I’m not sure how I created this curve, so I can’t reproduce this, but in this case I can’t set any continuity options for sweep2 without rebuilding the curve.cant sweep2 tangent.3dm (61.0 KB)

The curve is rational. The continuity options only work with non-rational curves. *Added:* Rebuilding creates a non-rational curve.

From https://docs.mcneel.com/rhino/7/help/en-us/index.htm#commands/sweep2.htm?

#### Edge continuity

Continuity is only enabled if the rails are surface edges and the shape curves are non-rational, that is, all control-point weights are 1. Exact arcs and ellipse segments are rational.

Only continuity options that the curve structure (point count and rational/non rational) supports will be available.