Aider is a terminal coding agent that works directly on a git repo. Its defining habit: it commits every edit it makes, so every change is reviewable and reversible.
1. Install it
The recommended install, on any OS:
python -m pip install aider-install
aider-install
There are also one-line installers. macOS and Linux:
curl -LsSf https://aider.chat/install.sh | sh
Windows (PowerShell):
powershell -ExecutionPolicy ByPass -c "irm https://aider.chat/install.ps1 | iex"
2. Launch it with a model
Aider is model-agnostic — you pick the model and supply the key:
aider --model sonnet --api-key anthropic=<key>
aider --model o3-mini --api-key openai=<key>
Run this from inside your repo. If the directory isn’t a git repo, Aider asks to create one.
You can also keep keys out of your shell history by configuring them in your environment or
config file instead of --api-key — run aider --help for the exact names your version
accepts.
3. Make your first edit
Describe the change in plain English, one job at a time:
Add input validation to parse_config() and raise a clear error for a missing "port" key.
Aider finds the relevant code, edits the files, and shows you what it did. Type /help inside
the session to see the in-chat commands your version supports.
4. The git part
Whenever Aider edits a file, it commits those changes with a descriptive commit message. That means:
- Don’t like a change?
/undodiscards the last one. - Want to keep control of history? Start it with
--no-auto-commits:
aider --no-auto-commits --model sonnet --api-key anthropic=<key>
Auto-commits are the safety net that makes an agent editing your files tolerable — leave them on until you have a reason not to.
Next: Codex CLI first steps or giving a coding agent the right context.