/**
 * Progress reporting — emits __progress__ JSON lines that ab-agent's
 * executor parses (see apps/ab-agent/src/skills/executor.ts).
 *
 * Always writes to stdout because the consumer reads stdout line-by-line.
 * Each event is a single JSON object on its own line, with the marker
 * field `__progress__: true` so non-progress stdout content is ignored.
 *
 * The consumer flattens the entire parsed JSON into `extra`, so any
 * additional context (model id, generationId, ...) can be passed as
 * top-level keys and will reach the SSE client unchanged.
 */
export interface ProgressEvent {
    /** Pipeline phase, e.g. `gen-image:request`. */
    phase?: string;
    /** 0..1 progress fraction. */
    progress?: number;
    etaSeconds?: number | null;
    elapsedSeconds?: number | null;
    /** Free-form context — flattened into the parsed JSON line. */
    [key: string]: unknown;
}
export declare function emitProgress(ev: ProgressEvent): void;