Sensitivity of the reflation mechanism on mantle oxidation state, atmospheric escape efficiency, planetary semimajor axis, and initial hydrogen inventory. Reflation events occur most strongly at mantle oxidation state fO₂ ∼ IW, escape efficiency η ∼ 10⁻⁴ to 10⁻³, semimajor axis a ≲ 0.05 au, and initial hydrogen inventory ≳ 5 Earth oceans. The sensitivity matrices display the minimum normalized bulk density that is achieved across three projections of the simulation ensemble. We show a range of redox states (x-axis) and respective simulation parameters (y-axis). For example, among all simulations with a mantle redox state of IW + 0 and semimajor axis of 0.02 au in the middle panel (which includes all variability of escape efficiency and hydrogen inventory), the most reflated case reached an underdensity of ρ_bulk 58% relative to its postformation bulk density ρ_bulk,0.