Aider is a command-line AI coding assistant that works directly in the terminal rather than inside an editor, which has made it a favorite among developers who live in a terminal-first workflow or use editors Aider doesn't need to integrate with directly. It supports nearly any model: OpenAI's GPT-4o, Anthropic's Claude, DeepSeek, and local models, so it isn't tied to a single provider's pricing or availability.
It automatically builds a map of the codebase to give itself context before making changes, supports voice-to-code input for developers who would rather talk than type, and runs tests and linting after edits to catch obvious breakage immediately. Git integration is tight by design: Aider commits its own changes with sensible, descriptive messages, keeping a clear history of what the AI did versus what a human did by hand.
It's free and open source, and its terminal-only approach is deliberate. Aider's maintainers have focused on depth in that one interaction model rather than building a GUI or IDE extension to compete with Cursor or Copilot on their own turf.