Google's Agent Sandbox, Rebuilt on Firecracker: 64 VMs Share 3 MiB Each

Google Described Its Agent Sandbox. I Built One with Firecracker and Measured It

Google's Agent Compute Engine gives every AI agent session its own checkpointed microVM, but it isn't available yet and ships no numbers. So I rebuilt the pattern on Firecracker in about 2,200 lines of Go: warm snapshots shared copy-on-write, tool-call-driven checkpointing, and a guest with no network card whose only exit is vsock to a credential-holding proxy. Sixty-four idle forks of a 512 MiB VM cost roughly 3 MiB of host memory each; a snapshot restore answers in 25 ms on bare metal, versus 150 ms for 64 simultaneous forks. Nested virtualization on a Mac mini broke at twelve forks — and taught me the most.