One of the reasons for using Team Foundation Service and others hosted services is not worrying about technology updates as they are carried on by the provider.
Team Foundation Service is no exception and today, together with the Preview’s release of Visual Studio 2013 and Windows 8.1, the Hosted Build Server got upgraded to Windows 8.1 as well!
But, but. You won’t be able to select them in Visual Studio as a beginning. You have to browse to your Team Foundation Service instance, and enable them for the required project:
Just after doing that you’d be able to select the required Build Controller:
Man forewarned is forearmed :)