Worked on hardening the mcuboot bootloader for Zephyr RTOS, focusing on improving reliability during image upgrades. Addressed a critical bug in the zephyrproject-rtos/mcuboot repository by correcting the bootstrap copy size calculation in swap move mode. The solution involved using the secondary region size, excluding the swap sector, to accurately determine the copy length and prevent over-copying during upgrade and bootstrap operations. This fix resolved a regression that could cause upgrade failures, demonstrating careful attention to memory region management. The work was implemented in C, leveraging expertise in embedded systems and bootloader development, and was reviewed and acknowledged by peers.