Wanting just some outputs of a CA derivation that needs to be resolved should not bring in other output

[Ericson2314]

This is a small regression in an unstable feature that #13181 would cause. I know how to fix as later as part of the changes needed for #11928.

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/2025-05-21-nix-team-meeting-minutes-228/65204/1