QEMU
Open-source software that creates virtual machines, the standard way of giving untrusted code a padded cell to run in.
QEMU is the free software most of the world uses to run virtual machines: complete simulated computers running inside a real one. It is usually paired with KVM, a component built into Linux that lets the simulated machine use the real processor directly, which is what makes it fast enough to be practical.
For AI work, QEMU matters because a virtual machine has long been the default answer to “where do I let this agent run code safely?” The virtual machine is supposed to contain whatever happens inside it. Security research in 2026 showed that assumption is weaker than it looks: a capable agent given hours to work can find and chain flaws in QEMU and its supporting libraries until it reaches the host machine.