/**
 * Accumulates per-request metrics for Provider API calls.
 *
 * Created once per incoming request (in the start middleware), threaded through Context and RequestOptions,
 * incremented by Provider on each API call, and logged by the finish middleware.
 */
export declare class RequestMetrics {
    private _apiCallCount;
    private _totalApiDurationNs;
    private _totalThrottleDelayNs;
    private _requestStartTime;
    private constructor();
    static startRequest(): RequestMetrics;
    endRequest(): {
        durationNs: bigint;
        apiCallCount: number;
        totalApiDurationNs: number;
        totalThrottleDelayNs: number;
    };
    /**
     * Record a completed API call.
     * Increments the call counter and accumulates the call's network duration and pre-flight
     * throttle delay (time spent waiting in the rate limiter before the request was dispatched).
     */
    recordExternalApiCall(duration: number, throttleDelay: number): void;
}