aider is a terminal-based AI pair programming tool that auto-commits every change to git. Created by Paul Gauthier, it's known for its elegant diff-based edit strategies (aider can use different 'edit formats' for different models to maximize reliability), git-native workflow, and small readable codebase that you can understand end-to-end in an afternoon.
Run `aider` in your project directory. It starts a REPL where you describe what you want in plain English. aider automatically determines which files are relevant, reads them, makes edits, and commits the changes to git with descriptive messages. If you don't like a change, `git reset` undoes it. Supports all major LLMs (Claude, GPT, Gemini, DeepSeek, local via Ollama) and automatically picks the right edit format for each model.
aider is free and open source. You pay for LLM API usage (typically $1-5 per coding session depending on model). The aider CLI has no subscription, no middleman, no telemetry.
Terminal-first developers, open-source contributors, and engineers who want git-native AI coding. Particularly popular among Rust, Go, and systems programmers.