I was using Visual Studio code in one qube. Then I went to open a browser in another qube by clicking on the Q-menu, and two windows openned: The browser, and also a code window in thesys-firewallqube.
It is strange enough that a second window would automatically open like that but I have some more questions:
I don’t recall ever installing code in the debian-11-dvm template, which is the template for sys-firewall (why would anyone put a coding IDE is the firewall qube?) Is code installed by default in the debian templates?
It’s not installed by default, code is not even in the debian repos. Is it possible you accidentally installed code onto debian-11-dvm and set it as one of the selected applications for the template? If not, sounds like a graphical glitch. If you did accidentally modify the template, there is a guide for reinstalling templates.
Debian-11-dvm is a qube (a dvm template) based on Debian-11. Anything you install on Debian-11 ends up available in Debian-11-dvm too. If you don’t want this to happen, you can clone the Debian-11 template and install code in one of them only, while using the other one as the template for Debian-11-dvm.
There’s a fundamental misunderstanding here that may lead you astray.
If an application is “selected”, that simply means that it appears in
the Qubes Menu.
If it is installed in the template it will be installed in the qube, and
can be run. It won’t appear in the menu unless you have selected it.
You say that you downloaded the package in debian-11 - that’s a
template, which is normally not network connected. You don’t say how
you downloaded it.
Nor do you say how you got it running in the “one qube”.
If you downloaded it in the template, it’s likely that you installed it
there, which means that it can be run in every qube that uses that
template, disposables and all. To repeat, this is regardless of whether
you have “selected” the application.
Check to see if the package is installed in the template.
There are no applications in the menu, i.e. selected, for debian-11-dvm, but code is installed in that qube.
As to how I installed it in debian-11: I downloaded the .deb package in one of my AppVMs. Then I used the qubes file transfer feature to copy the .deb to debian-11 so that I could install it there.
As for how I got code running: I have an AppVM based on the debian-11 template. This AppVM does have code selected. And I simply ran code by selecting it from the menu of this AppVM.
This still doesn’t explain the bizarre thing where when I opened an unrelated AppVM (not based on debian-11) a code window popped up stating in the title bar: "[sys-firewall] …" I still believe this is disconcerting though I supposed @mako may be right about a “graphical glitch”.