In the title molecule, C₂₃H₂₀Cl₂N₄O₃S, the thiazole ring is planar while the pyrimidine unit fused to it adopts a screw-boat conformation. In the crystal, thick sheets parallel to the bc plane are formed by N—H...N, C—H...N and C—H...O hydrogen bonds together with π–π interactions between the formamido carbonyl groups and the thiazole rings. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (30.9%), Cl...H/H...Cl (20.7%), C...H/H...C (16.8%) and O...H/H...O (11.4%) interactions.

In the title compound, C₂₄H₂₃FN₄O₄S·0.25H₂O, the dihydropyrimidine ring is distinctly non-planar, with the flap C atom deviating by 0.297 (2) Å from the least-squares plane. In the crystal, zigzag chains are formed by N—H...N hydrogen bonds parallel to [010] and are connected into layers parallel to (100) by O—H...O, O—H...F, C—H...O, C—H...F and C—H...N hydrogen bonds. Additional C—H...O hydrogen bonds connect the layers into a three-dimensional network. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from H...H (42.6%), O...H/H...O (16.8%) and C...H/H...C (15.5%) contacts.