[Bug]: Talk system messages delay loading

[MPStudyly]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

One of our company-wide chatrooms recently got cleaned up, i.e. ~50 old/inactive/deleted users were removed at once. This generated the according amount of system messages mentioning the removal of each specific user. These messages also get merged into a single appearing line just fine as expected. Though due to them being so many, I assume it takes quite a while for the client to start loading in previous messages. So when a user opens up the chat, he sees the system messages only (basically an empty chat), having to wait for previous messages to load in.

Steps to reproduce

1. Create a group with 50+ users.
2. Remove 50 users from the chat at once.
3. Reload the chat window (Ctrl + F5)

Expected behavior

The merged system messages (single line) and X previous messages load in right away. I.e. system messages do not count against the default count of messages to be loaded when opening a chat.

Nextcloud Server version

32

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

[nickvergessen]

It's condensed to a single line and then the rest is empty?

[MPStudyly]

It's condensed to a single line and then the rest is empty?

I assume you mean the "removed user xyz" messages being merged into a single line. In that case, yes. You see just that, nothing below (until new messages are sent into the chat) and nothing above until loading older messages starts (which is notably delayed and IMO unexpected/a bug).
I've adjusted the description accordingly. I also clarified that I just assume the merged messages still counting individually, delaying loading older messages.

[Antreesy]

Yes, although some system messages are collapsed, when coming from server, we still count them as visible; so 50 SM would occupy all the request context.
Contrary, if you have 50 reactions in that context, they're not counted towards visible threshold, and client would trigger 'load 100 more messages'. We should probably apply the same logic to collapsible messages