Eugene Leko enhanced HTTP header handling in the Blargian/ClickHouse repository by implementing case-insensitive header comparison, addressing edge cases in forward header and authentication parameter processing. Using C++ and leveraging custom comparison logic, he introduced a ci_less struct for std::set, ensuring reliable header matching regardless of case. In the ClickHouse/ClickHouse repository, Eugene refactored the HTTP Authentication Client, encapsulating comparison logic and transitioning header storage from set to vector to improve code organization and maintainability. His work focused on code style, refactoring, and networking, resulting in more robust, readable, and future-proof authentication and header processing components.