Bun Runtime

A comprehensive reference for Bun as a runtime, package manager, bundler, and test runner. It covers the key decision of when to use Bun over Node (speed matters, new projects, Vercel deployments) and when to stick with Node (maximum compatibility, legacy tooling). You get practical migration notes like swapping `node` for `bun run` and `npm install` for `bun install`, plus Vercel-specific config. The examples show file handling, the built-in server API, and Jest-like testing. Most useful when you're actively adopting Bun or debugging why a Node project won't run under it. The lockfile note is important: current Bun uses text `bun.lock`, older versions used binary `bun.lockb`.

skills.sh installs: 5.8K
GitHub stars: 300.3K
last updated: Aug 21, 2026

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Install

$ npx -y skills add affaan-m/ecc --skill bun-runtime --agent claude-code

Installs into .claude/skills of the current project.

Files

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.