/**
 * NDJSON (Newline-Delimited JSON) writer for headless mode.
 *
 * Each line is a self-contained JSON object with a `type` discriminator
 * and an ISO-8601 `timestamp`. Consumers can parse line-by-line.
 */
export interface NDJSONEvent {
    type: string;
    timestamp: string;
    [key: string]: unknown;
}
/**
 * Write a single NDJSON event to stdout.
 * Automatically adds an ISO timestamp.
 */
export declare function writeNDJSON(event: Omit<NDJSONEvent, 'timestamp'>): void;