The Magellanic Bridge connects the Clouds with gas, stars, and in-situ star formation, but its context is the needle: a tightly bound unequal binary surviving gigayears of mutual interaction independently, then arriving at the Milky Way on first infall, mid-bridge, with the right stripped mass and metallicity (Besla 2010; Nidever 2013). Each piece is modelable; the conjunction is luck.
Stochastic hierarchical assembly treats the SMC and LMC as independent accretion events that happened to bind, survive, and interact on schedule. A long-lived dwarf binary is already rare in the model; one delivering a fully developed bridge precisely at first infall stacks improbabilities the framework can only price as coincidence.
SCT removes the luck by removing the independence. The SMC and LMC are sibling fragments of the same debris field, condensed near each other from the same deposit with related inherited J (P31, P32), so the bound pair is not an improbable capture but a birth configuration: fragments born adjacent with correlated kinematics bind naturally and stay bound. Their gigayears of mutual interaction, the tidal episodes the Bridge records, are the ordinary history of a born binary rather than a rare arranged marriage, and the first-infall timing stops being a delivery problem because the pair travels as the unit it always was.
The Bridge itself is then standard physics on an inherited configuration: tidal stripping and ram pressure acting on gas the siblings have exchanged since formation, with the chemically inhomogeneous material reflecting both the deposit's intrinsic heterogeneity (P25) and the accumulated exchange. The same debris-field reading places the Clouds within the Milky Way's satellite-plane architecture (recid 130), where the LMC complicates ΛCDM's plane statistics but simply joins the shared geometry in SCT. The inheritance mechanics are in Paper 5, From Chaos To Corotating Hierarchies, with the debris-field formalism in Paper 6, From Chaos to Cosmic Collisions.
Keystone economy: P31 binds the pair at birth; everything after is textbook tides. The needle ΛCDM must thread was never a needle, just a family arriving together.
Proper-motion and chemical archaeology carry the kill: if Gaia-era kinematics and stellar population reconstruction demonstrate the SMC and LMC formed far apart with independent early histories, binding only through late capture, the born-binary reading is refuted. SCT separately requires the pair's orbital angular momentum to sit within the Local Group's shared J architecture; a Magellanic orbital pole unrelated to the satellite-plane geometry at high significance would break the common-descent account.