David Sannier enhanced the srwi/qmk_firmware repository by expanding the One-shot Layer (OSL) functionality to support chaining with other layer-switching keys, including MO, TG, TO, DF, and LT. He implemented this feature in C and C++, focusing on embedded systems and firmware development for custom keyboards. To ensure robust dynamic layer management, David developed automated tests that validated chained activation behavior and confirmed that releasing an OSL would not disrupt other active layers. His work improved the reliability and flexibility of layer switching in QMK firmware, demonstrating a thoughtful approach to both feature implementation and comprehensive test coverage.