[web] [beta] Mobile web prepending data causes jumps with maintainVisibleContentPosition

[austin43]

When prepending data on mobile web in Safari, Chromium, or Firefox I get janky "jump-back" behavior when scrolling up and using maintainVisibleContentPosition. Here is a basic reproduction you can see when scrolling up.

https://github.com/austin43/legend-list-prepend

I have only seen this on mobile web browsers

Mobile chrome inspector, desktop web, and native all work as expected.

To reproduce, open the dev server using your mobile web browser and scroll up until you trigger onStartReached. You will see it engage loading at item 1000 then jump back to item 1020.

ScreenRecording_03-03-2026.12-19-24_1.mp4

[PaulSenon]

Hey @austin43 can you check if any changes after beta-41 ? just to know

[austin43]

@PaulSenon Still broken on beta-41 and beta-42 unfortunately. Tested today on safari mobile and brave mobile.

[PaulSenon]

@austin43 Good point, so I think we can keep our issues distinct for now.
I'll probably ask you for another feedback once things are fully fixed on my initial issue, then if still present I might help creating the reproduction example

[jmeistrich]

I think this might be fixed in 3.0.0-beta.47. Can you please give that a try and let me know if it's working better?

[PaulSenon]

it is fixed for my use case, can you double check on yours @austin43 ?

[austin43]

@jmeistrich @PaulSenon It appears to still be happening in safari and chromium (brave) on my end (real device running iOS 26), as of my test just now with beta 47.

[PaulSenon]

Are you talking about ios browsers only ? (when talking about safari and brave ?)
If that's the case, FYI on ios/ipadOs EVERYTHING is webkit. yes. even chrome. apple's constraints.

And to follow up on this webkit case:
I didn't opened an issue yet because wanted for things to be stable everywhere else first, without spamming noise, but nothing is quite working near usable yet on anything webkit (desktop/ios) so I guess that's a real topic here.

(and some weird behaviour are probably just fixable but I'm scared scroll height change while scrolling is one for the thing webkit is terrible at. at the point other virtualizer libs like virtua have explicit disclaimer on degraded experience on ios)

So let me know if this wasn't webkit only related,
if it's only webkit related I'll link to this issue if I creat a webkit focused one.

[jmeistrich]

Oh yes, Safari is a whole other thing. We use scrollBy to adjust the scroll position as sizes change, which works well on Chrome and Firefox. But on Safari it breaks momentum scroll and in some cases seems to not work at all. I have a set of tasks on my list to try to fix Safari specifically. So if this issue is fixed in non-Safari browsers then I think we can close it, and have a separate issue specific to Safari.

[austin43]

Ah @PaulSenon I see. @jmeistrich feel free to close in lieu of that ticket. Thank you both.