The relic neutrino sea is confirmed only indirectly, through free-streaming signatures on the CMB acoustic peaks, while direct detection at 10⁻⁴ eV borders on impossible (Planck 2018; PTOLEMY 2019). The N_eff inference flexes between datasets and is model-dependent throughout, computed assuming ΛCDM acoustic physics.
The model fixes N_eff = 3.046 from standard decoupling and reads it back through damping-tail morphology calculated with its own sound-speed history. The circularity is mild but real: the radiation density is constrained inside the framework being tested, so any modified acoustic physics shifts the books without anyone noticing.
SCT keeps the neutrinos and changes the audit. The cascade terminated before one second (P40), so neutrino decoupling proceeds under standard thermal physics and the relic sea exists exactly as the Standard Model describes; the Plasma Equivalence Theorem (P29, P30) carries the acoustic structure. But the framework's derived radiation bookkeeping differs: SCT's cascade geometry, the SO(3) mode count with QCD boundary and photon-heating corrections, yields a derived N_eff of 2.514 ± 0.050, sitting 2.8σ from Planck's 2.99 ± 0.17 under ΛCDM assumptions. The comparison is model-inconsistent by construction, Planck's posterior assumes ΛCDM's sound-speed history rather than SCT's modified acoustics, so the gap is an open question rather than a falsification, and SCT registers it as the first of its evaluated predictions not already aligned with existing constraints.
The discriminating instrument is named and the forecast registered: CMB-S4's design precision of 0.030 yields a forecast separation of 17.7σ between the SCT and Standard Model values, making this sector one of the framework's sharpest scheduled tests. The derivation chain runs through the cascade-geometry work of Paper 17, From Chaos To Coalescent Parsimony, with the acoustic framework in Paper 16, From Chaos To Codified Acoustics.
OPEN TENSION. The derived N_eff = 2.514 sits 2.8σ from the Planck value under ΛCDM assumptions; the comparison is model-inconsistent, and resolution requires running the SCT-modified Boltzmann hierarchy against the Planck spectra with N_eff free.
The kill is registered with numbers: CMB-S4 measuring N_eff above 2.80 at 3σ after full marginalization over helium, neutrino mass, and running would falsify the cascade-geometry chain behind the 2.514 derivation. The shared half cuts both ways: any confirmed direct detection of the relic sea at standard temperature and density is welcome to both frameworks, while its absence where PTOLEMY-class experiments should see it would wound both equally.