Function nix_withheld 

pub fn nix_withheld(
    target: &Utf8Path,
    recorded: Option<&Manifest>,
) -> Result<Option<String>>

Why the flake half of the Nix capability stays out of this landing, or None where the pair lands whole.

The pair is all-or-nothing: a target that already carries a flake.nix or flake.lock of its own keeps its pair — a seed lock beside a foreign flake describes the wrong input graph — and the rendered workflow is withheld with it, because a green check that never builds the landed expression proves nothing. A pair the record names is release-kit’s own landing and is never withheld.

Errors

Any read failure other than the files being absent.