basal-client (Rust)

Async Rust SDK for the native Basal API (POST /v1/basal), using Hyper HTTP/1 with Rustls and the platform certificate verifier. No dependency on the inference engine or GPU libraries. Rust 1.95+; a Tokio runtime is required.

This package is versioned independently. Release tag: sdk-rust-vX.Y.Z. Changelog.

cargo add basal-client
cargo add tokio --features macros,rt-multi-thread

use basal_client::{choice, noul, questions, Client};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new("http://127.0.0.1:8000")?;
    let department = choice(
        "Do którego działu skierować zgłoszenie?",
        &[("returns", "Zwroty"), ("support", "Wsparcie techniczne")],
    )?;
    let urgent = noul("Czy sprawa jest pilna?")?;
    let questions = questions! {
        department: &department,
        second_department: &department,
        urgent: &urgent,
    }?;
    let response = client.decide("Klient prosi o zwrot pieniędzy za uszkodzony telefon.", &questions).await?;
    let answers = response.answers()?;
    println!("Dział: {}, P(tak): {}", answers.department.choice, answers.urgent.noul);
    println!("Drugie pytanie: {}", answers.second_department.choice);
    Ok(())
}

For choice/score, set question.criteria to an ordered serde_json::Value object/array. Question and request extra maps accept native extension fields (evidence, costs, facts etc.). Do not duplicate explicit fields in extra. JSON object order is retained through serde_json's preserve_order and indexmap. The float_roundtrip feature preserves binary64 values when parsing wire probabilities, without extra dependencies or arbitrary_precision feature unification. Add serde_json directly (cargo add serde_json --features preserve_order) to construct structured JSON with its json! macro.

models() reads /v1/models. Use Client::with_options(ClientOptions { ... }) for a bearer token or a different timeout. The timeout (default 120 seconds) includes response-body reading. Dropping the request future cancels client-side I/O. Clone/reuse the client to share its connection pool. Use the server root (possibly with a proxy prefix), without /v1. HTTPS is required except for loopback HTTP, suitable for a local server or SSH tunnel. URL credentials/query/fragment are rejected. DNS names must be ASCII; use punycode for IDN. The client ignores environment proxies, uses a per-client ring crypto provider, and verifies TLS with platform roots. It does not enable HTTP/2 or install a process-global crypto provider. ring includes a native build step; this SDK does not depend on AWS-LC or CMake. max_response_bytes defaults to 8 MiB and limits the actual stream, including error bodies; oversized responses return Error::ResponseTooLarge, deadlines return Error::Timeout.

Error::Http provides status, body and raw retry_after. Error::Transport, Error::Encode and Error::Protocol preserve their causes. No automatic retries or redirects. Responses deserialize into native DTOs; extra JSON fields are retained. HTTP 422 and overload 529 remain distinct. Display and Debug omit HTTP bodies and nested transport details; access them explicitly when needed.

Native choice/score accepts 2–255 options for format-2 models (older model limits are checked by the server); multi uses independent probabilities and set_confidence. Evidence offsets count Unicode characters, not UTF-8 bytes. The SDK does not execute selected actions.

Factories return distinct QuestionSpec<...> types. Default factories take only their required arguments; choice_with_options, noul_with_options, score_with_options, multi_with_options, act_with_options accept type-specific options.

Starting with 0.2.0, questions! infers the answer kind for each named field. Field names become request keys. A definition or its clone can appear under several keys; each field reads its own answer. Expressions are evaluated once. response.answers()? returns borrowed views with required fields, so answers.department.choice is &str and answers.urgent.noul is f64, without optional fields or casts. Choice keys remain strings in Rust; the SDK validates them against the requested criteria at runtime. ? propagates a validation error, rather than unwrapping a nullable field.

For keys loaded dynamically, use the ordered map builder:

let questions = Questions::new()
    .with("department", &department)?
    .with("second_department", &department)?;
let response = client.decide(state, &questions).await?;
println!("{}", response.choice("department")?.choice);
println!("{}", response.choice("second_department")?.choice);

Import basal_client::Questions for this variant. response.answer("department")? returns the AnswerResult enum; match its variants for heterogeneous dynamic keys. The choice, noul, score, multi and act accessors return checked views by key and reject a different answer kind. response.answers()? on a dynamic map returns an ordered map of these enum variants. Unknown keys are errors, including extra answers that were not requested. Duplicate request keys are rejected.

Migrating from 0.1.0: replace response.answer(&question)? with the named fields from questions!, or a keyed accessor such as response.choice("department")?. Question object identity no longer determines which answer is returned. This is a breaking API change; other SDK package versions are independent.

Views borrow the response without copying probability maps. Use decide_with_options for model/facts, response.raw() for native DTOs, and decide_request(&request) for the full raw request (Rust has no method overloading).

Full documentation and publication setup.

Basal 2.0 and Omni

Typed choice/score and act outcomes allow 2–255 options. The server remains responsible for limits of older models and for calibration/model capabilities. tool accepts OpenAI, MCP and Anthropic definition objects, optional non-tool choices (answer_directly, ask_user, none), ranking, multi selection and certified deferral. The SDK returns the decision; it never executes tools.

Multi selection supports threshold, exact, iou and f1, count limits, exclusive, fallback and fallback_threshold. threshold is optional in results because objective-based responses instead contain objective and expected_score; constraint diagnostics remain available. Single tool selection can be null on certified deferral, while multi mode returns a tool list.

Typed request options include lang (pl/en), ordered inline media and detail (default/high). Media helpers accept encoded bytes, base64 or a data URL; they never fetch URLs. Read files explicitly in your application. Decoding, model support and resource limits are checked by the server. Omni requires a CUDA server started with media enabled. calibration: "text" means text calibration applied to media, not validated calibration for images/audio.

Usage exposes longest_prompt_tokens, second_order_branches and media counts, soft tokens and detail. Discovery exposes prompt_format, orders, enabled media and calibration temperatures. Model names remain strings: use exact names from model discovery, not a hardcoded model enumeration. Keep old models and raw JSON access available. The server validates each model’s capabilities. Basal 2.1 task helpers are described below.

use basal_client::{tool_with_options, ToolOptions, ToolExtra, DecisionOptions, Language, MediaInput, questions};
let definitions = [serde_json::json!({"name":"inspect","description":"Inspect material","inputSchema":{"type":"object"}})];
let routing = tool_with_options("Choose a tool.", &definitions, ToolOptions { extra: Some(&[ToolExtra::None]), rank: Some(2), description_chars: Some(120), ..Default::default() })?;
let questions = questions! { route: &routing }?;
let media = [MediaInput::image(&std::fs::read("photo.jpg")?)];
let response = client.decide_with_options("Inspect the supplied material.", &questions, DecisionOptions {
    model: Some("basal-omni-1.0-mini"), lang: Some(Language::En), media: Some(&media), ..Default::default()
}).await?;
println!("{:?}", response.answers()?.route.tool);

Rust 0.3 adds a Tool question/answer variant and fields to request options and metadata. When constructing option structs use ..Default::default(); multi threshold is now Option<f64>. MultiOptions borrows constraint keys. Existing request factories and raw response access remain available.

Tool descriptions are normalized by the server. Omit description_chars (DescriptionChars in .NET) to keep the default cap of 300 Unicode code points; use 0 to disable truncation. Descriptions longer than a positive cap are shortened at a word boundary where possible, with an ellipsis appended. The SDK forwards this option without changing the supplied tool definitions.

Experimental Basal 2.1 tasks

Typed classify, verify, compress and extract factories preserve nullable task automation, Unicode code point offsets and nested JSON extraction values. Task answers do not share the primitive probabilities field. See task semantics and SDK examples. These source changes require a server with the experimental task layer; installing an SDK does not update the inference server.