FA-76224 / Chat ordering and read receipts / Member archive

Place "seen by" avatars under the latest read message: bisect side · case 04

A reader whose marker sits exactly on a message is shown under the previous message.

Member previewVariant 4 · 3 implementations · 6 checks per implementation

Case contract

messages are ascending [seq, author] of the visible window. reads maps user -> [read_seq, read_at]. Each user other than me gets an avatar under the latest visible message with seq <= read_seq; users whose read_seq is before the first visible message get none. Avatars under one message are ordered by read_at descending, then user id. Result: [[seq, [users...]]...] by seq.

Why this case matters

"Seen by" rows show how far each participant has read; misplacement misreports who saw what.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
read exactly a message	`[[10, ["bo"]]]`	`[[12, ["bo"]]]`	Failed

MEMBER ARCHIVE

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