We study boundary observability and control for a degenerate Timoshenko beam whose shear and bending stiffnesses may vanish independently at one endpoint. A classical multiplier approach leads to a restrictive smallness condition involving the degeneracy and the shear–bending coupling. We show that this restriction is not intrinsic for Dirichlet and Neumann observation. By exploiting an exact space–time cancellation of the coupling term, together with sidewise energy estimates and a compactness–uniqueness argument, we establish boundary observability in the full subcritical regime where both optical lengths are finite. The corresponding exact boundary controllability follows from the Hilbert Uniqueness Method. We also discuss the role of optical geometry and the transition toward the critical regime of infinite optical distance.
