Guide · Agent skill

How to use the Bun Runtime Guide agent skill

Updated 2026-10-29 · written with AI from the project's own documentation and checked against our catalogue data

This guide shows you how to install and use the bun-runtime agent skill, a set of instructions that teaches an AI coding agent how to work with Bun, a JavaScript and TypeScript toolkit that runs code, installs packages, bundles apps and runs tests. You do not need prior experience with agent skills. After reading, you will know how to add the skill, how to ask for Bun help in plain language, and what the skill can and cannot do for you.

Bun Runtime Guideaffaan-m/ECC · MIT Download the skill

Quick start

1Download the ZIP. Get the bun-runtime skill ZIP from this page.
2Unzip the skill. Extract it into ~/.claude/skills/ for personal use or into your project's .claude/skills/ folder for one project.
3Or upload it in the Claude apps. Go to Settings, then Capabilities, then Skills, and upload the ZIP.
4Confirm Bun is installed. Run bun --version in a terminal to check that Bun is available.
5Ask in plain language. Describe your goal, such as migrating a Node project or setting up bun test, and include any error text.
6Review and test the changes. Read the commands and edits the agent proposes, then run them in a branch and check that tests pass.

What does the bun-runtime skill make the agent do?

Once installed, the agent knows when Bun is a better choice than Node.js, how to migrate a Node project to Bun, which built-in Bun APIs to prefer, and how to configure Bun on Vercel. The skill is written as instructions and examples. It does not run anything by itself; any commands the agent suggests are for you or the agent to run in your project.

Choose between Bun and Node for a new or existing project
Move a Node project to Bun, including npm script and install equivalents
Write and debug Bun scripts and tests with bun test
Use built-in APIs such as Bun.file, Bun.serve and bun:sqlite
Configure Bun for Vercel deployments and other platforms

How do you install the bun-runtime skill?

Download the ZIP file for the skill from this page. Unzip it into one of two places. For a personal setup, use ~/.claude/skills/. For a single project, put it in that project's .claude/skills/ folder. The skill's files are SKILL.md and agents/openai.yaml.

You can also upload the skill in the Claude apps. Open Settings, go to Capabilities, then Skills, and add the ZIP there.

Personal install: unzip into ~/.claude/skills/
Project install: unzip into the project's .claude/skills/ folder
Claude apps: Settings → Capabilities → Skills, then upload the ZIP

Check that Bun is installed

The skill needs Bun on your machine before it can help with real commands. Run the command below in a terminal. If it prints a version number, Bun is installed. The guidance targets Bun 1.4.x, and the skill tells the agent to check your version before relying on specific flag names, because CLI flags can change between releases.

bun --version

How do you trigger the skill with natural requests?

You do not need a special command. Describe what you want in plain language and mention Bun or the task. The skill is meant for adopting Bun, migrating from Node, writing or debugging Bun scripts and tests, and configuring Bun on Vercel or other platforms.

Good requests name the goal and the project context, for example which files exist or what error you see. Paste the error message when you have one.

Migrate this Node project to Bun and tell me what to change in package.json
Should this new TypeScript CLI use Bun or Node?
Set up bun test for this repo and show me a first test
Why does my install fail on Bun but work on Node?
Configure this app to deploy with the Bun runtime on Vercel

What can you ask it to do with tests, dependencies and deployment?

For CI, the skill lists options such as bun test --changed for affected tests, --isolate for a fresh global per file, --parallel for worker processes and --shard for partitioning. The skill notes that --isolate is not a process or security sandbox. For Vercel, it covers setting bunVersion in vercel.json, the build command bun run build, and bun install --frozen-lockfile for reproducible deploys.

For dependencies, the skill covers bun add, bun remove, bun update and bun outdated. It explains that bun audit only reads advisories and does not change your files, while bun audit fix does change the lockfile and installed packages, so you should review it as a modifying operation.

Run affected tests only with bun test --changed
Use bun install --frozen-lockfile in deploy pipelines
Check outdated packages with bun outdated before upgrading

bun test --changed
bun install --frozen-lockfile
bun outdated

What does the skill need, and what are the safety notes?

The skill itself runs no scripts and makes no network calls. Bun must be installed on your machine. A Vercel account and project are only needed for the deployment steps. Registry access is needed for bun audit. Redis, S3 or SQL services are only needed if your project uses the Bun APIs that connect to them.

Review what the agent suggests before running it, especially on production code. The skill warns that compatibility is not guaranteed. Native Node addons and Node-internal APIs can fail under Bun. Before sending private package metadata to a registry for bun audit, check that the destination is one you approve.

Test migrations in a branch or staging environment first
Commit bun.lock so installs are reproducible
Expect failures with native addons and less-common node: internal APIs

What people use it for

Starting a new JavaScript or TypeScript project with one toolchain for running, installing and testing
Migrating an existing Node.js project to Bun one step at a time
Setting up bun test for a repository and adding tests that run in CI
Deploying a Bun-based app to Vercel with a reproducible install step
Replacing small npm packages with built-in Bun APIs such as Bun.file or Bun.sql

Frequently asked questions

How do I install the bun-runtime agent skill?

Download the skill ZIP from this page and unzip it into ~/.claude/skills/ for personal use or into a project's .claude/skills/ folder. You can also upload the ZIP in the Claude apps under Settings, then Capabilities, then Skills.

What do I need to use the bun-runtime skill?

You need Bun installed on your machine, which you can confirm with bun --version. A Vercel account and project are optional and only needed for deployment steps. Registry access is needed for bun audit.

Is the bun-runtime skill free?

The skill is licensed under MIT, as stated in its SKILL.md file. This page does not list any price for it, and the skill itself does not run anything or make network calls.

Should I use Bun or Node.js for my project?

The skill suggests Bun for new JavaScript or TypeScript projects, scripts where install and run speed matters, Vercel deployments with the Bun runtime, and when you want one toolchain. It suggests Node for maximum ecosystem compatibility, legacy tooling that assumes Node, or when a dependency has known Bun issues.

Why does my project fail on Bun after migrating from Node?

The skill warns that Bun is not fully Node-compatible. Some native addons, less-common node: internal APIs and packages that depend on Node-specific internals can fail. Check the failing package first, and if it cannot be fixed, the skill suggests keeping that project on Node.

Does the skill run commands or change my files on its own?

No. The skill is instructions and examples and does not run anything itself. Commands it suggests, such as bun audit fix, can change your lockfile and installed packages, so review them before running.

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Our verdict

Use this skill if you are starting a JavaScript or TypeScript project on Bun, moving a Node project over step by step, or deploying Bun to Vercel and want guidance from an agent. Pick something else, or stay on Node, if your project depends heavily on native Node addons or Node-internal APIs, or if you plan to apply the agent's suggestions to production without testing them first.

Download the skill