Or, Developer Preview 6 if you prefer. Whereas the previous Mavericks developer beta (13A538G) brought a bunch of new and updated apps, OS X 10.9 13A558 seems to be all about bug fixes and tweaks, though the release notes are silent on what’s new.

Informants have told the Fairer Platform that iBooks, which fist appeared in the August 8 seed, is still in need of work — i.e. heavy CPU loads on some Macs.

There’s a fresh build of Mail 7 in this beta, but no apparent new features say insiders.

Join the conversation on the OS X 10.9 Facebook Page

iTunes 11.1 b48, a.k.a. Beta 2, comes baked into OS X 10.9 13A558 and is believed to carry the iTunes in iCloud bug fix.

Apple has said OS X 10.9 will ship this Fall.

Anything else going on in this seed? Sound off in the comments below…

Sources: MacRumors and the usual suspects

Related posts:
— OS X 10.9 13A538G Includes iBooks, iPhoto, iTunes Betas
— Can My Mac Run OS X 10.9 Mavericks
— New in OS X 10.9: OpenGL 4.1, OpenCL 1.2
— What’s New in OS X 10.9 Mavericks
— What’s New in OS X Mail 7