Compact-binary gravitational-wave standard sirens provide a direct distance-ladder-independent measurement of luminosity distance from the GW waveform. Combined with host-galaxy redshifts, they yield H₀ estimates that emerge as a third independent probe in the Hubble tension. GW170817 and subsequent events give H₀ broadly consistent with both CMB and distance-ladder ranges but with wide posteriors hinting at the 67 to 73 km/s/Mpc band (Schutz 1986; Abbott 2017; Chen 2018).
The standard model assumes a single global FLRW expansion history with constant Λ. Every probe of H₀ in every direction at every redshift must converge on one universal value. As GW standard-siren precision improves, the third independent local probe must agree with the SH0ES Cepheid value or with the Planck CMB value, and the model has no way to absorb a real systematic difference.
SCT replaces the hot-dense-center with a superluminal collision and the thermalized debris field that became our visible universe. From this single change, Λ becomes the dynamical ratio Λ_eff(x,t) = κ · U_local(x,t) / U_parent(x,t) (P17). GW standard sirens at the cosmological-distance regime sample a path-integrated H(z) along their line of sight from the source to us. Different sources at different sky directions integrate through different segments of the Λ_eff field and correctly report different inferred H₀ values.
Sources within or near the local KBC supervoid traverse less mass than the cosmic average, encountering enhanced Λ_eff (P19) that pushes the locally inferred H₀ about 2 to 3 km/s/Mpc above the cosmic-mean value. Sources at larger distances (deep into the cosmic web outside the void) sample more representative Λ_eff and recover values closer to Planck's CMB-extrapolated 67 km/s/Mpc. Hereditary time (P10) introduces additional path-integrated frequency shifts along the GW propagation, contributing a small systematic offset that depends on the cumulative parent-frame mesh structure between source and observer.
The same M5 framework that resolves the SH0ES Cepheid distance ladder, the Pantheon+ supernovae (recid 7), the H0LiCOW time-delay lensing (recid 44), and the megamaser disk distances accommodates GW standard sirens. Different probes sample different volumes of the dynamical Λ_eff field, so their H₀ values disagree systematically and predictably. There is no need for evolving supernova systematics, modified-gravity GW propagation, or unidentified peculiar-velocity contamination.
If LIGO O5 plus Einstein Telescope era GW standard-siren samples show no systematic environmental offset in inferred H₀ (void-direction sources at the same value as cluster-direction sources at the 1% level after peculiar-velocity corrections), the M5 environmental-Λ_eff explanation is refuted. The cleanest signature is GW sirens at z > 1 (sampling well outside the local void) converging to the Planck H₀ value, while local-void sirens stay anchored at the SH0ES value.