Dash CSS and Authentication Issue

I’m currently using css automatically served from an assets folder, which works no problem.

I then introduced basic authentication:

auth = dash_auth.BasicAuth(
    app,
    VALID_USERNAME_PASSWORD_PAIRS
)

Which itself works fine - I’m prompted for user name and password, entering then loads the working dash app except that the css isn’t applied.

However, when re-loading the page I’m not asked again for the password (I assume this is saved somehow) and the css is now successfully applied. Why is this?

Thanks in advance!