Meet the Terminal Agents

A terminal agent is an AI assistant that runs inside the terminal and can work on the files in a folder. You describe what you want in normal language; it reads, plans, edits, and runs commands, then shows you what it did.

The best-known ones come from the big AI companies. Claude Code comes from Anthropic, Codex CLI from OpenAI, and Gemini CLI from Google. Open-source options exist too, such as OpenCode and Aider, which let you plug in different models. They share the same basic idea and differ in the model behind them, how they handle permissions, how they are priced, and how much text they can keep in mind at once.

For a beginner, the honest way to choose is boring: pick the one that matches an AI account you already pay for or already trust, and that has a free or low-cost way to try it. Comparisons published this year rank them differently depending on the task, which tells you the gap between them is smaller than the marketing suggests.

One warning: this space moves fast. Names, plans and free allowances change every few months, so check the current pricing page before you decide, and treat any comparison, including this one, as a snapshot.

Takeaway: terminal agents are interchangeable in principle. Choose by the account you already have and the price you can live with, then check current terms.

Tools, prices and features in this area change quickly. Last reviewed September 2026.