My Bolt worked perfectly until a second user signed on

Last month, I developed a grocery list app in Bolt over the weekend. It was beautiful. We used it with my partner for three days and then I invited my sister to use it.

She kept overwriting our changes because the model was storing the entire list in one record for each account, and every save would overwrite everything else. Since I never specified any conflict resolution, there was none.

This particular lesson has been learned by me: AI builds the happy path for one user until I specify otherwise. From now on, I will always start with "assume multiple users editing concurrently."

What is your equivalent assumption that you always specify?