Link to the code that reproduces this issue

https://codesandbox.io/p/devbox/n9rftd

To Reproduce

1. <Suspense><ServerComponent> <ClientComponentDoingClone> <OtherClientComponent /> </ClientComponentDoingClone> <ServerComponent/><Suspense/>
2. Create production build next build
3. Start production build next start

Current vs. Expected behavior

Current behavior (since 15.4.1):

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

The Component doing cloneElement gets the following value for children which then causes the error:

{
  '$$typeof': Symbol(react.lazy),
  _payload: Promise { status: 'pending', value: null, reason: null },
  _init: [Function: P]
}

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP PREEMPT_DYNAMIC Sun Aug  6 20:05:33 UTC 2023
  Available memory (MB): 4102
  Available CPU cores: 2
Binaries:
  Node: 20.12.1
  npm: 10.5.0
  Yarn: 1.22.19
  pnpm: 8.15.6
Relevant Packages:
  next: 15.4.6 // Latest available version is detected (15.4.6).
  eslint-config-next: N/A
  react: 19.1.1
  react-dom: 19.1.1
  typescript: 5.3.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

React

Which stage(s) are affected? (Select all that apply)

Other (Deployed), next start (local)

Additional context

See #81876

This seems to be some kind of optimization around suspense boundaries, as it only occurs in production build and only after a certain amount of DOM elements (or React components??)

Some takeaways from my repro above:

• This issue only occurs, if I have a <Suspense> boundary, containing a server component (be it sync or async) that in turn has a client component that does cloneElement on another client component.
• Additionally, this only appears after a certain amount of components. In my production app, it takes four table rows to trigger this. In my repro example, it takes over 50.
• This exclusively happens with production builds.
• When this issue does NOT appear, children.'$$typeof' is Symbol(react.transitional.element), whereas when this issue happens it is Symbol(react.lazy)