Worked on the renesas/zephyr repository to address a critical issue in Bluetooth Hands-Free Profile (HFP) telephony. Focused on embedded systems and C programming, the developer delivered a targeted bug fix that improved the handling of 3-way call direction flags during multi-call scenarios. By replacing read-only bit tests with atomic_set_bit operations, the update ensured accurate state tracking for incoming and outgoing calls when multiple calls were active. This change enhanced the reliability of call routing and reduced inconsistencies in edge cases, ultimately strengthening the core Bluetooth telephony experience for hands-free devices, particularly in automotive and embedded environments.