Giant polarized synchrotron loops cross the high-latitude radio sky, Loop I alone spanning 100 degrees, with contested distances, magnetic coherence that remnant evolution does not naturally build at those sizes, and demonstrated leakage into cosmological polarization channels. Template-based cleaning assumes a statistically well-behaved synchrotron sky, while the loops are singular coherent objects: the exact failure mode that turns foreground residue into false primordial B-modes.
The standard inventory makes the loops a handful of local bubbles in a disordered field, statistically separable from the cosmological sky. Their size, coherence, and high-latitude reach keep exceeding that biography, and every B-mode forecast quietly assumes the excess can be templated away.
SCT expects the local magnetic sky to be organized rather than statistically tame: the interstellar field rides flux inherited from pre-collision material (P25, the premise's verbatim inheritance of magnetic configurations) and recycled through the eternal cascade (P28), with the deposition geometry organizing coherent structures along inherited directions (P33, P34). Giant coherent polarized arcs, larger and more ordered than remnant bubbles should be, are the predicted local texture of an inherited field topology that supernova shells illuminate and distort but did not create. The loops' awkward properties, coherence over 100 degrees, contested shell distances, high-latitude extensions, read naturally as flux architecture predating its illuminating events.
The practical consequence sharpens the B-mode warning: a foreground that is inherited architecture rather than random bubbles carries large-scale phase coherence that template cleaning systematically underestimates, so SCT's directional expectation is that loop-correlated polarized residue will keep surfacing in cosmological channels as sensitivity grows, and that its geometry will correlate with the larger inherited structure (the local J alignment family) rather than with star-formation geography alone. For the primordial program this is a registered caution: SCT predicts no tensor signal (r below 10⁻⁵), so any future B-mode claim must survive precisely this foreground class.
This is the same inherited-flux reading behind the void magnetogenesis entry, observed from inside our own galaxy. There is no need to assume the loops are tame to keep the cosmology clean; the cosmology must be cleaned around their architecture.
The biography is testable: distance ladders and polarization tomography (starlight polarization with Gaia distances) establishing every major loop as an ordinary nearby remnant shell, with field topology fully generated by the shells themselves and no residual large-scale inherited coherence, would remove the architecture reading. The B-mode stake is shared: a confirmed primordial B-mode at r above 0.01, surviving loop-aware foreground analysis, falsifies SCT's tensor floor regardless of the loops.