Aider is an open-source AI pair programming tool that operates from the terminal, allowing developers to pair program with LLMs to start new projects or build on existing codebases. Unlike many AI coding assistants that integrate only with specific IDEs, Aider works directly with local git repositories, automatically committing changes with sensible commit messages so that developers can easily diff, manage, and undo AI changes using familiar Git tools. The tool works with most popular programming languages (Python, JavaScript, Rust, Ruby, Go, C++, PHP, HTML, CSS, and dozens more) and maps the entire codebase to help it work well in larger projects. Aider supports both cloud-based LLMs (Claude 3.7 Sonnet, DeepSeek R1 & Chat V3, OpenAI o1, o3-mini & GPT-4o) and local models, making it flexible for different privacy and cost requirements. Additional features include voice-to-code input, image and web page attachments for visual context, linting/testing integration that automatically fixes problems, and a copy/paste workflow for interacting with any LLM via its web chat interface.