Butterfish wraps an existing bash or zsh shell with AI prompting, functioning like autocomplete for the terminal itself rather than for code in an editor. Starting a line with a capital letter asks the underlying model a question, like asking for a command to accomplish something specific, while prefixing with an exclamation point lets it act more like an agent that can run and debug commands on its own.
Beyond shell interaction, it supports indexing a directory of files with embeddings for semantic search, so a developer can run butterfish index to build an index and butterfish indexsearch to query it later, turning it into a lightweight local search tool as well as a shell assistant. It reads an OpenAI API key from a config file and installs through Homebrew or go install.
Released under the MIT license and still actively maintained on GitHub, it occupies a narrow but genuinely useful niche: AI help that enhances an existing shell rather than replacing it with something new to learn.