# Radio

Level: atom.

## Purpose and use

Represent one option in an exclusive choice. The enclosing composition must maintain the selected item; do not treat a collection of these standalone controls as a complete Radio Group API.

## Anatomy and behavior

A native radio is wrapped by a label with optional description and decorative hint. User selection emits `selectedChange`; parent state drives `selected`. Disabled suppresses changes, and error sets aria-invalid. Description appears only with visible text.

## Accessibility and content

Each control has native radio semantics and a generated ID. With hidden text, `label` remains the accessible name. The current API has no `name` or group input and no group keyboard controller: exclusive selection and arrow-key group navigation are not provided by this component.

## Open Questions

A receiving composition needs a verified grouping and keyboard contract before presenting multiple instances as one accessible radio group.

## Local component contract

This is the current owned contract for `component.radio`. Behavior above was checked
against the local implementation, template and focused tests listed below.
Historical migration evidence does not override these current sources.

### Public type values

`WblRadioSize`: `S | M`. State flags are booleans; `selectedChange` emits a boolean.

### Classes and selectors

- `WblRadioComponent` — `wbl-radio` (src/app/design-system/primitives/radio/radio.component.ts).

### Inputs

- `WblRadioComponent.size = input<WblRadioSize>('M')`
- `WblRadioComponent.selected = input(false)`
- `WblRadioComponent.disabled = input(false)`
- `WblRadioComponent.error = input(false)`
- `WblRadioComponent.text = input(true)`
- `WblRadioComponent.label = input('Label')`
- `WblRadioComponent.description = input(false)`
- `WblRadioComponent.descriptionText = input('Desc')`
- `WblRadioComponent.hint = input(false)`

### Models

- None.

### Outputs

- `WblRadioComponent.selectedChange = output<boolean>()`

### Slots and projection markers

- The exact template has no Angular content-projection slot.

### Local evidence

- Behavior/template: `src/app/design-system/primitives/radio/radio.component.html` (reviewed in D-025, 2026-09-05).

- Code: `src/app/design-system/primitives/radio/radio.component.ts`.
- Focused test: `src/app/design-system/primitives/radio/radio.component.spec.ts`.
- Public export: `export * from './primitives/radio/radio.component';` in `src/app/design-system/index.ts`.
- Storybook: `storybook/stories/radio.stories.ts` (`Design System/Primitives/wbl-radio`).

## Figma status

This runtime contract does not infer a Figma owner. Assembly evidence, when
verified, is maintained separately through the inventory-linked sidecar.

## Provenance

The archived source-document copy is historical evidence only. The active
resolver is local code/test/export and the exact Storybook story above.