/**
 * Shared Fallback Handler
 *
 * Handles POST /sms/fallback and /whatsapp/fallback — called by Twilio
 * when the primary incoming message webhook URL cannot be reached or
 * throws a runtime exception.
 *
 * Twilio sends the same payload as the incoming message webhook.
 * The fallback handler responds with a safe error message so the
 * end user is not left without a response.
 */
import type { Context } from "hono";
import type { MessagingChannel, TalkerDependencies } from "../../types";
/**
 * Handle a fallback webhook from Twilio.
 * Called when the primary incoming URL fails.
 * Returns a safe error message TwiML to the user.
 */
export declare function handleFallback(c: Context, deps: TalkerDependencies, channel: MessagingChannel): Promise<Response>;