‘Seamless updates’, first introduced back in 2016 and arrived on every Google Pixel phone, allows for firmware updates to be installed to a secondary partition while the phone remains in use. This eliminates downtime between firmware updates to a single reboot, after which the secondary partition becomes the main one and the update has already completed. This also acts as a failsafe in case an update goes wrong – the system can fall back on the previous partition.
Update notification on a Samsung Galaxy S21 Ultra
Google has backed off on this requirement since it’s no longer in the Android CDD (Compatibility Definition Document). The CDD acts as a guideline for Android OEMs and lists what Google requires from OEMs for their devices to be compatible with the newest version of Android.
It’s presumed that the requirement was backed off by pressure from OEMs like Samsung, who’s latest Galaxy S21 smartphones do not have the framework to support seamless updates. Android Police has confirmed that the new Samsung Galaxy S21 Ultra does not support the feature. While Google had previously planned to require the feature, it is now mentioned in the CDD that OEMs “SHOULD” support a/b system updates. The “a” and “b” refer to the identical partitions that alternate between firmware updates.
Without seamless updates, an Android device will need to spend several minutes of downtime on a bootloader screen, without the ability to use any applications or make any phone calls, even of the emergency kind. Samsung’s reasoning for delaying such a feature is unknown.