Mac mini M4 & Studio Display: Brightness control locked when booting from external NVMe

Hi everyone,

I’m experiencing a consistent bug with my new Mac mini M4 and Apple Studio Display.

I boot macOS from an external NVMe SSD via Thunderbolt. Every time I perform a cold boot, the brightness control for the Studio Display is locked/grayed out.

It seems like a Thunderbolt bus handshake issue: the M4 chip prioritizes the boot drive traffic and fails to initialize the monitor's data channel.

The only way to fix it is to hot-plug the Thunderbolt cable after the OS has loaded. This is quite frustrating for a premium setup.

Is anyone else seeing this on the M4? Any word on a firmware fix?

Thanks!"