OpenAI adds Microsoft MXC-based sandbox mode to Codex on Windows 11

OpenAI Developers announced that Codex on Windows now has a new sandbox mode built on Microsoft's Execution Containers (MXC).

OpenAI says the mode offers faster setup, stronger network enforcement, and granular file access controls, and it requires a compatible Windows 11 device.

According to Microsoft's announcement, as cited in the same report, MXC is now generally available on Windows 11 and keeps agents within boundaries the operating system enforces. These are OpenAI's and Microsoft's own claims; the report does not provide independent verification of the performance or security benefits.