Apple has updated the firmware for all AirPods 4 models. There are no release notes, so it’s uncertain what the update entails.
Installation is automatic when the AirPods are in their charging case, the case is plugged into a charger, and the linked iPhone is in close proximity and connected to Wi-Fi. You can check the installed firmware revision in the “General” settings menu, by selecting “About,” then “AirPods.”
