import type { TTSChunk, TTSMetadata, TTSOptions, TTSResult } from "../types/index.js";
/**
 * Preserve source-stream backpressure while interleaving incremental TTS audio.
 * Source chunks are yielded before their derived audio, and TTS failures degrade
 * to the unchanged source stream.
 */
export declare function interleaveTTSStream<T>(params: {
    stream: AsyncIterable<T>;
    provider: string;
    options: TTSOptions;
    onComplete?: (result: TTSResult | undefined, error?: NonNullable<TTSMetadata["error"]>) => void;
}): AsyncGenerator<T | {
    type: "tts_audio";
    audio: TTSChunk;
}>;