I am attempting to use a guard pattern in layout.tsx, e.g.

export default async function MainLayout(props: { children: ReactNode }) {
  const authState = await getAuthState(); // not necessarily an authentication guard, just as an example
  if (!authState) {
    redirect("/signin");
  }
  return props.children;
}

But this doesn't work too well, if there is a child page assuming that the user is signed-in, it will throw an error since in RSC children is rendered before being passed to the layout. Are there better patterns of having guards in layouts?

Note:
Why I am not using middleware.ts: I also want to co-locate the code (imagine I have several of these checks and each of them have different children, it would be a nightmare to manage).