diff --git a/pages/sut/ui/cross-origin-iframes.jsx b/pages/sut/ui/cross-origin-iframes.jsx
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+import Head from 'next/head';
+
+/**
+ * SUT fixture: cross-origin iframe capture.
+ *
+ * Hidden test page (not linked from anywhere in the app) used by the A11y Engine
+ * P1 sanity/WA suites to verify that, with the cross-origin iframe capture flag
+ * ON, the engine surfaces accessibility violations that live inside cross-origin
+ * iframes. Reachable only by direct path: /sut/ui/cross-origin-iframes
+ *
+ * NOTE: unlike the sibling /sut/ui/* pages this fixture is intentionally NOT
+ * gated behind the sutSessionId cookie. The A11y scanner loads it with no
+ * session, so an auth redirect would stop it before the iframes ever render.
+ *
+ * Iframes (both genuinely cross-origin to bstackdemo.com):
+ *   1. Our A11y demo page (browserstack.github.io) - the deterministic source of
+ *      in-iframe violations the assertion is baselined against.
+ *   2. https://www.qualified.com/ - stands in as a third-party "ad" slot to prove
+ *      capture works across an unrelated external origin too.
+ */
+export default function CrossOriginIframes() {
+  return (
+    <>
+      <Head>
+        <title>Cross-Origin Iframe Fixture - SUT</title>
+        <meta name="robots" content="noindex, nofollow" />
+        <link rel="icon" href="/favicon.svg" />
+      </Head>
+      <main style={styles.container}>
+        <header style={styles.header}>
+          <h1 id="fixture-title" style={styles.title}>StackDemo Partner Showcase</h1>
+          <p style={styles.text}>
+            A sample page that embeds partner content from other origins. Used to
+            exercise accessibility scanning across cross-origin iframe boundaries.
+          </p>
+        </header>
+
+        <section aria-labelledby="primary-frame-heading" style={styles.section}>
+          <h2 id="primary-frame-heading" style={styles.subtitle}>Accessibility demo content</h2>
+          <iframe
+            id="cross-origin-frame-primary"
+            title="A11y demo content (cross-origin)"
+            src="https://browserstack.github.io/bs-a11y-checks/all/index.html"
+            style={styles.frame}
+          />
+        </section>
+
+        <section aria-labelledby="ad-frame-heading" style={styles.section}>
+          <h2 id="ad-frame-heading" style={styles.subtitle}>Sponsored</h2>
+          <iframe
+            id="cross-origin-frame-ad"
+            title="Sponsored partner (cross-origin)"
+            src="https://www.qualified.com/"
+            style={styles.frame}
+          />
+        </section>
+      </main>
+    </>
+  );
+}
+
+const styles = {
+  container: {
+    maxWidth: '900px',
+    margin: '40px auto',
+    padding: '20px',
+    fontFamily: 'Inter, sans-serif',
+  },
+  header: {
+    marginBottom: '24px',
+  },
+  title: {
+    color: '#1f2937',
+    marginBottom: '10px',
+  },
+  subtitle: {
+    color: '#374151',
+    marginBottom: '12px',
+  },
+  text: {
+    fontSize: '1.05rem',
+    color: '#4b5563',
+  },
+  section: {
+    marginBottom: '32px',
+  },
+  frame: {
+    width: '100%',
+    height: '600px',
+    border: '1px solid #d1d5db',
+    borderRadius: '8px',
+  },
+};
