Build and evolve Java Spring Boot 4 backend features with clean architecture, REST APIs, validation, security, persistence, testing, and Spring Modulith foundations. Use when scaffolding or refactoring Spring Boot services/controllers/entities/repositories, aligning dependencies with Boot 4 starter/module conventions, or introducing application module boundaries with spring-modulith-starter-core.
Implement baseline Spring Boot backend changes with Boot 4 and Modulith guardrails.
<feature>/controller, <feature>/service, <feature>/repository, <feature>/model, <feature>/dto).spring-boot-starter-<technology>spring-boot-starter-<technology>-testspring-boot-starter-flyway or spring-boot-starter-liquibase.spring-modulith-starter-core for module model/runtime support.spring-modulith-starter-test when writing module integration tests.jakarta.validation annotations and @Valid.@RestControllerAdvice.@Version) for mutable aggregate roots.spring-boot-starter-security-test for security test utilities).spring-modulith-starter-test for application-module verification and integration tests.references/base-patterns.md for reusable endpoint, persistence, security, and testing checklists before implementing medium or large backend changes.references/modulith-boot4-conventions.md before changing dependencies, migration rules, or module boundaries.