Aider

Aider is an open-source AI pair programming tool that runs in your terminal, letting you have a conversation with an AI that can directly read and edit your local source files. Every AI-generated change is automatically committed to git with a descriptive message, giving you a clean history and easy rollback if needed.

• Direct file editing — the AI reads your source files and makes surgical edits based on your natural language instructions
• Git integration — every change is auto-committed with a meaningful commit message; easy to review diffs and revert
• Multi-file edits — add multiple files to the conversation and make coordinated changes across them
• Model flexibility — works with OpenAI, Anthropic, local models, and dozens of other LLM providers via a unified interface
• Linting & testing — can run your linter and test suite after edits and automatically fix any issues

Experienced developers who prefer working in the terminal use Aider for targeted code changes, refactoring, test writing, and bug fixes. Its git-native workflow means you always have a safety net — every AI change is a commit you can inspect and roll back.

Aider is fully open source and has one of the most active developer communities among AI coding tools. It consistently ranks among the top performers on coding benchmarks and supports virtually every LLM provider.

1. Install Aider via pip or pipx:

   pip install aider-chat
   # or
   pipx install aider-chat

2. Set your preferred AI provider's API key as an environment variable:

   # For Anthropic (recommended)
   export ANTHROPIC_API_KEY=sk-ant-...
   
   # For OpenAI
   export OPENAI_API_KEY=sk-...

3. Navigate to a git repository and launch Aider:

   cd your-project
   aider

4. Add files to the conversation using /add filename.py and start describing the changes you want. Aider edits the files and auto-commits the changes.
5. Pricing: Aider itself is free and open source. You pay only for the API tokens consumed by whichever LLM provider you choose (e.g., Anthropic Claude, OpenAI GPT-4o, etc.).