What it is
Aider is a command-line coding assistant powered by LLMs. Its core idea is not a separate editor, but work inside an existing Git project: choose files, discuss a task, get edits, and inspect the diff.
It became popular because it fits developer habits: terminal, Git, commits, and local files remain the main environment.
What is inside
The repository contains Python CLI code, Git integration, file context handling, model support, chat commands, tests, and documentation.
The tool does not replace project understanding. Users still need to read diffs, run tests, and judge code quality.
How it is used
A typical flow is to open a repository, add files to context, describe the task, inspect edits, run tests, and commit with Git.
Aider fits local edits, refactoring, tests, small features, and code explanation. Larger product decisions still need manual decomposition and review.
Strengths and limits
The strength is simple integration with a real repository and transparent Git diffs.
The limit is dependence on context and model quality. Too little context can lead to wrong edits.
Aider works best in repositories with good tests and clear structure. Changes can be checked quickly and the model gets better boundaries. In a chaotic project it can still work, but the user spends more time reviewing and correcting edits.
Aider also shows the value of Git as a safety layer. Even if the model edits several files, the developer sees the exact diff, can revert part of the change, and split the result into proper commits.
That keeps the human developer in charge of the final state while still allowing the model to perform useful editing work.
Example
Starting Aider in a repository
This shows the working shape: open a project, pass files, and ask for a change.
cd my-project
aider app.py tests/test_app.py
# then in chat: add empty-input validation and a test