tsconfig

• Type: string | boolean
• Optional

Defined in: packages/rolldown/src/options/input-options.ts:809

Configures TypeScript configuration file resolution and usage.

Options

Auto-discovery mode (true)

When set to true, Rolldown enables auto-discovery mode (similar to Vite). For each module, both the resolver and transformer will find the nearest tsconfig.json.

If the tsconfig has references, Rolldown resolves them the way TypeScript does: a referenced project that includes the file takes precedence over the root. Each referenced project uses its own allowJs, so a .js/.jsx/.mjs/.cjs file is only included by projects that enable it. If no referenced project includes the file, Rolldown falls back to the root tsconfig.

export default {
  tsconfig: true,
};

Explicit path (string)

Specifies the path to a specific TypeScript configuration file. You may provide a relative path (resolved relative to cwd) or an absolute path.

If the tsconfig has references, this mode behaves like auto-discovery mode for reference resolution.

export default {
  tsconfig: './tsconfig.json',
};

export default {
  tsconfig: '/absolute/path/to/tsconfig.json',
};

TIP

Rolldown respects references and include/exclude patterns in tsconfig, while esbuild does not. If you need esbuild-compatible behavior, specify a tsconfig without references. You can use extends to share the options between the two.

What's used from tsconfig

When a tsconfig is resolved, Rolldown uses different parts for different purposes:

Resolver

Uses the following for module path mapping:

• compilerOptions.paths: Path mapping for module resolution
• compilerOptions.baseUrl: Base directory for path resolution

Transformer

Uses select compiler options including:

• jsx: JSX transformation mode
• experimentalDecorators: Enable decorator support
• emitDecoratorMetadata: Emit decorator metadata
• verbatimModuleSyntax: Module syntax preservation
• useDefineForClassFields: Class field semantics
• And other TypeScript-specific options

Example

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "ESNext",
    "jsx": "react-jsx",
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"],
      "@components/*": ["src/components/*"]
    }
  }
}

With this configuration:

• JSX will use React's automatic runtime
• Path aliases like @/utils will resolve to src/utils

Priority

Top-level transform options always take precedence over tsconfig settings:

export default {
  tsconfig: './tsconfig.json', // Has jsx: 'react-jsx'
  transform: {
    jsx: {
      mode: 'classic', // This takes precedence
    },
  },
};

TIP

For TypeScript projects, it's recommended to use tsconfig: true for auto-discovery or specify an explicit path to ensure consistent compilation behavior and enable path mapping.

Default

true