Use when you need to design, review, or improve modular monoliths with Spring Modulith in Spring Boot applications - including application module package structure, ApplicationModules verification, named interfaces, allowed dependencies, domain events, @ApplicationModuleTest, Scenario-based module tests, generated documentation, actuator exposure, observability, and event publication registry choices. This should trigger for requests such as Add Spring Modulith to a Spring Boot application; Review Spring Modulith module boundaries; Improve modular monolith architecture in Spring Boot; Add @ApplicationModuleTest tests; Generate Spring Modulith documentation. Part of cursor-rules-java project