Jev

Ask Jev typed questions about one state and get probabilities back, with no Nuxt required.

Why Jev?

A generative model answers a yes or no question with a paragraph. Your code then parses prose and guesses what it meant.

• 🧾 Prose instead of answers: You parse free text to get a boolean, a label, or a rank.
• 💥 Thrown failures: An HTTP error, a timeout, or a malformed answer throws in the middle of your request.
• 🔑 Unstable journal keys: The same state with keys in a different order hashes to a new digest, so a stored answer never gets reused.
• 🎚️ Thresholds picked by feel: Nothing tells you whether a probability band agrees with the answers you already have.

Jev is a System One judge. It answers typed questions about one state with probabilities. It never generates text. This package is the Nuxt-free client for it: pure TypeScript with one dependency, ohash, for sync digests. It has no Nuxt, Nitro, or h3 code, and runs on Node 20+ and workers. For the Nuxt module, the decision runner, and the drizzle schema, use @harlan-zw/nuxt-jev.

Features

• ⚖️ Typed questions: noul, choice, and score return a probability, a picked option, or a rubric level, never prose.
• 🏷️ ask tags: Put the state and the question in one tagged template, and send a batch in one call.
• 🧯 Failures as values: Every call resolves Ok or a tagged JevFailure, so nothing throws and nothing rejects.
• 🔁 Retries in the client: The HTTP client retries with backoff inside one timeout window and validates each answer.
• 🔑 Order-stable digests: digestKey and canonicalJson give the same key for the same state, whatever the key order.
• 📊 Eval replay math: summarizeReplay and suggestBand measure agreement before you move a threshold.

Installation

pnpm add @harlan-zw/jev

[!TIP] Generate an Agent Skill for this package using skilld:

npx skilld add @harlan-zw/jev

What you get

| Export | What it gives you | | --- | --- | | createJevHttpClient | The tagged-failure HTTP client over Cloudflare /ai/run: retries, backoff, one timeout window, and answer validation. | | noul, choice, score | Question builders with typed answers. | | ask, ask.choice, ask.score, ask.chance, askIf | Tagged-template sugar over the client. | | digestKey, canonicalJson | Order-stable digests for journal keys. | | agreement, summarizeReplay, suggestBand, replayAnswer | Pure eval replay math. |

Failure style

Failures are values. Nothing throws and nothing rejects.

The client resolves { _tag: 'Ok', result } or { _tag: 'Err', failure }. Every failure is one tagged JevFailure: Http, Invalid, Network, or Timeout.

The ask API keeps the same contract. A batch resolves to { _tag: 'Ok', answers } or { _tag: 'Err', failure }. An awaited tag on its own resolves to its answer or the same tagged failure.

ask

import { ask } from '@harlan-zw/jev'

const result = await ask(
  { title: 'Crash on login', body: 'Anyone can log in as admin with an empty password.' },
  {
    security: 'Does this describe a security vulnerability?',
    kind: ask.choice`What kind of issue is this?`({ bug: 'Something is broken', other: null }),
    severity: ask.score`How severe?`(['Cosmetic', 'Workaround exists', 'Blocks production']),
  },
  { accountId, apiToken },
)
if (result._tag === 'Ok') {
  result.answers.security.chance // 0.9
  result.answers.kind.choice // 'bug'
  result.answers.severity.ratio // score scaled to 0 to 1
}

Each interpolated object goes once into input, and its slot becomes a path. The state travels with the question. If you await a tag on its own, it sends on its own. askIf resolves to a boolean above a threshold. Credentials come from options, or from CLOUDFLARE_ACCOUNT_ID and CLOUDFLARE_API_TOKEN.

Client

import { createJevHttpClient, noul } from '@harlan-zw/jev'

const client = createJevHttpClient({ apiToken, accountId })
const call = await client.systemOne({
  state: { query: 'nuxtseo' },
  questions: { brand: noul('Is `query` a search for the site brand?') },
})
if (call._tag === 'Ok')
  call.result.answers.brand.noul

Jev 1.13 jagged edges

The model's own docs list its failure modes (jaggedness). This package and its consumers follow these rules:

• Math, counting, dates stay in code. Never ask the model to tally, compare numbers, or order dates. Compute counts and buckets in code, then pass the value or a named bucket in state. Use Score answers to rank and threshold. Never infer a magnitude between two rubric levels.
• Literal reading. Write the exact condition in instructions. Put boundary cases in criteria. If a question needs interpretation, split it into two literal questions and combine them in code.
• Criteria extend the instruction. A true that means "no" gives worse answers. Keep the two aligned.
• Thresholds do not carry across question types. A Noul band and a Choice confidence answer different questions. noul compares with probabilities['yes'], not with confidence. A question and its negation do not sum to 1. Tune each threshold on its own question. Never expect arithmetic identities between separate answers.
• Choice settles "which"; Noul settles "whether". A Choice is relative: it picks one option. Each Noul is absolute: all of them can be low. If you need both answers, ask both on the same shortlist.
• Filter state before sending. Unrelated detail costs accuracy (context rot), and the context window has a limit. Send only the fields the question names.
• Adversarial content is data the model does not treat as hostile. Frame untrusted text as measurements to judge, never as instructions. Test those edges before you act on answers in production.
• No generation. If the answer space is bounded, extract the options in code or with a generative model. Then let Jev pick one.

Sponsors

License

Licensed under the MIT license. Forked from pithings/advocaat (MIT); question and answer shapes mirror github.com/typesafe-ai/typesafe-sdk-js.