Observations of luminous quasars hosting black holes with masses ?10?–10¹° M? at redshifts z ? 6–7 imply that supermassive black holes (SMBHs) assembled within the first ~0.8–1 Gyr of standard cosmic time, which is difficult to reconcile with growth from stellar-mass seeds under Eddington-limited accretion and typical merger rates (Haiman 2013; Wu et al. 2015). ΛCDM models invoke either very massive “direct collapse” seeds, episodes of sustained or super-Eddington accretion, or rare special environments to reach these masses so early, but each option strains assumptions about gas cooling, feedback, and duty cycles, leaving the rapid appearance and abundance of high-z SMBHs as a key timing and efficiency challenge (Bromm & Yoshida 2011; Inayoshi et al. 2020).