Nature Communications, Published online: 05 August 2026; doi:10.1038/s41467-026-76371-0 Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in space, yet astrochemical models fail to reproduce their observed abundances because known growth mechanisms are far too slow. Here, the authors report a plausible pathway for rapid PAH mass growth mediated by multi-ring aryl radicals via the aryl addition–dehydrocyclization mechanism.