We here at Macworld encourage users to install OS updates sooner rather than later, less because of the new features (if there are any) and mostly because of the important security and bug fixes. However, there are plenty of good reasons to turn off automatic update installs in System Settings and skip the occasional OS update. But, as it turns out, that update may install even if you don’t want it to.

Developer Howard Oakley has documented on his blog how macOS installs updates even when you have the setting to install updates turned off. In Oakley’s instance, he decided to stop updating his iMac Pro after a “slightly traumatic” experience with Sequoia 15.1.1. Oakley continued to get notifications for Sequoia 15.2, 15.3, and 15.3.1 which he subsequently declined. But he eventually received a notification to install the 15.3.1 update now or later, without any option to decline. A background activity was added to his Mac that scheduled the update to install in the middle of the night. Oakley posted the logs of the activity to show the process at work.

The logs even show how some processes that typically appear to the user during an installation are not shown and local authentication (a.k.a. asking for user input) is disabled. However, if the user sets macOS to do an update in the middle of the night, macOS skips those items (such as the license agreement) because the system asks the user to click a button to proceed. There’s a presumption that the user isn’t available to click those buttons.

Oakley didn’t offer a solution because he doesn’t know of one. If you get one of those notifications without a decline option, you could presumably select Install later, turn off Wi-Fi, and shut down your Mac, but the notification will eventually re-appear until the update installs. This behavior doesn’t sound like a bug, as Apple has a history of “encouraging” users to install the latest versions of its OSes and it appears that Apple is forcing the updates after a set period of time between updates.

Be sure to check out Oakley’s blog, which is a terrific mix of Mac technical articles and posts about painting. Oakley is a longtime Mac developer who has written several great Mac utilities.