gVisor and Firecracker: How Cloud AI Sandboxes Isolate Code and Whether They Work Locally

Managed cloud AI agent services from AWS and Google rely on two distinct isolation technologies — Firecracker microVMs and gVisor's syscall-intercepting Sentry process — to secure code execution environments. Firecracker spins up a dedicated lightweight virtual machine per session, while gVisor achieves isolation without a VM by intercepting system calls in userspace. Both are open source and can be run locally, though Firecracker requires Linux with KVM support and additional tooling, making it a heavier lift than simply switching a Docker runtime. gVisor is easier to adopt locally by switching Docker's runtime to runsc, adding kernel-level process isolation on top of other sandbox protections. On macOS, Docker Desktop and OrbStack already introduce an extra VM layer between containers and the host OS, reducing the practical need for gVisor in local developer setups.