/**
 * Normalizes configured thinking-message variants to a non-empty trimmed list.
 *
 * @param thinkingMessages Raw thinking-message variants.
 * @returns Trimmed non-empty variants or the shared defaults.
 * @private internal helper for Promptbook chat placeholders
 */
export declare function normalizeThinkingMessageVariants(thinkingMessages?: ReadonlyArray<string>): ReadonlyArray<string>;
/**
 * Returns a random delay used between browser-side thinking-message rotations.
 *
 * @returns Delay in milliseconds.
 * @private internal helper for Promptbook chat placeholders
 */
export declare function getRandomThinkingMessageDelayMs(): number;
/**
 * Selects one random thinking-message variant, avoiding the previous variant when possible.
 *
 * @param variants Available thinking-message variants.
 * @param excludeVariant Variant to avoid repeating immediately.
 * @returns Selected thinking-message variant.
 * @private internal helper for Promptbook chat placeholders
 */
export declare function getRandomThinkingMessageVariant(variants: ReadonlyArray<string>, excludeVariant?: string): string;
