The Lyman-alpha forest reads the small-scale matter power spectrum low: a 3 to 5σ deficit at k near 1 h/Mpc against the Planck extrapolation (Palanque-Delabrouille 2020; Rogers 2024), and every repair carries a price: heavy neutrinos conflict with mass bounds, warm dark matter erases needed dwarfs, running tilt strains inflation.
The model extrapolates one primordial power law from CMB scales down four orders of magnitude in scale, with cold collisionless particles preserving the power undiminished. A small-scale deficit therefore requires new physics chosen from a menu where every item breaks something else, because the extrapolation itself is not negotiable.
SCT predicts the deficit as a registered feature: matter power spectrum suppression at wavenumbers beyond k_c near 0.5 h/Mpc, where coherence decoherence sets in. The dark-matter phenomenology is the coherent amplification of baryonic structure (P50, P52), and coherence is scale-limited: below the decoherence scale the constructive superposition that amplifies large-scale power no longer adds in phase, so small scales carry genuinely less effective gravitating structure than a cold-particle extrapolation predicts. The forest, probing precisely the wavenumbers past the registered threshold, reads the suppression directly; no neutrino mass, warm particle, or running tilt is conscripted.
The direction and company are diagnostic: the same coherence physics that trims small-scale power lifts none of the dwarf-scale structure SCT builds by deposit (recid 128), evading the warm-dark-matter trap, and it sits naturally beside the S₈ deficit (recid 2) as the small-scale face of one amplification framework, formalized in Paper 13, From Chaos to Coherent Gravity, with the deposited small-scale structure context in Paper 4, From Chaos To Collisothermal Cosmogenesis. The registered test is the threshold itself: the suppression should onset near k_c rather than tilt smoothly across all scales as neutrino or running-index repairs predict, a shape discriminant DESI's percent-precision forest measurement can resolve.
Keystone economy: P50 and P52 amplify where coherence holds; the deficit is where it lets go.
The registered kill is the shape: DESI forest power showing a smooth scale-independent amplitude shift, or suppression onsetting far from k_c near 0.5 h/Mpc, would refute the decoherence threshold and favor the particle-sector repairs. Conversely, the deficit resolving entirely into thermal and ionization nuisance parameters of the forest modeling would remove the cosmological signal both frameworks are fitting.