Simon Willison’s Weblog

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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. Writing code is cheap now
    2. Hoard things you know how to do
    3. Anti-patterns: things to avoid
  2. Testing and QA
    1. Red/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