Aider

Aider is an open-source command-line tool for pair programming with a language model. You start it in a git repository, add the files you want it to work on, and describe the change. It edits those files directly and commits each change with a descriptive message, so every step can be reviewed or undone with git.

It works with many models, both hosted APIs and local models, and builds a map of the repository so the model can see how files relate without loading everything. Developers who live in the terminal like it because it fits the existing git workflow.

You bring your own model API keys, so cost and data handling follow the provider you choose. Keep its commits on a branch and review them before merging.