# Split Button

> Primary action joined to a dropdown of alternatives, like GitHub's merge button. Choosing an option makes it the new primary action rather than running it; async actions show a spinner. Controlled or uncontrolled, built on the Base UI dropdown menu.

- Slug: `split-button`
- Category: [Buttons](https://www.assembli.design/category/buttons.md)
- Type: component
- Tags: split-button, dropdown, button-group, actions
- npm dependencies: lucide-react
- shadcn/ui dependencies: dropdown-menu
- Added: 2026-10-14
- Live preview: https://www.assembli.design/preview/split-button
- Page: https://www.assembli.design/components/split-button

## Install

One-time setup (needs a subscription):

1. Add the registry to the project's `components.json`: `{"@assembli":{"url":"https://www.assembli.design/r/{name}.json","headers":{"Authorization":"Bearer ${ASSEMBLI_API_KEY}"}}}` (merge into `"registries"`).
2. Put an API key from https://www.assembli.design/account in `.env.local` as `ASSEMBLI_API_KEY=asm_…`.

Then install with the shadcn CLI (writes `components/split-button/split-button.tsx` and installs dependencies):

```bash
npx shadcn@latest add @assembli/split-button
```

Registry item JSON: https://www.assembli.design/r/split-button.json (send `Authorization: Bearer <api key>`)

## Code

> Component source needs an Assembli subscription ($12/month) and an API key sent as `Authorization: Bearer <key>`. To get one without copying anything, POST https://www.assembli.design/api/agent/login (or call the MCP tool connect_account), show the user the link it returns, and poll https://www.assembli.design/api/agent/token for the key. Or subscribe at https://www.assembli.design/pricing and create a key at https://www.assembli.design/account.