Does a typed client actually stop me from sending a bad request?

For the parts it models, yes. A choice needs named options, a score needs ordered levels and a noul needs neither, and each is a record or sealed type, so the compiler rejects a malformed request instead of the API returning a 422. That guarantee stops at construction: state is typed as Object and serialized by Jackson, so context shape errors still surface at runtime.

Why read outcomes() when choice() already gives the answer?

Because choice() flattens two very different situations to the same string. The SDK's own example sits at confidence 0.54, and the README argues a 0.51/0.49 split is not the same decision as 0.95/0.05. outcomes() returns the distribution sorted most-likely first, so outcomes().get(0) is always the selected choice and the runner-up stays visible.

Is this official, and which repository do I add?

It is unofficial — the README states it is not affiliated with or endorsed by TypeSafe AI. You add no repository and authenticate against nothing, because it is published to Maven Central: com.luigivismara:jev-sdk-java, currently 0.1.0, requiring Java 21+ with Jackson Databind as the sole runtime dependency. mvn install builds it from source instead.

How does this get billed — are output tokens charged?

According to the README, output tokens are free on TypeSafe's published rate card, so only usage().inputTokens() costs you. That makes batching the default advice: one request carrying several named questions is one billed pass over the content, and the SDK explicitly says to prefer it over three separate calls. Duplicate question names are rejected at build time so batching cannot quietly lose an answer.

What Java version and dependencies does it need?

Java 21 or newer; the only runtime dependency is Jackson Databind, and HTTP goes through the JDK's own java.net.http.HttpClient.

How does the Java client read the API key?

JevClient.fromEnv() reads JEV_API_KEY and throws if it is unset, or JevClient.of() takes a key from your own secret manager; the SDK never logs or echoes the key.

Can I pass my own object as the state?

Yes. state is typed as Object and serialized by Jackson, so a plain string or a record/POJO works, and passing a domain record means its field names become part of the context the model reads.

CommunityJev Repos & SDKs

Jev SDK Java

An unofficial Java 21 client for the Jev decision API that replaces maps with records and sealed types, so a malformed choice, score or noul question fails to compile instead of coming back as a 422.

See highlights

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Stars: 6
Language: Java
License: MIT
Published by: Community
Author: luigivis
Last verified: Oct 2026

luigivis/jev-sdk-java

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Type-safe Java 21 client for the TypeSafe AI Jev (System One) decision API

Forks: 1
Last pushed: Updated Sep 2026

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About this project

A small, type-safe Java 21 client for the TypeSafe AI Jev (System One) decision API. Jev is a decision model, not a chat model: you hand it some content and a set of typed questions, and it hands back structured answers with calibrated probabilities. This SDK models that contract with Java's own type system — enums for the parts the API fixes, sealed interfaces and records for the parts you fill in — so a decision request that compiles is a decision request the API accepts. Score — rate on a rubric.

Quoted from the project's README. Read the full README.

Tagscommunity jevbest catalog-import awesomejev

Works forJev for Classification

Used inJev for Software & DevTools

Languages: Java

Highlights

No maps in the API: options, rubric levels and question names are records, and answers are a sealed interface, so a switch over them is exhaustive.
Duplicate option names and colliding question names are rejected when you build the request, rather than silently dropping an answer at runtime.
Score answers merge the API's separate legend and probability objects into one ordered rubric, with a weighted average, nearestLevel and per-level odds.
Jackson Databind is the only runtime dependency; HTTP goes through the JDK's own HttpClient, and the client is immutable and thread-safe.

Watch out

This is an unofficial community SDK, and the README says plainly that it is not affiliated with or endorsed by TypeSafe AI, with the credit going to them. The published artifact is 0.1.0 and requires Java 21+, so expect the surface to move. The typing is asymmetric: question shapes are checked at compile time, but state is typed as Object and handed to Jackson, so a malformed context still goes out and fails on the response rather than on the build. Runtime lookups can throw as well — probabilityOf on an option you never defined, levelAt on a level that does not exist — so the compile-time guarantee covers construction, not every access afterwards. Auth reads JEV_API_KEY from the environment and refuses to start without it; the client never logs or echoes the key, and the README's advice for a key that reached a log or a commit is to rotate it in the TypeSafe console. On cost, output tokens are free on the published rate card, so only input tokens bill, which is why batching named questions into one request is the cheap path. Copy reviewed against the repository README on 2026-10-04, not from running it.

Questions about this entry

Short answers drawn from the linked project or page.

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