Simon Willison explores his latest approach to running untrusted Python code safely within applications by utilizing MicroPython inside a WebAssembly (WASM) sandbox. The project addresses the security risks of plugin systems where code normally executes with full privileges, potentially leading to data leaks or system compromise. By leveraging wasmtime and an alpha package called micropython-wasm, Willison demonstrates how to enforce memory and CPU limits while providing controlled access to host functions through a custom thread-based request queue for persistent interpreter state.
Main topics:
- Security challenges in Python plugin systems
- Advantages of WebAssembly as a sandboxing technology
- Building the micropython-wasm alpha package
- Implementation details for persistent state and host functions
- Integration with Datasette Agent to execute code via LLMs
Main topics:
- Security challenges in Python plugin systems
- Advantages of WebAssembly as a sandboxing technology
- Building the micropython-wasm alpha package
- Implementation details for persistent state and host functions
- Integration with Datasette Agent to execute code via LLMs
Python 3.15 is set to introduce transformative improvements including lazy imports to defer library loading costs, a new immutable frozendict type, significant enhancements to the native JIT compiler, and an explicit roadmap for WebAssembly support via PEP 816. The article also highlights recent developments in the Python ecosystem such as using Rust to build standard library components, tools for exploring profiler data, and security insights regarding package compromises.
This article details a method for training large language models (LLMs) for code generation using a secure, local WebAssembly-based code interpreter and reinforcement learning with Group Relative Policy Optimization (GRPO). It covers the setup, training process, evaluation, and potential next steps.
