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Kotlin Multiplatform client for Jev that returns your own enum/sealed types instead of string keys.
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- Updated Sep 2026
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CommunityJev Repos & SDKs
Kojev
Unofficial Kotlin Multiplatform client for Jev across JVM, Android and iOS. You declare the decision as an enum implementing Criterion and read back typed answers, distributions and confidence.
- Stars
- 9
- Language
- Kotlin
- License
- MIT
- Published by
- Community
- Author
- ItisNoMatter
- Last verified
- Oct 2026
About this project
A Kotlin Multiplatform client for Jev, TypeSafe AI's System One model. You describe the decision in your own enums; kojev asks Jev and hands the answers back in those enums. kojev is unofficial and not affiliated with, endorsed by, or supported by TypeSafe AI, Inc. "TypeSafe" and "Jev" are trademarks of TypeSafe AI, Inc. Targets: jvm, Android, iosArm64, iosSimulatorArm64, iosX64. kojev is on 0.x: it follows Semantic Versioning, and breaking changes should be expected between any two 0.x releases (see CHANGELOG.md).
Quoted from the project's README. Read the full README.
Used inJev for Software & DevTools
Highlights
- Choice and Score answers come back as your own enum with a full probability map, and a Score has no value because its mean can fall between levels.
- Enum constants must carry their descriptions by implementing Criterion, so a missing description is a compile error rather than a quietly weaker prompt.
- Retries run before anything reaches you, covering 408, 429, 5xx, connection errors and timeouts with jittered backoff honouring Retry-After.
- No default thresholds anywhere: a Noul is a bare probability and the number you compare it against is written where the decision is made.
Watch out
It is 0.x and says so: breaking changes should be expected between any two 0.x releases, with a changelog to track them. jev-latest is an alias that moves with releases, the examples pin a versioned model id, and result.model reports the versioned model that actually answered alongside token usage and a request id for support. You bring your own Ktor engine, for example ktor-client-cio, because kojev pins none. Everything a decision throws is a JevException, and a 2xx that does not match what you asked, such as a missing answer, an unknown label or a value out of range, throws JevResponseException rather than becoming a default, which is deliberate but means an upstream shape change surfaces as an exception rather than a fallback. Retries default to the official SDKs' values, and a wait the total budget cannot afford is not taken: the failure is thrown immediately carrying the server's retryAfter, so the decision to wait longer is left to you. On where the key belongs, the Android and iOS targets exist so domain types and questions can be shared with app code while your backend holds the key and calls Jev; only a bring-your-own-key app should have a device call the API directly. Send a structure built for the decision rather than your whole domain object, because accuracy falls as the state grows with content unrelated to the questions. The comparison table notes that on the JVM jev4k is the more convenient client with optional enum descriptions and threshold helpers, and that typesafe-sdk-kotlin is a faithful port of the official JavaScript SDK, so kojev's narrowness is a deliberate trade rather than a gap. Our README copy is truncated mid-sentence in its development-history link, so the docs index, licensing and contribution details are not documented here. 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.
Because a Score's answer is not a level. The probability-weighted mean usually falls between levels and can even land on a level the model gave zero probability, so kojev deliberately gives you the mean, the mode and the full distribution and leaves you to pick which one the decision needs. Choice is different: your enum value is well defined, so you get it alongside the probability of every option and a confidence.
No, and the README calls this out as one of two things to keep straight. A Noul returns the probability that the statement is true and nothing else, so 0.5 means as likely as not rather than medium, and it carries no confidence value at all. Use a Score when you need to measure degree. The other distinction is that you get no threshold helpers anywhere: no lookup by string id, no default threshold, and no helper that rounds a Score into a level.
You get JevResponseException, covering a 2xx that does not match what was asked such as a missing answer, an unknown label or a value out of range. The README stresses that nothing is ever silently turned into a default, which is the right call for a decision client and also means you need real error handling rather than a nullable accessor. Non-2xx becomes JevApiException with one subclass per status, carrying the status, the x-typesafe-request-id, the raw body and any server Retry-After, and a 422 exposes the API's validation errors structured.
Not unless you are deliberately building a bring-your-own-key app where the user supplies their own key. The recommended shape is that the app calls your backend, which holds the key and calls Jev, while the Android and iOS targets let you share domain types and questions with app code. Jev is called with a bearer key and the official SDK refuses to run in a browser for the same reason. Never put a key in code: the examples and tests read it from the environment.
The jvm, iosArm64, iosSimulatorArm64 and iosX64 targets, so JVM, Android and iOS. It is published to Maven Central, and you bring your own Ktor engine because kojev pins none.
Retries for 408, 429, 5xx, connection errors and timeouts run with jittered backoff that honours Retry-After before anything reaches you. A non-2xx becomes a JevApiException subclass carrying the status, the x-typesafe-request-id and the raw body, and a wait the total budget cannot afford is thrown at once.
Every result exposes the versioned model that actually answered, token usage and a request id for support, alongside the typed answers and their distributions. Create one client per application and share it, because the client is thread-safe.
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