Agent Substrate

Zero-trust sandboxing for millions of agents on Kubernetes.

Quickstart · Security · Architecture · Contributing

What is Agent Substrate?

Agent Substrate is a security-hardened, zero-trust runtime for sandboxed agents, engineered to safely run millions of agents and tools with 10x higher density than standard containers. Purpose-built for the era of autonomous agents, Substrate delivers fast resume operations in less than 500ms, with more than 500 activations per second. Agents get isolated compute, identity, networking, and storage. Sensitive credentials are kept out of reach from untrusted code. It supports multiple sandbox technologies, including microVMs and gVisor, while enabling a consistent lifecycle and management of all sandboxes.

At its core, Agent Substrate maps a larger set of “actors” (stateful workloads such as agents) onto a smaller pool of ready “workers”. Because agents spend most of their lives waiting on models, tools, or humans, Substrate snapshots idle actors out of memory and restores them when a request arrives.

Substrate is a low-opinion runtime, not an agent SDK. The workloads it runs do not have to be AI agents, though autonomous, untrusted, mostly-idle agents are the target for its isolation and scheduling model. It runs on standard Kubernetes: Pods, autoscaling, NetworkPolicies. It adds agent-specific scheduling, snapshotting, identity, and network mediation. This allows agentic, inference, training, and reinforcement learning workloads to share one infrastructure plane.

Security Model

Substrate treats every actor as untrusted and mutually hostile, so tenants can share physical nodes without sharing a security boundary. Every control operates within the cold-start and resume budget. See the Security Guide for the full list of security principles and threat model.

• Always sandboxed, VM-grade boundaries: Every actor runs inside a dedicated gVisor (runsc) or Cloud Hypervisor microVM sandbox with segregated compute, network, and storage. Plain Linux containers are not supported.
• Per-agent cryptographic identity: Every active actor receives a short-lived SPIFFE X.509 certificate by default, and the egress gateway can mint per-actor JWTs on demand when an egress policy calls for one. Both carry the actor identity and atespace (the Substrate namespace grouping), and are designed to federate with external identity systems.
• Zero credentials in the sandbox: Actors never hold actor identity JWTs/certs, API keys, or cloud tokens. The built-in egress gateway (atenet-egress) injects credentials into approved outbound requests outside the sandbox, so a prompt-injected or compromised agent has nothing to exfiltrate.
• Default-deny networking: Actors start with a private network stack, no inbound path except through the ingress router (atenet-router), no lateral actor-to-actor or control-plane access, and outbound traffic restricted by the egress gateway.
• Pluggable policy at the edge: The egress gateway acts as an external Policy Enforcement Point (PEP) that is fully replaceable, allowing you to attach your own authorization, DLP, prompt-injection scanning, or cloud IAM policy engine without placing policy code inside the untrusted sandbox.

Performance & Multiplexing

Watch the Agent Substrate cluster multiplex ~250 stateful actors across just 8 physical pods.

This demo highlights the core developer experience and "Agentic Infrastructure" capabilities of Substrate:

1. Actor Teleport: Suspend and resume actors onto any available worker in the pool, when needed.
2. Full-State Persistence: Working memory (RAM) and filesystem state are captured in snapshots and restored intact across hibernation cycles, without losing in-flight sessions or tool state.
3. 10x–30x Oversubscription: Multiplex a large registry of stateful actors onto a small pool of warm worker pods, paying for compute only while an agent is actively thinking or executing a tool.

To reproduce this demo in your own cluster, see the Counter Demo. For more walkthroughs, visit the agent-substrate YouTube channel.

Star History

Framework Agnostic & Compatibility

Agent Substrate is framework and agent harness agnostic. Because it runs standard OCI container images inside gVisor or microVM sandboxes and enforces security outside the workload, it hosts agents built on any stack without SDK changes:

This is the beginning of the README. Read the rest at the original. Read the full README ↗