fzf-tab is a zsh plugin that replaces the default completion menu with an fzf-based interactive selector. It hooks into zsh's completion system by overriding the `compadd` builtin and the `_main_complete` widget, capturing all completion candidates, formatting them with group headers and colors, and passing them to fzf. The user's selection is then applied back to the command line. The plugin supports multiple selection, continuous completion (e.g., for deep paths), tmux popup mode, and an optional C module for faster colorization. The architecture is a single zsh script (`fzf-tab.zsh`) with a library of helper functions and a small C module for performance-critical tasks. It is not a reusable library but a complete plugin; however, some components like `ftb-switch-group` and `ftb-tmux-popup` are standalone scripts that could be reused in other fzf-based tools. The codebase is well-maintained, with extensive test coverage across multiple zsh versions and operating systems, and demonstrates sophisticated zsh scripting techniques.