FA-74913 / CRDT convergence / Member archive

LWW element set with add bias: equal add and remove timestamps hide the element · case 03

An element added and removed at the same timestamp disappears, contrary to the add-wins tie rule.

Member previewVariant 3 · 3 implementations · 9 checks per implementation

Case contract

Each replica keeps add and remove timestamp maps. ["add"|"rem", r, e, t] records t when it exceeds the stored timestamp. ["merge", s, d] folds both maps of s into d by maximum. An element is a member when it has an add timestamp that is greater than or equal to its remove timestamp (ties favour add). Return sorted members per replica.

Why this case matters

LWW element sets resolve add/remove races by timestamp and need a deterministic tie bias.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
add and remove at the same timestamp keep the element	`[[], []]`	`[["x"], []]`	Failed

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