Mac storage basics · Purgeable space and local snapshots
What is a com.apple.os.update snapshot?
Short answer: A snapshot macOS takes when installing an update so it can finish or roll back safely. It's managed by macOS and often required; leave it alone.
macOS takes a snapshot of the system when it installs an update, so it can complete or roll back the update safely. You'll see it named with com.apple.os.update in Disk Utility or tmutil listings.
It's managed by macOS and is often required — leave it alone. Snapshots you can safely release are the Time Machine ones (named com.apple.TimeMachine). Storage Studio's Local Snapshots window marks system-required snapshots and never removes them.