Whetuu: A Zero-Config, Cross-Shell Prompt in Zig

whetū /ˈfɛ.tuː/ — derived from the Māori word for "star" — is an opinionated, zero-configuration prompt designed to work across multiple shells, engineered entirely in the Zig language. 󰦥

The core philosophy is simplicity: a single compiled binary produces one curated prompt experience that is identical for every user.

There are ~~no configuration files~~, no themes to tweak, and no parameters to tune.

It is compatible with fish, bash, and zsh, boasting a render speed of approximately $2\text{ms}$ .

🚀 Installation

Getting started requires only a single command for macOS and Linux users.

Detects host platform
Verifies download via SHA256SUMS
Installs binary to ~/.whetuu/bin
Appends two lines to your active shell configuration

curl --proto '=https' --tlsv1.2 -fsSL https://yamafaktory.github.io/whetuu/install.sh | sh

Alternative Setup Methods

Dry Run: Execute the installer with WHETUU_NO_MODIFY=1 to see the required config lines without applying them.
Manual Init: Run whetuu init <shell> to generate the integration script and identify the target config file.

🎨 Prompt Anatomy

The prompt utilizes Nerd Font glyphs for language logos, git branches, and the primary prompt character. Segments are dynamic; they only appear when relevant.

Segment Details

Segment	Description	Visual Nuance
`user_host`	`user@host`	Bold Green normally; Bold Red for root or SSH sessions.
`directory`	Current path	Shows the anchor and as many trailing folders as the width allows.
`git branch`	Current branch	Magenta text with a branch glyph; shows `(detached)` if applicable.
`git state`	Active operations	Yellow text for `(rebasing 2/7)`, `(merging)`, or `(cherry-picking)`.
`git status`	Repo health	A bracketed group: `[conflicts, stashes, staged, modified, untracked, ahead, behind]`.
`language`	Toolchain version	Brand-colored logo and version for 39 different tools/languages.
`cmd_duration`	Execution time	Timer glyph appears if the last command took $\ge 2\text{s}$ .
`character`	The prompt end	A purple star (or the current language's brand color).

🔍 The History Picker

By pressing the Up Arrow, users access a sophisticated history picker. To keep the list clean, only commands that exited successfully are recorded.

Features

Context Awareness: Defaults to the current directory's history, falling back to global history if the local list is empty.
Visuals: Rows feature syntax highlighting. Colors for flags, paths, and operators are pulled from your existing terminal theme.
Smart Truncation: Long commands are truncated in the middle (using …) rather than the end, ensuring unique prefixes remain visible.

Picker Controls

Ctrl+G: Toggle between directory-specific and global history.
Tab: Copy the current selection into the search bar for editing.
Esc: Cancel and return to the command line.

🛠️ Command Reference

While the shell hook handles most tasks, whetuu provides a few manual commands:

whetuu init fish|bash|zsh: Outputs the integration script for eval or source.
whetuu paths: Displays the locations of the version cache and history store.

Note: whetuu paths will explicitly mark missing files rather than hiding them until the first command is cached/recorded. It requires $HOME or XDG variables to be set to function.

⚡ Performance

Because a prompt runs before every single command, speed is critical. Whetuu achieves its $\approx 2\text{ms}$ render time by using std.Io to run all disk-reading modules concurrently.

Benchmarks

Measured with hyperfine on an i9-13900H (ReleaseFast).

Scenario	Total Render Time	Bottleneck
No repo / No toolchain	$2.3\text{ms}$	N/A
Zig repo (35 files)	$3.0\text{ms}$	Zig version probe ( $3.1\text{ms}$ )
Monorepo (8259 files)	$20.2\text{ms}$	Git status ( $19.3\text{ms}$ )

Worst-Case Scenario: If git hangs for 30 seconds, the prompt will still return in approximately $257\text{ms}$ due to the concurrent execution of the toolchain probe ( $\approx 200\text{ms}$ ) and git ( $\approx 250\text{ms}$ ).

🛡️ Security & Privacy

Since a prompt has visibility into every command, Whetuu is designed with a strict security posture:

Zero Networking: The binary contains no HTTP clients, sockets, or synchronization logic.
Strict Permissions: The history store is created with mode 600 and reset to this on every write.
XDG Compliance: Data is stored in ~/.cache/whetuu/versions and other XDG-compliant paths, separate from the installation directory.
Easy Removal: Running rm -rf ~/.whetuu removes the application without deleting your history.
Privacy Mode: Starting any command with a leading space prevents it from being recorded in the history.

Subprocess Logic: Whetuu only ever spawns two types of subprocesses: git and the specific toolchain version probe.