We study the Auslander–Reiten conjecture (ARC) through stable GPC, the assertion that the stable category of Gorenstein-projective modules has no nonzero presilting objects. We characterize ARC by stable GPC and a finiteness condition on Gorenstein-projective dimension. Periodicity gives self-extension nonvanishing and projective dimension tests. We apply these results to acyclic quiver extensions and separable Frobenius extensions. In particular, a non-Gorenstein Nakayama family yields CM-infinite triangular algebras satisfying ARC and GARC, for which vanishing of the second self-extension detects projectivity among semi-Gorenstein-projective modules.