WASM Skill

Rust to WebAssembly scaffolds and interop - an Agent Skill for Rust 1.97.0 and browser or WASI deployments.

What This Skill Does

Creates cdylib crates with wasm-bindgen, wasm-pack build, JS glue, and size-tuned release profiles. Reviews #[wasm_bindgen] exports and panic hooks for browser consoles.

When to Invoke

• Porting compute-heavy Rust to the browser
• Sharing logic between native CLI and web UI
• Building WASI modules for edge runtimes
• Reviewing wasm bundle size regressions

Inputs

Outputs

• Cargo.toml with crate-type = ["cdylib"]
• wasm-pack build scripts
• wee_alloc or default allocator choice documented
• index.html demo or npm pkg/ publish layout
• Size report from twiggy or wasm-objdump

Guardrails

1. Release profile opt-level = "s" or "z" for size-sensitive WASM.
2. Avoid panics across boundary - map to Result in exports.
3. No filesystem assumptions - browser sandbox differs from native.
4. Feature-gate console_error_panic_hook - dev only when possible.
5. Test in headless browser CI - wasm-bindgen-test or playwright smoke.

Recipe

wasm-pack build --target web --release
wasm-opt -Oz -o pkg/my_module_bg.wasm pkg/my_module_bg.wasm

Working Example

use wasm_bindgen::prelude::*;
 
#[wasm_bindgen]
pub fn add(a: u32, b: u32) -> u32 {
    a + b
}

FAQs

Related

• WASM basics
• wasm-bindgen
• Performance Skill
• Crate Publishing Skill

Stack versions: This page was written for Rust 1.97.0 (edition 2024), Tokio 1.x, Axum 0.8, serde 1.0, sqlx 0.8, clap 4, and Polars 0.46+.