Xamarin.Mac and Xamarin.iOS have always been close sister projects, sharing much of their underlying tooling and infrastructure. One of the features in the upcoming version of Xamarin.Mac that we are very excited about is the runtime unification.

Underlying any application that uses Xamarin.Mac (or Xamarin.iOS) is a runtime that manages interactions with the objective-c runtime. It handles exposing your C# objects to objective-c and your calls into various Apple APIs. Up until now we had two separate runtimes, one for iOS and one for OS X.

The runtime unification effort changes that, we now have the same runtime powering our Mac and iOS products. This will bring bug fixes and performance work done on iOS to OS X and enable many of the features that were pioneered in iOS to come to the Mac platform,  such as the new refcount system.

While we have worked hard to test these runtime changes internally, such a far reaching change has the potential to introduce bugs in many places.

We are releasing a preview version of the upcoming Xamarin.Mac to the alpha channel for an extended period of time for testing.

While the runtime unification work is the major feature of this preview release, this alpha also adds support for these 64-bit frameworks:

• Accounts
• GameController
• EventKit
• MapKit
• MediaAccessibility

in addition to the frameworks provided in the previous alphas:

• CloudKit
• GLKit
• JavaScriptCore
• LocalAuthentication
• SpriteKit

We are asking you to test your applications with it and report any issues you might find.