/**
 * Sanitize model output for plain-text messaging surfaces.
 *
 * LLMs occasionally produce HTML tags (`<br>`, `<b>`, `<i>`, etc.) that render
 * correctly on web but appear as literal text on WhatsApp, Signal, SMS, and IRC.
 *
 * Converts common inline HTML to lightweight-markup equivalents used by
 * WhatsApp/Signal/Telegram and strips any remaining tags.
 *
 * @see https://github.com/openclaw/openclaw/issues/31884
 * @see https://github.com/openclaw/openclaw/issues/18558
 */
/** Returns `true` when the channel cannot render raw HTML. */
export declare function isPlainTextSurface(channelId: string): boolean;
/**
 * Convert common HTML tags to their plain-text/lightweight-markup equivalents
 * and strip anything that remains.
 *
 * The function is intentionally conservative — it only targets tags that models
 * are known to produce and avoids false positives on angle brackets in normal
 * prose (e.g. `a < b`).
 */
export declare function sanitizeForPlainText(text: string): string;