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An idiomatic Zig client for the TypeSafe AI API
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- Updated Sep 2026
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CommunityJev Repos & SDKs
Typesafe.zig
An unofficial Zig client for TypeSafe's System One API where answer types come from your questions at compile time: Choice returns your own enum, Score returns a fixed-size probability array.
- Stars
- 1
- Language
- Zig
- License
- MIT
- Published by
- Community
- Author
- mattneel
- Last verified
- Oct 2026
About this project
Zig client for TypeSafe's System One API and its Jev model. Ask typed Noul, Choice and Score questions about your application's state in one request, and get back a struct of answers whose types come from your questions at compile time. This is an unofficial community client. It is not an official TypeSafe SDK, and it is not affiliated with or endorsed by TypeSafe. The client returns judgments as data. Thresholds and policy stay in your code.
Quoted from the project's README. Read the full README.
Works forJev for Classification
Used inJev for Software & DevTools
Highlights
- A misspelled question id, an option missing from your enum, or a Score with one level is a compile error, not a runtime surprise.
- client.ask returns typesafe.Result(@TypeOf(questions)), so answers.answers.field names and types are all inferred.
- Standard library only — std.http, std.json, std.Io — with no C dependencies, so it cross-compiles like any Zig code.
- State, instructions, criteria and score levels accept JSON structure from std.json, including runtime strings and RawJson.
Watch out
Unofficial and unaffiliated with TypeSafe, at v0.1.0, and it needs Zig 0.16.0 or later, which is a tight coupling to a language still shipping breaking changes — the sample even uses the newer std.process.Init entry point. Memory is manual: everything pointing into the result's arena, meaning model, request_id, body and a Score answer's legend, is freed by deinit, while Noul and Choice answers and the Score numbers and enum are plain values you copy out first. Values are known at run time but the shape must not be — ids, enum options and level count are compile-time, and dynamic questions are the separate path for even less. Validation before sending catches invalid UTF-8, NaN or infinite floats, bad RawJson, nesting past 256 levels, a state that is not a string, object or array, an empty Noul and a null Score level, naming the offending path, with one deliberate exception: any type with its own jsonStringify is written unchecked. Option order is part of what the model reads, so keep an enum's declaration order stable across calls whose answers you compare. 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.
It is real on the Zig side of the wire, and the README is explicit that nothing there is stringly typed: a Choice answer's choice is your enum, its probabilities are a struct with one f64 per tag, and a Score answer's probabilities are [N]f64. A misspelled question id, an option that is not in the enum, or a single-level Score fails to compile. What the server returns is still JSON, and the client only promises to be strict about the fields it relies on.
copy the numbers and enums out before you call deinit. Noul and Choice answers, plus a Score answer's score, probabilities and confidence, are plain values. Everything that points into the arena — model, request_id, body and the Score legend — is freed by deinit, so touching those afterwards is a use-after-free.
Partly. Any field of a struct literal can hold a runtime string or number, so instructions, descriptions, state and criteria are all fine as runtime data, and there is a separate path for dynamic questions when even the ids, enum options or level count come from data. Decoding is strict about what the client depends on and lenient about everything else, so unknown response fields will not break you.
Before. The client validates what it encodes, including the contents of a std.json.Value, and returns error.InvalidRequest naming the offending path such as state.ticket.text — invalid UTF-8, NaN or infinite floats, invalid RawJson, nesting deeper than 256 levels, a state that is not a string, object or array, a Noul whose instructions and criteria both end up empty, or a null Score level. The single hole is your own type with a jsonStringify method, which is written unchecked.
Add it with zig fetch --save git+https://github.com/mattneel/typesafe.zig#v0.1.0, then wire the module into build.zig. It needs Zig 0.16.0 or later and uses only the standard library, std.http, std.json, and std.Io, with no C dependencies, so it cross-compiles like any Zig code.
model records the concrete build that answered, such as jev-1.13.0, even when you asked for jev-latest. usage holds input_tokens and output_tokens as optional u64s, request_id is the x-typesafe-request-id header, attempts counts tries including the first, and body is the raw response text.
NoulAnswer has isYes(threshold); Choice answers offer probability(tag), ranked(), and margin(); Score answers add probability(level), expectedLevel(), maxLevel(), and ranked(). margin() is the top probability minus the second, rounded to 10 decimal places.
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