Ultimate Bun Development

A Claude Code skill for building fast, modern JavaScript/TypeScript applications with the Bun runtime. Covers Bun's built-in features — bundler, test runner, package manager, HTTP server — and migration patterns from Node.js, with a focus on performance and developer experience.

When to Use This Skill

Choose Ultimate Bun Development when:

• You're starting a new JavaScript/TypeScript project and want maximum performance
• You want to use Bun's built-in tools instead of separate packages (bundler, test runner, etc.)
• You're migrating a Node.js project to Bun for performance improvements
• You need a fast HTTP server with minimal boilerplate
• You want to take advantage of Bun's native SQLite, FFI, or file I/O

Consider alternatives when:

• You need maximum Node.js ecosystem compatibility (use Node.js)
• You want serverless deployment (check Bun support for your provider)
• You need Windows support (Bun's Windows support is still maturing)

Quick Start

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# Install Bun
curl -fsSL https://bun.sh/install | bash

# Install the skill
claude install ultimate-bun-development

# Create a new project
bun init my-app

# Create an HTTP server
claude "Create a Bun HTTP server with routing, middleware, and JSON responses"

# Run tests
claude "Set up Bun's built-in test runner with mocking, snapshots, and coverage"

Core Concepts

Bun Built-In Features

Feature	Bun	Node.js Equivalent
Package Manager	bun install	npm, yarn, pnpm
Bundler	bun build	webpack, esbuild, Vite
Test Runner	bun test	Jest, Vitest
TypeScript	Native, zero-config	ts-node, tsx
HTTP Server	Bun.serve()	Express, Fastify
File I/O	Bun.file(), Bun.write()	fs module
SQLite	bun:sqlite	better-sqlite3
.env	Built-in loading	dotenv
Watch Mode	bun --watch	nodemon

HTTP Server Pattern

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Bun.serve({
  port: 3000,
  fetch(req) {
    const url = new URL(req.url);

    if (url.pathname === '/api/users' && req.method === 'GET') {
      return Response.json({ users: [] });
    }

    if (url.pathname === '/api/users' && req.method === 'POST') {
      const body = await req.json();
      return Response.json({ created: body }, { status: 201 });
    }

    return new Response('Not Found', { status: 404 });
  },
});

Performance Comparison

Benchmark	Bun	Node.js	Improvement
Package Install	~1s	~8s	8x faster
TypeScript Startup	~10ms	~500ms	50x faster
HTTP Requests/sec	~100K	~30K	3x faster
File Read	~3x faster	baseline	3x faster
Test Suite	~2x faster	baseline	2x faster

Configuration

Parameter	Type	Default	Description
project_type	string	"server"	Type: server, cli, library, fullstack
framework	string	"none"	Framework: none, hono, elysia, express
database	string	"sqlite"	Database: sqlite (built-in), postgres, mysql
testing	string	"bun"	Testing: bun (built-in), vitest
deploy_target	string	"docker"	Deploy: docker, fly.io, railway, vercel

Best Practices

1. Use Bun's built-in features first — Before installing a package, check if Bun has a built-in equivalent. Built-in file I/O, SQLite, HTTP server, and test runner are faster and require zero dependencies.

2. Use Hono or Elysia for routing — Bun's built-in fetch handler is low-level. For applications with many routes, use Hono (universal, works anywhere) or Elysia (Bun-optimized, fastest) as your routing framework.

3. Take advantage of native TypeScript — Bun runs TypeScript directly without compilation. Don't add ts-node or tsx — just bun run file.ts. This eliminates build steps during development and speeds up startup dramatically.

4. Use bun:sqlite for local data — Bun's built-in SQLite is faster than external packages and requires no native compilation. It's perfect for local databases, caching, and development without running a database server.

5. Check Node.js compatibility before migrating — Most npm packages work with Bun, but some Node.js APIs have partial support. Check Bun's compatibility page for your critical dependencies before committing to a migration.

Common Issues

npm package doesn't work with Bun — Some packages that use Node.js-specific APIs (like child_process edge cases or native addons) may not work. Check the Bun GitHub issues for known incompatibilities and use the --bun flag to force Bun's runtime.

Bun process uses too much memory — Bun's garbage collector behaves differently from Node's V8 GC. For memory-intensive applications, monitor usage with process.memoryUsage() and consider manual garbage collection hints.

Tests pass in Bun but fail in CI — If your CI uses Node.js, tests may behave differently. Either run CI with Bun installed, or ensure your tests don't rely on Bun-specific APIs. Use the bun test command in CI with the Bun setup action.