pwasm 0.2a0
Simon Willison’s Weblog Simon Willison
pwasm 0.2a0 is out: Claude helped turn a vibe-coded Python WebAssembly engine into something much more complete. It now runs MicroPython, QuickJS, and Micro QuickJS builds, though the author still wouldn’t trust it.
Based on reporting by Simon Willison’s Weblog, Simon Willison — read the original for the full story.
Summary, retelling and take written by AI under human oversight; images are AI-generated illustrations. How we work · Report an error
Simon Willison has put out pwasm 0.2a0, and the story here is less about a polished release than about what happened when he handed an old side project to Claude Opus 5.5. pwasm started in January as what he calls a folly project: an entirely vibe-coded pure Python WebAssembly engine. Then it sat untouched for months.
When he came back to it, he gave Claude a blunt brief: assess the current state, figure out what it would take to run the MicroPython and micro JavaScript experiments from his research repo, and see what could be done to speed it up. After 42 commits, and with minimal follow-up prompting, the project had moved a long way.
The new version now handles almost all of the WASM specification. That’s a big jump for something that began as a deliberately experimental build, especially because the wheel on PyPI now bundles working WASM builds of MicroPython, QuickJS and Micro QuickJS.
Willison is not pretending this is production-ready. He says he wouldn’t trust it at all, which is exactly why it’s tagged alpha. But that hesitation is part of the point: this is a clean example of today’s models improving code that was itself written in the first flush of AI enthusiasm, and doing it in a way that leaves a surprisingly capable result behind.
My take — AI-written commentary, not fact-checked reporting
This is the kind of AI demo that actually matters: not a shiny chatbot trick, but a model grinding through ugly code and making it better. The caution tag is doing real work here, because “it works” and “I’d trust it” are not the same sentence, no matter how loud the hype gets. Sometimes the future arrives wearing an alpha label and a healthy dose of suspicion.
Read more about this at: Simon Willison’s Weblog
