Apple has released the first beta version of OS X 10.11.4 to developers. It can be found now at the Mac Developer Resource Center, or from the Updates section of the Mac App Store on a machine with the previous beta installed.

There's no word yet on what's been included in this first beta version. It should be noted that this release is for developers only and is not available yet for public beta testers of OS X El Capitan.

Source: Apple