In the title mol­ecule, C12H12N4O3S, there is an intra­molecular O—H⋯N hydrogen bond. The dihedral angle between the benzene and triazine rings is 65.9 (3)°. In the crystal, N—H⋯S and O—H⋯N hydrogen bonds link the mol­ecules into chains along [010]. In addition, there are weak π–π stacking inter­actions between symmetry-related triazine rings with a centroid–centroid distance of 3.560 (3)°.

The title compound, C15H13ClN6, contains two pyrimidine rings and one benzene ring, where the dihedral angle between the planes through the pyrimidine rings is 81.57 (10)°, and those between the pyrimidine rings and the benzene ring are 84.02 (8) and 89.46 (7)°, indicating that the three rings are almost perpendicular. In the crystal, inter­molecular N—H⋯N hydrogen bonds link the mol­ecules into infinite chains along (100).