Preprint of the manuscript submitted to Foundations of Physics on 10 May 2026 (passed technical checks 2026-05-13). Proposes a clean three-channel taxonomy of light–gravity coupling in the linearised limit of general relativity coupled to electromagnetism: gravitoelectric (mass-induced redshift, lensing, time dilation), gravitomagnetic (rotation-induced Lense–Thirring effect, gravitational Faraday rotation), and Λ-cosmological (cosmological redshift, integrated Sachs–Wolfe effect, de Sitter horizon thermodynamics). Headline falsifiable prediction: the Skrotskii–Mashhoon polarisation rotation Δχ ≈ 35 μrad at b = 100 RS, a* = 0. 7, detectable at ≳ 16σ/campaign by ngEHT around 2030. Companion computational audit with 56 simulators + 836 unit tests at https: //github. com/LeKCei/bipartite-universe-corpus.
Alexei Lemos Cavalcante Ferreira (Sat,) studied this question.