[MetallFoX]

Topic creation is the environment's job, and the declared case already works: EmbeddedKafkaSystem("topic-a", "topic-b") passes the topics to the broker, so they exist before anything connects.

What was missing is the same guarantee for a topic that shows up later, and leaving it to the broker's on-demand creation does not provide it. Measured on the embedded KRaft broker: the topic is created, but it is absent from the response to the first partitionsFor call — that call is what triggers the creation. A client that assigns partitions right after connecting therefore keeps an empty assignment, and every later poll or seek fails with:

IllegalStateException: Consumer is not subscribed to any topics or assigned any partitions
IllegalStateException: No current assignment for partition <topic>-0

The embedded ZK broker used to win that race, so specs that never declared their topics worked by accident; on KRaft they die in class initialisation, before a single assertion.

addTopics(vararg String) waits for the creation to finish and fails with the broker's own error if it cannot, so a spec can add a topic mid-flight and use it at once. topics() exposes what the environment holds, which is what a spec asserts against.

Verified twice: a test here adds a topic to a running environment and checks both topics() and AdminClient.listTopics; and downstream in the platform, an Exam KafkaConsumeAndSendTester on a topic that the environment did not declare fails without this change and passes with it.

[MetallFoX]

Closing: not needed, and adding it would be the wrong shape.

The declared path already covers the contract — EmbeddedKafkaSystem("topic-a", "topic-b") creates the topics before anything connects. A second entry point for adding topics to a running environment invites specs to depend on order of operations instead of declaring what they need up front, and it does not fix the case it looks like it fixes: a topic nobody declared still is not there when a client asks for its metadata the first time.

So the rule stays simple and is the one we document for consumers: declare the topics your specs use when you build the environment. Auto-creation by the broker is not a supported path for specs — it worked on the ZK broker by winning a race, and KRaft does not.