In the title compound, C(21)H(21)N(5)O(4)S·0.5C(3)H(7)NO, the heterocyclic thia-zine ring adopts a half-chair conformation, with the S and N atoms displaced by -0.451 (5) and 0.233 (5) Å, respectively, from the plane formed by the remaining ring atoms. The asymmetric unit contains a disordered half-mol-ecule of solvent lying close to inversion centers. The crystal structure is stabilized by weak inter-molecular N-H⋯O and C-H⋯O inter-actions.