Bun Cursor Rules Template

---
description: "Bun Runtime Features"
alwaysApply: false
---
- Use Bun's built-in APIs: Bun.file(), Bun.write(), Bun.serve() instead of Node.js equivalents.
- Use Bun's native TypeScript support — no need for ts-node or separate compilation step.
- Use Bun's built-in test runner (bun test) instead of Jest or Vitest for new projects.
- Use Bun's native SQLite client (bun:sqlite) for embedded database needs.
- Use Bun's built-in environment variable support via Bun.env instead of process.env.
- Use Bun.password for password hashing and Bun.randomUUIDv7 for unique IDs.
- Leverage Bun's fetch() built-in — no need for node-fetch or axios for HTTP.

---
description: "Performance Patterns"
alwaysApply: false
---
- Use Bun's native file I/O (Bun.file, Bun.write) which is significantly faster than Node.js fs.
- Use Bun.spawn() for subprocess management — faster and simpler than child_process.
- Prefer Bun.serve() over Express or other Node HTTP frameworks for maximum throughput.
- Use Bun's built-in WebSocket support for real-time applications.
- Avoid blocking the event loop — use async/await and Bun's Promise-based APIs.
- Use Bun's bundler (Bun.build) for production builds with tree-shaking and minification.
- Leverage Bun's transpiler for JSX/TSX without additional Babel or TypeScript config.

---
description: "Project Structure & Configuration"
alwaysApply: false
---
- Use bunfig.toml for project-level Bun configuration (install settings, lockfile path).
- Use bun.lockb as the lockfile — commit it to version control for reproducible installs.
- Use    spaces for indentation in .ts/.tsx files.
- Use camelCase for variables and functions.
- Use {{QUOTES}} quotes for strings.
- Use ESM imports/exports — Bun is ESM-first.
- Organize code by feature: src/features/<feature>/ with index.ts barrel exports.
- Use bun add for package installation and bun remove for removal.