Simon Willison’s Weblog

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.

1. Principles
   1. What is agentic engineering?
   2. Writing code is cheap now
   3. Hoard things you know how to do
   4. AI should help us produce better code
   5. Anti-patterns: things to avoid
2. Getting started
   1. How coding agents work
3. Testing and QA
   1. Red/green TDD
   2. First run the tests
   3. Agentic manual testing
4. Understanding code
   1. Linear walkthroughs
   2. Interactive explanations
5. Annotated prompts
   1. GIF optimization tool using WebAssembly and Gifsicle
6. Appendix
   1. Prompts I use