Apple Seeds OS X 10.9.3 Beta 9
Apple today has seeded OS X 10.9.3 beta 9 to developers. This version includes some minor bug fixes and improvements. It also includes Retina support for 4K displays connected to MacBook Pros with Retina Display. Apple is still asking developers to focus their testing on graphics drivers, audio, mail, and contacts and calendar sync.
Developers can update to beta 9 in the Mac App Store > Updates > Software updates > OS X 10.9.3 seed 9. If you don’t have it yet you can download it for the first time from the Mac Developer Center.