No, layouts shouldn’t be re-rendered. I think that’s because of React Strict Mode, try running it in production mode and test if it’s still rerendered?

It still re-renders in production, and strict mode is off

It only re-renders when I update a searchParam in a child RSC with router.push.

It is not supposed to do so, even the docs mentions that it won’t be rerendered because it doesn’t receive search parameters

https://nextjs.org/docs/app/api-reference/file-conventions/layout

How do you test it out? Is it a console.log in the layout?

Yep

The docs I linked also mention that it shouldn't re-render, but it does.

It manifested when there was layout shift in a child framer-motion layout animation

I investigated which resulted in me finding out that the layout was re-rendering whenever I changed searchParams

Here's a video showing the reproduction

Is it because we're reading from cookies in the layout body?