/** Discriminates the success vs. error variant of the callback page. */
export type HTMLInput = {
    kind: "success";
} | {
    kind: "error";
    reason: string;
    description?: string;
};
/** Content-Security-Policy header value sent with every callback page. */
export declare const CSP_HEADER: string;
/** Renders the loopback callback page shown in the user's browser. */
export declare function renderHTML(input: HTMLInput): string;