Apple today seeded the first build of OS X 10.9.5 to developers, one month after . The new beta is available through the Software Update mechanism in the Mac App Store should be listed soon in the Mac Dev Center. The software has a build number of 13F7. OS X 10.9.5 follows new seeds of 7.0.6 and 6.1.6 for Mavericks and Mountain Lion, which were released to developers last night. It is unclear what improvements the 10.9.5 update will bring to Mavericks, but it is likely to include bug fixes and stability enhancements. The last Mavericks update, 10.9.4, added several Wi-Fi fixes and improved wake from sleep reliability.
