What is agentic engineering? – Agentic Engineering Patterns – Simon Willison’s Weblog
March 17, 2026
I use the term agentic engineering to describe the practice of developing software with the assistance of coding agents.
What are coding agents? They’re agents that can both write and execute code. Popular examples include Claude Code, OpenAI Codex, and Gemini CLI.
What’s an agent? Clearly defining that term is a challenge that has frustrated AI researchers since at least the 1990s but the definition I’ve come to accept, at least in the field of Large Language Models (LLMs) like GPT-5 and Gemini and Claude, is this one:
A new chapter from Simon Willis’ agentic engineering patterns looks at the definition of agentic engineering and the nature of agents in this context.
