...

Node grouping. A nodeGroup field on TopologyNode for UI grouping, requiring an extension to the public TopologyDescription.Node interface in Kafka Streams — best addressed in a follow-up KIP.

Test Plan

Integration Tests

Broker:

• UpdateStreamsGroupTopologyDescriptionRequestTest (new) — push happy path; permanent and transient plugin failures; heartbeat-flag gating; member/group/MemberId fencing; explicit DeleteGroups ordering.
• UpdateStreamsGroupTopologyDescriptionNoPluginRequestTest (new) — broker without plugin: pushes rejected, flag never set, describe returns NOT_STORED.
• AuthorizerIntegrationTest — READ ACL on the GROUP resource for the new RPC.

...

• TopologyDescriptionFormatterTest (new) — each TopologyDescriptionStatus, the pretty-print format, and the exit-code mapping.
• StreamsGroupCommandTest — the --topology sub-action against a populated group.

System Tests

New ducktape suite streams_topology_description_plugin_test.py driving the Java harness TopologyDescriptionPluginSystemTest:

...