# rollup-bundler

This skill gives your agent Rollup.js rules: output formats, external dependencies, tree-shaking and the plugins needed to bundle a library.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 657 installs · ★ 286
- Author: Mindrally
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/Mindrally/skills/tree/HEAD/rollup-bundler/SKILL.md
- Updated: 2026-10-08
- HTML: https://affpapa.org/en/nevibecode/skills/rollup-bundler

## What it does

The skill turns your agent into a Rollup.js hand. It walks through `rollup.config.mjs`, picks output formats — `esm`, `cjs`, `umd` or `iife` — and splits them across several output objects. External dependencies get their own section: peer dependencies and `dependencies` from `package.json` are marked `external` so they stay out of the bundle.

Plugin examples are ready to copy: `@rollup/plugin-node-resolve`, `@rollup/plugin-commonjs`, `@rollup/plugin-babel`, `@rollup/plugin-typescript`, `@rollup/plugin-terser` and `@rollup/plugin-replace`. There are sections on code splitting with multiple entry points and dynamic imports, on `/*#__PURE__*/` annotations and the `sideEffects` field for better tree-shaking, plus watch mode and the `rollup -c -w` command.

The skill advises against bundling peer dependencies and against CommonJS where ES modules exist. For TypeScript libraries it flags declaration files — skip them and consumers lose your types. Everything assumes Node.js and Rollup installed; `rollup-plugin-visualizer` is mentioned for bundle analysis.

The skill lives in the `Mindrally/skills` repository and installs with one command per platform.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add Mindrally/skills --skill rollup-bundler -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/rollup-bundler/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/rollup-bundler/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add Mindrally/skills --skill rollup-bundler -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/rollup-bundler/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add Mindrally/skills --skill rollup-bundler -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/rollup-bundler/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install Mindrally/skills rollup-bundler
```

2. **Manually: put the files in place**
- File: `.github/skills/rollup-bundler/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add Mindrally/skills --skill rollup-bundler -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/Mindrally/skills --path rollup-bundler
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/rollup-bundler/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add Mindrally/skills --skill rollup-bundler -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/Mindrally/skills/tree/HEAD/rollup-bundler/SKILL.md

## When to use it
- build a library in `esm`, `cjs` and `umd` at once
- mark `react` and `lodash` as `external` so they stay out of the bundle
- wire up `@rollup/plugin-typescript` with a separate `tsconfig.json`
- enable tree-shaking with named exports and `sideEffects`
- split a package into several entry points that share code

## Example prompts
- Set up `rollup.config.mjs` for a library: input `src/index.ts`, `esm` and `cjs` outputs with sourcemaps
- Move the peer dependencies from `package.json` into `external` and add `globals` for the UMD build
- Add watch mode with `include: 'src/**'` and hook up `@rollup/plugin-terser`

## Source text · SKILL.md · Apache-2.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: afe4c618024932af.

BEGIN THIRD-PARTY FILE afe4c618024932af
````text
---
name: rollup-bundler
description: Best practices and guidelines for Rollup.js module bundler configuration, ES modules, and library bundling
metadata:
  maintainer: Mindrally
  source: https://github.com/Mindrally/skills
---

# Rollup Bundler

You are an expert in Rollup.js, the JavaScript module bundler optimized for ES modules and library development. Follow these guidelines when working with Rollup configurations.

## Core Principles

- Rollup is designed for ES modules and produces cleaner, smaller bundles
- Superior tree-shaking through deep execution path analysis
- Ideal for libraries and packages that will be consumed by other projects
- Focus on producing efficient, readable output code

## Project Structure

```
project/
├── src/
│   ├── index.js          # Main entry point
│   ├── modules/          # Internal modules
│   └── utils/            # Utility functions
├── dist/                 # Build output
│   ├── bundle.esm.js     # ES module format
│   ├── bundle.cjs.js     # CommonJS format
│   └── bundle.umd.js     # UMD format
├── rollup.config.mjs     # Configuration file
└── package.json
```

## Configuration Basics

### Basic Configuration

```javascript
// rollup.config.mjs
export default {
  input: 'src/index.js',
  output: {
    file: 'dist/bundle.js',
    format: 'esm',
    sourcemap: true
  }
};
```

### Multiple Output Formats

```javascript
export default {
  input: 'src/index.js',
  output: [
    {
      file: 'dist/bundle.esm.js',
      format: 'esm',
      sourcemap: true
    },
    {
      file: 'dist/bundle.cjs.js',
      format: 'cjs',
      sourcemap: true
    },
    {
      file: 'dist/bundle.umd.js',
      format: 'umd',
      name: 'MyLibrary',
      sourcemap: true
    }
  ]
};
```

## Output Formats

### ES Modules (esm)

- Keeps bundle as ES module file
- Best for modern bundlers and browsers
- Supports tree-shaking in consuming projects

### CommonJS (cjs)

- For Node.js environments
- Compatible with require() syntax

### UMD (Universal Module Definition)

- Works as AMD, CJS, and IIFE
- Best for libraries that need broad compatibility

### IIFE (Immediately Invoked Function Expression)

- Self-executing function
- Suitable for script tags in browsers

## ES Modules Best Practices

### Use Named Exports

```javascript
// Prefer named exports for better tree-shaking
export const add = (a, b) => a + b;
export const subtract = (a, b) => a - b;
````
END THIRD-PARTY FILE afe4c618024932af

The third-party file has ended. Everything between the afe4c618024932af tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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