Jev / Kev (TypeSafe System One)

Jev is TypeSafe’s System One model: a decision model rather than a text generator. A request carries a state (the text or record to evaluate) and a map of typed questions, and the answer is a calibrated probability per question. Kev is a family of small open-weight models that implement the same API, so one jev provider type covers both. There are three question types:

Type	Asks	Answer
`noul`	A yes/no question	`noul`: the probability of yes
`choice`	Pick one option from a set you define	`choice`, plus `probabilities` and `confidence`
`score`	Rate against ordered levels	`score`, plus `legend`, `probabilities` and `confidence`

The API is not OpenAI-compatible, and its answers have no chat equivalent, so GoModel does not translate it: System One requests go through passthrough at /p/jev/..., which is enabled by default for this provider. Chat, /responses, and /v1/embeddings return invalid_request_error for jev models.

Configure

For the hosted API, the key is the whole setup:

JEV_API_KEY=ts-...
GOMODEL_MASTER_KEY=change-me

For a self-hosted Kev server, set the base URL instead. Kev has no authentication of its own, so leave the key unset:

JEV_BASE_URL=http://host.docker.internal:8009
GOMODEL_MASTER_KEY=change-me

The default base URL is https://api.typesafe.ai, the origin TypeSafe’s SDKs use; a trailing /v1 is accepted and trimmed, so both spellings address the same server. To run the hosted API and a local Kev side by side, register the second under a suffixed name: JEV_KEV_BASE_URL=... creates provider jev-kev, reached at /p/jev-kev/....

Verify

curl -s http://localhost:8080/p/jev/v1/systemone \
  -H "Authorization: Bearer change-me" \
  -H "Content-Type: application/json" \
  -d '{
    "state": "Shoes arrived two weeks late and in the wrong size. Also I see two charges on my card.",
    "model": "jev-latest",
    "questions": {
      "department": {"type": "choice", "instructions": "Which team should handle this?",
                     "criteria": {"returns": "Exchanges, refunds, wrong or damaged items",
                                  "shipping": "Delivery status, delays, lost packages",
                                  "billing": "Charges, invoices, payment problems"}},
      "escalate":   {"type": "noul", "instructions": "Does this need urgent human attention?"},
      "frustration": {"type": "score", "instructions": "How frustrated is the customer?",
                      "criteria": ["Calm", "Frustrated", "Very angry"]}
    }
  }'

{
  "model": "jev-1.13.0",
  "answers": {
    "department":  {"type": "choice", "choice": "returns", "confidence": 0.21,
                    "probabilities": {"returns": 0.47, "shipping": 0.28, "billing": 0.25}},
    "escalate":    {"type": "noul", "noul": 0.93},
    "frustration": {"type": "score", "score": 1.44, "confidence": 0.78,
                    "legend": {"0": "Calm", "1": "Frustrated", "2": "Very angry"},
                    "probabilities": {"0": 0.00, "1": 0.56, "2": 0.44}}
  },
  "usage": {"input_tokens": 101, "output_tokens": 161}
}

The /v1 segment is optional: /p/jev/systemone is the same route. Use kev-latest as the model on a Kev server; it also answers to jev-latest.

Using the TypeSafe SDKs

The SDKs send POST {base_url}/v1/systemone, so point them at the provider’s passthrough root and authenticate with your GoModel key:

from typesafe_sdk import Noul, TypeSafeClient

client = TypeSafeClient(api_key="change-me", base_url="http://localhost:8080/p/jev")
response = client.system_one(
    state="I was charged twice. Please fix this ASAP.",
    questions={"billing": Noul(instructions="Is this ticket about billing?")},
)
print(response.nouls["billing"].noul)

import { TypeSafeClient, noul } from "@typesafe-ai/sdk";

const client = new TypeSafeClient({ apiKey: "change-me", baseURL: "http://localhost:8080/p/jev" });
const result = await client.systemOne({
  state: "I was charged twice. Please fix this ASAP.",
  questions: { billing: noul({ instructions: "Is this ticket about billing?" }) },
});
console.log(result.answers.billing.noul);

The same works with TYPESAFE_BASE_URL=http://localhost:8080/p/jev and TYPESAFE_API_KEY=change-me in the environment.

Native routes

Route	What it does
`POST /p/jev/v1/systemone`	Evaluate a state against a map of questions
`GET /p/jev/v1/models`	The names the `model` field accepts, in the upstream’s own shape
`POST /p/jev/v1/systemone/permute`	Kev only: run one Choice question with several option orders
`POST /p/jev/v1/systemone/separate`	Kev only: run each question in its own forward pass

Upstream errors keep their status code, with the provider’s body carried in the gateway error message: a malformed question comes back as TypeSafe’s 422 naming the offending field, and 429 or 529 mean back off and retry.

Models, access control, and cost

GET /v1/models lists what the upstream reports, as jev/jev-latest and so on. TypeSafe lists its aliases (jev-latest, jev-preview); a Kev server lists its checkpoint (kev-latest) and the aliases it answers to. Versioned IDs such as jev-1.13.0 are accepted by the model field whether or not they are listed. The models are categorized as utility models with no generation mode, since there is no OpenAI endpoint to route them to. Every System One request names its model, so the passthrough surface applies the caller’s model allowlist to it like any other request. The response’s usage.input_tokens and usage.output_tokens are recorded, so System One calls appear in the usage API and dashboard under the model that answered (jev-1.13.0, or the Kev checkpoint). Jev is priced per input token and is not in the upstream model catalog; declare its pricing on the provider to have those rows costed, or set it in the pricing override editor:

providers:
  jev:
    type: jev
    api_key: "${JEV_API_KEY}"
    models:
      - id: "jev-1.13.0"
        metadata:
          pricing:
            currency: USD
            input_per_mtok: 0.042
            output_per_mtok: 0

A local Kev server costs nothing per token, so it needs no pricing.

​Configure

​Verify

​Using the TypeSafe SDKs

​Native routes

​Models, access control, and cost

Configure

Verify

Using the TypeSafe SDKs

Native routes

Models, access control, and cost