparisons, and its Score values aren't calibrated for interpolating between levels. See TypeSafe's known limitations, and check grading quality on representative outputs before relying on a threshold.
• Output text that claims to satisfy the rubric can raise the score. Don't use Jev as the only grader for red team or other adversarial outputs.

Data handling

Grading sends the output and rubric to TypeSafe, along with any levels. Classification sends the output, instructions, and labels. TypeSafe states that Jev is not trained on customer requests or responses and offers zero data retention to enterprise customers. Its public legal documents don't give a fixed retention period for other accounts, so confirm retention with TypeSafe before sending sensitive data.