FA-76108 / Chat ordering and read receipts / Member archive

Aggregate emoji reactions with a per-user limit: seq order · case 03

A remove that overtook its add leaves the reaction stuck on the message.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

events [seq, user, emoji, action] are applied in seq order. A user holds each emoji at most once and at most `limit` distinct emoji per message; an add beyond the limit is ignored. A remove only releases a reaction the user holds. Result rows [emoji, count, mine] for emoji with at least one user, ordered by the seq at which the emoji most recently went from zero to one user.

Why this case matters

Reaction chips reorder and recount live; wrong state handling shows phantom or misordered reactions.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
remove delivered before add	`[["up", 1, false]]`	`[]`	Failed

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