React: What are React 19 improvements to Suspense?

1import { Suspense, use } from "react";
2
3function App() {
4  return (
5    <div>
6      <Header />
7      <Suspense fallback={<PageSkeleton />}>
8        <MainContent />
9      </Suspense>
10      <Footer />
11    </div>
12  );
13}
14
15async function MainContent() {
16  const data = await fetchData(); // Suspends here
17  return <div>{data.content}</div>;
18}

1<ErrorBoundary fallback={<ErrorPage />}>
2  <Suspense fallback={<Loading />}>
3    <AsyncComponent />
4  </Suspense>
5</ErrorBoundary>

1<Suspense fallback={<PageSkeleton />}>
2  <Header />
3  <Suspense fallback={<ContentSkeleton />}>
4    <Content />
5  </Suspense>
6  <Suspense fallback={<SidebarSkeleton />}>
7    <Sidebar />
8  </Suspense>
9</Suspense>

1function UserProfile({ userId }) {
2  const { data } = useQuery({
3    queryKey: ["user", userId],
4    queryFn: () => fetchUser(userId),
5    suspense: true,
6  });
7
8  return <div>{data.name}</div>;
9}
10
11<Suspense fallback={<Spinner />}>
12  <UserProfile userId={1} />
13</Suspense>