Does anyone know if it’s possible to go from black box dye to brunette with highlights in one session?

You’re best to talk to your local hairdresser and see what they think

@fairue Probably but it will take a long time. They might just rather do multiple sessions

Unlikely, that sounds like two or three separate sessions already

unlikely ^^ as someone who has dyed their hair loads, if they do manage to do it in one it’ll damage it, will probably require a few sessions

a professional hair dresser might do that for you however i think you would be at the salon for hours. i managed to do this in one session however i spent nearly 5 hours there and my hair was bleached twice, even then the black did not budge and eventually it grew out