Hi! For the past three months I’ve been working on boomkat, a fully ES compatible, strict-only engine. It was written from scratch using the C3 language, with Duktape and QuickJS as reference engines. It’s still a work in progress but finally got to a point I think is worth sharing.

- Architecture: one-pass compiler (no AST), register VM, NaN-boxed values

- Performance: my initial goal was to beat Duktape, but ended up matching/surpassing QuickJS in a few areas

- Compatibility: 100% pass rate across 50k tests from test262 (excludes sloppy mode, legacy and proposal stage features)

- TypeScript: the engine can run TS projects natively, including imports, and is able to run the TS compiler itself

It compiles to a ~2MB executable. It’s about 10x faster than Duktape + supports all modern JS features and TypeScript.

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Personally, this was an experiment in how far I could take AI-assisted development. If was built with a mix of several open-weight models and harnesses, with Claude Code as reviewer. I’ve probably poured 300+ hours of my own time into it, + agents running nearly 24/7 for 12 weeks. About €300 spent in total.

I didn’t actually expect to complete it. Getting to 3% pass rate felt amazing, reaching 99% felt unreal. It would take several years to achieve this alone, I think the near future is looking very interesting for software engineering in general.

As the README warns, this is not production-ready code. While the full test262 suite passes, third-party libraries load, I still find small issues here and there - for example, the console methods were breaking emoji characters until yesterday.

It’s released with the BUSL license for unrestricted use in open source and small scale commercial projects.

Would love to hear your thoughts on the implementation and development process.

X262: X264 with MPEG-2 Support