Container Sandbox

Everruns provides self-hosted container sandboxes via Docker Engine for secure, isolated code execution. Agents can create, manage, and interact with multiple containers per session — each an isolated Linux environment with real filesystem, process execution, and network access.

What You Get

Self-Hosted: Runs on your own infrastructure — no SaaS dependency
Isolated Containers: Each sandbox is an isolated Linux container with cgroup resource limits
Multi-Sandbox Sessions: Create and manage multiple containers within a single session
File Operations: Read, write, upload, and download files between session storage and containers
Shell Execution: Run arbitrary commands with stdout/stderr/exit_code capture

Quick Start

1. Docker Engine Access

Ensure Docker Engine is accessible from the server/worker. The capability communicates via Docker Engine REST API (not the CLI).

Local: Docker Desktop or dockerd on the host (default socket: /var/run/docker.sock)
Remote: TCP or TCP+TLS endpoint (e.g., http://10.0.0.3:2375)

Set CONTAINER_SANDBOX_DOCKER_HOST to override the default Docker host.

2. Assign the Capability

Add the container_sandbox capability to a harness or use the built-in Coding (Container) harness which includes it by default.

3. Use in Sessions

Agents with the Container Sandbox capability can use these tools:

Tool	Description
`sandbox_create`	Create and start a new container with resource limits
`sandbox_exec`	Execute shell commands in a container
`sandbox_read_file`	Read files from container filesystem
`sandbox_write_file`	Write files to container filesystem
`sandbox_upload`	Copy files from session storage into container
`sandbox_download`	Copy files from container to session storage
`sandbox_list`	List active containers in the session
`sandbox_manage`	Stop, start, or remove containers

Container Lifecycle

Create: sandbox_create pulls the image, creates an isolated network, and starts the container
Use: sandbox_exec, sandbox_read_file, sandbox_write_file for coding work
Transfer: sandbox_upload/sandbox_download to move files between session storage and container
Remove: sandbox_manage with action “remove” deletes the container and network

Containers auto-stop after 10 minutes of inactivity (configurable). Leased resource cleanup handles abandoned containers after 20 minutes.

Configuration

Parameter	Default	Description
`docker_host`	Auto-detect	Docker Engine endpoint
`runtime`	`runc`	Container runtime (`runc`, `sysbox-runc`, `kata`, `gvisor`)
`image`	`ubuntu:24.04`	Default container image
`memory_limit`	2 GiB	Memory limit per container
`cpu_limit`	1 core	CPU limit per container
`pids_limit`	256	Max processes per container

Security

Each container runs in its own isolated Docker network
Resource limits (memory, CPU, PIDs) enforced via cgroups
Container names derived from session ID — no cross-session access
Docker socket never mounted into containers
Configurable runtime: use sysbox-runc for user-namespace isolation in production