JWST found the engines of reionization and discovered they are too powerful for the job history says they did. Reionization's end is anchored by the Lyman-alpha forest at redshift 5.3 and the CMB optical depth, together requiring a late, gradual process. JWST then measured the two quantities that set the ionizing budget: the abundance of faint early galaxies (higher than expected) and their ionizing photon production efficiency xi_ion (substantially higher than assumed), while low-redshift escape-fraction analogs imply healthy leakage. Multiply them and the universe finishes reionizing near z of 8 to 9, far too early: an overproduction of ionizing photons by roughly a factor of two or more, formalized as the "photon budget crisis" (Munoz et al. 2024, arXiv:2404.07250).
A model can survive missing photons by appealing to undiscovered sources; surplus photons are worse, because something must absorb them. The proposed sink is enhanced recombination: a clumpier intergalactic medium with more dense absorbing structures taxes the photon supply, and radiative-transfer simulations calibrated to the forest can accommodate higher clumping (arXiv:2412.01906). But the required clumping exceeds what ΛCDM small-scale structure natively provides, the escape fractions could instead be argued down only against the analog data, and each rescue is a post-hoc recalibration of exactly the quantities JWST was supposed to pin.
The standing is an active crisis of surplus: the sources are measured, the timeline is anchored at both ends, and the budget does not close without modifying the absorber population. JWST spectroscopy of xi_ion evolution and direct IGM clumping diagnostics are converging on whether the sink exists or the timeline must move.