“…Planetary mass is intimately linked to the formation history of a given system (e.g., Adams et al 2020a;Adams et al 2020b) and is itself only significantly altered by large-scale, multibody dynamical phenomena (e.g., Izidoro et al 2017;Goldberg & Batygin 2022;Lammers et al 2023). Conversely, planetary size may be modulated to order unity by the growth or removal of a gaseous envelope that accounts for only a few percent of the total planetary mass (e.g., Owen & Wu 2013), and while the removal of such atmospheres may indeed correlate strongly with prior interplanetary interactions (Ghosh et al 2023), their presence and appearance are strongly governed by planet-dependent processes that lie distinct from system-level evolution. Examples of such phenomena include, but are not limited to, atmospheric erosion via core-powered processes (e.g., Ginzburg et al 2018;Berger et al 2023) or photoevaporation (e.g., Owen & Wu 2017;Mordasini 2020), inflation from tidal heating (Millholland 2019), surface-atmosphere chemical reactions , secondary outgassing (Kite & Barnett 2020), partial retention of a hydrogen envelope (Misener & Schlichting 2021), and mixing of an extended H/He envelope with steam (Burn et al 2024).…”