I modified an InputMethodKit example (fairly recent one from github, compiled fine and worked as expected on my machine as it was) to create a window with a WKWebView and the window doesn't load. I know that loadView is getting called, but the window never appears after calling showWindow on the window controller and there is a mysterious error in the console: bootstrap_check_in(): (os/kern) unknown error code (44c) From googling this it seems App Sandbox related, but I think I have everything set up correctly (App Sandbox on with outgoing connections allowed) Totally stumped, any help or ideas would be appreciated Here's the relevant code: View controller import Foundation import WebKit import AppKit class InputWindowViewController: NSViewController, WKUIDelegate { var webView: WKWebView! override func loadView() { NSLog("LoadView") webView = WKWebView() self.view = webView webView.uiDelegate = self webView.needsDisplay = true } override func viewDidLoad() { super.viewDidLoad() webView.load(URLRequest(url: URL(string:"https://www.apple.com")!)) } } Window controller import AppKit import Foundation import WebKit class InputWindowController: NSWindowController { var controller: InputWindowViewController? override init(window: NSWindow?) { controller = nil super.init(window: window) } override func loadWindow() { self.window = NSWindow(contentViewController: controller!) } required init?(coder: NSCoder) { controller = nil super.init(coder: coder) } } AppDelegate import Cocoa import InputMethodKit import WebKit // Necessary to launch this app class NSManualApplication: NSApplication { private let appDelegate = AppDelegate() override init() { super.init() self.delegate = appDelegate } required init?(coder: NSCoder) { // No need for implementation fatalError("init(coder:) has not been implemented") } } @main class AppDelegate: NSResponder, NSApplicationDelegate { var server = IMKServer() var candidates = IMKCandidates() var inputWindowController = InputWindowController() func applicationDidFinishLaunching(_ notification: Notification) { // Insert code here to initialize your application server = IMKServer(name: Bundle.main.infoDictionary?["InputMethodConnectionName"] as? String, bundleIdentifier: Bundle.main.bundleIdentifier) inputWindowController = InputWindowController() inputWindowController.controller = InputWindowViewController() inputWindowController.loadWindow() inputWindowController.showWindow(self) candidates = IMKCandidates(server: server, panelType: kIMKSingleRowSteppingCandidatePanel, styleType: kIMKMain) NSLog("tried connection") } func applicationWillTerminate(_ notification: Notification) { // Insert code here to tear down your application } } This code is probably awful in a lot of other ways I don't realize, but I wanted to get a webview window up before I put a bunch of time into this thing XCode 13.4 MacoOS 12.7.4