import type { IRouter } from 'express';
export interface ProxyOptions {
    /**
     * Lazy accessor for the upstream base URL — must include the scheme
     * (e.g. `http://127.0.0.1:3010` or `https://server:3010`). Returns
     * null when the backup-server isn't ready; those requests get a 503.
     */
    getUpstreamBase: () => string | null;
    /** Optional debug logger. */
    log?: (msg: string) => void;
}
export declare function registerProxy(router: IRouter, opts: ProxyOptions): void;
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