Apple on Tuesday supplied to developers and public testers a fourth pre-release beta of macOS 10.12.1, a forthcoming maintenance and security update for the Sierra operating system which could ship on next-generation MacBook Pros.

macOS Sierra 10.12.1 beta 4 is identified as build 16B2548a. Registered machines can access it through the Mac App Store.

The fourth build comes eight days after Apple provided beta 3 of macOS 10.12.1. It's been rumored that new MacBook Pro models, featuring a thinner design and OLED touch bar, will ship with macOS 10.12.1 later this month.

The software on the new MacBook Pro will be essential, because Apple is expected to introduce new ways of interacting with the notebook, headlined by an OLED touch-sensitive menu bar that is rumored to replace the current row of physical function keys.