Simon Willison’s Weblog

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Guides

Agentic Engineering Patterns

Patterns for getting the best results out of coding agents like Claude Code and OpenAI Codex. See my introduction for more on this project.

11 chapters: Writing code is cheap now, Hoard things you know how to do, Anti-patterns: things to avoid, AI should help us produce better code, Red/green TDD, First run the tests, Agentic manual testing, Linear walkthroughs, Interactive explanations, GIF optimization tool using WebAssembly and Gifsicle, Prompts I use