export type JsonlTransportOptions = {
    /**
     * - Writable stream to write JSONL lines to. Defaults to process.stdout.
     */
    output?: NodeJS.WritableStream | undefined;
};
/**
 * JSONL transport: one JSON object per line to a writable stream.
 * Default: process.stdout. Pipe-friendly, parseable by any language.
 *
 * Debug output goes to stderr (never pollutes stdout).
 */
/**
 * @typedef {object} JsonlTransportOptions
 * @property {NodeJS.WritableStream} [output] - Writable stream to write JSONL lines to. Defaults to process.stdout.
 */
export class JsonlTransport {
    /**
     * @param {JsonlTransportOptions} [options={}]
     * @when you want to pipe structured Stream events as JSONL to a writable stream — pipe-friendly observability
     * @fails never throws on write; defaults to process.stdout when no output stream is given.
     * @example
     *   const stream = new Stream({ transport: new JsonlTransport() });
     */
    constructor(options?: JsonlTransportOptions);
    _output: NodeJS.WritableStream | (NodeJS.WriteStream & {
        fd: 1;
    });
    /**
     * @param {*} event - Event object to serialize as one JSON line.
     * @returns {void}
     */
    write(event: any): void;
}