FA-76314 / Chat ordering and read receipts / Member archive

Count unread mentions and choose the jump target: seq order · case 04

The jump button targets a later mention because messages are scanned in arrival order.

Member previewVariant 4 · 3 implementations · 6 checks per implementation

Case contract

messages are [seq, author, mentions]. A message after the marker, not written by me, counts when it mentions me directly or mentions "@everyone" while the room does not suppress @everyone. Messages are evaluated in seq order and the jump target is the earliest counted seq. Result {count, jump}.

Why this case matters

Mention counters and "jump to mention" buttons need the same filter as the unread state.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
out of order arrival	`{"count": 2, "jump": 13}`	`{"count": 2, "jump": 4}`	Failed

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