Pre-join UISI hiding logic is somehow broken

[dkasak]

Steps to reproduce

1. Open the !RqphPmfqRYPWcDpkqi:matrix.org room (you can message me privately on Matrix to find out which room this is)
2. Scroll up until you reach a Figma screenshot and then a bit beyond that.
   This one:

1. While scrolling beyond the screenshot in 2, the client suddenly jumps to an earlier point of history. Attempting to scroll upwards again now shows a message from Amandine as the first message in the room:

The earlier screenshot from step 2 is now unreachable.

Outcome

What did you expect?

I expect the client not to randomly hide a chunk of the room from me.

What happened instead?

The client hid a chunk of the room from me and prevented me from scrolling beyond. I suspect this is related to the pre-join UISI hiding logic, since at the point the jump happens, the following happens in the console:

I must admit the pre-join UISI hiding has so far proven to be more of a nuisance than anything useful.

Operating system

Arch Linux

Application version

Element version: 1.10.15 Olm version: 3.2.8

How did you install the app?

Arch Linux repository

Homeserver

termina.org.uk, Synapse 1.60.0

Will you send logs?

Yes

[SimonBrandner]

Possibly related matrix-org/matrix-react-sdk#8563

[dkasak]

I just had a similar thing happen in another room, though without any jumping behaviour. I'm just suddenly not able to access the room's history beyond a certain point a few days ago, due to reaching the "You can't see earlier messages" badge which wasn't there before (since the room is quite old). I'll send logs.

[dkasak]

And now after a switch to another room and then back, I can again scroll upwards beyond this point, so there may be some race condition at play?

[z411]

I"m also affected by this; indeed other clients show an undecryptable event just before the join, thus Element shows this message with the checkForPreJoinUISI: did not find pre-join UISI log message and hides all history with the You can't see earlier messages box. Switching rooms doesn't fix it for me.

[richvdh]

seems to be a duplicate of #22544?

[t3chguy]

Fixed by matrix-org/matrix-react-sdk#12464 which removes the checkForPreJoinUISI code