Sandboxes

What are Sandboxes?

Sandboxes are isolated execution environments — lightweight virtual machines — where AI agents can safely run code, install packages, manipulate files, and execute long-running processes without affecting your host infrastructure.

Each sandbox is a Firecracker microVM powered by E2B, providing full Linux environments with hardware-level isolation.

Key Features

• Sub-200ms cold start — Sandboxes boot faster than a container
• Full Linux environment — Install packages, run processes, use the filesystem
• Hardware-level isolation — Firecracker microVMs, not containers
• Multiple runtimes — Python 3.12, Node.js 20, Deno out of the box
• Network isolation — Configurable network access per sandbox
• Resource limits — CPU, memory, and disk quotas per sandbox
• Auto-cleanup — Sandboxes are destroyed after timeout or explicit teardown
• Snapshot/restore — Save sandbox state and resume later

When to Use Sandboxes

Sandboxes are ideal when your agent needs a full environment:

For quick, stateless script execution, consider Code Execution instead.

How It Works

Your Agent
    |
    v
tx.sandboxes.create({ runtime: 'python-3.12' })
    |
    v
+---------------------------+
|  Firecracker microVM      |
|  - Isolated filesystem    |
|  - Dedicated CPU/memory   |
|  - Network namespace      |
|  - Auto-cleanup on expiry |
+---------------------------+
    |
    v
tx.sandboxes.run(id, { command: '...' })
    |
    v
tx.sandboxes.destroy(id)

1. Create — A microVM boots with your chosen runtime in under 200ms
2. Execute — Run commands, install packages, read/write files
3. Destroy — Sandbox is torn down and all resources are released

Resource Limits

Each sandbox has configurable resource limits:

Security Model

Sandboxes provide strong isolation:

• Firecracker microVMs — Each sandbox runs in its own microVM with a dedicated kernel, not a shared container runtime
• No host access — Sandboxes cannot reach the host machine or other sandboxes
• Network policies — Outbound network access can be restricted or disabled entirely
• Resource caps — CPU, memory, and disk are hard-limited to prevent resource exhaustion
• Ephemeral by default — All state is destroyed when the sandbox is torn down

Pricing

Sandboxes are billed per second of uptime:

Next Steps

• Quickstart — Create your first sandbox
• Runtimes — Available runtimes and custom templates
• Architecture — How sandboxes fit into the agent platform