We are introducing a new stack type this week: Previous Xamarin, Visual Studio for Mac, Stable channel, on macOS. 
This stack is the previous, snapshot version of “Xamarin, Visual Studio for Mac, Stable channel, on macOS”. When we roll out an updated version of “Xamarin, Visual Studio for Mac, Stable channel, on macOS” we will keep the last one as the new “previous”. Once a machine image is marked as “previous” we only update the Bitrise CLI and caches on it.
This stack type can come in handy if you experience issues with the latest Visual Studio for Mac Stable stack type. At the time of writing this, the “previous” is fixed on Xcode 9.0 and “current” is on Xcode 9.1.
For the complete list of preinstalled tools and versions please see this stack’s system report: https://github.com/bitrise-io/bitrise.io/blob/master/system_reports/osx-vs4mac-previous-stable.log
Happy building! 