Hello, After upgrading to macOS 26.2, I’ve noticed a significant performance regression when calling evaluateJavaScript in an iOS App running on Mac (WKWebView, Swift project). Observed behavior On macOS 26.2, the callback of evaluateJavaScript takes around 3 seconds to return. This happens not only for: evaluateJavaScript("navigator.userAgent") but also for simple or even empty scripts, for example: evaluateJavaScript("") On previous macOS versions, the same calls typically returned in ~200 ms. Additional testing I created a new, empty Objective-C project with a WKWebView and tested the same evaluateJavaScript calls. In the Objective-C project, the callback still returns in ~200 ms, even on macOS 26.2. Question Is this a known issue or regression related to: iOS Apps on Mac, Swift + WKWebView, or behavioral changes in evaluateJavaScript on macOS 26.2? Any information about known issues, internal changes, or recommended workarounds would be greatly appreciated. Thank you. Test Code Swift class ViewController: UIViewController { private var tmpWebView: WKWebView? override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view. setupUserAgent() } func setupUserAgent() { let t1 = CACurrentMediaTime() tmpWebView = WKWebView(frame: .zero) tmpWebView?.isInspectable = true tmpWebView?.evaluateJavaScript("navigator.userAgent") { [weak self] result, error in let t2 = CACurrentMediaTime() print("[getUserAgent] \(t2 - t1)s") self?.tmpWebView = nil } } } Test Code Objective-C - (void)scene:(UIScene *)scene willConnectToSession:(UISceneSession *)session options:(UISceneConnectionOptions *)connectionOptions { NSTimeInterval startTime = [[NSDate date] timeIntervalSince1970]; WKWebView *webView = [[WKWebView alloc] init]; dispatch_async(dispatch_get_main_queue(), ^{ [webView evaluateJavaScript:@"navigator.userAgent" completionHandler:^(id result, NSError *error) { NSTimeInterval endTime = [[NSDate date] timeIntervalSince1970]; NSLog(@"[getUserAgent]: %.2f s", (endTime - startTime)); }]; }); }