> ## Documentation Index
> Fetch the complete documentation index at: https://docs.crossmint.com/llms.txt
> Use this file to discover all available pages before exploring further.

# CrossmintOtpPromptBuilder

> Flutter Type Alias

**Type Alias**

Builds a widget that owns the OTP signer prompt UI for the wallet provider.

```dart theme={null}
typedef CrossmintOtpPromptBuilder = Widget Function( BuildContext context, CrossmintWalletOtpController otpController, Widget child, )
```

The provider invokes this builder when its wallet controller has a pending
OTP challenge so that consumers can render the prompt with their own design
system. Pass `crossmintDefaultOtpPromptBuilder` (from
`crossmint_flutter_ui.dart`) for the Material default that mirrors the
React Native SDK; supply a custom builder for headless integrations.