The Stress-Sign Stratification of Four Labeled Points in Three Dimensions

We classify the stress-sign stratification of all labeled four-point configurations in R^3 for the complete graph K_4, including coincident points and every affine-rank degeneration. There are exactly 65 connected strata: two of affine rank three, 25 of affine rank two, 37 of affine rank one, and the diagonal. We give their dimensions and the entire closure order, with 800 strict incidences and 207 Hasse edges. Rank-two strata are indexed by mixed affine-dependence sign vectors modulo reversal, and collinear strata by ordered coincidence partitions modulo reversal. Their boundary relation is a closed-interval intersection condition; an explicit matrix perturbation realizes every asserted rank-two degeneration. In each ambient dimension d>=4 the two top strata merge, giving 64 strata. This answers only the B_3(K_4) component of Karpenkov's Problem 1. The B_2(K_6) and B_3(K_5) components are not resolved here. This is a self-audited, unrefereed preprint, with exact-arithmetic supplementary checks; no independent review, formal verification or absolute priority is claimed.