Celesto

Secure, persistent computers for AI agents

OpenMuse · Quickstart · Python API · Agents and automation · Runtimes · Examples · Docs · Discord

Celesto gives an AI agent its own computer for running code, browsing the web, and using desktop apps. You can run that computer on your machine during development or in Celesto Cloud for remote and production work.

Each sandbox is a lightweight virtual machine, starts in about 500 ms, and can keep files and state between sessions. Because the agent runs in a separate virtual machine instead of a process on your computer, Celesto provides a stronger boundary for untrusted code.

Built with Celesto: OpenMuse

OpenMuse is our open-source computer coworker, built end to end on Celesto. It browses public websites in its own disposable Linux desktop while you watch, approve clicks and form changes, or take control.

Explore OpenMuse →

OpenMuse is a preview. Clone this repository to run it locally.

Quickstart

1. Install Celesto

On Linux or macOS, this command installs the Celesto CLI and Python SDK, prepares the machine, and checks that it is ready:

curl -fsSL https://celesto.ai/install.sh | bash

pip install celesto
celesto setup
celesto doctor

2. Create a sandbox

Give the sandbox a name so later commands can find it:

celesto computer create --name my-sandbox

celesto sandbox remains an equivalent spelling for every celesto computer subcommand.

3. Run a command

Everything after -- runs inside the sandbox:

celesto computer exec my-sandbox -- python --version

4. Delete the sandbox

Delete it when you no longer need its files or state:

celesto computer delete my-sandbox

Use celesto computer stop my-sandbox instead when you want to keep it for later. Restart it with celesto computer start my-sandbox.

Use the Python API

The installer includes the Python SDK. The with block creates a local sandbox when the block starts and deletes it when the block ends:

from celesto import Computer

with Computer() as computer:
    result = computer.run("echo 'Hello from Celesto!'")
    print(result.stdout)

Run in Celesto Cloud

Cloud sandboxes do not require virtualization software on your machine. First, set your API key:

export CELESTO_API_KEY="your-api-key"

Then run the same Python code with the cloud provider:

from celesto import Computer

with Computer(provider="cloud") as computer:
    result = computer.run("echo 'Hello from Celesto Cloud!'")
    print(result.stdout)

Agents and automation

Celesto commands print readable output by default. Add --json when a script or agent needs stable, machine-readable output. Every JSON response contains ok, command, exit_code, data, and error fields.

Check the machine before accepting work. --strict makes warnings fail the check:

celesto doctor --strict --json

Create a named sandbox and capture the JSON response:

celesto computer create --name agent-job --json

Run a command without opening an interactive shell:

celesto computer exec agent-job --json -- python -m pytest

Always clean up the sandbox by its exact name when the job ends:

celesto computer delete agent-job --json

Use unique names for concurrent jobs. Prefer exec for automation; reserve shell, ssh, and desktop for interactive work. Commands return a nonzero exit code on failure, and JSON errors include a recovery command when Celesto can provide one.

For a coding agent with its CLI already installed, start a preset directly:

celesto codex start

Celesto also provides presets for Claude Code, Pi, Hermes, OpenCode, and OpenClaw. See the agent presets guide for credentials, naming, and unattended usage.

Inspect and connect

Use celesto computer list to see sandboxes, celesto computer logs my-sandbox to inspect startup output, or celesto computer shell my-sandbox to open a fast interactive shell.

Add --follow to stream logs. Use celesto computer ssh my-sandbox when you need an SSH session. See the CLI reference for every command and shell completion.

Choose a runtime

Celesto exposes one default API and focused APIs for browser and desktop work:

Use Computer for the common command sandbox path. Use the Celesto factories for focused browser and desktop runtimes. Use Celesto(...) directly when you need low-level VM options such as the backend, communication channel, guest OS, mounts, or network policy.

Core capabilities

Browser

Use a browser sandbox when an agent only needs Chromium. Celesto exposes a CDP endpoint for automation and, in visible mode, URLs for live view and screen control.

from celesto import Celesto

with Celesto.browser(headless=False) as browser:
    print(browser.cdp_url)
    print(browser.viewer_url)
    print(browser.display_url)

• cdp_url: connect Playwright or another CDP client.
• viewer_url: watch the browser from another browser.
• display_url: connect a VNC client or computer-use agent.

Use headless=True when the agent only needs CDP. Start a visible browser from the CLI with:

celesto browser start --live

See examples/browser_sandbox.py for a complete example.

Linux computer

Use a Linux computer when an agent needs a visible desktop with more than a browser. The default image includes Chromium, a terminal, a file manager, and a text editor.

from celesto import Celesto

with Celesto.computer() as computer:
    print(computer.display.viewer_url)
    print(computer.browser.cdp_url)

    computer.files.write("/workspace/task.txt", "Review this file")
    print(computer.run("ls -la /workspace").stdout)

The API groups screen access under computer.display and Chromium access under computer.browser. If Chromium closes while the desktop stays active, call computer.browser.launch().

The first start downloads and verifies the Linux desktop image. Later starts reuse the cached image, so Docker is not required.

celesto computer create --desktop --name assistant
celesto computer open assistant
celesto computer delete assistant --desktop

See the Linux computer guide for Python and TypeScript examples.

Windows sandbox

Use a Windows sandbox when an agent must run PowerShell or Windows software. Celesto can boot Windows 11 from a baseline image, upload files, set environment variables, and start multiple guests from the same image.

from celesto import Celesto

with Celesto(
    os="windows",
    image="~/.celesto/images/win11.qcow2",
    ssh_user="celesto",
    ssh_password="celesto",
) as vm:
    print(vm.run("Write-Output 'hello from windows'").stdout)

Create an image from a Windows ISO:

celesto windows build-image \
    --iso ./Win11.iso \
    --virtio-win-iso ./virtio-win.iso \
    --output ~/.celesto/images/win11.qcow2

Windows guests require a Linux host with KVM. Host mounts, network controls, and snapshots remain Linux-only. See the Windows guide for image setup and guest requirements.

macOS desktop preview

On an Apple Silicon Mac, Celesto can create a temporary macOS desktop for app and installer tests without changes to your main system.

Prepare the reusable local image:

celesto setup --macos

Create and open a desktop:

celesto computer create --os macos --name test-mac
celesto computer desktop test-mac

The first setup downloads macOS from Apple, requires about 50 GB, and takes 20–40 minutes. The image stays on the Mac that created it. Celesto supports at most two macOS guests at once. See the macOS desktop guide for limits, shared folders, and cleanup.

Common workflows

Mount a host directory

Give a local sandbox access to an existing project without a copy step:

celesto computer create --name my-sandbox --mount ~/Projects/my-app
celesto computer shell my-sandbox
ls /workspace

Host mounts are read-only by default. The sandbox can read the source files, but writes under /workspace stay in the VM overlay and do not change the host copy.

Choose a guest path or mount multiple directories:

celesto computer create \
    --mount ~/Projects/my-app:/code \
    --mount ~/data:/mnt/data

Add --writable-mounts only when the sandbox must change the host files:

celesto computer create \
    --mount ~/Projects/my-app \
    --writable-mounts

The flag applies to every mount in that command. Do not combine a writable project directory with a directory that must remain unchanged.

The same option exists in Python:

from celesto import Celesto

with Celesto(mounts=["~/Projects/my-app"], writable_mounts=True) as vm:
    vm.run("echo hello > /workspace/from-sandbox.txt")

Upload one file

Copy a config, script, or small input into a live sandbox:

celesto computer file upload my-sandbox ./prompt.txt /tmp/prompt.txt

Or upload a file to a temporary sandbox from Python:

from celesto import Celesto

with Celesto() as vm:
    vm.upload_file("./prompt.txt", "/tmp/prompt.txt")

The destination must be an absolute guest path. Celesto replaces any file that already exists at that path.

Restrict network access

Sandboxes have internet access by default. On Linux with Firecracker, use vsock to keep command and file-transfer access while you disable outbound network access:

from celesto import Celesto

with Celesto(
    backend="firecracker",
    comm_channel="vsock",
    internet_settings={"mode": "off"},
) as vm:
    print(vm.run("echo hello").stdout)

Use mode="restricted" with allowed_cidrs to allow specific IPv4 addresses or ranges. The restricted modes require private network mode and do not support host mounts or exposed ports. Explicit command output and file downloads still work when outbound access is off.

An allowed_domains list resolves domains during setup and permits the resulting IP addresses. It does not check the hostname on each connection. DNS servers do not receive automatic access. See the network guide for supported combinations.

Start a code agent

Run a supported code agent in its own sandbox so it can edit and execute code without direct access to your host environment:

celesto codex start
celesto claude start
celesto pi start
celesto hermes start
celesto opencode start
celesto openclaw start --name openclaw-work --no-attach

Open the private OpenClaw dashboard after the sandbox starts:

celesto openclaw open-ui openclaw-work

The first OpenClaw start can take several minutes while Celesto installs its supported Node.js runtime and pinned OpenClaw release. See the agent presets guide for credentials and dashboard access.

Examples

Start here

Agent framework integrations

Each example includes any extra package command it requires.

Security

Each sandbox runs in its own virtual machine, which provides a stronger isolation boundary than process-level containers. Isolation still depends on secure host, hypervisor, image, credential, mount, and network configuration.

Celesto trusts a new local sandbox on its first connection to simplify development. Do not expose sandbox ports to the public internet without authentication and network controls. Treat writable mounts, forwarded credentials, and host-accessible services as explicit trust decisions.

See SECURITY.md for the security policy, threat model, and disclosure process.

Performance

The benchmark suite measures cold start, time to interactive, pause and resume, and snapshot create and restore. It uses the public Python SDK with the native host backend: Firecracker on Linux and QEMU on macOS.

uv run python scripts/benchmarks/bench.py

See the benchmark guide for flags, output, and metric definitions.

Contributing

See CONTRIBUTING.md to set up a development environment and submit a change. Coding agents should also read AGENTS.md for repository-specific commands, CLI conventions, release checks, and writing guidelines before editing the project.

License

Apache 2.0. See LICENSE for details.