zsh-config-expert

Add `zmodload zsh/zprof` to the top of your .zshrc and `zprof` at the bottom, then open a new shell to see which plugins or functions take the longest. Defer or lazy-load anything taking more than about 50ms, and measure improvement with `time zsh -i -c exit`.

.zshenv loads for every zsh invocation and should hold environment variables like PATH. .zprofile runs only for login shells, suited for one-time setup like Homebrew shellenv. .zshrc runs for interactive shells and holds aliases, completions, prompt, and plugins.

Initialize the completion system with `autoload -Uz compinit && compinit` in .zshrc, then add `zstyle ':completion:*' matcher-list 'm:{a-zA-Z}={A-Za-z}'`. You can also enable menu selection and completion caching for faster, interactive completion.

Zsh arrays are 1-indexed, unlike bash which is 0-indexed, so `$arr[1]` returns the first element. Negative indexing also works, so `$arr[-1]` returns the last element.

Put `eval "$(brew shellenv)"` in .zprofile, not .zshrc. .zprofile runs once per login shell, while placing it in .zshrc re-runs it for every interactive shell, adding unnecessary startup overhead.

This Skill does not cover bash-only scripting that never touches zsh, writing new shell scripts from scratch, or non-shell configuration files. It focuses on configuring and troubleshooting existing zsh environments rather than general shell programming.