VoiceOver: Opening a chat focuses on arbitrary message

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Bug description

When opening a chat or group chat, VoiceOver focuses on a seemingly arbitrary older message or date label, rather than the most recent/oldest unread message—the behaviour of the app for sighted users. This requires VoiceOver users to manually skip over a varying number of already read messages to get to the relevant messages.

Steps to reproduce

1. as a sighted user, at the root of the “Chats” tab, with VoiceOver disabled, tap on a conversation to open it
2. take note of the message(s) visible to you
3. navigate back to the “Chats” view and enable VoiceOver
4. select and open the same chat again
5. compare the visible messages to the results of step 2.
6. navigate to the most recent message using VoiceOver gestures (this may take a while)
7. with VoiceOver still active, navigate back to the “Chats” list
8. with VoiceOver still active, open the same chat again

Actual result: The chat is scrolled to a completely different, typically much older set of messages in step 5 than in step 2. Rather than having immediate access to the latest messages, VoiceOver users are presented with outdated information, whenever they open a chat—typically several screens full of messages!
Navigating into and out of a chat repeatedly reproduces the complete loss of position. (Steps 7 and 8)

Expected result:

1. In step 5, the same messages as in step 2 should be immediately available to VoiceOver users, without any further need of navigation gestures
2. Navigating out of and into a chat mustn’t lose reading position by several screens full of content.

With no unread messages in a chat, VoiceOver focus should be at the latest message. (Compare to Messages.app.)
With unread messages, VoiceOver focus should be at a position to achieve a behaviour comparable to the experience for sighted users. (E.g. the “Unread messages” label, or the oldest unread message, or …)

Screenshots

Not applicable

Device info

Device: iPhone 14

iOS version: 18.7.1

Signal version: 7.84

Link to debug log

No source files or tests are named. Start by reproducing the VoiceOver behavior on iOS using the listed steps, then trace chat opening, message scrolling, and accessibility focus restoration. Done means opening a chat focuses the latest message when there are no unread messages and an appropriate unread position otherwise, without losing position when reopening it.