jevper¶

Typed questions for OpenAI-compatible models. jevper turns a state string and noul, choice, or score questions into typed answers with probabilities and confidence.

jevper is an independent implementation of the documented System One wire format. It is not affiliated with, endorsed by, or supported by TypeSafe AI. The package does not call the hosted TypeSafe API and does not import an OpenAI or Anthropic SDK at runtime.

Install¶

Python 3.10 or newer is required. Install the package from PyPI:

pip install jevper

The only runtime dependency is pydantic>=2.7. You provide a client object; jevper does not read credentials or provider configuration from the environment.

First call¶

from openai import OpenAI
from jevper import Choice, SystemOneClient

client = SystemOneClient(OpenAI(), model="gpt-5.6-terra")

response = client.system_one(
    state="I was charged twice for the same subscription this month.",
    questions={
        "intent": Choice(
            instructions="Pick the intent of the message.",
            criteria={
                "billing": "money, invoices, refunds, charges",
                "technical": "errors, crashes, login or performance problems",
                "sales": "pricing, plans, purchasing, upgrades",
            },
        )
    },
)

answer = response.answers["intent"]
print(answer.choice, answer.probabilities, answer.confidence)

method="auto" is the default: jevper uses logprobs when the provider returns a usable distribution and falls back to structured output when it does not. The method, surface, retries, and per-question usage are available in response.debug and response.usage.

Choose a page¶

How a call is selected¶

flowchart LR
    A["State and typed questions"] --> B["Validate and render prompt"]
    B --> C{"method and surface"}
    C -->|logprobs| D["Provider logprobs"]
    C -->|grammar| E["Constrained label"]
    C -->|structured or discrete| F["JSON answer"]
    D --> G["Read distribution"]
    E --> G
    F --> G
    G --> H["Typed answer, usage, and debug data"]

Start with Getting started for the smallest working path, then use Methods and Local servers to tune the provider surface.