TiNiSn half-Heusler in the correct C1b ordering (F-43m, a=5.94 Å): Ti and Sn on the rock-salt 4a/4b sites, Ni on 4c, 4d empty. Known-answer control for the Thermoelectrics API: PBE gap ~0.45 eV, dynamically stable, |S| > 100 µV/K at 1e20 cm⁻³.