Aider

Aider is an open source AI pair programming tool that runs in your terminal and works directly on your existing codebase. You start it inside a project directory and chat with a large language model about the code in front of it, asking for new features, test cases, or bug fixes, and Aider edits the files in place instead of returning code for you to copy across. It works best with the frontier models its homepage names, including Claude, DeepSeek, and OpenAI models, but it can connect to almost any LLM, including local models, and it can also work with an LLM through its web chat interface by streamlining the copy and paste between browser and terminal. Aider makes a map of your entire codebase, which helps it work well in larger projects where a change in one file depends on code in many others, and it works with most popular programming languages, including Python, JavaScript, Rust, Ruby, Go, C++, PHP, HTML, and CSS, and dozens more. Every change is committed automatically with a sensible commit message, so you can use familiar git tools to diff, manage, and undo AI changes, which makes its work easy to review and easy to reverse. You can also use Aider from within your favorite IDE or editor by adding comments to your code and letting it act on them. The chat accepts more than text: you can add images and web pages to provide visual context, screenshots, and reference documentation, and you can speak with Aider about your code using your voice and let it implement the changes you describe. After each change, Aider can automatically lint and test your code, and it can fix problems that your linters and test suites detect, closing the loop between editing and verification. Getting started is a pip install followed by launching Aider in your codebase with the model you want to use. Pick Aider when you want a terminal first coding assistant that keeps your repository, your git history, and your choice of model at the center of the workflow, rather than moving your work into a hosted editor or a single vendor model.