# Split Button (Lumen Halo): prompt.md (v1.0.0)

- id: `lumen-split-button` · version 1.0.0 · component · pro (Pro)
- category: Actions
- build: Base UI (one set of files; its dependencies follow the build)
- install (this build): `npx shadcn@latest add @beautiful-ui-pro/lumen-split-button`
- npm dependencies: none
- registry dependencies: utils, @beautiful-ui/lumen-button, @beautiful-ui-pro/lumen-dropdown-menu, https://beautiful-ui.dev/r/lumen-foundation.json
- docs: https://beautiful-ui.dev/components/lumen-split-button
- The install command carries everything this item needs (files, CSS, tokens, npm and registry dependencies). Prefer it to copying source by hand.

One main action with its alternatives a chevron away, joined into one pill. Use it for other things to do (Save, with Save as draft), or let the menu choose what the main button does and keep showing it (Squash and merge).

## Build it
- Stack: React 19 (`ref` is a plain prop), TypeScript, Tailwind CSS v4 utilities, a shadcn-initialised project with the `@/*` alias.
- Packages: none beyond React.
- Files: `components/ui/lumen/controls/split-button.tsx`.
- Registry dependencies, installed with it automatically: shadcn `utils` (cn), `lumen-button`, `lumen-dropdown-menu`, `lumen-foundation`.
- Builds: one set of files for both, but its dependencies come in Base UI and Radix builds. Install the one that matches the project (see Install): a free item's bare URL installs the Base UI build of it and its dependencies.
- Exports to keep: `SplitButton`, and every exported type.
- CSS: the install merges this item's rules (the registry `css` field) into your global stylesheet, in `@layer components`, and adds the lumen foundation (tokens, keyframes, motion levels) once. Nothing to import by hand.
- Re-running `add` (or `--overwrite`) re-applies those rules: put overrides in your own CSS, never in the installed rules.
- Tokens: retheme with the `--lumen-*` custom properties (`--lumen-accent`, `--lumen-accent-foreground`, `--lumen-accent-text`, `--lumen-bad`, `--lumen-bad-text`, `--lumen-chart-accent`, `--lumen-chart-accent-foreground`, `--lumen-chart-accent-text`, `--lumen-focus`, `--lumen-good`, `--lumen-good-text`, `--lumen-hairline`, `--lumen-ink`, `--lumen-muted-ink`, `--lumen-series-1`, `--lumen-series-2`, `--lumen-series-3`, `--lumen-series-4`, `--lumen-series-5`, `--lumen-series-6`, `--lumen-warn`, `--lumen-warn-text`). Never add Tailwind colour classes inside the component.

```tsx
import { SplitButton } from "@/components/ui/lumen/controls/split-button";
```

## Parts

| Part | data-slot | What it is for |
|---|---|---|
| `SplitButton` | — | The main button and its menu. |

## Sound
- Keep every `data-slot` and `data-sound` attribute: the sound layer reads them.
- Installing this item adds no audio. Nothing plays until the app mounts `GlassSoundProvider` once (install: `npx shadcn@latest add https://beautiful-ui.dev/r/glass-sound.json`, import from `@/components/beautiful-ui/glass-sound`); `GlassSoundToggle` is its mute control. Without a provider the audio engine never loads.

## Match the original
- Read `components/ui/lumen/controls/split-button.tsx` as the reference implementation before changing or recreating anything, and match it: sizes, colours per theme, motion timings, copy and behaviour.
- If you deviate (a prop you can't honour, a style you changed, a dependency you swapped), say so in your reply, part by part.
- Keep the accessibility contract, the keyboard map and the motion levels listed below.

## Use it when
- split button, dropdown button, button with menu, save options, merge options, export format, Lumen
- A main action with two to six close alternatives
- A repeated action whose kind people pick once and reuse (export format, merge strategy)

### Not when
- Unrelated actions: use a Dropdown Menu on a ghost button
- Two equal actions: use two buttons in a Button Group

## Mistakes
- Keep the main action the one people want most; don't hide it in the menu
- With choices, run the chosen one in onClick (read value)

## Usage

```tsx
"use client";

import * as React from "react";
import { SplitButton } from "@/components/ui/lumen/controls/split-button";

// Actions: the menu holds other things to do.
export function PublishButton() {
  return (
    <SplitButton
      onClick={() => console.log("publish")}
      actions={[
        { label: "Schedule…", onSelect: () => console.log("schedule") },
        { label: "Discard draft", onSelect: () => console.log("discard"), destructive: true },
      ]}
    >
      Publish
    </SplitButton>
  );
}

// Choices: the menu picks what the main button does.
const formats = [
  { value: "csv", label: "Export CSV" },
  { value: "xlsx", label: "Export Excel", description: "One sheet per tab" },
  { value: "pdf", label: "Export PDF" },
];

export function ExportButton() {
  const [format, setFormat] = React.useState("csv");
  return <SplitButton variant="secondary" choices={formats} value={format} onValueChange={setFormat} onClick={(f) => console.log("export as", f)} />;
}
```

## Props

| Prop | Type | Default | What it does |
|---|---|---|---|
| `motion` | `"full" \| "subtle" \| "off"` | `"full"` | As on Button: subtle is shorter on a calm curve; off is instant. Reduced motion is respected automatically. |
| `children` | `ReactNode` |  | The main label. With choices it's optional: the chosen label shows. |
| `onClick` | `(value: string) => void` |  | The main action. With choices it receives the chosen value; the menu is disabled while state is "loading". |
| `actions` | `{ label, description?, onSelect, destructive?, disabled? }[]` |  | Other things to do. Destructive ones go last, after a separator, in the danger colour. |
| `choices / value / defaultValue / onValueChange` | `{ value, label, description? }[]` |  | What the main button can do; the menu picks one (a radio group with a check). |
| `variant` | `"default" \| "secondary" \| "outline" \| "destructive"` | `"default"` | Both halves share it. |
| `size` | `"xs" \| "sm" \| "default" \| "lg"` | `"default"` | Both halves share it. |
| `icon / state` | `Button props` |  | On the main half, as on Button (state: loading, success, error). |
| `menuLabel` | `string` | `"More options"` | The chevron's accessible name. |

Full docs: https://beautiful-ui.dev/components/lumen-split-button

## Customising
- Motion: `motion="full"` (default) | `"subtle"` | `"off"`. prefers-reduced-motion is always respected.
- Colours: set the `--lumen-*` tokens on `:root`, or on a container with the `lumen-scope` class to retheme one area. Add the `lumen-inherit` class to follow your shadcn palette instead (`--chart-N`, `--destructive`).
- Dark mode follows the `.dark` class on an ancestor (the shadcn and next-themes convention).
- Update later by re-running the install with `--overwrite` (review the diff if you edited it). Changelog: https://beautiful-ui.dev/r/changelog.json

## Keyboard

| Keys | Action |
|---|---|
| Tab | Main action, then the chevron |
| Enter, Space or Arrow down | Open the menu (on the chevron) |

## Motion inventory

| Interaction | What moves |
|---|---|
| Open | The chevron turns; the menu opens as every Lumen menu does |

## Accessibility contract (preserve when editing)
- Two real buttons: the main action, and a named menu button (aria-haspopup, aria-expanded)
- Choices are a radio group in the menu, so the current one is announced as checked

## Install

```bash
npx shadcn@latest add @beautiful-ui-pro/lumen-split-button
```

Pro item: needs the `@beautiful-ui-pro` registry in `components.json` and `BEAUTIFUL_UI_TOKEN` in `.env.local` (https://beautiful-ui.dev/account). Setup: https://beautiful-ui.dev/docs/pro. Your components.json `style` picks the build: radix-*, new-york and default get Radix, base-* gets Base UI.

## Credits
- Built on shadcn/ui (https://ui.shadcn.com)

The lumen foundation (the tokens listed above, keyframes and motion levels) installs once with the first component; its CSS is public at https://beautiful-ui.dev/r/lumen-foundation.json.