Background secuirty update

Allow them to be installed.  Apple will do the magic on the backend - no need to force them via DDU.

Have allowed them via blueprints.

Does it allow a user schedule the reboot.

I ran manually on my own Macbook and it did require a restart. From the reading I have done some sugguest it install sliently in the background. I understand its all been deployed in blocks. So even if you are on 26.3.1, it might not install straightaway.

Thanks 

All of ours have required a restart and it happened in the most Apple way possible (notification with a 59 second countdown ha!).  

To deploy the Background Security Improvement (BSI) update, in Blueprint you add a custom declaration:

In the custom payload:

{  "TargetOSVersion": "26.3.1",  "TargetBuildVersion": "25D771280a",  "TargetLocalDateTime": "2026-03-18T14:30:00"}

Just note, this only applies to Mac’s that are already on 26.3.1.