Server SDK

The Server SDK runs inside the sandbox. It is the HTTP service the image keeps listening on, port 9000 by default. The package is agent-sandbox-server. Import agent_sandbox.server. A template's commands.py uses it to register commands, turn capabilities on, and call start(9000).

pip install agent-sandbox-server

from agent_sandbox.server import command, start


@command(description="Say hello")
def hello(name: str = "world") -> dict:
    return {"message": f"Hello, {name}!"}


if __name__ == "__main__":
    start(9000)

This code does not create a cloud sandbox and does not read a sandbox API key. Creating the sandbox and calling these routes is the Client SDK or the abx CLI.

Start here

Guide	What it covers
Authoring templates	`template.yaml`, the Dockerfile, `commands.py`
Template server HTTP API	The routes the process actually serves
Best practices	The server carries no provider; turn groups on only when needed
Fine-grained capabilities	Enable routes one endpoint at a time
File and command controls	Limit paths and commands
Agents API	HTTP sessions for Codex and Qwen Code inside the sandbox
Hosted agents	How those routes refuse and what they return

Reference: Server HTTP API, template.yaml, Agents API reference, Server API design.

Examples

These commands.py files start with the image. See the example index:

examples/templates/python-hello/commands.py — the smallest command server
examples/templates/agents-cli/commands.py — only the session Agents routes are open

examples/templates/python-hello/call_api.py is not the Server SDK. It runs outside the sandbox and sends HTTP to a server that is already listening. That script is a Client SDK example.