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During this transition the assignment topology (advanced synchronously when a new-epoch member heartbeats) and the description topology (advanced asynchronously via the plugin) can briefly disagree: StreamsGroupDescribe may report the new topologyEpoch while TopologyDescription is still null with status NOT_STORED until the first push for the new epoch succeeds. The two reconverge once any member at the new epoch pushes its description.

DeleteGroups can newly fail on streams groups when a topology description plugin is configured and its deleteTopology call fails. Brokers without a configured plugin keep today's behaviour. Older admin clients receive the new STREAMS_TOPOLOGY_DESCRIPTION_DELETE_FAILED code (136) as UNKNOWN_SERVER_ERROR via the standard forward-compatibility fallback in Errors.forCode; the group is still not tombstoned, so an idempotent retry of DeleteGroups converges once the plugin recovers. No client-side change is required.

Future Work

Hash-based mismatch detection. A future enhancement could introduce a topology hash to detect clients on different topology descriptions reporting the same topology epoch.

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