{
    match upstream_result {
        Ok(Ok(mut response)) => {
            if let Some(fallback) = execute_error_fallback(
                state.clone(), peer, local, &snapshot, &host, tls, route,
                response.status(), &fallback_request, &fallback_body,
            ).await {
                return fallback;
            }
            let (origin_validation_headers, origin_plan, origin_reason, mut response) =
                include!("success_prepare.rs");
            include!("success_finish.rs")
        }
        Ok(Err(cause)) => {
            if let Some(session) = h2_direct_session.take() {
                session.cancellation().cancel();
            }
            let elapsed = upstream_started.elapsed();
            let connect_failure = cause.is_connect();
            let detail = upstream_failure_detail(&cause, &active_backend, elapsed, connect_failure);
            let failure_class =
                upstream_health_error_class(&cause, connect_failure, &active_backend);
            let graceful_h2_close = matches!(
                failure_class,
                "h2_graceful_goaway" | "h2_graceful_close"
            );
            if let Some(exchange) = &exchange {
                exchange.websocket_error("upstream_request_failed", "upstream_http_error");
                *exchange.upstream_error.lock().unwrap_or_else(|e| e.into_inner()) = Some(detail.clone());
            }
            if let Some(lease) = &active_lease {
                lease.error_detail(failure_class, &detail, final_attempt_elapsed);
            }
            if connect_failure {
                tracing::warn!(
                    backend = %active_backend.id,
                    origin = %active_backend.origin,
                    request_origin = %active_backend.request_origin,
                    tls_verify = active_backend.tls_verify,
                    elapsed_ms = elapsed.as_millis(),
                    error = %detail,
                    "upstream connection failed"
                );
            } else if graceful_h2_close {
                tracing::trace!(
                    backend = %active_backend.id,
                    origin = %active_backend.origin,
                    elapsed_ms = elapsed.as_millis(),
                    error = %detail,
                    "upstream H2 graceful close left an unrecovered request"
                );
            } else {
                tracing::debug!(
                    backend = %active_backend.id,
                    origin = %active_backend.origin,
                    elapsed_ms = elapsed.as_millis(),
                    error = %detail,
                    "upstream HTTP request failed"
                );
            }
            let status = if connect_failure {
                StatusCode::SERVICE_UNAVAILABLE
            } else {
                StatusCode::BAD_GATEWAY
            };
            let stale_class = classify_stale_error(&cause);
            if cache_settings.allows_stale_error_class(stale_class) {
                if let Some(stale) = serve_stale("cache_stale_if_error", elapsed, &active_backend.id, None) {
                    return stale;
                }
            }
            if let Some(fallback) = execute_error_fallback(
                state.clone(), peer, local, &snapshot, &host, tls, route,
                status, &fallback_request, &fallback_body,
            ).await {
                return fallback;
            }
            let mut response = error(
                status,
                if status == StatusCode::SERVICE_UNAVAILABLE {
                    "RustProxy: upstream unavailable (DNS, TCP or TLS connection failed)\n"
                } else {
                    "RustProxy: upstream did not provide a valid HTTP response\n"
                },
            );
            response
                .headers_mut()
                .insert("cache-control", HeaderValue::from_static("no-store"));
            if status == StatusCode::SERVICE_UNAVAILABLE {
                response
                    .headers_mut()
                    .insert("retry-after", HeaderValue::from_static("1"));
            }
            response
        }
        Err(_) => {
            if let Some(session) = h2_direct_session.take() {
                session.cancellation().cancel();
            }
            if let Some(exchange) = &exchange {
                exchange.websocket_error("upstream_timeout", "header_timeout");
                *exchange.upstream_error.lock().unwrap_or_else(|e| e.into_inner()) = Some("response_header_timeout".into());
            }
            if let Some(lease) = &active_lease {
                lease.error_detail(
                    "response_header_timeout",
                    "response_header_timeout",
                    final_attempt_elapsed,
                );
            }
            if cache_settings
                .allows_stale_error_class(crate::cache::StaleErrorClass::Timeout)
            {
                if let Some(stale) =
                    serve_stale("cache_stale_if_error", upstream_started.elapsed(), &active_backend.id, None)
                {
                    return stale;
                }
            }
            if let Some(fallback) = execute_error_fallback(
                state.clone(), peer, local, &snapshot, &host, tls, route,
                StatusCode::GATEWAY_TIMEOUT, &fallback_request, &fallback_body,
            ).await {
                return fallback;
            }
            error(
                StatusCode::GATEWAY_TIMEOUT,
                "RustProxy: upstream response deadline exceeded\n",
            )
        }
    }
}