This is the first "chapter" in a not-quite-book I've started working on - I have an introductory post about that here: https://simonwillison.net/2026/Feb/23/agentic-engineering-pa...

The second chapter is more of a classic pattern, it describes how saying "Use red/green TDD" is a shortcut for kicking the coding agent into test-first development mode which tends to get really good results: https://simonwillison.net/guides/agentic-engineering-pattern...