WKNavigationActionPolicy of "cancel" prints stack trace to console

Starting in iOS 26 (tested on 26.1), when I use any of the “policy” methods of WKNavigationDelegate to return an action policy of cancel I get a trace like this printed to console:

1   0x18de71bbc WebKit::WebFramePolicyListenerProxy::ignore(WebKit::WasNavigationIntercepted)
2   0x18db3dd50 WebKit::NavigationState::NavigationClient::decidePolicyForNavigationAction(WebKit::WebPageProxy&, WTF::Ref<API::NavigationAction, WTF::RawPtrTraits<API::NavigationAction>, WTF::DefaultRefDerefTraits<API::NavigationAction>>&&, WTF::Ref<WebKit::WebFramePolicyListenerProxy, WTF::RawPtrTraits<WebKit::WebFramePolicyListenerProxy>, WTF::DefaultRefDerefTraits<WebKit::WebFramePolicyListenerProxy>>&&)::$_0::operator()(WKNavigationActionPolicy, WKWebpagePreferences*)
3   0x100189e5c $sSo24WKNavigationActionPolicyVIeyBhy_ABIeghy_TR
4   0x100189d38 $s16WebkitPolicyTrap14ViewControllerC03webD0_06decideB3For15decisionHandlerySo05WKWebD0C_So18WKNavigationActionCySo0lmB0VctF
5   0x100189df4 $s16WebkitPolicyTrap14ViewControllerC03webD0_06decideB3For15decisionHandlerySo05WKWebD0C_So18WKNavigationActionCySo0lmB0VctFTo
6   0x18db255c0 WebKit::NavigationState::NavigationClient::decidePolicyForNavigationAction(WebKit::WebPageProxy&, WTF::Ref<API::NavigationAction, WTF::RawPtrTraits<API::NavigationAction>, WTF::DefaultRefDerefTraits<API::NavigationAction>>&&, WTF::Ref<WebKit::WebFramePolicyListenerProxy, WTF::RawPtrTraits<WebKit::WebFramePolicyListenerProxy>, WTF::DefaultRefDerefTraits<WebKit::WebFramePolicyListenerProxy>>&&)
7   0x18dea9848 WebKit::WebPageProxy::decidePolicyForNavigationAction(WTF::Ref<WebKit::WebProcessProxy, WTF::RawPtrTraits<WebKit::WebProcessProxy>, WTF::DefaultRefDerefTraits<WebKit::WebProcessProxy>>&&, WebKit::WebFrameProxy&, WebKit::NavigationActionData&&, WTF::CompletionHandler<void (WebKit::PolicyDecision&&)>&&)
8   0x18dea7a34 WebKit::WebPageProxy::decidePolicyForNavigationActionAsync(IPC::Connection&, WebKit::NavigationActionData&&, WTF::CompletionHandler<void (WebKit::PolicyDecision&&)>&&)
9   0x18d9cbbf4 void IPC::handleMessageAsync<Messages::WebPageProxy::DecidePolicyForNavigationActionAsync, IPC::Connection, WebKit::WebPageProxy, WebKit::WebPageProxy, void (IPC::Connection&, WebKit::NavigationActionData&&, WTF::CompletionHandler<void (WebKit::PolicyDecision&&)>&&)>(IPC::Connection&, IPC::Decoder&, WebKit::WebPageProxy*, void (WebKit::WebPageProxy::*)(IPC::Connection&, WebKit::NavigationActionData&&, WTF::CompletionHandler<void (WebKit::PolicyDecision&&)>&&))
10  0x18d9c7728 WebKit::WebPageProxy::didReceiveMessage(IPC::Connection&, IPC::Decoder&)
11  0x18e49a0d8 IPC::MessageReceiverMap::dispatchMessage(IPC::Connection&, IPC::Decoder&)
12  0x18df1908c WebKit::WebProcessProxy::dispatchMessage(IPC::Connection&, IPC::Decoder&)
13  0x18d9dfc28 WebKit::WebProcessProxy::didReceiveMessage(IPC::Connection&, IPC::Decoder&)
14  0x18e47f72c IPC::Connection::dispatchMessage(WTF::UniqueRef<IPC::Decoder>)
15  0x18e47fac4 IPC::Connection::dispatchIncomingMessages()
16  0x199ad3758 WTF::RunLoop::performWork()
17  0x199ad4eb0 WTF::RunLoop::performWork(void*)
18  0x1804563a4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__
19  0x1804562ec __CFRunLoopDoSource0
20  0x180455a78 __CFRunLoopDoSources0
21  0x180454c4c __CFRunLoopRun
22  0x18044fcec _CFRunLoopRunSpecificWithOptions
23  0x1926be9bc GSEventRunModal
24  0x18630f0d8 -[UIApplication _run]
25  0x186313300 UIApplicationMain
26  0x18554ac38 block_destroy_helper.15
27  0x10018a70c $sSo21UIApplicationDelegateP5UIKitE4mainyyFZ
28  0x10018a67c $s16WebkitPolicyTrap11AppDelegateC5$mainyyFZ
29  0x10018a818 __debug_main_executable_dylib_entry_point
30  0x1000cd3d0 29  dyld                                0x00000001000cd3d0 start_sim + 20
31  0x1002bab98 30  ???                                 0x00000001002bab98 0x0 + 4297829272

This doesn’t happen in 18.6. Also, it doesn’t seem to have any negative consequences other than the console spam? But then, the navigation is being cancelled anyway, so maybe it’s trapping and just happens to have the effect of not loading the request?

Anyway, I guess I can’t upload zips. But it’s pretty easy to reproduce. Just assign a WKWebView a navigationDelegate with an implementation like:

func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping @MainActor (WKNavigationActionPolicy) -> Void) {
  decisionHandler(.cancel)
}

and then have it .load() anything. Have I been doing this wrong and 26 exposes it? Or is this a bug in 26? If the latter, any downstream consequences I should be looking out for?

• macOS 15.7.1 (24G231)
• Xcode 26.1.1 (17B100)
• iOS 26.1 (23B86)