Bun Runtime Skill for Claude

Bun as runtime, package manager, bundler, and test runner. When to choose Bun vs Node, migration notes, and Vercel support.

649 tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

265

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/loulanyue/awesome-claude-notes --skill bun-runtime

The instruction itself

9 sections, as written by the author

Bun Runtime

Bun is a fast all-in-one JavaScript runtime and toolkit: runtime, package manager, bundler, and test runner.

When to Use

Prefer Bun for: new JS/TS projects, scripts where install/run speed matters, Vercel deployments with Bun runtime, and when you want a single toolchain (run + install + test + build).
Prefer Node for: maximum ecosystem compatibility, legacy tooling that assumes Node, or when a dependency has known Bun issues.

Use when: adopting Bun, migrating from Node, writing or debugging Bun scripts/tests, or configuring Bun on Vercel or other platforms.

How It Works

Runtime: Drop-in Node-compatible runtime (built on JavaScriptCore, implemented in Zig).
Package manager: bun install is significantly faster than npm/yarn. Lockfile is bun.lock (text) by default in current Bun; older versions used bun.lockb (binary).
Bundler: Built-in bundler and transpiler for apps and libraries.
Test runner: Built-in bun test with Jest-like API.

Migration from Node: Replace node script.js with bun run script.js or bun script.js. Run bun install in place of npm install; most packages work. Use bun run for npm scripts; bun x for npx-style one-off runs. Node built-ins are supported; prefer Bun APIs where they exist for better performance.

Vercel: Set runtime to Bun in project settings. Build: bun run build or bun build ./src/index.ts --outdir=dist. Install: bun install --frozen-lockfile for reproducible deploys.

Examples

Run and install

# Install dependencies (creates/updates bun.lock or bun.lockb)
bun install

# Run a script or file
bun run dev
bun run src/index.ts
bun src/index.ts

Scripts and env

bun run --env-file=.env dev
FOO=bar bun run script.ts

Testing

bun test
bun test --watch

// test/example.test.ts
import { expect, test } from "bun:test";

test("add", () => {
  expect(1 + 2).toBe(3);
});

Runtime API

const file = Bun.file("package.json");
const json = await file.json();

Bun.serve({
  port: 3000,
  fetch(req) {
    return new Response("Hello");
  },
});

Best Practices

Commit the lockfile (bun.lock or bun.lockb) for reproducible installs.
Prefer bun run for scripts. For TypeScript, Bun runs .ts natively.
Keep dependencies up to date; Bun and the ecosystem evolve quickly.

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How to use it

Copy the folder

Take loulanyue/bun-runtime from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.

Install what it needs

The instructions reference npm. Without those the skill loads but fails at the first command.