The first acoustic peak's angular scale is measured to one part in thirty thousand (100 theta_star = 1.04110 +/- 0.00031), and the full peak structure encodes pre-recombination physics no instrument has independently checked: the plasma sound speed is computed, not measured. The peaks are where every alternative cosmology must report for execution, and where ΛCDM's own strains, lensing smoothing, multipole splits, calibration drifts, quietly concentrate.
The model's peak positions follow from an assumed acoustic medium: a photon-baryon fluid with CDM loading and sound speed c_s² = c²/[3(1+R_b)]. Every inference from the peaks inherits that assumption, so the spectacular fit certifies the package, not each ingredient, and a different medium reproducing the same peaks would be observationally indistinguishable at current precision.
SCT meets the checkpoint in two steps. First, the equivalence: once the cascade terminates before one second (P40) and the plasma reaches the same six thermodynamic state parameters, the acoustic physics at multipoles above 30 is governed by the identical Boltzmann-Einstein system regardless of origin, the Plasma Equivalence Theorem of Paper 3, From Chaos To Concordance Spectra (P29, P30). The peak structure ΛCDM fits so well is therefore SCT's peak structure too, not by tuning but by theorem: thermodynamic states have no memory of how they were prepared. The first-peak geometry is explicitly preserved, with the SCT distance and sound-horizon ratios matching the ΛCDM combination by construction.
Second, the wager: SCT's late-time Λ_eff dynamics shift the angular diameter distance to recombination by 0.043 percent, displacing theta_star to 1.04155, sitting 1.5σ from Planck's value (Paper 11, From Chaos to Covariant Completeness), a registered prediction at the fourth decimal place that current precision cannot resolve and CMB-S4 can. The most precise ruler in science becomes the discriminating instrument rather than the executioner, and the model has placed its number on the table in advance.
Two premises secure the agreement and one mechanism signs the wager; the same equivalence theorem underwrites every CMB entry in this catalog, which is why the cascade can replace the origin story without disturbing the acoustics ΛCDM is celebrated for.
The registered kill is numerically explicit: future measurement settling 100 theta_star at 1.04110 +/- 0.00005 would falsify the SCT shift at more than 5σ, executing the Λ_eff distance modification by the fourth decimal. Conversely, the peaks moving toward 1.04155 as precision tightens would be among the cleanest confirmations available to the framework, a pre-registered number with nowhere to hide.