An expected segment was not rendered during instant UI validation

Why This Error Occurred

Next.js attempted to validate that navigation to the affected route is able to be rendered instantly without waiting on a server request or data loading.

In this instance Next.js was unable to verify that the navigation would be instant because something prevented the necessary page data from rendering during validation.

Common Causes

A parent layout conditionally omits a parallel slot

If a layout receives multiple slot props (e.g. children, @modal, @sidebar) but only renders some of them based on a condition, the omitted slot's content never renders.

// app/dashboard/layout.tsx
export default function Layout({
  children,
  modal,
}: {
  children: React.ReactNode
  modal: React.ReactNode
}) {
  return (
    <main>
      {children}
      {
        // `modal` is only rendered conditionally.
        showModal ? modal : null
      }
    </main>
  )
}

A client component does not render its children during SSR

If a client component does not render during SSR, any segments it would have rendered as children cannot be validated for instant UI.

import dynamic from 'next/dynamic'

// This component and its children will not render during SSR.
const ClientOnly = dynamic(() => import('./my-component'), { ssr: false })

export default async function Layout({ children }) {
  // The children of this layout won't appear in the SSR HTML
  // but can render fine on client navigation
  return <ClientOnly>{children}</ClientOnly>
}

How to Fix It

If the missing segment is intentional

If you expect this segment to sometimes not render (for example, a modal slot that only appears on certain routes), you can opt it out of instant UI validation:

// app/dashboard/@modal/page.tsx
export const instant = false

export default function ModalPage() {
  // ...
}

If the missing segment is unintentional

Check the parent layouts above the reported segment. Make sure every layout renders its slot props (children and any named parallel routes). If a client component wraps the segment, ensure it renders its children during SSR.