Apple has today seeded the third beta of macOS Sierra 10.12.1 to developers. This comes almost one week after the second update. Right now we’re not sure what’s new with this version. However, it likely has bug fixes and performance improvements.
To get the latest update, developers and public beta testers can go to the Mac App Store and find it there. If you don’t have it yet, you can download the installer from the developer center.