@ngompa : can you clarify your request with some example please ?
I see that python-rpmautospec needed packages are available/built for Stream 10 :
https://kojihub.stream.centos.org/koji/buildinfo?buildID=65111
https://kojihub.stream.centos.org/koji/buildinfo?buildID=65205

So in theory, for SIGs tags/target already relying on centos10s-buildroot external repo (from CBS PoV), it should find and install the needed packages in the buildroot.

I agree though that for consistency reasons, we can just rebuild these two packages in cbs itself, and so not having to pull from external repo.

Just curious about an example for which it would fail in actual env

It apparently didn't work for @daandemeyer when working on the Hyperscale systemd package, so I filed this request to get things in place.

@daandemeyer : can you point us to a failed build so that @nphilipp and myself can have a look ?
FWIW, the builders are still RHEL8 based, and have the python-rpmautospec-core pkg installed/enabled. So the way it should work is : when detecting %autorelease (or other rpmautospec macros), it should automatically install in the buildroot the python-rpmautospec pkg itself.
We'd like to see in the logs why it can't find it (assuming it's really looking at the centos10s-buildroot repo to install it)

That doesn't change the fact that we'll rebuild these in cbs, but more curious about why it doesn't work in actual setup/repos combination

FWIW, we got request for rpmautospec for virt SIG and it worked (as long as centos10s-buildroot repo is added for builds) : https://pagure.io/centos-infra/issue/1465

So do you still have the issue ?

@daandemeyer : as we got feedback from other SIGs that rpmautospec is working for them, as long as centos10s-buildroot repo is there, can you point us to what's failing at your side wrt rpmautospec ?

FWIW, I rebuilt needed packages so that we don't have to depend on centos10s-buildroot and they are tagged in (inherited for all SIGs) buildsys10s-release tag.
I then gave it a try with a package using rpmautospec (scratch build) in your hyperscale10s-packages-experimental-el10s target and it worked :
https://cbs.centos.org/koji/taskinfo?taskID=4139304

So closing this request as it's all working