alt Hacker NewsSnapshotting a filesystem is trivial with e.g. btrfs. You can hook snapshot creation in your agent.
That is a single one liner of btrfs subvolume snapshot, in a single hook configuration file, ready to be valued at $10B as quantum agentic versioned sandbox startup.
Part of the appeal (subjective, I know) of versioning is stuff like human-in-the-loop approvals. Think of a pull request: a change is requested by an agent, a human approves, changes get merged atomically. Even if other changes were applied since creation.