Windows: severe UI lag opening group chats — possible regression in 8.32 beta #8070

Using a supported version?

• I have searched open and closed issues for duplicates.
• I am using Signal-Desktop as provided by the Signal team, not a 3rd-party package.

Overall summary

Severe UI lag when opening group chats in Signal Desktop 8.32.0-beta.1 and 8.33.0-beta.1 on Windows. The account belongs to dozens of groups, some with up to 1,000 members. This did not happen before recent updates; the exact last unaffected version is unknown.
Possible regression: commit c1e8345d, first included in 8.32.0-beta.1, added shared-group checks during avatar processing. These may repeatedly scan all groups and their members before checking the avatar cache.

Steps to reproduce

1. Use an account with dozens of large group chats.
2. Open a group chat and attempt to scroll or type.
3. Wait approximately one minute, then scroll again.
   Performance was profiled for 77 seconds, covering the initial lag and subsequent recovery.

Expected result

Opening a group chat and refreshing member profiles should keep input and scrolling responsive.

Actual result

Input and scrolling are barely responsive for approximately one minute, then improve substantially.
Profiling identified 12 main-thread tasks totaling 54.6 seconds, with the longest lasting 5.95 seconds.

Screenshots

No response

Signal version

8.32.0-beta.1 and 8.33.0-beta.1

Operating system

Windows 11

Version of Signal on your phone

No response

Link to debug log

No response