Aider

Aider is the open-source command-line AI coding assistant that pioneered editing your repo from the terminal before the GUI agents arrived. You run aider in your project directory, point it at a model (Anthropic Claude, OpenAI GPT-4/5, DeepSeek, Gemini, local via Ollama, or any LiteLLM-compatible endpoint), and chat about what you want changed. Aider builds a treesitter-based repo map, sends only the relevant files to the model, applies the diff, and commits the change with a sensible message inside your normal git workflow. Because every edit is a commit, rolling back is just git revert and you never lose track of what the AI did. Aider consistently posts top scores on real-world coding benchmarks (SWE-bench Verified, the polyglot benchmark) precisely because of its strict diff-edit format. Features include voice coding, web scraping for in-context docs, image and screenshot input, linter/test integration with automatic retry, and an architect/editor split mode that uses a strong reasoning model for planning and a cheaper model for edits. Aider is free, fully open source, and the go-to tool for engineers who prefer the terminal over a chat panel.