Thunder Sandbox for Python

Create short-lived GPU sandboxes, run commands over SSH, and move files with a small, typed Python API.

Thunder Sandbox uses the same account and credentials as the Thunder CLI. It handles sandbox lifecycle, SSH key creation, waiting for readiness, command execution, uploads, and downloads through one synchronous and asynchronous Python API.

Installation

Thunder Sandbox requires Python 3.10 or newer.

pip install thunder-sandbox

To install the current development branch directly from GitHub:

pip install git+https://github.com/Thunder-Compute/thunder-sandbox.git

Authenticate with the Thunder CLI before using the library:

tnr login

Alternatively, set TNR_API_TOKEN and, when using a non-default API endpoint, TNR_API_URL. API endpoints must use HTTPS.

Quick start

import thunder_sandbox as thunder

sandbox = thunder.Sandbox.create(
    cpu=4,
    memory=32,
    storage=50,
    gpu_type=thunder.GPUType.A6000,
    gpu_count=1,
    timeout=900,
)

try:
    sandbox.wait_until_ready()

    process = sandbox.exec("nvidia-smi")
    stdout = process.stdout.read()
    exit_code = process.wait()
    if exit_code != 0:
        raise RuntimeError(process.stderr.read())
    print(stdout)
finally:
    sandbox.terminate()

wait_until_ready() asks Thunder to hold the request open until the sandbox is ready, so it returns moments after startup finishes rather than on the next poll. Its timeout is enforced on the client: each held request is bounded here and retried until the sandbox is ready, fails, or the timeout passes. An API without this endpoint is polled instead.

Sandboxes are addressed by id. Sandbox.create() generates an Ed25519 key pair and stores it under ~/.thunder/sandbox_keys/<sandbox-id>. The public key is immutable for the lifetime of the sandbox.

A name is an optional label. It must be free of any other live sandbox in the organization, and it is released once a sandbox finishes, so the same label can be reused later. A name never addresses a sandbox:

sandbox = thunder.Sandbox.create(name="training-run", gpu_type=thunder.GPUType.H100)
print(sandbox.id, sandbox.name)

# Claiming a name a live sandbox already holds raises ConflictError.
# Looking one up searches live sandboxes; prefer Sandbox.from_id.
same = thunder.Sandbox.from_name("training-run")

Handling errors

Conditions worth retrying are typed, so they can be caught without matching on message text. Each carries the API's code, the HTTP status, and the server's retry_after hint when one was sent:

try:
    sandbox = thunder.Sandbox.create(gpu_type=thunder.GPUType.H100)
except thunder.CapacityError as exc:
    # No free GPU of that type right now; the request was fine.
    time.sleep(exc.retry_after or 30)
except thunder.RetryableError:
    # Rate limited, or Thunder could not service the request.
    ...

Run commands

Pass command arguments separately to avoid local shell interpretation:

process = sandbox.exec("python3", "-c", "print('hello from Thunder')")
print(process.stdout.read())
exit_code = process.wait()

Commands can set a working directory, environment variables, a timeout, or a pseudo-terminal:

process = sandbox.exec(
    "python3",
    "train.py",
    workdir="/home/ubuntu/project",
    env={"MODEL": "llama", "DEBUG": "1"},
    timeout=600,
)

Transfer files

sandbox.upload("model.py", "/home/ubuntu/model.py")
sandbox.upload("dataset", "/home/ubuntu/dataset", recursive=True)

sandbox.download("/home/ubuntu/results.json", "results.json")
sandbox.download("/home/ubuntu/checkpoints", "checkpoints", recursive=True)

Network policies

Sandboxes have unrestricted outbound access by default. Restriction is always explicit:

# No outbound internet access.
closed = thunder.Sandbox.create(block_network=True)

# Only the specified CIDRs and domains are permitted.
restricted = thunder.Sandbox.create(
    outbound_cidr_allowlist=["203.0.113.0/24"],
    outbound_domain_allowlist=["pypi.org", "files.pythonhosted.org"],
)

CIDR and domain allowlists are independent. Supply both when restricted workloads need both direct IP and DNS-based access.

For policy updates, None leaves that dimension unrestricted, while an empty sequence blocks it. Each call replaces the complete policy rather than merging with the previous allowlists.

Replace the complete outbound policy of a running sandbox with the same options used at creation:

# Permit package downloads while blocking other destinations.
restricted.update_network_policy(
    outbound_domain_allowlist=["pypi.org", "files.pythonhosted.org"],
)

# Block all outbound network access.
restricted.update_network_policy(block_network=True)

# Restore unrestricted outbound access.
restricted.update_network_policy()

update_network_policy() returns after Thunder accepts the desired policy; enforcement on the sandbox's node converges asynchronously. Tightening a policy blocks new connections but does not currently guarantee that already-established connections are terminated.

Environment and lifetime

sandbox = thunder.Sandbox.create(
    env={"EXPERIMENT": "baseline"},
    timeout=3600,
)

timeout is the sandbox lifetime in seconds. Set it to None to create a sandbox without an enforced TTL.

Work with existing sandboxes

with thunder.Client.from_cli() as client:
    for sandbox in client.list_sandboxes():
        print(sandbox.id, sandbox.status.value)

    sandbox = client.get_sandbox("sbx-0123456789abcdef")
    sandbox.wait_until_ready(timeout=300)
    print(" ".join(sandbox.ssh_command))

The private SSH key must still exist locally to execute commands or transfer files against an existing sandbox.

Async API

Every blocking operation has an awaitable _async twin on the same public class. This makes it possible to use one import and pass Client, Sandbox, and Process objects between synchronous and asynchronous application code:

import asyncio
import thunder_sandbox as thunder


async def main() -> None:
    sandbox = await thunder.Sandbox.create_async(
        gpu_type=thunder.GPUType.A6000,
        gpu_count=1,
    )
    try:
        await sandbox.wait_until_ready_async()
        process = await sandbox.exec_async("nvidia-smi")
        exit_code = await process.wait_async()
        if exit_code != 0:
            raise RuntimeError(await process.stderr.read_async())
        print(await process.stdout.read_async())
    finally:
        await sandbox.terminate_async()


asyncio.run(main())

An image-backed sandbox ignores the image's ENTRYPOINT and CMD and keeps the container alive for the sandbox lifetime. Commands run inside that container through sandbox.exec(...):

sandbox = thunder.Sandbox.create(image=thunder.Image.from_registry("ubuntu:24.04"))
process = sandbox.exec("sh", "-c", "echo hello")

Positional arguments to Sandbox.create start the first process through the same exec path after the sandbox becomes ready. Without an image, exec runs directly in the guest VM.

Configuration

Configuration is resolved from the following sources:

1. Explicit ClientConfig values.
2. TNR_API_TOKEN and TNR_API_URL environment variables.
3. Thunder CLI state in ~/.thunder/cli_config.json.
4. The default Thunder API endpoint.

Set TNR_HOME to use a different directory for CLI state and sandbox SSH keys.

License

Thunder Sandbox is available under the Apache License 2.0.