This weekend, Apple seems to have updated the OS X Mavericks Golden Master (GM) version to a new build. The new build is 13A603 while the original GM seed was 13A598. It’s not common for Apple to change the GM build for a Mac OS, but it is not without precedent. Apple has altered GM iOS seeds before they shipped to customers on a few occasions in the past. Users of the new build have not reported any noticeable user-facing alterations…

The new Mavericks build is not available via the Mac Developer Portal or via Software Update. Instead, it is appearing for users installing OS X Mavericks GM for the first time. Additionally, multiple readers have had success installing the new build by re-installing the Mavericks GM over the 13A598 version. It is currently unclear why Apple felt it necessary to create a new GM build, but it is likely built to squash some remaining bugs. Also unclear: which build Apple plans to actually ship and if this new silent 13A603 release is simply an error.

In early September, we reported that OS X Mavericks will ship in late October, and recent information has pinpointed a release later this week. The new Mac OS will arrive alongside new MacBook Pros, with the new Mac Pro to ship in the coming months. It’s unclear if the new GM of Mavericks will push back the launches as the new build would likely require Apple to re-install Mavericks on the new Macs.

SystemMigration.framework: BaseSystemBinaries/System/Library/PrivateFrameworks/SystemMigration.framework Essentials/System/Library/PrivateFrameworks/SystemMigration.framework

Mail + supporting stuff (build # went 1812 -> 1816): Essentials/Applications/Mail.app Essentials/System/Library/InternetAccounts/Mail.iaplugin Essentials/System/Library/InternetAccounts/SetupPlugins/MailAccountSetup.iaplugin Essentials/System/Library/PrivateFrameworks/EmailAddressing.framework Essentials/System/Library/PrivateFrameworks/IMAP.framework Essentials/System/Library/PrivateFrameworks/Mail.framework Essentials/System/Library/PrivateFrameworks/MailCore.framework Essentials/System/Library/PrivateFrameworks/MailService.framework Essentials/System/Library/PrivateFrameworks/MailUI.framework Essentials/System/Library/QuickLook/Mail.qlgenerator Essentials/System/Library/Spotlight/Mail.mdimporter

This file went down in size by ~50% (maybe debug symbols were compiled in originally): BSD/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/scipy/linalg/calc_lwork.so

A single element in this XML file changed: Essentials/System/Library/Frameworks/OpenCL.framework/Versions/A/Resources/BridgeSupport/OpenCL.bridgesupport

As you can see, it’s mostly Mail.app-related. Nothing to do with SMB shares as some guy out there is reporting.