bolt.new/app/types/global.d.ts

interface Window {
  showDirectoryPicker(): Promise<FileSystemDirectoryHandle>;
}

interface FileSystemDirectoryHandle {
  getDirectoryHandle(name: string, options?: { create?: boolean }): Promise<FileSystemDirectoryHandle>;
  getFileHandle(name: string, options?: { create?: boolean }): Promise<FileSystemFileHandle>;
}

interface FileSystemFileHandle {
  createWritable(): Promise<FileSystemWritableFileStream>;
}

interface FileSystemWritableFileStream extends WritableStream {
  write(data: string | BufferSource | Blob): Promise<void>;
  close(): Promise<void>;
}