`StreamsKafkaClient` takes a `StreamsConfig` and calls `values` on it to create a `ChannelBuilder`. `values` creates a `Map` with parsed values for defined config names. `StreamsConfig` doesn't define security settings itself and hence the security configs are dropped.
For `KafkaProducer` and `KafkaConsumer` used by Streams, there is some code that gets the original configs (using `originals` instead of `values`) and passes them to the `KafkaConsumer` and `KafkaProducer` constructors (both of which define the security configs).
The suggested solution is to create a config definition for `StreamsKafkaClient` thas includes a copy of the `StreamsConfig` definition combined with the security configs definitions.