Bun Runtime Skill | Agent Skills

Bun Runtime

Use Bun as the default JavaScript/TypeScript runtime and package manager.

Command Mappings

| Instead of | Use | |------------|-----| | node file.ts | bun file.ts | | ts-node file.ts | bun file.ts | | npm install | bun install | | npm run script | bun run script | | jest / vitest | bun test | | webpack / esbuild | bun build |

Bun automatically loads .env files - don't use dotenv.

Bun-Specific APIs

Prefer these over Node.js equivalents:

| API | Purpose | Don't use | |-----|---------|-----------| | Bun.serve() | HTTP server with WebSocket, HTTPS, routes | express | | bun:sqlite | SQLite database | better-sqlite3 | | Bun.redis | Redis client | ioredis | | Bun.sql | Postgres client | pg, postgres.js | | Bun.file() | File operations | node:fs readFile/writeFile | | Bun.$\cmd`| Shell commands | execa | |WebSocket` | WebSocket client (built-in) | ws |

Testing

Use bun:test for tests:

import { test, expect } from "bun:test";

test("description", () => {
  expect(1).toBe(1);
});

Run with bun test.

Frontend Development

Use HTML imports with Bun.serve() instead of Vite. Supports React, CSS, Tailwind.

Server:

import index from "./index.html"

Bun.serve({
  routes: {
    "/": index,
    "/api/users/:id": {
      GET: (req) => Response.json({ id: req.params.id }),
    },
  },
  development: { hmr: true, console: true }
})

HTML file:

<html>
  <body>
    <script type="module" src="./app.tsx"></script>
  </body>
</html>

Bun's bundler transpiles .tsx, .jsx, .js automatically. CSS is bundled via <link> tags.

Run with bun --hot ./server.ts for HMR.

Documentation

For detailed API docs, see node_modules/bun-types/docs/**.md.

Agent Skills: Bun Runtime