Getting Started

Kyushu is an open source CLI for running JavaScript and TypeScript workers in a WebAssembly sandbox. This guide walks you through getting your first worker up and running.

Install

Open a terminal window and install the command line tool kyu.

curl -fsSL https://kyushu.dev/install | bash

Or download a pre-built binary from the releases page.

Quick start

The following steps take you from a blank TypeScript file to a running HTTP handler.

Write a worker

Create src/index.ts with a simple fetch handler:

import type { ExportedHandler } from "kyushu-types";

export default {
  async fetch(request) {
    return {
      status: 200,
      headers: { "content-type": "application/json" },
      body: JSON.stringify({ hello: "world" }),
    };
  },
} satisfies ExportedHandler;

Build the worker

Run this on your development machine. It bundles your code and produces a self-contained .wasm file.
Terminal window
```
kyu build
```
You should see worker/__kyushu_worker.wasm appear.
Run the worker

Run this wherever you want to serve requests.
Terminal window
```
kyu run
# Listening on http://0.0.0.0:5987
```
Test it:
Terminal window
```
curl http://localhost:5987
# {"hello":"world"}
```

TypeScript types

For autocompletion, install the kyushu-types library. See the TypeScript reference for the full API.