Overview
Pydantic released Monty, a sandboxed Python subset written in Rust that can run LLM-generated code safely. The author successfully compiled it to WebAssembly for browser execution, creating both standalone WASM and Pyodide-compatible versions.
The Breakdown
- Monty provides microsecond startup times compared to hundreds of milliseconds for container-based sandboxes - crucial for LLM agents that need to execute code quickly
- The sandbox completely blocks host environment access (filesystem, network, env variables) and only allows developer-controlled function calls
- LLMs can iterate against Monty’s error messages - when code uses unsupported features like classes, the AI can adapt and try different approaches
- WebAssembly compilation enables browser-based sandboxing - both standalone WASM and Pyodide-compatible wheel versions work in web environments
- Claude Code successfully automated the entire build process - from cloning the repo to creating HTML demos and test scripts