Apple today seeded build 13D43 of OS X 10.9.3 to developers



From MacRumors:

Apple continues to ask developers to focus on Graphics Drivers and Audio, and Safari. As was discovered with the first beta, 10.9.3 adds new support for 4K displays, offering “Retina” resolutions that improve readability along with support for 60Hz output from the Retina MacBook Pro.

  Apple Seeds OS X Mavericks 10.9.3 Build 13D43 to Developers