How to configure Zsh completion styles

Completion styles change how Zsh presents and matches command completions after the completion system is enabled. Use them when completion works, but the completion list needs menu selection or case-insensitive matching adjusted.

The zstyle command stores values against completion contexts. A broad context such as :completion:* applies across the completion system, while narrower contexts can target one completer, command, or tag later without replacing the general defaults.

A safe update backs up ~/.zshrc, writes the style lines near compinit, and starts a fresh interactive Zsh process to read back the stored styles. Syntax checking catches a broken startup file before the next terminal session depends on it.

Steps to configure Zsh completion styles:

Confirm that Zsh can start and report its version.

$ zsh --version
zsh 5.9 (aarch64-unknown-linux-gnu)

Back up ~/.zshrc before editing completion behavior.
```
$ if [ -f ~/.zshrc ]; then cp ~/.zshrc ~/.zshrc.bak; fi
```
No output means the command copied an existing file or skipped the backup because no ~/.zshrc file was present.
Add completion initialization and styles to ~/.zshrc.
~/.zshrc
```
autoload -Uz compinit
compinit -d "${ZDOTDIR:-$HOME}/.zcompdump"
zstyle ":completion:*" menu select
zstyle ":completion:*" matcher-list "m:{a-zA-Z}={A-Za-z}"
```
The menu select style starts menu selection for completion lists. The matcher-list value makes letter-case differences less strict when matching completion candidates. If ~/.zshrc already has a compinit block, keep one copy and add the zstyle lines near it.
Check the startup file for syntax errors.
```
$ zsh -n ~/.zshrc
```
No output from zsh -n means Zsh parsed the startup file without finding a syntax error.

Start a new interactive Zsh shell and confirm the menu style.

$ zsh -ic 'zstyle -L ":completion:*" menu'
zstyle ':completion:*' menu select

Confirm the case-insensitive matcher style.

$ zsh -ic 'zstyle -L ":completion:*" matcher-list'
zstyle ':completion:*' matcher-list 'm:{a-zA-Z}={A-Za-z}'

Confirm that completion initialization still loaded command completions.
```
$ zsh -ic 'printf "cd_completion=%s\n" "${_comps[cd]:-missing}"'
cd_completion=_cd
```
If the completion check returns missing, confirm that compinit runs before the style check and that it did not stop on insecure completion directories.