Deep holes of full-length Reed--Solomon codes

For every prime power $q>19683$, we settle the Cheng–Murray deep-hole problem for full-length Reed–Solomon codes in every dimension $2\le k\le q-2$, with the characteristic-two cases stated explicitly. For odd $q$, the deep holes are precisely the words of degree $k$. For even $q$ and $k\ge 3$, the same conclusion holds except for an additional family when $k=q-3$. In even characteristic and dimension two, every deep hole has a unique expression $ah(X)+bX+c$, where $a\mathrm{\ne }0$ and $h$ is a normalized $o$-polynomial. The proof combines quadratic quotient algebras, graph-theoretic weighted independent-set inequalities, and planar arc completion. We also obtain normal rational curve rigidity in the corresponding nonexceptional dimensions, the projective Reed–Solomon covering radii, and distinct-coordinate solvability and remainder criteria.