The radial acceleration relation (RAR) is organized by an acceleration scale near 1. 2×10⁻¹⁰ m s⁻². We test a conditional construction in which a declared present-horizon protocol reads one massless thermal budget on two matched supports. Its exact support-rescaling identity gives a₀ = cH₀/ (2π Ω_Λ^ (3/8) ) = 1. 2005×10⁻¹⁰ m s⁻² for Planck 2018 inputs. The exponent 3/8 = (3/2) (1/4) combines the flat-FLRW support-volume ratio with the three-dimensional thermal budget; neither the exponent nor the normalization is fitted to galaxy kinematics. A separately declared minimal closure gives gₒbs² = gbar² + a₀ gbar (1+√ (3/2) √y) e^ (−y/2), y = gbar/a₀. On the SPARC Q=1 sample (93 galaxies, 2060 radial points, fixed catalogue mass-to-light ratios), an effective-scatter likelihood with galaxy-block uncertainties yields a₀ = (1. 213±0. 084) ×10⁻¹⁰ m s⁻², 0. 15σ from the prediction. With a₀ fixed, the declared readout coupling is Cg = 0. 996±0. 064. The envelope coefficients are consistent with but weakly constrained by the data; fitted alternatives are statistically unresolved under galaxy-clustered comparisons. The construction is not an unconditional derivation from partial observation: the horizon, thermal state, support pairing, unit normalization, channel list, and profile branch are explicit gates. It is falsifiable through those gates, including a positive-semidefinite one-sided response, a gate-conditional ℓ∈0, 2 sky pattern, and an exponential high-acceleration tail on the source-rate branch. This record contains the Letter and its Supplemental Material (exact support trace, complete gate ledger, envelope derivation, likelihood audit, robustness tests, and reproduction instructions) as two files. Theory companion paper: doi: 10. 5281/zenodo. 21423426. Preprint version v0. 6. 2; submitted to Physical Review D (Letters).
Yi (Sat,) studied this question.