Abstract: The OSV conjecture relates a black-hole partition function in four-dimensional $\mathcal{N}=2$ supergravity to the absolute square of the topological-string partition function. I will revisit the conjecture using modern gravitational path-integral techniques. Using finite-temperature Bates–Denef geometries and equivariant localization, we show that the higher-derivative supergravity on-shell action is a sum of prepotentials evaluated at the two poles of the Euclidean horizon; through the standard $\mathcal{N}=2$ supergravity/topological-string dictionary, these become the topological-string free energy and its conjugate, producing the characteristic $|Z_{\rm top}|^2$ factorization. We also determine the gravitational ensemble and boundary terms for which this factorization holds. Finally, I will describe non-perturbative corrections in the small-$G_N$ expansion arising from a tower of multi-centered “shifted” saddles related by large gauge transformations.