How to use Aider: AI pair programming in your terminal Aider, an open-source AI pair programmer that runs in the terminal and git-commits every change it makes, is installed with two commands — `python -m pip install aider-install` followed by `aider-install` — according to Aider's own install docs read 15 August 2026. Aider is model-agnostic, supporting Claude, GPT (o3, o4-mini, GPT-4.1), Gemini 2.5 and DeepSeek, and can be pointed at OpenRouter for a free tier or at Ollama for zero per-token cost on local hardware. The tool's `/undo` command reverts the last Aider commit, and `/add`, `/ask`, `/code`, `/architect`, `/run`, `/diff`, `/model` and `/commit` drive the in-chat workflow. The Primer · Tools & Stacks How to use Aider: AI pair programming in your terminal Vendor-neutral Aider is an open-source AI pair programmer that lives in your terminal, commits every change to git so you can always undo it, and points at almost any model, including a free local one. Here is the whole thing: install, run it in a repo, the commands you will use, and how to wire it to Claude, to OpenRouter, or to Ollama running on your own machine for zero per-token cost. Aider is the tool for people who want an AI coding agent that lives in the terminal, not in an editor, and who want to own the model it runs on. It describes itself in four words, “AI pair programming in your terminal”, and the two things that make it distinctive both follow from that: it commits every change it makes to git, so nothing it does is ever unrecoverable, and it connects to almost any model, including a free one running on your own machine. For a vibe coder who watches the meter and keeps their hands near git, that combination is the pitch. Here is the whole answer up front. Install Aider with two commands, run aider inside a git repository, and it pair-programs with you, committing each edit as it goes so /undo can always walk it back. Point it at Claude or GPT if you want the strongest model, at OpenRouter if you want a free tier, or at Ollama if you want zero per-token cost on your own hardware. Everything below is the how, section by section. Install it From Aider’s own install docs, read 15 August 2026. The quick start is two commands: python -m pip install aider-install aider-install aider-install also installs a separate Python 3.12 to run Aider with, so it does not disturb your project’s Python. If you prefer, there are three other supported paths: uv tool install --force --python python3.12 --with pip aider-chat@latest , a direct python -m pip install -U --upgrade-strategy only-if-needed aider-chat on Python 3.9 to 3.12, or pipx . Any of the four gets you the aider command. Run it in your git repo This is the habit that defines Aider. Start it inside a git repository, and Aider will git commit all of its changes, each with a sensible message, so you can diff, track, and undo them with the git tools you already use. That is not a safety feature bolted on; it is how the tool works. When the model does something you did not want, you type /undo , which the docs define exactly as “undo the last git commit if it was done by aider,” and you are back where you were. If you are new to it, run aider in a small repo, ask it to make one change, and watch it commit. Seeing the commit appear is the moment Aider clicks, because it means every step is a checkpoint you can return to. The commands you will actually use Aider is driven by in-chat slash commands. From the command reference, the ones that carry most of the work: - /add puts files into the chat so Aider can edit them; /drop removes them again. - /ask asks a question about the code without editing it. - /code requests a change; /architect runs the two-model workflow below. - /run runs a shell command and can feed the output back into the chat. - /diff shows what changed since your last message; /undo reverts the last Aider commit. - /model switches which model you are talking to mid-session; /commit commits edits you made outside the chat. You will spend most of your time in /add then plain requests, with /undo as your safety net and /run to let Aider see your test output. Point it at any model Aider is model-agnostic, and this is where it separates from a tool locked to one lab. Its own docs list the models it works best with, Claude, GPT o3, o4-mini, GPT-4.1 , Gemini 2.5, and DeepSeek, and note that it can connect to almost any LLM besides. You supply a key on the command line with --api-key anthropic=