name: ruby-cli description: Build and maintain Ruby CLI tools using Thor and Zeitwerk. Use when creating new Ruby CLI gems, adding commands, editing CLI code, refactoring, or enhancing existing CLI tools. Triggers on "Ruby CLI", "Thor CLI", "command-line tool in Ruby", or when working on files in a Thor/Zeitwerk CLI codebase.

Ruby CLI Development

Build Ruby CLI tools using Thor for commands and Zeitwerk for autoloading.

Quick Navigation

• Starting a new CLI gem from scratch? See references/bootstrap.md
• Adding commands or subcommands? See references/patterns.md
• Thor syntax reference? See references/patterns.md
• Rich terminal UI with Gum? See references/gum.md

Core Principles

• Use compact class declarations: class GemName::Cli::Main < GemName::Cli::Base
• Use extend self instead of module_function for utility modules
• Keep the Base class lean - add helpers as patterns emerge

Output Styling

For basic output, use Thor's built-in say "message", :color.

For rich terminal UI (headers, tables, spinners, confirmations), use the Gum gem:

ui.header("Section Title")    # branded header with border
ui.success("Done!")           # green checkmark
ui.error("Failed")            # red X
ui.table(rows, columns: [...]) # formatted table
ui.spin("Working...") { ... } # spinner during work

See references/gum.md for setup and full API.

Tips & Gotchas

• Add # rubocop:disable Rails/Output to UI modules (stdout is intentional in CLIs)
• Gum requires brew install gum on the host machine