aider-ai/aider

Aider is a command-line tool that lets you work with an AI language model as a pair programming partner directly in your terminal, within your existing code repository. The problem it solves is that using AI to help write or edit code through a web chat interface, like pasting code in and copying results back out, is slow and error-prone. Aider instead integrates directly with your codebase and your version control system (git), so the AI can read your files, propose changes, apply them automatically, and commit them with meaningful messages. The key mechanism is that Aider builds a "repository map", a compact structural summary of your entire codebase showing how files, classes, and functions relate to each other, and includes the relevant parts of this map in each conversation with the AI. This helps the model understand context from across the codebase without you having to paste everything manually. You describe what you want in plain English in the terminal: "add a login endpoint" or "fix the bug in the payment module" or "write tests for the auth class," and Aider figures out which files to edit, makes the changes, and optionally runs your linter and test suite to verify the result. If the tests fail, it can try to fix the problem automatically. Changes can be reviewed with standard git tools and easily undone. You would use Aider when you want AI-assisted coding that works with your local project files and git history, supports over 100 programming languages, and connects to multiple AI providers including Claude, OpenAI's GPT-4 and o-series models, DeepSeek, and local models. It is installed via pip, written in Python, and runs on the command line on macOS, Linux, and Windows.