Abstract: A resolution of the black hole information problem requires a breakdown of isometricity in the bulk-to-boundary map. The degree of this non-isometricity is conjectured to be governed by the “bulge” quantum extremal surface lying inside the black hole interior, though a derivation of this has remained open. I will present recent progress toward such a derivation within the framework of the gravitational path integral. Work in progress with Geoff Penington, and Pratik Rath.