Divider resolves to undefined when passed via Stack's divider prop in a React Server Component

[iliarubashkin-movecars]

Steps to reproduce

Live example: https://github.com/iliarubashkin-movecars/mui-stack-divider-rsc-bug

Steps to reproduce:

1. Create a server component (page.tsx, no "use client" directive)
2. Use <Stack divider={}> with 2+ children
3. The page crashes with:

Error: Element type is invalid: expected a string (for built-in components)
or a class/function (for composite components) but got: undefined

Current behavior

When <Divider> is passed via Stack's divider prop inside a React Server Component, it resolves to undefined during server rendering. With 1 child nothing breaks (no divider is inserted), but with 2+ children Stack injects the undefined component between them, causing a runtime crash.

Next.js automatically handles the "use client" boundary for MUI components when they are rendered as direct JSX children — but this mechanism does not work when a client component is passed as a prop value. This likely affects any MUI client component passed as a prop value in a server component, not just Divider.

The error message gives no indication that this is an RSC boundary issue, making it extremely difficult to debug.

Expected behavior

Stack with divider={<Divider />} should render dividers between children in a server component, the same way it works when <Divider> is used as a direct JSX child. Next.js should handle the "use client" boundary for components passed as prop values the same way it handles them as JSX children.

Context

Building a company profile page in Next.js App Router where the page component is an async server component (it fetches data via GraphQL). Using <Stack divider={<Divider />}> to visually separate sections of the profile. The page must remain a server component because it performs data fetching — adding "use client" to the entire page is not an option.

Your environment

npx @mui/envinfo

System:
  OS: Linux 6.8 Linux Mint 21.3 (Virginia)
Binaries:
  Node: 24.12.0 - /home/movecars/.asdf/installs/nodejs/24.12.0/bin/node
  npm: 11.6.2 - /home/movecars/.asdf/plugins/nodejs/shims/npm
  pnpm: 10.29.3 - /home/movecars/.asdf/shims/pnpm
Browsers:
  Chrome: 146.0.7680.177
  Firefox: 149.0

The issue is present in both Firefox and Chrome

Search keywords: Divider, Stack, divider prop, server component, RSC, undefined, Element type is invalid, use client, Next.js, App Router