October 9, 2026
MXC: Codex on Windows gets a sandbox that needs no admin rights
OpenAI's docs as of Oct 10: MXC mode in Codex CLI 0.162.0 and newer requires no administrator approval and creates no Windows user accounts. It is enabled with one line in config.toml.
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An update for those working with Codex on Windows: We built a new sandbox mode on top of Microsoft Execution Containers (MXC) from @Microsoft. Setup is faster, network control is stricter, and file access is more precise to configure. You need a compatible Windows 11 computer.
Today, we announced new @Windows platform capabilities and @surface devices built to empower people and organizations for the era of hybrid intelligence. Here are some of the highlights: - It all starts with trust. Microsoft Execution Containers (MXC) is now generally available on Windows 11, keeping agents contained within boundaries the operating system enforces. - HydraFusion brings hybrid intelligence to life, allowing models to run locally while seamlessly accessing the cloud when more scale or capability is needed. We're working with @github to extend HydraFusion to Windows. - This fall, Search on the taskbar adds thousands of quick actions, making it easier to adjust settings and get things done as fast as you can type. - @MSFTCopilot is getting more powerful on Windows. With hybrid intelligence, it can tap into your PC's local capabilities and turn your requests into action, while keeping you in control. - Local agents are coming to Windows too. Muse is on its way as a native Windows app with MXC integration, and Hermes, OpenClaw, and Perplexity are already building local experiences on Windows. - Surface Laptop Ultra, built with NVIDIA RTX Spark, is the most powerful Surface we've ever built. It's available for pre-order today, along with the Surface RTX Spark Dev Box and new RTX Spark PCs from our partners. Call of Duty is coming to RTX Spark in 2027. Read more on the Windows Blog: https://blogs.windows.com/windowsexperience/2026/10/07/building-windows-for-hybrid-intelligence/
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Compared with the older Codex sandbox on Windows, the new MXC-based mode requires no administrator approval and creates no separate Windows user accounts or local firewall rules. On Oct 7, Microsoft said MXC already supports agents from OpenAI's Codex and GitHub Copilot.
How to enable it. Add the line prefer_mxc = true to the [features] section of config.toml. You need Codex CLI 0.162.0 or newer and either Windows 11 24H2 build 26100.9278 or newer, or 25H2 build 26200.9278. To check without saving settings, run: codex -c windows.sandbox=mxc sandbox --include-managed-config --permission-profile :workspace -- cmd.exe /d /c echo MXC_OK. Output of MXC_OK with exit code 0 means the mode works.
Limits. Networking in a managed environment requires allow_local_binding = true, and child processes end together with the main command. An organization can block the mode with allow_mxc = false in the [windows] section of requirements.toml.
Microsoft has not set a date yet for Micro-VM, the third isolation level of MXC.