Major volatiles, such as carbon, water, nitrogen, sulfur, and halogens, are fundamental to the physical and chemical evolution of planetary interiors. From the earliest stages of accretion through the Hadean and Archean on Earth, volatiles influence magma ocean dynamics, mantle rheology, crustal differentiation, and the onset of plate tectonics. Despite their importance, key questions remain: How and when were volatiles delivered and sequestered into planetary interiors? How did volatile cycling between the surface and mantle evolve through time? And how did early volatile budgets set the conditions for long-term planetary habitability? This session invites contributions that investigate the role of volatiles in planetary evolution across a broad range of approaches. Comparative perspectives from other rocky bodies in the Solar System and beyond are also welcome. Together, this session will advance our understanding of how volatile budgets govern early planetary evolution and its subsequent trajectories as a potentially habitable planet.