diff --git a/apps/web/src/components/PluginDetailsModal.tsx b/apps/web/src/components/PluginDetailsModal.tsx
index 306a75503..3a2a6f13c 100644
--- a/apps/web/src/components/PluginDetailsModal.tsx
+++ b/apps/web/src/components/PluginDetailsModal.tsx
@@ -19,6 +19,7 @@
 // same callback wiring.
 
 import type { InstalledPluginRecord } from '@open-design/contracts';
+import { createPortal } from 'react-dom';
 import { inferPluginPreview } from './plugins-home/preview';
 import { PluginScenarioDetail } from './plugin-details/PluginScenarioDetail';
 import { PluginExampleDetail } from './plugin-details/PluginExampleDetail';
@@ -39,9 +40,10 @@ export function PluginDetailsModal({
   isApplying,
 }: Props) {
   const preview = inferPluginPreview(record);
+  let detail: JSX.Element;
 
   if (preview.kind === 'media') {
-    return (
+    detail = (
       <PluginMediaDetail
         record={record}
         onClose={onClose}
@@ -49,10 +51,8 @@ export function PluginDetailsModal({
         isApplying={isApplying}
       />
     );
-  }
-
-  if (preview.kind === 'html') {
-    return (
+  } else if (preview.kind === 'html') {
+    detail = (
       <PluginExampleDetail
         record={record}
         exampleStem={
@@ -63,10 +63,8 @@ export function PluginDetailsModal({
         isApplying={isApplying}
       />
     );
-  }
-
-  if (preview.kind === 'design') {
-    return (
+  } else if (preview.kind === 'design') {
+    detail = (
       <PluginDesignSystemDetail
         record={record}
         onClose={onClose}
@@ -74,14 +72,17 @@ export function PluginDetailsModal({
         isApplying={isApplying}
       />
     );
+  } else {
+    detail = (
+      <PluginScenarioDetail
+        record={record}
+        onClose={onClose}
+        onUse={onUse}
+        isApplying={isApplying}
+      />
+    );
   }
 
-  return (
-    <PluginScenarioDetail
-      record={record}
-      onClose={onClose}
-      onUse={onUse}
-      isApplying={isApplying}
-    />
-  );
+  if (typeof document === 'undefined') return detail;
+  return createPortal(detail, document.body);
 }
diff --git a/apps/web/tests/components/PluginDetailsModal.layering.test.tsx b/apps/web/tests/components/PluginDetailsModal.layering.test.tsx
new file mode 100644
index 000000000..4294f7f16
--- /dev/null
+++ b/apps/web/tests/components/PluginDetailsModal.layering.test.tsx
@@ -0,0 +1,86 @@
+// @vitest-environment jsdom
+
+import { cleanup, render } from '@testing-library/react';
+import type { InstalledPluginRecord } from '@open-design/contracts';
+import { afterEach, describe, expect, it } from 'vitest';
+
+import { PluginDetailsModal } from '../../src/components/PluginDetailsModal';
+import { I18nProvider } from '../../src/i18n';
+
+function makePlugin(
+  id: string,
+  preview?: Record<string, unknown>,
+): InstalledPluginRecord {
+  return {
+    id,
+    title: id,
+    version: '0.1.0',
+    sourceKind: 'bundled',
+    source: '/tmp',
+    trust: 'bundled',
+    capabilitiesGranted: [],
+    manifest: {
+      name: id,
+      version: '0.1.0',
+      title: id,
+      od: {
+        kind: 'scenario',
+        ...(preview ? { preview } : {}),
+        useCase: {
+          query: 'Generate a preview.',
+        },
+      },
+    },
+    fsPath: '/tmp',
+    installedAt: 0,
+    updatedAt: 0,
+  };
+}
+
+function renderInsideStackingContext(record: InstalledPluginRecord) {
+  const host = document.createElement('div');
+  host.className = 'composer';
+  document.body.appendChild(host);
+
+  render(
+    <I18nProvider>
+      <div className="composer-shell">
+        <PluginDetailsModal record={record} onClose={() => {}} onUse={() => {}} />
+      </div>
+    </I18nProvider>,
+    { container: host },
+  );
+
+  return host;
+}
+
+describe('PluginDetailsModal layering', () => {
+  afterEach(() => {
+    cleanup();
+    document.body.innerHTML = '';
+  });
+
+  it('portals rich preview details to the document body so sticky chat and workspace headers cannot cover them', () => {
+    const host = renderInsideStackingContext(
+      makePlugin('video-plugin', {
+        type: 'video',
+        poster: 'https://cdn.example/poster.jpg',
+        video: 'https://cdn.example/clip.mp4',
+      }),
+    );
+
+    const backdrop = document.body.querySelector('.ds-modal-backdrop');
+    expect(backdrop).toBeTruthy();
+    expect(backdrop?.parentElement).toBe(document.body);
+    expect(host.querySelector('.ds-modal-backdrop')).toBeNull();
+  });
+
+  it('portals fallback scenario details through the same top-level layer', () => {
+    const host = renderInsideStackingContext(makePlugin('scenario-plugin'));
+
+    const backdrop = document.body.querySelector('.plugin-details-modal-backdrop');
+    expect(backdrop).toBeTruthy();
+    expect(backdrop?.parentElement).toBe(document.body);
+    expect(host.querySelector('.plugin-details-modal-backdrop')).toBeNull();
+  });
+});