For many spin glass models, the Parisi formula identifies the large-N limit of the free energy as the minimum of the Parisi functional over a space of probability measures. In this talk, I will present a recent result regarding the de Almeida–Thouless transition surface. Specifically, we characterize the conditions under which the minimizer is a Dirac measure in the multi-species Sherrington–Kirkpatrick model with a centered Gaussian external field and a positive-semidefinite variance profile matrix.