SWR + React 19: Tests with Suspense fail to transition from loading state

[mori-hisayuki]

Bug report

Description / Observed Behavior

When using SWR with Suspense mode (suspense: true) in React 19, tests fail to transition from loading to success/error states. Components remain stuck in the loading state and tests timeout.

Expected Behavior

Components should:

1. Show loading state initially
2. Transition to success/error state after data loads

Repro Steps / Code Example

Using SWR:

const { data } = useSWR(key, fetcher, { suspense: true });

Test case:

test('transition from loading to success', async () => {
  render(
    <Suspense fallback={<Loading />}>
      <Component />
    </Suspense>
  );

  expect(screen.getByTestId('loading')).toBeInTheDocument();
  await waitForElementToBeRemoved(() => screen.getByTestId('loading'));
});

Additional Context

Environment:

SWR 2.3.0
React 19.0.0
@testing-library/react 16.1.0