import type { Express } from 'express';
export type ExpressVersion = 4 | 5 | 'unknown';
export interface DetectionResult {
    version: ExpressVersion;
    /**
     * The router object to walk. For v4, this is `app._router` (or `undefined`
     * for routeless apps). For v5, this is `app.router` (the function itself
     * has a `.stack` property).
     */
    router: {
        stack: unknown[];
    } | undefined;
}
/**
 * Detects whether the given app is Express 4, Express 5, or neither.
 *
 * Heuristic:
 *
 * - Express 4: `app._router` is truthy after first route registration.
 * Express 4's `_router` is a function (Router extends Function) that also has a `.stack`.
 * - Express 5: `app._router` is undefined; `app.router` is a function with a `.stack`.
 *
 * For an Express 4 app with no routes registered, `app._router` is undefined
 * AND accessing `app.router` throws (the deprecated 3.x→4.x tripwire). The
 * try/catch handles this — we report `version: 4, router: undefined`, and the
 * dispatcher returns an empty array (matching the post-1.1.0 fix behavior).
 */
export declare const detectExpressVersion: (app: Express) => DetectionResult;