### What?
When a layout segment forces dynamic rendering (such as with
`force-dynamic` or `revalidate: 0`), navigating to sub-pages of that
layout will attempt to re-render the layout, also resulting in side
effects re-running. This means if your layout relies on a data fetch and
you render the result of that data in the layout, it will unexpectedly
change when navigating between sub-paths, as described in #57326.
As a separate issue (but caused by the same underlying mechanism), when
using `searchParams` on a dynamic page, changes to those search params
will be erroneously ignored when navigating, as described in #57075
### Why?
As a performance optimization we generate static prefetch files for
dynamic segments ([original
PR](https://github.com/vercel/next.js/pull/54403)). This makes it so
that when prefetching is turned on, the prefetch can be served quickly
from the edge without needing to invoke unnecessarily. We're able to
eagerly serve things that can be safely prefetched. This is nice for
cases where a path has a `loading.js` that we can eagerly render while
waiting for the dynamic data to be loaded.
This causes a problem with layouts that opt into dynamic rendering: when
the page loads and a prefetch is kicked off for the sub-page, it'll load
the static prefetch, which won't be generated with the same router state
as the dynamically rendered page. This causes a mismatch between the two
trees, and when navigating within the same segment, a refetch will be
added to the router because it thinks that it's navigating to a new
layout.
This also causes issues for dynamic pages that use `searchParams`. The
static prefetch will be generated without any knowledge of search
params, and when the prefetch occurs, we still match to the prefetch
generated without search params. This will make the router think that no
change occurs, and the UI will not update to reflect the change.
### How?
There's ongoing work by @acdlite to refactor the client router.
Hopefully it will be easier to re-land this once that work is finished.
For now, I've reverted the behavior as it doesn't seem to be worth the
bugs it currently causes. I've also added tests so that when we do
re-land this behavior, we can catch these subtleties.
Fixes#57326Fixes#57075
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>
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