Professionalism isn’t about how long you stay at a job, it’s about how you act around work, which includes joining and leaving a company. There are ways of quit

Professionalism isn’t about how long you stay at a job, it’s about how you act around work, which includes joining and leaving a company. There are ways of quitting which are unprofessional but not the act of quitting itself. How much detail you tell them is up to you but don’t feel pressured to go into detail if you don’t want to. As for career/CV, it’s only a flag for me if there are a lot of instances of short jobs that were obviously meant to be permanent. Personally I still ask the candidate about why that is. If it’s any consolation, my shortest resignation from a perm job was the morning of the third day. The MD’s motivational strategy turned out to be angrily shouting at people.