TanStack: Keep Start's document shell out of stories

code/frameworks/tanstack-react/src/routing/duplicate-tree.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it, vi } from 'vitest';
 import {
   createMemoryHistory,
   createRootRoute,
@@ -34,6 +34,25 @@ function buildAuthedTree(layoutOptions: Record<string, unknown> = {}) {
   return { root, layout, dashboard };
 }
 
+describe('duplicateRouteTree root options', () => {
+  it('copies root behavior but never the document shell', () => {
+    const RootComponent = () => null;
+    const rootBeforeLoad = vi.fn();
+    const Shell = ({ children }: { children: unknown }) => children;
+    const root = createRootRoute({
+      component: RootComponent,
+      beforeLoad: rootBeforeLoad,
+      shellComponent: Shell,
+    } as any);
+
+    const { root: cloned } = duplicateRouteTree(root as any);
+
+    expect((cloned as any).options.component).toBe(RootComponent);
+    expect((cloned as any).options.beforeLoad).toBe(rootBeforeLoad);
+    expect((cloned as any).options.shellComponent).toBeUndefined();
+  });
+});
+
 describe('duplicateRouteTree with pathless layout routes', () => {
   it('preserves a code-based pathless layout (explicit id, no path)', async () => {
     const root = createRootRoute();

code/frameworks/tanstack-react/src/routing/duplicate-tree.ts

@@ -129,7 +129,17 @@ export function duplicateRouteTree(
   // one story is mounted in the same browser session (e.g. HMR, navigation).
   // We strip `id` from spread options so TanStack assigns the canonical
   // `__root__` id itself.
-  const { id: _rootId, getParentRoute: _rootGetParent, ...restRoot } = rootOptions;
+  // `shellComponent` is also stripped: it is TanStack Start's document shell
+  // (`html`/`head`/`body`), which React refuses to nest inside the story
+  // canvas and whose head content hoists into the page, hijacking the
+  // document title from inside a story. All other root behavior (component,
+  // notFoundComponent, errorComponent, beforeLoad context) is kept.
+  const {
+    id: _rootId,
+    getParentRoute: _rootGetParent,
+    shellComponent: _rootShell,
+    ...restRoot
+  } = rootOptions;
   const newRoot = createRootRouteWithContext()({
     ...restRoot,
     ...rootOverride,