In December 2025, Jonathan Kaplan developed a reactive API version resolution feature for the spring-projects/spring-framework repository, focusing on Spring WebFlux. He updated the ApiVersionResolver to return a Mono<String>, enabling asynchronous version resolution and aligning API versioning with reactive programming models. This approach improved compatibility for reactive endpoints and addressed the need for non-blocking operations in modern Java applications. Jonathan utilized Java, the Spring Framework, and reactive programming techniques to deliver this feature, linking the implementation to issue GH-36084 for traceability. The work demonstrated a focused, in-depth contribution to API development within a complex, production-grade codebase.