Function loft_profile_brep_guided_frame 

pub fn loft_profile_brep_guided_frame(
    sections: &[Vec<NurbsCurve>],
    guide: &NurbsCurve,
    name: Option<&str>,
) -> Result<BrepSolid, String>

Rotation-to-frame guided loft (§5.8): like loft_profile_brep_guided, but intermediate sections ROTATE with the guide’s rotation-minimizing moving frame (double-reflection RMF, the same frames the path sweep uses) instead of keeping their world orientation.

Each user section is expressed in the LOCAL frame at its own guide station, the local representations are blended, and the blend is mapped back through the frame at each output station. Because localize→reconstruct through the SAME frame is the identity, every user section is still reproduced EXACTLY at its own station — the rotation only shapes the flow between sections. The relative rotation between two stations is independent of the arbitrary initial frame normal (a start-normal change conjugates every frame by the same constant), so the result is deterministic.