FA-095 / Distributed coordination / Member archive

A revoked consumer acknowledges a new assignment's message · case 05

An acknowledgment from a prior assignment is accepted after a rebalance reuses the message identifier.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

The active delivery is [assignment generation,message ID]. Acks have the same shape. Return whether any acknowledgment exactly matches both fields. Other deliveries do not share this state.

Why this case matters

Models fencing of consumer acknowledgments across partition ownership changes; unlike checkpoint prefix accounting, the failure concerns ownership of a particular in-flight delivery.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
prior owner late ack	`true`	`false`	Failed

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