Aider

Aider is a free, open-source CLI tool that pairs an AI editor with your local git repo. You point it at your repo, tell it what to change, and it reads files, writes patches, runs your tests, and commits the result with a structured commit message — all from the terminal.

The design is opinionated and elegant. Treating git as the canonical source of truth means Aider works with whatever IDE you happen to use (or none), composes cleanly with shell workflows, and produces actual readable git history.

It's BYO API key, which means costs are at the underlying LLM's rate (often cheaper than monthly subscription tools, sometimes pricier depending on usage). No GUI, no chat panel, no autocomplete — if those are your priorities, Aider isn't the right fit.