1
The agent prompt
Paste one prompt into Claude Code or Codex. It installs MXC, writes a small sandbox command and runs three tests in front of you.
Free guide · Microsoft MXC 1.0
Lock your coding agent in a sandbox with Microsoft MXC in 5 minutes
MXC is Microsoft's free sandbox for code that comes from an AI model. Commands run with no internet and only your project folder writable, so your SSH keys and home folder stay out of reach. This guide sets it up for Claude Code, Codex or any agent with a terminal.
- A ready prompt that lets your coding agent build a sandbox command for you
- The one setting that turns MXC on in Codex for Windows
- 5 steps with screenshots and three tests that prove the sandbox holds
- What it costs, what it can't block on a Mac and fixes for the errors people hit
A look inside
What's inside
2
Codex on Windows
Codex already ships MXC support. One test command and one setting in config.toml switch it on.
3
What it blocks and what it doesn't
The sandbox blocks the network and your home folder and lets the agent work in the project folder. On a Mac it can't filter by website, and the guide shows what that means.
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Questions, answered
Is this guide free?
Yes. You sign up with your email once and get this guide plus every other guide in the library.
Is Microsoft MXC free?
Yes. MXC is open source under the MIT license and needs no account. It contains no AI model, so it adds no model costs. Telemetry only exists on Windows and stays off unless the user agrees and the app asks for it.
Does it work with Claude Code?
Not as a built-in setting. Codex on Windows has MXC support built in. For Claude Code and every other agent, the guide uses the official Node package: your agent sends risky commands through a small sandbox script instead of running them directly.
What happens after I enter my email?
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