Yan Wang focused on stabilizing the U-Boot boot subsystem in the flipperdevices/u-boot repository by addressing a critical build and runtime issue related to spin table error handling. He resolved undefined symbol errors for ENODEV and ENOSPC by correctly including errno.h in spin_table.c, following the removal of a legacy header. This targeted bug fix ensured that error codes were properly recognized, reducing build failures and runtime misbehavior. Working primarily in C and leveraging his expertise in embedded systems and kernel development, Yan improved the reliability of the bootloader codebase and minimized downstream debugging time for future development and integration.