Late Time Weak Field Scaling Consistency Test for the Hubble and S8 Cosmological Tensions

High-precision cosmological probes show persistent, probe-dependent shifts in inferred late-time parameters, notably (i) the difference between early-time(CMB-inferred) and late-time determinations of the Hubble constant H0, and(ii) the lower late-time clustering amplitude inferred from weak lensing, often summarized by S8 ≡ σ8√(Ωm/0.3). We present a deliberately minimal and falsifiable consistency diagnostic for ΛCDM rather than a complete modified-gravity theory: we introduce a single phenomenological parameter s that rescales the effective weak-field amplitude relevant for time delays and lensing, activated only below a fixed redshift gate z∗ (fiducial value z∗ = 0.7). Under a conservative observable-level mapping (no scale dependence, no gravitational slip, and no modification to the background expansion), the same s maps onto strong-lens time-delay distance likelihoods and (approximately) onto the cosmic-shear amplitude direction. Using publicly released time-delay distance likelihood products from strong-lens cosmography and the publicly released KiDS-1000 cosmic shear posterior, we obtain slens = 0.9156 (+0.0245 / -0.0212) and sWL = 0.9023 (+0.0280 / -0.0303) (68% credible intervals), with posterior overlap O = 0.7626 and a descriptive difference-of-means proxy T = 0.4297σ. Rather than proposing a new cosmological model, this work introduces a one-parameter weak-field scaling diagnostic that can be applied directly to existing late-time observational data.The full analysis is reproducible withan open notebook that downloads the public products and records provenanceincluding repository commit identifiers and SHA-256 hashes.