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Butterfish

Butterfish adds AI assistance to your shell commands.

Checked 3 Oct 2026 Reviewed by Alex Listed since September 2024

Screenshot of Butterfish

At a glance

Starts at Free No paid plan found on the vendor's site, September 2026.
Free tier Yes
Platforms macOS, Linux
Best for Power users, developers
Not for Users needing csh or fish shell support

3.9 out of 5

Scored by Alex after real use

Our verdict

It enhances the command line experience with AI prompts and suggestions but requires an API key for setup.

✓What it does well

AI assistanceStart commands with a capital letter to get context-aware AI prompts.
Command history integrationThe AI considers your shell command history for more relevant suggestions and responses.
Autocomplete supportGPT suggests commands that you can complete with Tab, based on recent interactions.

✕Where it falls short

Manual API key setup requiredFirst use requires manual entry of an OpenAI API token.
Limited to bash and zshCurrently only works with bash and zsh, not other shell types like fish or csh.
No built-in model switching in UISwitching between models requires command-line configuration rather than a GUI.

Key features

CLI accessAccess through CLI, no web interface provided.
Customizable promptsEdit the prompt wrappers in ~/.config/butterfish/prompts.yaml for more control.
Goal mode executionUse goal mode to let an agent execute commands and reach a specified goal.
Configurable PromptsEdit prompt wrappers in configuration file.

Questions about Butterfish

What does Butterfish do?

Butterfish adds AI assistance to shell commands. Starting a command with a capital letter brings up context-aware AI prompts, the AI takes shell command history into account for more relevant answers, and GPT suggests commands that can be completed with Tab.

Is Butterfish free?

Yes. Butterfish is free, and Toolio found no paid plan on the vendor's site in September 2026. First use does require manually entering an OpenAI API token, which the reviewer lists as a setup hurdle.

Which shells does Butterfish support?

Butterfish currently works only with bash and zsh, not other shells such as fish or csh, so Toolio lists it as not for users who need those. It runs on macOS and Linux and is accessed through the CLI, with no web interface.

What is goal mode in Butterfish?

Goal mode in Butterfish lets an agent execute commands to reach a goal the user specifies. For more control, users can also edit the prompt wrappers in its prompts.yaml configuration file.

How does Toolio rate Butterfish?

Alex scored Butterfish 3.9 out of 5 on 3 Oct 2026, and Toolio lists it as best for power users and developers. The reviewer notes one more limit: switching between models requires command-line configuration rather than a GUI.

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