/**
 * Calculate exponential backoff delay
 * @param attempt - Attempt number (0-indexed)
 * @returns Delay in milliseconds
 */
export declare function calculateBackoff(attempt: number): number;
/**
 * Check if an error is fatal (should stop retrying)
 * @param err - Error to check
 * @returns true if error is fatal
 */
export declare function isFatalError(err: Error): boolean;