Title: Atmospheric compositions of hot Jupiters as tracers of planet formation history.
Abstract: Atmospheric abundances of giant exoplanets are increasingly used to infer their formation pathways, motivating upcoming population studies with facilities such as the ESA Ariel mission. However, the extent to which such inferences depend on assumptions about protoplanetary disk physics remains poorly understood. We present a population synthesis study of giant planet formation that combines pebble and planetesimal accretion with a simple equilibrium C–O chemistry model, and explicitly contrast disks dominated by viscous or magnetically-driven wind accretion. We show that bulk abundance ratios anchored to refractory elements (e.g. O/Si, C/Si) provide useful diagnostics of solid enrichment history, and reveal population-level differences between giant planets that end up within or beyond 1AU after 3 Myr. Moreover, in wind-driven disks these ratios retain partial sensitivity to the initial formation radius even in the presence of substantial migration, making them effective tracers of planet formation history.