Michal Boris focused on backend reliability improvements in the symfony/symfony repository, addressing HTTP semantics in November 2025. He fixed the EventStreamResponse header by correcting the misnamed 'Expire' header to the standard 'Expires', ensuring proper client-side caching behavior and interoperability. To reinforce this change, he implemented regression tests that verify both the presence and value of the Expires header in event stream responses. Working primarily with PHP and leveraging his skills in backend development and unit testing, Michal delivered targeted, well-tested code changes that enhanced the robustness of HTTP responses without introducing new features, demonstrating careful attention to protocol compliance.