There appears to be incorrect quoting of --extra-repository arguments when running with -sbuild-experimental-aspcud. ie when running with --dry_run we can see:

 commandline: [sbuild --arch-all --dist=unstable --extra-repository='deb-src http://deb.debian.org/debian unstable main' --extra-repository='deb http://deb.debian.org/debian experimental main' --extra-repository='deb-src http://deb.debian.org/debian experimental main' --build-dep-resolver=aspcud --aspcud-criteria='-count(down),-count(changed,APT-Release:=/experimental/),-removed,-changed,-new' --add-depends='librust-jsonschema-dev (= 0.58.6-1)' --nolog jujutsu_0.46.0-2 --extra-package=librust-jsonschema-dev_0.58.6-1_amd64.deb]

And without --dry_run there is this failure:

+------------------------------------------------------------------------------+
| Update chroot                                Wed, 28 Oct 2026 18:16:16 +0000 |
+------------------------------------------------------------------------------+

E: Type ''deb-src' is not known on line 1 in source list /etc/apt/sources.list.d/sbuild-extra-repositories.list
E: The list of sources could not be read.
E: apt-get update failed

Where you can see the extra leading '.