Aider

Aider is a terminal-based coding assistant. You start it inside a project, tell it which files to work on, and describe the change you want; it edits the files directly and commits each change to git with a descriptive message, so every step is easy to review or undo. It builds a map of the repository to give the model context about the wider codebase.

It suits developers comfortable on the command line who want to choose their own model, whether from Anthropic, OpenAI, DeepSeek or a locally hosted LLM. It works alongside any editor rather than replacing one.

Aider itself is free and released under the Apache 2.0 licence. You bring your own API keys, so the real cost is whatever the chosen model provider charges for usage, which can add up on large codebases or long sessions.