There seem to be some gaps in the development experience for building a theme app extension that depends on the customer being logged in.
From what I can gather through trial and error, but haven’t been able to locate any documentation on, new customer accounts aren’t supported at all, because the logged in user session is not transferred between the new accounts dashboard and the extension dev URL (http://127.0.0.1:9293/)
If the development store is switch to use legacy customer accounts, it seems that you can log in at http://127.0.0.1:9293/account/login and the logged in user is accessible while developing a theme app extension. However, the session is terminated frequently - whenever the dev server stops or times out, if there is a server error in the app while developing, and seemingly at random after X amount of time.
There is a possibly-related thread in the Partner’s Slack: Slack
Wondering if this is a known issue or if there are any workarounds available?
