Pre-Registered Prediction: S8 from UNIONS Weak Lensing — Geometric Relay Programme Predictions CRT-01 and P4

This short note pre-registers a falsifiable prediction of the Geometric Relay Programme (GRP) for the forthcoming UNIONS weak-lensing cosmological results. The UNIONS collaboration has released its first weak-lensing shape catalogue over approximately 3,500 square degrees of the northern sky, containing 62 million galaxies with an effective source density of 4.96 arcmin^-2. Companion UNIONS papers are expected to provide cosmological constraints on the structure-growth parameter S8 = sigma8 sqrt(Omega_m/0.3). The GRP prediction is registered before the publication of those UNIONS cosmological results. It is based on the CRT-01 and P4 predictions of the GRP, built on the Entangled Relativity action of O. Minazzoli. In this framework, the scalar relay sigma mediates a dynamical coupling between matter and geometry, producing a saturation of the strong branch outside the strictly adiabatic regime. The pre-registered prediction is: S8(UNIONS) in [0.74, 0.80] as a strong-success interval, consistent with the compressed growth amplitudes reported by KiDS and DES. A weak-success outcome is defined as S8(UNIONS) < 0.81 with insufficient precision to discriminate. A failure outcome is defined as S8(UNIONS) > 0.81, statistically consistent with Planck and inconsistent with the GRP prediction interval. The S8 prediction interval is obtained by propagating the P4 saturation ratio eta0(z=1.3)/eta0(z=0.4) in [0.324, 0.785] through the lensing kernel integral for a Stage-III survey depth, using the effective relation S8 ~ sigma8,Planck sqrt(eta0,eff). The mapping is documented in CRT V3, section 10.3. This note does not claim confirmation of the GRP. It fixes a falsifiable prediction before the relevant UNIONS cosmological results are known. No parameter will be adjusted after the UNIONS result.