Hi, i would like to create a new user (without admin rights) but i get the message “Username “xxx” already exists”. The user was weeks ago deleted and is not listed anymore in command ha auth list or in the desktop gui. Running HAOS on ProxMox, Home Assistant OS 15.2, HA Core 2025.5.2. What can i do now ? I wouldn’t reluctantly change the name of the new user 
HA can be a bit confusing in that it have both persons and users.
Selecting the person does not delete the user.
In the setting for persons/users there are tabs to change the view, so make sure that the user is also deleted.
Thanks you the hint and sorry about the missing information. In the user view is also no “old/deleted” user visible. It has to be somewhere else remaining information about the deletes user exits.
Then I am clueless.
I have never been in that situation before. 
In .storage, there is a file auth. Stop HA before you modify it. And check with a json validator if you modify anything, one , to much or to little can stop HA from starting again.
ok, i checked content of /config/.storage/auth there is no entry/information regarded the old user id. But i found in /config/.storage/auth_provider.homeassistant an entry with the old/deleted userid. Does anyone in this circle know what purpose this file serves?
That file only contains my username, so that might be the file you are looking for.