Simon Willison locks GPT-5.5 in a 362KB WASM sandbox and dares it to escape.

On June 6, Willison released micropython-wasm, an alpha package that runs untrusted Python inside a WebAssembly binary with enforced memory, CPU, and file/network limits. He wired it into a Datasette Agent plugin, put GPT-5.5 xhigh inside, and challenged it to break out. So far it hasn't. Source: simonwillison.net This is the practical answer to the RCE story above. If your agent executes model-generated code, you need a sandbox, and renting a cloud VM per execution is slow and expensive. A 362KB container-free primitive you self-host is a different proposition. Worth a real look for anyone running code-execution agents.