Runtime layer

The runtime layer is the Infra substrate responsible for creating, starting, stopping, inspecting, and deleting isolated workloads. In GlobalStacks, the primary workload unit is a sandbox.

Studio and Products consume this layer through higher-level objects such as workspaces, tasks, product environments, applications, and deployments. Those objects may use sandboxes for secure execution, but sandbox records stay infrastructure-scoped runtime instances.

Sandboxes can run on different runtime profiles. The runtime profile describes the required runtime kind, isolation class, agent traits, and minimum agent version. Placement uses that profile to decide which connected agent can safely run the workload.

Runtime profiles

Initial runtime profiles include:

• microvm: Firecracker-backed micro virtual machine (microVM) runtime for GlobalStacks-managed capacity.
• bare_metal: direct hardware capacity profile for future specialized workloads.
• existing Docker-backed paths for bring your own (BYO) and development scenarios.

Docker and Firecracker are not interchangeable. A Docker-capable host reports container isolation. A Firecracker-capable host reports hardware-virtualized micro virtual machine (microVM) isolation.

Agent reporting

Agents report structured runtime inventory:

• runtime kind, such as docker or firecracker_microvm
• isolation kind, such as process_container or hardware_virtualized_microvm
• runtime health and readiness reason
• supported runtime profiles
• resource accounting mode
• runtime feature flags

Firecracker-capable managed agents report traits such as:

• runtime.firecracker
• runtime.microvm
• isolation.hardware_virtualized
• isolation.guest_kernel
• host.kvm
• host.cgroup_v2
• host.tap
• host.nftables

Docker traits do not satisfy micro virtual machine (microVM) placement requirements.

Managed capacity

Managed-capacity agents enroll with scoped tokens. They cannot use normal bring your own (BYO) host bootstrap tokens, and they cannot expose host terminal access to tenant users.

Before a machine can serve managed micro virtual machine (microVM) workloads, the agent must pass runtime readiness checks for Kernel-based Virtual Machine (KVM), Firecracker, jailer, cgroups, tap networking, firewall policy, and writable volume attachment.