The Sandboxer MCP server

What can an agent do through the MCP server?

Through the MCP server, an agent can run the whole life of a sandbox. Per Sandboxer's MCP docs, it can create Linux sandboxes, run commands in the foreground or background, read and write files, put a port on an HTTPS URL, save and reuse snapshots, and stop or delete sandboxes when it is done. Everything runs in Sandboxer microVMs, not on your own computer.

The hosted server exposes 18 tools. Some of the main ones:

How do you connect Claude to Sandboxer?

In claude.ai or Claude Desktop, add Sandboxer as a custom connector. The steps, from the docs and the Claude connector guide:

1. Open Customize > Connectors and choose Add custom connector.
2. Enter https://sandboxer.com/mcp and add it.
3. Connect, sign in to Sandboxer and click Allow.
4. In a chat, turn the connector on from + > Connectors.

For Claude Code, one command adds the hosted server, and you sign in from the /mcp menu:

claude mcp add --transport http --scope user sandboxer https://sandboxer.com/mcp

How do other clients connect?

Any client that speaks the Streamable HTTP transport can connect to the same URL. ChatGPT adds it as a custom MCP server with OAuth; the ChatGPT guide covers the steps. Codex reads an API key from an environment variable:

# ~/.codex/config.toml
[mcp_servers.sandboxer]
url = "https://sandboxer.com/mcp"
bearer_token_env_var = "SANDBOXER_API_KEY"

Cursor uses an mcp.json entry with the same URL. Other clients can use OAuth 2.1 or send an API key as a bearer token. The server is also listed in the official MCP Registry as com.sandboxer/mcp.

Should you use the hosted or the local server?

Use the hosted server when you want nothing to install, browser sign-in, or web clients like claude.ai and ChatGPT. Use the local stdio server, sbx mcp or npx -y sandboxer-mcp, when you want default sizes and auto-stop for every sandbox the agent creates, or the extra handoff_session tool. Both create the same cloud microVMs. Sandboxer explains the choice in local or hosted MCP.

claude mcp add sandboxer -- sbx mcp
sbx mcp --type small --ttl 1800   # defaults for sandboxes the agent creates

handoff_session moves a local Claude Code or Codex session and its repo into a new sandbox and resumes the agent there, so you can close your laptop.

How do keys and access work?

Any API key works with the MCP server, and its scopes apply tool by tool. A key with the ci preset, for example, can create sandboxes but delete only the ones it created. Signing in with OAuth instead grants the app full access to your account, and each connected app appears on the API keys page, where you can disconnect it at once.

• Sandboxes created through MCP stop after an hour unless the agent sets ttlSeconds
• MCP calls share the API rate limit of 600 requests a minute per key
• A non-zero exit code is returned as a normal result, so the agent can see and fix the problem

For a headless agent, keep the key in the SANDBOXER_API_KEY environment variable rather than in a committed file.