Simon Willison released version 0.2a0 of pwasm, a Python WebAssembly engine he built entirely by vibe coding in January. He left the project untouched for months before instructing Claude Opus 5.5 to evaluate its current state and identify improvements. The AI model made 42 commits with minimal follow-up prompting to reach this new milestone.
The updated engine now handles almost the entire WebAssembly specification. It successfully builds working versions of MicroPython and QuickJS from PyPI wheels. Willison explicitly states he would not trust the software for production use due to its alpha status. The project remains a personal folly rather than a commercial product.
* The original engine was created during a period of AI mania in January 2026.
* Modern models significantly improved upon the work generated ten months prior.
* The release tag indicates the software is not ready for general deployment.
