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In other words, late-arriving markers have always been a potential problem in TV0/TV1 — the system simply lacked the means to distinguish between themthe late markers and the markers belonging to the active transaction.

With TV2, the semantics change. The coordinator always bumps the producer epoch before sending the final marker, establishing a clear invariant: a valid EndTxn marker must have producerEpoch == current + 1 at the leader. Any marker arriving with equality (producerEpoch == current) can now be safely identified as late or duplicate and rejected. This closes a long-standing gap in transaction handling and prevents scenarios where multiple transactions could be conflated under the same epoch.

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