The increasing frequency of climate extremes calls the scientific community to a thorough reassessment of current and projected risk levels of rainfall-induced landslides. This paper focuses on a particularly damaging class of slope instabilities: flowslides. Often forming in unsaturated soil veneers, the initiation of such shallow landslides is chiefly regulated by moisture and suction fluctuations. At the same time, the dramatic post-failure dynamics of flow-like movements is explained by invoking soil liquefaction, a mechanism requiring high degree of saturation and positive pore water pressure to drive runout. Here, we review a series of modeling techniques aimed at bridging the gap between the triggering mechanics of failure in unsaturated ground and the subsequent coupled hydraulic transients leading to a chain process involving sharp saturation, spontaneous strength loss, and eventually high landslide velocity. To do so, we review and extend classic concepts of material stability analysis, such as the second-order work principle, to unsaturated soils and link them to analytical and computational methods for coupled deformation-fluid flow models for both saturated and unsaturated materials. This effort will show that: (i) it is possible to account for changes in saturation conditions on essential indicators of multi-modal soil instability (e.g., shear or flow failure) and that these indices can be converted into actionable metrics to assess the fate of flowslides in terms of triggering susceptibility, as well as their runout potential.