MicroVM Support Is Consolidating on Cloud Hypervisor

Sep 5, 2026

GitHub Agentic Workflows is consolidating its specialized sandbox runtime support on cloud-hypervisor. The gvisor and docker-sbx runtime options are deprecated and will be removed in a future release.

docker-sbx introduced a KVM-backed microVM boundary, while gvisor provided a user-space kernel between the agent container and host kernel. Maintaining both paths alongside Cloud Hypervisor created separate installation, compatibility, and troubleshooting surfaces. Consolidating on one microVM implementation makes the stronger isolation path more consistent and easier to evolve.

What changes

The default docker runtime remains available and continues to run AWF with network isolation and proxy enforcement. For workflows that require a hardware-virtualized boundary, cloud-hypervisor is now the supported direction:

---
on: issues
sandbox:
  agent:
    runtime: cloud-hypervisor
---

Investigate this issue.

Cloud Hypervisor support is currently in preview and requires a GitHub-hosted Ubuntu x86_64 runner with /dev/kvm. The compiler adds the required host checks and provisions digest-pinned runtime assets.

Migrating existing workflows

Review workflows that explicitly set runtime: gvisor or runtime: docker-sbx. Select cloud-hypervisor when the workflow runs on an eligible GitHub-hosted runner and needs a microVM boundary. Otherwise, remove the runtime setting to use the default Docker profile.

Compile each updated workflow and review the generated lock file:

gh aw compile

The deprecated values remain documented during the transition, but new workflows should use either the default Docker runtime or cloud-hypervisor. See Agent Runtime Selection for requirements and tradeoffs.