Apple this week updated macOS Sierra, likely for the last time other than to deliver security patches.
The update -- the sixth since Sierra debuted in September 2016 -- signaled that its successor, macOS High Sierra, may officially ship on the same timetable as its predecessor.
Sierra 10.12.6 resolved a Lilliputian list of stability and compatibility issues, among them unexpected restarts of Xsan clients; Xsan is Apple's storage area network (SAN) technology. The stability of Terminal, the operating system's command-line interface, was also improved, according to Apple.
The update patched 37 security vulnerabilities in more than a dozen of Sierra's components, including Bluetooth and the Intel graphics driver.
Sierra 10.12.6 will likely be the final non-security update to the current Mac operating system. El Capitan received the same number of updates in 2015-2016, for example. (The previous four editions got only five non-security updates.)
Apple has also gotten into the habit of ending the then-current edition's updates about five to nine weeks before its next OS goes public. Last year, for instance, El Capitan's 10.11.6 made the scene on July 18, or 64 days before its Sept. 20 debut. Yosemite's final non-security update, 10.10.5, reached users on Aug. 13, 48 days before El Capitan's launch.
Under the same schedule as 2016's Sierra, this year's High Sierra would be expected to hit the Mac App Store during the week of Sept. 17-23.
At the same time Apple distributed the Sierra non-security update, the company issued patches for OS X 10.11 El Capitan (quashing 13 security vulnerabilities) and OS X 10.10 Yosemite (12 bugs). The Yosemite update, labeled Security Update 2017-003 Yosemite, will be the last for the 2014 operating system.
Apple supports each version of its Mac operating system for three years before dropping it from the will-patch list.
A public beta version of High Sierra is also available for early-bird testers. The second update to that beta was released July 12.