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Best practices

How to run the in-sandbox server. Route shapes are in the template server HTTP API. Path and command limits are in File and command controls.

The server stays provider-free

agent_sandbox.server does not select a sandbox provider and does not read --provider. A template's commands.py imports only agent_sandbox.server and calls start(9000) under if __name__ == "__main__".

Which FROM line, whether the Dockerfile may contain CMD or ENTRYPOINT, and the platform start_cmd live in the CLI provider profile (abx-provider.toml [template], or the built-in alicloud-express constant). The HTTP routes do not change with that image. The client SDK does not pick the profile either.

Turn on only the groups you need

The server has nine capability groups. core stays on (GET /health, GET /capabilities). These start enabled: commands, file_ops, process, terminal, system. These start disabled: dev_tools, browser, agents.

A group is only a name for the endpoints that declare it; the endpoint rule is the one switch. Turn a default group off in the template policy, as a map:

server:
  groups:
    terminal: false
    process: false

core cannot be turned off. Turn an opt-in group on with a policy list (groups: [dev_tools]), with default_table().enable_group(CapabilityGroup.DEV_TOOLS) in commands.py, or with the environment variable ABX_SERVER_ENABLED_GROUPS=dev_tools. That variable only turns groups on; there is no variable that turns one off. GET /capabilities lists every endpoint with the rule that disabled it.

shell, code_run, and a PTY can run a program that reads any path the process can see. A path rule does not hold for an identity that also has those endpoints. For a template that only moves files, start from the transfer-only or read-only preset. See File and command controls.

Leave agents off until a session needs it

The Agents routes stay off until the process is started with ABX_SERVER_ENABLED_GROUPS=agents (or default_table().enable_group(CapabilityGroup.AGENTS) in commands.py, or groups: [agents] in the policy). With the group off, those paths answer 404 with code: endpoint_disabled and the rule that decided (default:opt-in:agents).

Codex and Qwen Code are supported today. Checklist, the local header, and the 404s: Hosted agents — Best practices.

One agent by default

Install only the CLI you are going to call. Installing both Codex and Qwen Code makes the image large.

The server's order is codex, then qwen-code. A request that does not name an adapter uses the first. GET /v1/agents/runtimes?order=asc returns them in that order. The list's default order is desc. default: true marks the one in effect. It does not follow the array index.

npm install -g @openai/codex

To use Qwen Code, send adapter, runtime, or the X-ABX-Adapter header, or set model to qwen-code (aliases qwen and qwencode). A model id such as gpt-5 is passed to the selected CLI. It does not switch the adapter.

Move the default off the first entry:

export ABX_AGENTS_DEFAULT=qwen-code

A JSON file named by ABX_AGENTS_CONFIG does the same with a top-level default or agents.default. claude-code, Cursor, and Qoder stay 404.

Open Agents routes one endpoint at a time

groups.agents: true is only the gate for this group. Each Agents route has its own endpoint id, the same way upload and shell do. The default scope is agents:use. This opens session create and nothing else:

from agent_sandbox.server import SandboxServer, ServerPolicy, default_table

policy = ServerPolicy.only("agents_sessions_create").with_options(groups={"agents": True})
server = SandboxServer(route_table=default_table(), policy=policy)

The same policy in YAML:

groups:
  agents: true
endpoints:
  "*":
    enabled: false
  agents_sessions_create:
    enabled: true

These endpoints do not accept paths or specialised params. A policy that sets either fails to load. The full endpoint id list is in Fine-grained capabilities.

Secrets are not echoed

GET /env omits a variable whose name contains TOKEN, SECRET, KEY, PASSWORD, or CREDENTIAL. When a policy is loaded it also omits ABX_SERVER_TOKEN, ABX_SERVER_POLICY, ABX_SERVER_POLICY_FILE, every token_env name, and every name that starts with ABX_SERVER_.

POST /env returns the names it updated ({"updated": [...]}), not the values. It refuses PATH, HOME, USER, SHELL, ABX_SERVER_TOKEN, and every ABX_* name. A policy can refuse more names with params.allow_vars / params.deny_vars on env_get and env_set.

A child process started while a policy with identities is active inherits the environment with those secret names removed. Passing one of them in a shell env object is env_var_not_allowed.

On the Agents routes, MCP header values come back as "***". A vault credential's value, prefix, length, and hash are absent from responses, errors, and events.