xml parsing error: undefined entity when running the hello word example as desktop app
When I run it, I get the following error:

It works if launched in a browser though (despite that it always opens two tabs).
Interesting. I cannot see where in our source we generate this code. Do you happen to use a title that includes this &symbol?
No. I haven't done anything beyond the hello world example. I suppose it is downloading some code from the local web server? How to manually download it or inspect the full file content?
This error seems to be occurring before the browser app has even started up.
What OS are you on?
As a workaround, you can always use a different runtime using launch, e.g. launch("browser"), launch("firefox-browser"), launch("chrome-app").