restage_a2ui 0.1.4

Fail-closed pre-render capability checks and the Restage capability sidecar for apps rendering cached A2UI (Google genui) surfaces.

example/README.md

restage_a2ui example

restage_a2ui is the app-side, fail-closed pre-render capability check for A2UI payloads. It verifies a payload against the catalog your app actually registered — and, for stamped payloads, the catalog version — before handing it to genui, so a payload your build can't render faithfully fails with a clean diagnostic instead of throwing mid-render.

Gate a payload before rendering

Build the check once (it is immutable — reuse it for every payload), then gate each payload before render:

import 'package:genui/genui.dart';
import 'package:restage_a2ui/restage_a2ui.dart';

// The genui catalog your build emitted, and what it provides.
final catalog = Catalog(buildRestageCatalogItems());
final installed = A2uiInstalledCapability.fromStampJson(restageCapability);

// One instance, reused for every payload.
final check = RestageA2uiPreRenderCheck(catalog: catalog, installed: installed);

Widget? renderCached(Map<String, Object?> payload) {
  switch (check.check(payload)) {
    case A2uiRenderable():
      return renderWithGenui(payload); // your genui render call
    case A2uiRejected(:final diagnostic):
      // Do NOT render — fall back to a built-in surface and log why.
      debugPrint('A2UI rejected: $diagnostic');
      return null;
  }
}

The check fails closed at every path — a malformed envelope, an unknown component, an unmet version, or an unverifiable stamped payload all yield an A2uiRejected, never a throw at the render seam.

See the package README for the capability sidecar, the version satisfaction rules, and how the catalog and stamp are produced.