/**
 * @fileoverview Handler for persisting a chat message, plus a driver-error formatting utility.
 *
 * createMessagesHandler validates and inserts a message row scoped to the
 * authenticated user; describeError flattens Drizzle/D1's wrapped `cause`
 * chain into a single readable string for logging.
 */
import type { MessagesDeps } from "../types";
/**
 * Flattens an error's `cause` chain into one string. Drizzle wraps driver
 * errors (e.g. D1's "no such column" / constraint failures) in a generic
 * "Failed query" error and puts the real one in `cause`, which structured
 * log sinks drop unless serialized explicitly.
 */
export declare function describeError(err: unknown): string;
export declare function createMessagesHandler(deps: MessagesDeps): {
    POST: (req: Request) => Promise<Response>;
};