FA-75049 / CRDT convergence / Member archive

Bounded counter with rights transfer: rights are computed from the global value · case 04

Two replicas both spend the whole observed balance and the merged counter drops below zero.

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Case contract

Replicas share maps P (increments by replica), D (decrements by replica) and T ("from>to" transferred rights). A replica's rights are its own P minus its own D plus transfers to it minus transfers from it, all read from its local view. ["inc", r, k] grows P[r]; ["dec", r, k] and ["move", r, to, k] are rejected (event index recorded) unless rights >= k. ["sync", s, d] folds s's maps into d by maximum. Return values (sum P - sum D), rights, and rejected indices.

Why this case matters

Bounded counters keep a global non-negativity invariant without coordination by escrowing rights per replica.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
each replica spends only its own rights	`{"rejected": [], "rights": [0, 4, 0], "values": [0, 4, 0]}`	`{"rejected": [2], "rights": [0, 0, 0], "values": [0, 5, 0]}`	Failed

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