Agentic Engineering Patterns

Properties5

Type	Article
Author	Simon Willison
URL	https://simonwillison.net/guides/agentic-engineering-patterns/
Note created	Mar 5, 2026
Last updated	Apr 1, 2026

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. Writing code is cheap now.
   2. Hoard things you know how to do
   3. Anti-patterns: things to avoid
2. Testing and QA
   1. green TDD
   2. First run the tests
3. Understanding code
   1. Linear walkthroughs
   2. Interactive explanations
4. Annotated prompts
   1. GIF optimization tool using WebAssembly and Gifsicle
5. Appendix
   1. Prompts I use