Butterfish

Butterfish, developed by Peter Bakkum and open source under the MIT license, is a shell wrapper that integrates AI capabilities directly into bash and zsh terminals. Users prompt an AI assistant from the command line by starting commands with capital letters, enabling contextual questions about shell operations, such as why a command failed, without copy-pasting into a separate chat window. It offers command autosuggest functionality similar to GitHub Copilot, a 'Goal Mode' that lets AI agents execute commands autonomously to accomplish stated objectives, support for OpenAI models and compatible APIs, customizable system prompts stored in configuration files, and a Neovim plugin integration. Butterfish itself is free and open source; it requires an OpenAI API key for functionality, so users pay OpenAI directly for API usage, with autosuggest typically incurring the highest costs unless disabled or adjusted.