AI in the Terminal (CLIs)

Most people meet AI through a chat box. You type, it talks back, you copy what it gives you and paste it somewhere useful. That works, but there's a whole other shape of AI tool that a lot of developers have quietly moved to: an agent that runs in your terminal, inside your actual project, and can read your files, run commands, and change your code - when you let it.

This guide is about that shape. It's written for someone who's comfortable opening a terminal and running a command, but who isn't necessarily a hardcore engineer. You don't need to know how these tools work under the hood. You need to know what they do, what the day-to-day rhythm of using one feels like, and how to stay in the driver's seat instead of handing over the keys.

We'll go in three steps. First, why putting an agent in your terminal is a real shift and not a gimmick - the difference between a chatbot that suggests and an agent that acts. Then the everyday loop: how a normal task actually goes, from describing what you want to reviewing what changed and approving or pushing back. Finally, an honest look at the three main terminal coding agents - Claude Code, OpenAI's Codex CLI, and Google's Gemini CLI - what they have in common, where they differ, and how to pick one without overthinking it. By the end you should be able to install one, run a small task on a real project, and trust yourself to know when to say yes and when to say no.