Read the pairwise exchange couplings J_ij straight from Prophet-Spin's exchange layer in a supercell at least twice the exchange cutoff wide. The checkpoint is Heisenberg-form, so at fixed moment magnitudes E = E0 + Σ J_ij m_i·m_j is the model's exact energy, not a fit. Moments come from a magCIF's _atom_site_moment loop (for example the relax route's output) or are predicted from the lowest collinear ordering. Reports the mean-field ordering temperature, which overestimates, and the susceptibility peak of classical Heisenberg Monte Carlo, with the order-parameter curve and exchange shells (J_meV = -J_ij|m_i||m_j|; positive favors parallel moments). The Monte Carlo order parameter follows the ordering the couplings prefer (the leading mean-field modes). mean_field_ordering_overlap near 1 means that ordering is the input moments' pattern; near 0 means the couplings favor a different, possibly non-collinear, order. Classical spins with rigid magnitudes: no quantum statistics or longitudinal fluctuations.