Star-planet interaction regimes in mass and radius ratio space. Blue points correspond to observed exoplanets in the NASA Exoplanet Archive (Akeson et al. 2013), assuming they will be engulfed when their host stars grow to their current separations (R_⋆ → a). Square markers highlight specific hot Jupiters while the diamond markers indicate planetary engulfment scenarios explored in past simulations. The solid line is the approximate boundary that determines whether gravitational drag or ram-pressure/hydrodynamical drag dominates in the engulfment process. The shaded area represents an unpopulated region where a planet would exceed its Roche lobe and engage in mass transfer, thus avoiding direct impact with the stellar surface. Planets that are dynamically scattered deep within this region would experience tidal disruption.