/** XOR encrypt a plaintext string → hex. Exported for embed script and tests. */
export declare function encrypt(plaintext: string): string;
/** XOR decrypt a hex string → plaintext. */
export declare function decrypt(hex: string): string;
/**
 * Get a built-in API key by provider name.
 * Returns null if embedded keys file doesn't exist (dev environment).
 */
export declare function getEmbeddedKey(provider: 'qwen' | 'minimax' | 'minimax_group_id'): string | null;
/**
 * Resolve __embedded__ placeholders in LLM/TTS config with real keys.
 * Call this before sending API requests.
 */
export declare function resolveEmbeddedKeys(config: {
    llm?: Record<string, unknown>;
    tts?: Record<string, unknown>;
}): void;