Currently Foreman's Breadcrumb component (webpack/assets/javascripts/react_app/components/BreadcrumbBar/components/Breadcrumb.js) takes a configuration object with 'url' field, but AFAICT this does not allow for links to be React Router links. This means that when clicking the Hosts breadcrumb from the host details page, and you have the new All Hosts page setting turned on, the browser will reload the entire page rather than using React for the link.