---

## A2UIView
Renders a trusted-catalog A2UI (Agent-to-UI, v0.9.1 `basic`
subset) payload into live, interactive Urbicon components. Fail-loud and
whitelist-only: only the 12 mapped components and their declared props ever
reach the DOM — unknown components/props, prototype-pollution keys and
function-call bindings are rejected, never rendered, and surfaced through
`onValidationError` (spec-compatible issues a consumer can relay to the agent
as a `VALIDATION_FAILED` error). Inputs are two-way (typing writes into the
local data model; bound text updates live); actions dispatch a spec-exact
`A2uiActionEvent`. Images and links are gated by the same strict-by-default
`urlPolicy` as StreamingMarkdown. It is deliberately NOT a default ChatMessage
renderer — wire it in per surface via `partRenderers.a2ui` to keep it out of
the base bundle. Generate the agent-side prompt with the shipped
`a2uiSystemPrompt()`; validate a payload without a DOM with
`createA2uiProcessor()` — never hand-roll either.

**Import:** `import { A2UIView } from '@urbicon-ui/blocks';`

### Examples
```svelte
{#snippet a2uiPart(part)}
<A2UIView
payload={part.payload}
streaming={message.status === 'streaming'}
{urlPolicy}
onAction={(event) => sendUserTurn(`[ui-action] ${JSON.stringify(event)}`)}
onValidationError={(issues) => reportToAgent(issues)}
/>
{/snippet}
<ChatMessage {message} {urlPolicy} partRenderers={{ a2ui: a2uiPart }} />
```

```svelte
<A2UIView payload={envelopes} onAction={(e) => console.log(e)} />
```

### Api
| Prop | Type | Required | Default | Description |
| --- | --- | :---: | --- | --- |
| payload | `unknown` | yes |  | The A2UI payload. Accepts an array of envelopes (the accumulated JSONL sequence — stream by extending it immutably: `[...prev, envelope]`), a single envelope object, or the golden-file `{ messages: [...] }` wrapper. |
| ...HTMLAttributes<HTMLDivElement> | `HTMLAttributes` | no |  | HTML attributes (excluding: 'class') |
| blockedImageLabel | `string` | no | 'Image blocked' | Chip label shown in place of a policy-blocked image. |
| class | `string` | no |  | Extra classes merged onto the root element. |
| errorTitle | `string` | no | 'Invalid UI payload' | Title of the top-level error Alert for envelope-level faults. |
| onAction | `(event: A2uiActionEvent) => void` | no |  | Fired when a Button is activated, with the spec-exact resolved action event. |
| onValidationError | `(issues: A2uiValidationIssue[]) => void` | no |  | Fired whenever the validation-issue list changes (errors AND warnings, each with a `severity`). Relay error-severity issues to the agent as an A2UI `error` message. |
| pendingLabel | `string` | no | 'Loading UI' | Screen-reader label of the streaming placeholder. |
| preset | `string` | no |  | Apply a named preset registered via `<BlocksProvider presets={{ A2UIView: {...} }}>`. Prefer this over `class` overrides for reusable custom looks. |
| slotClasses | `Partial<Record<A2UIViewSlots, string>>` | no |  | Per-slot class overrides. Slots: `root`, `surface`, `errorList`, `errorChip`, `errorIcon`, `pending`, `column`, `row`, `list`, `listItem`, `heading`, `caption`, `inlineText`, `image`, `blockedChip`, `icon`, `svgIcon`, `choiceGroup`, `choiceLabel`. |
| streaming | `boolean` | no | false | While true, a reference to a not-yet-defined component renders a placeholder instead of a fault chip (mid-stream tolerance). Flip to false when the stream settles so dangling references become errors. |
| unstyled | `boolean` | no |  | Strip the component's default tv() classes. |
| unsupportedLabel | `string` | no | 'Unsupported component' | Fault-chip label for an unknown/unsupported/incomplete component. |
| urlPolicy | `MarkdownUrlPolicy` | no |  | URL policy for `Image` sources (and Text markdown links). Strict by default: every external image is blocked unless its prefix is allowlisted. Keep the object referentially stable. |

Inherited from:
- Omit<HTMLAttributes<HTMLDivElement>, 'class'> (omit-pattern)

### Types
```ts
interface MarkdownUrlPolicy {
/**
   * Allowed link protocols (with trailing colon). Relative URLs are always
   * allowed for links. @default ['http:', 'https:', 'mailto:', 'tel:']
   */
  allowedLinkProtocols?: string[];
  /**
   * Prefix allowlist for image sources, matched against the normalized
   * absolute URL. Empty (the default) blocks every external image; relative
   * sources are allowed. Prefer deep, specific prefixes — broad ones are
   * open-redirect bait. `data:` images are blocked unless a `data:` prefix
   * is listed explicitly.
   * @default []
   */
  allowedImagePrefixes?: string[];
  /** Observability hook — fires once per blocked URL occurrence. */
  onBlocked?: (kind: 'link' | 'image', url: string) => void;
}
```

```ts
interface A2uiActionEvent {
name: string;
  surfaceId: string;
  sourceComponentId: string;
  /** ISO 8601 timestamp (`new Date().toISOString()`). */
  timestamp: string;
  context: Record<string, unknown>;
}
```

```ts
interface A2uiValidationIssue {
severity: A2uiIssueSeverity;
  code: string;
  surfaceId?: string;
  path?: string;
  message: string;
}
```

```ts
type A2uiIssueSeverity = 'error' | 'warning'
```

```ts
type SlotNames = keyof ReturnType<T> & string
```