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I ported JustHTML from Python to JavaScript with Codex CLI and GPT-5.2 in 4.5 hours

simonwillison.net

I wrote about JustHTML yesterday—Emil Stenström’s project to build a new standards compliant HTML5 parser in pure Python code using coding agents running against the comprehensive html5lib-tests testing library. Last …

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The Architect vs Implementer Split in AI Native Development

When agents handle implementation, experienced engineers shift from typing code to architectural guidance. The division is about what gets delegated and what requires human judgment.

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Yulqen

An intentionally quiet and unassuming (and empty) blog

JustHTML: Addressing some questions

When Simon Willison wrote about JustHTML [1] [2], suddenly everyone was interested in giving their view. After reading through (what I think is) all of...

ClaudeCodingABlogPipeline

FindRecentClaudeCodingABlogPipelineDecember 27, 2025 Lately, I've been working on trying to get a blog publishing pipeline up and running for all t...

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HTML parsers in Portland

A small exploration of weird results when AI coding agents translate an HTML parser into different languages. 2000 words - 10 minutes

Porting an HTML5 Parser to Swift

How I built swift-justhtml with Claude - from 0% to 100% html spec test compliance, finding crash bugs with fuzzing, and the performance optimization needed to match javascript's speed in Swift

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