Aider

Aider is an open-source AI pair programming tool that runs in the terminal and edits code inside a git repository. It is released under the Apache 2.0 license, and its GitHub repository has 50k stars. The project's website reports 6.8 million installs and 15 billion tokens processed per week, which are the project's own figures.

The tool is free and has no paid tier. Users bring their own API key for a model provider, or run a local model, and pay that provider directly for usage. The documentation covers OpenAI, Anthropic, Gemini, DeepSeek, xAI, Groq, Cohere, Azure, Amazon Bedrock, Vertex AI, OpenRouter, Ollama, LM Studio and other OpenAI-compatible APIs. The project publishes no estimate of typical monthly API cost, which depends on the model chosen and how much it is used.

Each time Aider edits a file it commits the change to git with a descriptive commit message, so changes can be reviewed with ordinary git tools or reversed with the /undo command. Auto-commits can be switched off. It builds a map of the whole repository to give the model context in larger codebases, runs a built-in linter after each edit and offers to fix the errors it finds, and can run a project's tests after each change when that option is turned on. Other features include voice input, adding images and web pages to the chat, and a watch mode that picks up instructions written as code comments in any IDE or editor. The project's leaderboards compare how different models perform when editing code with Aider.

Cursor ($8/mo) and GitHub Copilot ($10/mo) work inside an editor with inline suggestions, while Aider works from the terminal. OpenCode and Claude Code are other terminal coding agents: OpenCode is also open source and works with many model providers, while Claude Code ($17/mo billed annually) comes with Anthropic's paid plans.

The project offers no commercial support, SLA or compliance certification for the tool itself, and help runs through GitHub issues and the project's Discord. How code and prompts are handled depends on the model provider a team connects. Analytics are opt-in and anonymous, and the project states they never collect code, chat messages or keys. The most recent commit on the GitHub repository is dated May 22, 2026, and the latest tagged GitHub release is v0.86.0 from August 9, 2025. The documentation does not cover MCP.