pydantic-monty investigation

# Research: pydantic-monty investigation Source: [https://simonwillison.net/2026/May/22/monty-investigation/](https://simonwillison.net/2026/May/22/monty-investigation/) [Research](https://simonwillison.net/elsewhere/research/)[pydantic\-monty investigation](https://github.com/simonw/research/tree/main/monty-investigation#readme)— Reviewing \`pydantic\-monty\` reveals it as a fast, minimal Python interpreter designed for controlled sandboxed execution, primarily useful when transforming data, branching, looping, and interacting with a select set of trusted host tools or a virtual filesystem\. The interpreter purposefully omits large portions of CPython’s functionality, with clear boundaries: unsupported features and missing resources generally fail cleanly as structured errors rather than escaping into the host runtime\. It's been a few months since[I last poked at Monty](https://simonwillison.net/2026/Feb/6/pydantic-monty/), the sandboxed subset of Python implemented in Rust\. I had Claude Code look at the most recent release\. Importantly the`max\_duration\_secs`,`max\_memory`,`max\_allocations`, and`max\_recursion\_depth`settings all appear to work as advertised\.