Apple today seeded build 13C48 of OS X 10.9.2 to developers, marking the fourth beta iteration of 10.9.2. The release comes a week after the third OS X 10.9.2 beta, build 13C44, and a little over a month after the first OS X 10.9.2 beta.
The update is available to registered developers through the Software Update mechanism in the Mac App Store as well as through the Mac Dev Center.
Apple continues to ask developers to focus on mail, messages, graphics drivers, VoiceOver, VPN, and SMB2. Earlier betas of OS X 10.9.2 began allowing Mac users to block people on iMessage and FaceTime, as can be done in iOS 7, and also introduced FaceTime Audio.
Top Rated Comments
The BEST OS for 4K displays... let's throw some subjective squabble out there rather than answering the actual point.
It clearly proves that Apple supports 4K displays (MULTIPLE 4K displays.) Some aren't supported and there will be subjective flaws...etc as usual, but there is support for 4K displays. Saying there isn't is incorrect...
Scaling is not reducing resolution.
Scaling is keeping high resolution and just making UI larger (which is perfectly fine and reasonable).
If you download the OpenGL Extensions Viewer (https://itunes.apple.com/app/opengl-extensions-viewer/id444052073?mt=12) and go to the "OpenGL", "Extensions", or "Report" tabs, you can see a list of what your system supports.
For reference, here is what's displayed in Mac OS 10.9.1 on my system: