Who this is for

You are a working programmer who can read and write code, has shipped something, and is comfortable in a terminal. You have used an AI assistant in your editor, or you have not; either is fine.

What the chapters ahead assume you have not done is written code that calls a model directly: not through a wrapper, a framework or a chat window, but a program of yours that makes an HTTP request to Anthropic and does something with the answer.