The structure holding the system's AI, and the mounting for the star-killing fuse.
The Containment Interface takes its name from what it reaches: "How it works is not important. It gives you access to the AI containment. Upon the containment is what the Mantids call 'the fuse.'"
It is the housing for The AI — the vessel in which a Mantid-made macro AI is installed and confined once a planetary system goes live. Nothing about its physical location or appearance is given; to a crawler it exists as a menu, one screen deep inside an illegal neural enhancement. What matters is what is bolted to it. The Fuse is mounted on the containment, and reaching the containment through the interface is the only route a human being has to the failsafe.
Access is not free. The enhancement that grants it only functions with the permission of the existing system, only within that system's enhancement zone, and only for a Natural Interface — and the controller itself can only be installed after the first part of the fuse has already been tripped.
Unseen and undescribed — encountered only as a new menu inside a crawler's interface.
The cage around the crawl's AI and the physical anchor of the failsafe that can end the system.