Worked on the Zephyr repository to address a reliability issue in the USB CDC ACM driver, focusing on accurate serial state notification for Rx Carrier reporting. Using C and leveraging expertise in device drivers and embedded systems, implemented a targeted bug fix that ensured the driver now reports the actual serial state value rather than a static flag. This change improved the accuracy of carrier status signals, reducing erroneous device state notifications in production environments. The solution was validated and merged into the zephyrproject-rtos/zephyr codebase, enhancing USB device behavior and contributing to more stable deployments for users relying on embedded USB connectivity.