chain-module-sdk-rust/README.md
flemming-it a5da67d0a3
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refactor: rename WIT contract fai:platform->chain:platform
Tracks the platform's WIT ABI rename. The module world package is now
chain:platform@1.0.0; generated binding paths + accessor names follow.
Modules built with this SDK now import chain:platform/host. SDK crate
names stay fai-* (vendor namespace) for now.

Signed-off-by: flemming-it <sf@flemming.it>
2026-06-15 22:17:28 +02:00

2.1 KiB

fai-module-sdk

Stable, ergonomic Rust surface for writing F∆I Platform modules.

A module written against this crate looks like:

use fai_module_sdk::prelude::*;

#[fai_module]
fn invoke(_ctx: Context, inputs: Inputs) -> Result<Outputs, ModuleError> {
    let text = inputs.require_text("input")?;
    Ok(Outputs::new().with_text("output", format!("echo: {text}")))
}

That single function — plus a Cargo.toml listing fai-module-sdk as a dependency — is the entire module. The #[fai_module] macro generates the wit_bindgen invocation, the Guest implementation, the type conversions, and the wit_bindgen::export! glue behind the scenes.

What the SDK gives you

You get Instead of
Inputs::require_text("name") manual match payload { Payload::Text(s) => ..., _ => ... }
Outputs::new().with_json(...)? building Vec<(String, Payload)> by hand
ModuleError::invalid_input("...") constructing WIT invocation-error variants
#[fai_module] wit_bindgen::generate! + Guest impl + export! + #![allow(unsafe_op_in_unsafe_fn)]

Stability

The SDK insulates module code from the underlying WIT contract (chain:platform, frozen at v1.0 in the platform repo). The WIT may evolve in additive minor versions or, eventually, a coordinated v2.0; the SDK absorbs that change so existing module code keeps compiling.

The SDK ships its own copy of wit/world.wit so that the proc-macro can embed the contract via include_str! at compile time. A snapshot test (crates/fai-module-sdk/tests/wit_freeze.rs) asserts the SHA-256 matches the platform's frozen hash — if the two ever drift, CI fails.

Versioning

Track Stability
WIT contract (chain:platform) Frozen at v1.0 in the platform repo
fai-module-sdk Rust API Semver; v0.x while ergonomics evolve
Per-module versions Each module repo's own concern

License

Apache-2.0. See LICENSE.

Author: Dr. Stefan Flemming, Flemming.AI platform@flemming.ai Repository: https://git.flemming.ai/fai/module-sdk-rust