Function fit_polyline_of_degree 

pub fn fit_polyline_of_degree(
    points: &[Vec3],
    tolerance: f64,
    maximum_points: usize,
    local_interpolation: bool,
    degree: usize,
) -> Result<PolylineFit, String>

fit_polyline with the GLOBAL lane’s interpolation degree chosen by the caller (the local lane is cubic Hermite whatever is asked). A marched section’s stations lie on both carriers to the march’s residual, and a degree-p interpolant through them errs by O(h^(p+1)) between stations: on BadBoolean’s sphere×bore rim at its own 135 stations the cubic sits 2.5e-7 off a carrier with a mean signed bias of −1.2e-8, the quintic 8.5e-9 and +6e-11 — the SAME stations, knots and control-point count, so nothing downstream that samples per knot pays for it (2026-09-27).