Bug: suspense fallback flickers with nested suspended components

[tien]

Suspense fallback flicker multiple times with nested suspended children, even after they have already resolved all promises.

Wrapping children in their own Suspense boundary doesn't stop parent fallback from flickering, implying a boundary leak.

This issue started happening from v19.1.0. On v19.0.0, the fallback is only shown once as expected.

I'm currently working on a minimal reproduction. Here's what it looks like in one of my application:

Screen.Recording.2025-04-01.at.2.38.41.PM.mov

[eps1lon]

It doesn't look like this bug report has enough info for one of us to reproduce it.

Please provide a CodeSandbox (https://react.new), or a link to a repository on GitHub.

Here are some tips for providing a minimal example: https://stackoverflow.com/help/mcve