pwasm 0.2a0

Simon Willison has released pwasm 0.2a0, an alpha version of his pure Python WebAssembly engine. He describes pwasm as a "folly project" that he originally vibe-coded in January, and says he had not touched it since then.

According to Willison, he decided to let Claude Opus 5.5 work on the project to see whether it could make significant improvements. His stated goals were to evaluate the current state of pwasm, consider what it would take to get the MicroPython and micro JavaScript experiments from the research repo working under it, and consider what it would take to speed it up.

After 42 commits, with what he describes as minimal follow-up prompting, Willison reports that pwasm now handles almost all of the WASM specification. The wheel published on PyPI bundles working WASM builds of MicroPython, QuickJS and Micro QuickJS.

Willison explicitly cautions against relying on the software. He writes that he "wouldn't trust this thing at all," which he cites as the reason for the alpha version tag. He adds that it is interesting to see how today's models can improve on the work of models from 10 months ago.

The release is tagged python, webassembly and vibe-coding. pwasm's repository contains builds of the two JavaScript engines alongside MicroPython in the distributed wheel.