Butterfish

About Butterfish

Butterfish adds AI prompting directly to bash and zsh without changing how you use the shell. Once `butterfish shell` is running, you use your terminal exactly as before, and any command that starts with a capital letter is routed to the model instead of the shell. Because Butterfish sits between you and the system shell it can see the recent command history and output, so contextual questions like "why did that command fail?" work without copying and pasting an error into a chat window — which is the interaction cost that makes most terminal AI tools not worth reaching for. Beyond one-off prompting it ships a Goal Mode, where you state an objective such as running a build and debugging whatever breaks, and Butterfish iterates on commands toward that goal while surfacing each step. A Neovim plugin extends the same model access into the editor. The project documents its architecture openly, including how it proxies API requests and how the shell-to-shell interface is implemented, which matters to developers who are cautious about what a tool with terminal access is transmitting. It works with OpenAI and any OpenAI-compatible endpoint, so self-hosted or alternative providers are supported, and it is distributed as a free open-source CLI for people who work primarily from the command line.

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