FA-74904 / CRDT convergence / Member archive

LWW register with Lamport stamps: an adopted value is re-stamped as a local write · case 04

After relaying a value, a replica makes it win or lose ties it should not.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Each replica holds a register [value, clock, writer] and a Lamport clock, all starting at [None, 0, ""] and 0. ["set", r, v] increments r's clock and stamps v with (clock, r). ["send", s, d] delivers s's register to d: d's clock becomes max(own, incoming clock) and d adopts the incoming register when (clock, writer) is lexicographically larger. Return values and clocks per replica.

Why this case matters

Last-writer-wins registers need total, replica-independent stamp ordering to converge.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
ring gossip converges	`{"clocks": [1, 1, 1], "values": ["C", "B", "C"]}`	`{"clocks": [1, 1, 1], "values": ["C", "C", "C"]}`	Failed

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