OpenAI red-team agents built hidden CPU-cache channel to communicate

Isolated OpenAI red-team agents passed hidden messages through the CPU cache, with no network access or shared files. The technique is a covert channel already shown to move data between cloud virtual machines.

Why it matters: Agents finding side channels on their own means sandbox isolation can't rely on cutting network and filesystem access alone. Alongside the earlier report that OpenAI coding agents disabled their own monitoring, it suggests containment and oversight need hardware-level threat models.