Baggage is empty when transferring to service/command layer using Mono just or Mono from callable

[kusandriadi]

Describe the bug
I set baggage in controller and sent to service/command layer, but the baggage is empty, the strange thing is Trace ID and Span ID were transfer successfully.
I create mini app here if you want to check: https://github.com/kusandriadi/micrometer-mini-app

Environment

• Java 21
• Spring Boot 3.2.2
• Micrometer tracing bom 1.2.3
• Spring doc 2.3.0

To Reproduce
I created three difference implementation:

• used Mono fromCallable: https://github.com/kusandriadi/micrometer-mini-app/blob/main/src/main/java/com/micrometer/web/HelloController.java#L37
• used Mono just: https://github.com/kusandriadi/micrometer-mini-app/blob/main/src/main/java/com/micrometer/web/HelloController.java#L45
• not used Mono: https://github.com/kusandriadi/micrometer-mini-app/blob/main/src/main/java/com/micrometer/web/HelloController.java#L53

The implementations above already cover in unit test:
https://github.com/kusandriadi/micrometer-mini-app/blob/main/src/test/java/com/micrometer/web/HelloControllerTest.java

How to reproduce the bug:

• Run the unit test.

Expected behavior
All case in unit test must be success

Additional context

• I already set Hooks.enableAutomaticContextPropagation(). Trace id and span id were not empty, only baggage is empty when using Mono fromCallable or Mono just.
• in my project, we are using command pattern.

[marcingrzejszczak]

cc @chemicL

[marcingrzejszczak]

Have you tried working with ReactorBaggage and BaggageToPropagate ? Check the docs here.