FA-75993 / Chat ordering and read receipts / Member archive

Place the "new messages" divider in a loaded window: send implies read · case 03

After the user replies in the middle of new messages, the divider still sits above messages they answered.

Member previewVariant 3 · 3 implementations · 6 checks per implementation

Case contract

messages are ascending [seq, author] pairs of the loaded window that starts at window_start. Sending a message implies having read everything before it, so the effective marker is the larger of marker and the highest seq authored by me. The divider goes before the first loaded message after the effective marker not written by me (index, or None). older_unread is true when some unread seq lies before the loaded window (effective marker < window_start - 1).

Why this case matters

The divider tells users where to resume reading; misplacing it hides or repeats unread history.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
interleaved own replies	`{"index": 0, "older_unread": false}`	`{"index": 4, "older_unread": false}`	Failed

MEMBER ARCHIVE

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