Simon Willison’s Weblog

A field guide to sandboxes for AI (via) This guide to the current sandboxing landscape by Luis Cardoso is comprehensive, dense and absolutely fantastic.

He starts by differentiating between containers (which share the host kernel), microVMs (their own guest kernel behind hardwae virtualization), gVisor userspace kernels and WebAssembly/isolates that constrain everything within a runtime.

The piece then dives deep into terminology, approaches and the landscape of existing tools.

I think using the right sandboxes to safely run untrusted code is one of the most important problems to solve in 2026. This guide is an invaluable starting point.