/**
 * Output formats accepted by OpenRouter's `/audio/speech` endpoint
 * (April 2026 docs). Only `mp3` and `pcm` are supported — narrower than
 * OpenAI's direct API which also exposes opus/aac/flac/wav.
 */
export type TtsResponseFormat = 'mp3' | 'pcm';
export interface TtsClientConfig {
    apiKey: string;
    /** Override base URL — useful for tests or pointing at OpenAI directly. Default: OpenRouter. */
    baseUrl?: string;
    /** Default model for this client. Default: `openai/gpt-4o-mini-tts`. */
    defaultModel?: string;
    /** Per-request timeout. Default: 30s. */
    timeoutMs?: number;
    /** Number of retry attempts on transient HTTP failures (5xx, network). Default: 2. */
    maxRetries?: number;
}
export interface TtsRequest {
    /** Text to synthesize. The provider rejects empty strings; keep chunks under ~4k chars. */
    text: string;
    /** Voice handle, e.g. 'nova', 'alloy', 'echo'. Provider-specific. */
    voice: string;
    /** Optional model override. Defaults to client.defaultModel. */
    model?: string;
    /** Output container/codec. Default: 'mp3'. */
    format?: TtsResponseFormat;
    /** Speaking-rate multiplier (0.25..4.0). Provider may clamp. Default: 1.0. */
    speed?: number;
    /** Optional abort signal for cancellation. */
    signal?: AbortSignal;
}
export interface TtsResponse {
    /** Raw audio bytes in the requested format. */
    audioBuffer: Buffer;
    /** Mime type matching the requested format. */
    mimeType: string;
    /** Audio duration in ms, measured via ffprobe on the produced buffer. */
    durationMs: number;
    /** Effective model used. */
    model: string;
    /** Voice used. */
    voice: string;
    /**
     * OpenRouter generation id for async cost resolution via /api/v1/generation.
     * Sourced from the `x-request-id` header. May be null if the provider does
     * not return one.
     */
    generationId: string | null;
}
export declare class TtsError extends Error {
    readonly status?: number | undefined;
    readonly providerBody?: string | undefined;
    constructor(message: string, status?: number | undefined, providerBody?: string | undefined);
}
/**
 * POST a single TTS chunk to the configured provider, retry on 5xx / network
 * errors up to `maxRetries`, then probe the resulting buffer for duration.
 *
 * Throws `TtsError` (with HTTP status when available) on permanent failure.
 */
export declare function generateTtsChunk(config: TtsClientConfig, request: TtsRequest): Promise<TtsResponse>;
/**
 * Mutable indirection used by `generateTtsChunk` to find its dependencies.
 * Tests reach into this object to swap `probeAudioDurationMs` for a fake
 * (ESM exports are immutable bindings, so a plain `vi.spyOn` on the named
 * export does not affect the in-module reference).
 */
export declare const ttsTestHooks: {
    probeAudioDurationMs: (audioBuffer: Buffer, format: TtsResponseFormat) => Promise<number>;
};
/**
 * Write the buffer to a tempfile, run ffprobe to get the format duration,
 * clean up. Errors propagate (caller can wrap as TtsError if needed).
 *
 * Exported under both the legacy name (`probeAudioDurationMs`) and via the
 * `ttsTestHooks` indirection so unit tests can override it.
 */
export declare const probeAudioDurationMs: typeof defaultProbeAudioDurationMs;
declare function defaultProbeAudioDurationMs(audioBuffer: Buffer, format: TtsResponseFormat): Promise<number>;
export {};