When an enhanced navigation fails (like when navigating to a non-Blazor page) the framework will retry the request as a normal navigation. You can prevent this duplicate request by disabling enhanced navigation when you know the endpoint isn't a Blazor endpoint using the data-enhance-nav attribute. But other than the duplicate request there isn't currently any indication that the original enhanced navigation failed. We should consider logging the enhanced navigation failure on the client so that the user has a more straight-forward way to discover that it happened.