tsdown SkillsSAFE

From the repository's own README, as read at the audited commit. Badges and raw HTML are left out.

npx skills add rolldown/tsdown

npx skills add rolldown/tsdown --skill tsdown

Set up tsdown to build my TypeScript library with ESM and CJS formats

Configure tsdown to generate type declarations and bundle for browsers

Add React support to my tsdown config with Fast Refresh

Help me migrate from tsup to tsdown

Set up a monorepo build with tsdown workspace support

The instruction file, verbatim from the audited commit — this is the text the model reads, and the surface the audit's instruction layer examines. Quoted here so you can judge it without cloning anything.

---
name: tsdown
description: Bundle TypeScript and JavaScript libraries with blazing-fast speed powered by Rolldown. Use when building libraries, generating type declarations, bundling for multiple formats, or migrating from tsup.
---

# tsdown - The Elegant Library Bundler

Blazing-fast bundler for TypeScript/JavaScript libraries powered by Rolldown and Oxc.

## Runtime Requirement

`tsdown` requires **Node.js 22.18.0 or higher to run** (build-time only). However, the bundled output can target much lower Node.js versions via the [`target`](references/option-target.md) option, so libraries built with tsdown are **not locked to Node.js 22+ at runtime**.

If your package needs to support Node.js 18 / 20:

- **Build with Node.js 22+ in CI** (e.g. set `target: 'node18'` or `target: 'node20'`).
- **Test the built output (or the packed tarball) on the lower Node.js versions** you intend to support — e.g. using a matrix job that runs the published package's tests on Node.js 18 / 20 / 22.

## When to Use

- Building TypeScript/JavaScript libraries for npm
- Generating TypeScript declaration files (.d.ts)
- Bundling for multiple formats (ESM, CJS, IIFE, UMD)
- Optimizing bundles with tree shaking and minification
- Migrating from tsup with minimal changes
- Building React, Vue, Solid, or Svelte component libraries

## Quick Start

```bash
# Install
pnpm add -D tsdown

# Basic usage
npx tsdown

# With config file
npx tsdown --config tsdown.config.ts

# Watch mode
npx tsdown --watch

# Migrate from tsup
npx tsdown-migrate
```

## Basic Configuration

```ts
import { defineConfig } from 'tsdown'

export default defineConfig({
  entry: ['./src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  clean: true,
})
```

## Core References

| Topic | Description | Reference |
|-------|-------------|-----------|
| Getting Started | Installation, first bundle, CLI basics | [guide-getting-started](references/guide-getting-started.md) |
| Configuration File | Config file formats, multiple configs, workspace | [option-config-file](references/option-config-file.md) |
| CLI Reference | All CLI commands and options | [reference-cli](references/reference-cli.md) |
| Migrate from tsup | Migration guide and compatibility notes | [guide-migrate-from-tsup](references/guide-migrate-from-tsup.md) |
| Plugins | Rolldown, Rollup, Unplugin support | [advanced-plugins](references/advanced-plugins.md) |
| Hooks | Lifecycle hooks for custom logic | [advanced-hooks](references/advanced-hooks.md) |
| Programmatic API | Build from Node.js scripts, in-memory builds (`write: false`) | [advanced-programmatic](references/advanced-programmatic.md) |
| Rolldown Options | Pass options directly to Rolldown | [advanced-rolldown-options](references/advanced-rolldown-options.md) |
| CI Environment | CI detection, `'ci-only'` / `'local-only'` values | [advanced-ci](references/advanced-ci.md) |

> For comprehensive migration assistance with complete option mappings, install the dedicated [`tsdown-migrate`](../tsdown-migrate/SKILL.md) skill: `npx skills add rolldown/tsdown --skill tsdown-migrate`

## Build Options

| Option | Usage | Reference |
|--------|-------|-----------|
| Entry points | `entry: ['src/*.ts', '!**/*.test.ts']` | [option-entry](references/option-entry.md) |
| Output formats | `format: ['esm', 'cjs', 'iife', 'umd']` | [option-output-format](references/option-output-format.md) |
| Output directory | `outDir: 'dist'`, `outExtensions` | [option-output-directory](references/option-output-directory.md) |
| Type declarations | `dts: true`, `dts: { sourcemap, compilerOptions, vue }` | [option-dts](references/option-dts.md) |
| Target environment | `target: 'es2020'`, `target: 'esnext'` | [option-target](references/option-target.md) |
| Platform | `platform: 'node'`, `platform: 'browser'` | [option-platform](references/option-platform.md) |
| Tree shaking | `treeshake: true`, custom options | [option-tree-shaking](references/option-tree-shaking.md) |
| Minification | `minify: true`, `minify: 'dce-only'` | [option-minification](references/option-minification.md) |
| Source maps | `sourcemap: true`, `'inline'`, `'hidden'` | [option-sourcemap](references/option-sourcemap.md) |
| Watch mode | `watch: true`, watch options | [option-watch-mode](references/option-watch-mode.md) |
| Cleaning | `clean: true`, clean patterns | [option-cleaning](references/option-cleaning.md) |
| Log level | `logLevel: 'silent'`, `failOnWarn: false`, `suppressWarnings: [...]` | [option-log-level](references/option-log-level.md) |

## Dependency Handling

| Feature | Usage | Reference |
|---------|-------|-----------|
| Never bundle | `deps: { neverBundle: ['react', /^@myorg\//] }` | [option-dependencies](references/option-dependencies.md) |
| Always bundle | `deps: { alwaysBundle: ['dep-to-bundle'] }` | [option-dependencies](references/option-dependencies.md) |
| Only bundle | `deps: { onlyBundle: ['cac', 'bumpp'] }` - Whitelist | [option-dependencies](references/option-dependencies.md) |
| Only import | `deps: { onlyImport: ['cac'] }` - Whitelist runtime imports in output | [option-dependencies](references/option-dependencies.md) |
| Externalize all | `deps: { neverBundle: true }` | [option-dependencies](references/option-dependencies.md) |
| Resolve subpaths | `deps: { resolveDepSubpath: true }` - Resolve external subpath imports (default `false`) | [option-dependencies](references/option-dependencies.md) |
| Auto external | Automatic dependency/peer/optional externalization | [option-dependencies](references/option-dependencies.md) |

## Output Enhancement

| Feature | Usage | Reference |
|---------|-------|-----------|
| Shims | `shims: true` - Add ESM/CJS compatibility | [option-shims](references/option-shims.md) |
| CJS default | `cjsDefault: true` (default) / `false` | [option-cjs-default](references/option-cjs-default.md) |
| Package exports | `exports: true` - Generate exports field | [option-package-exports](references/option-package-exports.md) |
|

SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.

What the source does

Filesystem

none-observed

Network

none-observed

Shell

none-observed

Dependencies

pinned

Secrets in source

none-found

Findings (1)

Load environment variables from file:

Gates applied: no_behavioural_pass.

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