/**
 * Prevents overlapping narration.generate runs for the same entry + field + voice.
 *
 * A second request fails immediately (no ElevenLabs call) so accidental
 * double-submit or parallel tabs do not double-charge. The lock entry stores
 * an acquisition timestamp; entries older than {@link DEFAULT_LOCK_TTL_MS}
 * are treated as stale (e.g. crashed handler that never reached `finally`)
 * and the new request is allowed to take over.
 */
/** Default 10 minutes — must comfortably exceed any realistic TTS timeout. */
export declare const DEFAULT_LOCK_TTL_MS: number;
export declare function makeNarrationGenerateLockKey(parts: {
    uid: string;
    documentId: string;
    attributeName: string;
    locale?: string | null;
    voiceId: string;
}): string;
export type AcquireLockOptions = {
    /** Acquired entries older than this are treated as stale. */
    staleAfterMs?: number;
    /** Override the clock for tests / fault injection. */
    now?: () => number;
};
export declare function acquireNarrationGenerateLock(lockKey: string, opts?: AcquireLockOptions): void;
export declare function releaseNarrationGenerateLock(lockKey: string): void;
/**
 * Drop all in-memory generate locks. Called from the plugin `destroy()` hook;
 * re-exported as `*ForTesting` for vitest cases that need a clean slate.
 */
export declare function clearNarrationGenerateLocks(): void;
export declare const resetNarrationGenerateLocksForTesting: typeof clearNarrationGenerateLocks;