Start: Updating search params when `ssr: false` causes page to unmount and remount

[MTG2000]

Which project does this relate to?

Router

Describe the bug

I noticed this issue on pages that have ssr: false

Normally, updating the search params on the same page doesn't cause a remount, just a re-render.
But in the case of ssr: false pages, the first time updating search params (by calling navigate) causes the page to remount.

I tested this by logging useId() hook value which shouldn't change when changing search params, but the first time they are changed it changes too.

See the reproduction below:

Your Example Website or App

https://github.com/MTG2000/tsr-remount-issue/blob/main/src/routes/posts_.%24postId.deep.tsx

Steps to Reproduce the Bug or Issue

• Go to the post deep page
• Check the console log to see the useId value
• Click on Update Search Params button & notice that the useId() value changed
• Click again and the useId value will NOT change anymore

Remove the ssr: false option & retry the above steps. You will notice that useId() value will not change at all.

Expected behavior

The page shouldn't remount on search params change.

Screenshots or Videos

20251124-1025-05.6674272.mp4

Platform

• Router / Start Version: 1.139.3

Additional context

No response

[MTG2000]

With further testing, the problem actually happens any time the search params value becomes empty OR get a value when it was empty.

I updated the repo code & here's a video showing the issue:

20251125-0928-59.9955446.mp4