diff --git a/apps/website/content/docs/chat/api/api-docs.json b/apps/website/content/docs/chat/api/api-docs.json
index 2dc3925dc..3b3a8ae14 100644
--- a/apps/website/content/docs/chat/api/api-docs.json
+++ b/apps/website/content/docs/chat/api/api-docs.json
@@ -1121,7 +1121,7 @@
       {
         "name": "spec",
         "type": "Signal<Spec | null>",
-        "description": "Convert the A2UI surface to a json-render Spec for rendering.",
+        "description": "Convert the A2UI surface to a json-render Spec for rendering.\n Prefers `state().surface` (the progressively-built wire surface)\n over the legacy `surface` input. surfaceToSpec handles\n children.explicitList → spec.children translation + reserved-key\n filtering + path-ref → $bindState rewriting; the rendered tree\n then uses render-element's standard input-mapping\n (`childKeys: el.children`) so catalog components receive the\n inputs they actually declare.\n\n This supersedes the earlier slot-based progressive renderer,\n which mounted root components but never populated their\n childKeys input — leaving Columns/Rows/etc. with no children.",
         "optional": false
       },
       {
diff --git a/libs/chat/src/lib/a2ui/surface.component.spec.ts b/libs/chat/src/lib/a2ui/surface.component.spec.ts
index 3da60db41..536f29e65 100644
--- a/libs/chat/src/lib/a2ui/surface.component.spec.ts
+++ b/libs/chat/src/lib/a2ui/surface.component.spec.ts
@@ -4,72 +4,88 @@ import { Component, ChangeDetectionStrategy } from '@angular/core';
 import { TestBed } from '@angular/core/testing';
 import { A2uiSurfaceComponent } from './surface.component';
 import type { A2uiSurfaceState } from './surface-store';
+import { createA2uiSurfaceStore } from './surface-store';
 import type { A2uiViews } from './views';
+import { a2uiBasicCatalog } from './catalog';
 
 @Component({ standalone: true, selector: 'a2ui-test-real', template: '<span data-role="real"></span>', changeDetection: ChangeDetectionStrategy.OnPush })
 class RealCmp {}
 @Component({ standalone: true, selector: 'a2ui-test-custom-fb', template: '<span data-role="custom-fb"></span>', changeDetection: ChangeDetectionStrategy.OnPush })
 class CustomFallback {}
 
-function makeState(componentViews: Map<string, unknown>): A2uiSurfaceState {
+function makeState(components: Array<{ id: string; type: string; props?: Record<string, unknown> }> = []): A2uiSurfaceState {
+  const compsMap = new Map<string, never>(
+    components.map((c) => [c.id, {
+      id: c.id,
+      component: { [c.type]: c.props ?? {} },
+    } as never]),
+  );
   return {
     surface: {
       surfaceId: 's1', catalogId: 'basic',
-      components: new Map(), dataModel: {},
+      components: compsMap, dataModel: {},
     } as never,
-    componentViews: componentViews as never,
+    componentViews: new Map() as never,
   };
 }
 
-describe('A2uiSurfaceComponent — progressive rendering', () => {
+describe('A2uiSurfaceComponent — empty surface', () => {
   beforeEach(() => TestBed.configureTestingModule({ imports: [A2uiSurfaceComponent] }));
 
-  it('renders the default fallback when state.componentViews is empty', () => {
+  it('renders the default fallback when state.surface has no components', () => {
     const fx = TestBed.createComponent(A2uiSurfaceComponent);
-    fx.componentRef.setInput('state', makeState(new Map()));
+    fx.componentRef.setInput('state', makeState([]));
     fx.componentRef.setInput('catalog', { t: RealCmp });
     fx.detectChanges();
     expect(fx.nativeElement.querySelector('.a2ui-default-fallback')).toBeTruthy();
   });
 
-  it('renders the catalog fallback when a component is not ready', () => {
-    const views = new Map<string, unknown>([['c1', {
-      id: 'c1', type: 't', bindings: ['$.x'], ready: false, props: {}, def: { t: {} },
-    }]]);
+  it('renders a custom fallback when surfaceFallback is set and surface is empty', () => {
     const fx = TestBed.createComponent(A2uiSurfaceComponent);
-    fx.componentRef.setInput('state', makeState(views));
-    fx.componentRef.setInput('catalog', { t: { component: RealCmp, fallback: CustomFallback } } satisfies A2uiViews);
+    fx.componentRef.setInput('state', makeState([]));
+    fx.componentRef.setInput('catalog', { t: RealCmp });
+    fx.componentRef.setInput('surfaceFallback', CustomFallback);
     fx.detectChanges();
     expect(fx.nativeElement.querySelector('[data-role="custom-fb"]')).toBeTruthy();
   });
+});
 
-  it('renders the real component when ready=true', () => {
-    const views = new Map<string, unknown>([['c1', {
-      id: 'c1', type: 't', bindings: [], ready: true, props: {}, def: { t: {} },
-    }]]);
-    const fx = TestBed.createComponent(A2uiSurfaceComponent);
-    fx.componentRef.setInput('state', makeState(views));
-    fx.componentRef.setInput('catalog', { t: { component: RealCmp } });
-    fx.detectChanges();
-    expect(fx.nativeElement.querySelector('[data-role="real"]')).toBeTruthy();
-  });
+describe('A2uiSurfaceComponent — nested children with real catalog (regression)', () => {
+  beforeEach(() => TestBed.configureTestingModule({ imports: [A2uiSurfaceComponent] }));
+
+  it('renders Column children defined via children.explicitList', () => {
+    // Reproduces the contact-form bug: a Column with explicitList children
+    // must actually render those children. Prior to the fix, the slot path
+    // pushed wrapped wire-format props onto the catalog component which
+    // had no matching `Column` input — so childKeys stayed empty and the
+    // Column rendered as an empty <div>.
+    const store = createA2uiSurfaceStore();
+    store.apply({ surfaceUpdate: {
+      surfaceId: 's1',
+      components: [
+        { id: 'root', component: { Column: {
+          children: { explicitList: ['leaf'] },
+          distribution: 'start',
+          alignment: 'stretch',
+        } } },
+        { id: 'leaf', component: { Text: {
+          text: { literalString: 'Hello' },
+          usageHint: 'h2',
+        } } },
+      ],
+    } } as never);
+    store.apply({ beginRendering: { surfaceId: 's1', root: 'root' } } as never);
+
+    const state = store.surfaceState('s1')();
+    expect(state).toBeDefined();
 
-  it('state takes priority over surface when both inputs are set', () => {
-    const views = new Map<string, unknown>([['c1', {
-      id: 'c1', type: 't', bindings: [], ready: true, props: {}, def: { t: {} },
-    }]]);
-    const legacySurface = {
-      surfaceId: 'legacy', catalogId: 'basic',
-      components: new Map(), dataModel: {},
-    };
     const fx = TestBed.createComponent(A2uiSurfaceComponent);
-    fx.componentRef.setInput('state', makeState(views));
-    fx.componentRef.setInput('surface', legacySurface);
-    fx.componentRef.setInput('catalog', { t: { component: RealCmp } });
+    fx.componentRef.setInput('state', state);
+    fx.componentRef.setInput('catalog', a2uiBasicCatalog());
     fx.detectChanges();
-    // state path mounts the real component via a2uiSlot
-    expect(fx.nativeElement.querySelector('[data-role="real"]')).toBeTruthy();
-    // legacy <render-spec> path must NOT have rendered
-    expect(fx.nativeElement.querySelector('render-spec')).toBeFalsy();
+
+    // The Text leaf must appear inside the rendered surface. If the
+    // Column's childKeys input was never set, no Text gets rendered.
+    expect(fx.nativeElement.textContent).toContain('Hello');
   });
 });
diff --git a/libs/chat/src/lib/a2ui/surface.component.ts b/libs/chat/src/lib/a2ui/surface.component.ts
index ba9b92ba1..067f876aa 100644
--- a/libs/chat/src/lib/a2ui/surface.component.ts
+++ b/libs/chat/src/lib/a2ui/surface.component.ts
@@ -32,27 +32,19 @@ import type { A2uiViews } from './views';
     '[style.font-family]': 'fontFamily()',
   },
   template: `
-    @if (state(); as st) {
-      @if (st.componentViews.size === 0) {
-        @if (surfaceFallback(); as fb) {
-          <ng-container *ngComponentOutlet="fb" />
-        } @else {
-          <a2ui-default-fallback />
-        }
-      } @else {
-        @for (id of rootIds(); track id) {
-          @if (st.componentViews.get(id); as view) {
-            <ng-container *a2uiSlot="view; views: catalog()" />
-          }
-        }
-      }
-    } @else if (spec(); as s) {
+    @if (spec(); as s) {
       <render-spec
         [spec]="s"
         [registry]="registry()"
         [handlers]="internalHandlers()"
         (events)="onRenderEvent($event)"
       />
+    } @else if (state(); as st) {
+      @if (surfaceFallback(); as fb) {
+        <ng-container *ngComponentOutlet="fb" />
+      } @else {
+        <a2ui-default-fallback />
+      }
     }
   `,
 })
@@ -109,11 +101,21 @@ export class A2uiSurfaceComponent {
     return [...st.componentViews.keys()].slice(0, 1);
   });
 
-  // ---- Legacy path (no state) ----
-  /** Convert the A2UI surface to a json-render Spec for rendering. */
+  /** Convert the A2UI surface to a json-render Spec for rendering.
+   *  Prefers `state().surface` (the progressively-built wire surface)
+   *  over the legacy `surface` input. surfaceToSpec handles
+   *  children.explicitList → spec.children translation + reserved-key
+   *  filtering + path-ref → $bindState rewriting; the rendered tree
+   *  then uses render-element's standard input-mapping
+   *  (`childKeys: el.children`) so catalog components receive the
+   *  inputs they actually declare.
+   *
+   *  This supersedes the earlier slot-based progressive renderer,
+   *  which mounted root components but never populated their
+   *  childKeys input — leaving Columns/Rows/etc. with no children. */
   readonly spec = computed(() => {
-    const surf = this.surface();
-    return surf ? surfaceToSpec(surf) : null;
+    const surf = this.state()?.surface ?? this.surface();
+    return surf && surf.components.size > 0 ? surfaceToSpec(surf) : null;
   });
 
   /** Convert ViewRegistry to AngularRegistry for RenderSpecComponent. */