TACHE (TensoriAl Classification of Hydrodynamic Elements) performs classification of the eigenvalues of either the tidal tensor or the velocity shear tensor at the point of a smoothed particle. This provides local information as to how matter is collapsing or flowing, respectively, in particular what stable manifold is being produced. The code reads in smoothed particle hydrodynamics (SPH) snapshot files in sphNG format and computes neighbor lists for SPH data and either the (symmetric) velocity shear tensor or tidal tensor and their eigenvalues/eigenvectors. It classifies fluid elements by number of "positive" eigenvalues and permits decomposition of snapshots into classified components; it also includes several Python plotting scripts.