How can we solve duplicate layout instances causing OOM in deeply nested App Router structures under Next.js 16?

Duplicate layout instances in deeply nested Next.js 16 App Router cause OOM by mounting multiple copies during navigation/prefetching. Next.js 16's layout deduplication + route groups fix this by sharing layouts across routes.

Solve OOM from duplicate layouts by using route groups (group) to create shared root layouts without affecting URLs, preventing nested layout stacking. Enable Next.js 16's automatic layout deduplication which caches shared layouts during prefetching. For deep nesting, hoist common layouts higher and use shouldRevalidate to control re-renders. Monitor with next build --debug to spot layout duplication, then refactor with parallel routes or intercepting routes for complex UIs without layout explosion.

Code

// app/(marketing)/layout.tsx
export default function MarketingLayout({ children }: { children: React.ReactNode }) {
  return (
    <div>
      <header>Marketing Header</header>
      {children}
    </div>
  );
}

// app/(dashboard)/layout.tsx
export default function DashboardLayout({ children }: { children: React.ReactNode }) {
  return (
    <div>
      <nav>Dashboard Navigation</nav>
      {children}
    </div>
  );
}

// next.config.js
export default {
  experimental: {
    layoutDeduplication: true, // Enable layout deduplication
  },
};