There is a persistent tension between the "instantaneous" reionization optical depth inferred from CMB polarization (which prefers a later, sharper reionization event around z~7.7) and the detailed history of reionization inferred from high-redshift quasars and Lyman-alpha emitters (which suggest a more extended, patchy process often ending as late as z~5.5 or starting much earlier). This mismatch—often quantified as a tension in the duration ($\Delta z$) or the precise midpoint ($z_{re}$) of the epoch of reionization—implies that the simple models used to map CMB optical depth to ionization history are missing complex, early sources or that the timeline of structure formation is fundamentally different from Lambda-CDM predictions (Planck Collaboration 2020; Bosman et al. 2022).