AI coding assistants have split into two camps: GUI-first tools that live inside an editor, and terminal-first agents that live where serious development already happens - the shell. CLI tools are composable, scriptable, SSH-friendly, and they slot into existing workflows (git hooks, CI, tmux) without asking you to switch editors.
This roundup covers the four CLI coding agents we see developers actually adopting, with notes on when each one shines.
Quick Comparison
| Tool | Company | Best For | Open Source |
|---|---|---|---|
| Claude Code | Anthropic | Deep agentic workflows | No |
| Codex CLI | OpenAI | Sandboxed execution | Yes |
| Gemini CLI | Free tier + huge context | Yes | |
| Aider | Community | Git-native pair programming | Yes |
Claude Code
Claude Code is Anthropic’s terminal agent and the current reference point for what “agentic coding” means. You give it a goal in natural language; it explores the codebase, edits files, runs tests, and iterates until the task is done - all from your shell.
npm install -g @anthropic-ai/claude-code
claudeWhat sets it apart:
- Agentic by default. It doesn’t just suggest diffs - it plans multi-step work, reads files on its own, and recovers from failing tests.
- Subagents and hooks. You can define specialized subagents and wire shell hooks into its lifecycle, making it automatable in team workflows.
- Strong reasoning on large refactors. It handles “rename this concept across 40 files and update the tests” style tasks better than most.
The trade-off is cost. Heavy usage on a metered plan adds up quickly, so many teams reserve it for tasks where its autonomy pays for itself.
Codex CLI
Codex CLI is OpenAI’s open-source terminal agent. Its defining feature is a sandboxed execution model: by default it can read your repo but runs commands in an isolated environment, so an agent gone rogue can’t rm -rf your home directory.
npm install -g @openai/codex
codexHighlights:
- Approval modes. Choose between suggest-only, auto-edit, and full-auto depending on how much you trust the run.
- Open source. The whole client is inspectable, and the community moves fast on it.
- Cloud handoff. Tasks can be delegated to cloud sandboxes when the job is too big for a terminal session.
If you want an agent you can point at an unfamiliar codebase without anxiety, Codex CLI’s sandboxing is the most reassuring model of the bunch.
Gemini CLI
Gemini CLI is Google’s entry, and it competes aggressively on two axes: price and context window.
- Generous free tier. Individual developers get a substantial free allowance just by signing in with a Google account - by far the cheapest way to try agentic coding seriously.
- 1M-token context. Point it at a monorepo and it can hold far more of your code in working memory than most rivals.
- Open source and extensible. MCP server support means you can bolt on custom tools.
The reasoning quality on tricky, multi-file refactors trails Claude Code in our experience, but for exploration, explanation, and everyday edits it’s excellent - and free is hard to argue with.
Aider
Aider is the veteran of the group and the most git-native of them all. Every change it makes is a commit with a sensible message, which makes reviewing AI work feel exactly like reviewing a human’s pull request.
pip install aider-chat
aiderWhy developers love it:
- Model-agnostic. Use Claude, GPT, Gemini, DeepSeek, or a local model - Aider doesn’t care. You can swap backends as the model market shifts.
- Repo-map magic. It builds a compressed map of your repository so the model understands structure without burning your entire context budget.
- Pair-programming feel. It’s less “autonomous agent” and more “very fast pair,” which many developers prefer for staying in control.
Which One Should You Pick?
- Maximum autonomy on hard tasks: Claude Code
- Safety-first execution on unfamiliar code: Codex CLI
- Budget-friendly exploration with huge context: Gemini CLI
- Git-centric, model-flexible pairing: Aider
The honest answer is that these tools compose well. Plenty of developers keep Aider for daily edits and pull in Claude Code when a task needs real autonomy. All four are in the directory with links and notes - try the free options first and see which mental model clicks for you.
This is the first post in our deep-dive series on AI coding tools. Next up: a full review of Cursor.