Nature Materials, Published online: 27 July 2026; doi:10.1038/s41563-026-02707-2Hydrogen compromises the mechanical performance of metallic materials, but hydrogen–material interactions at high temperatures remain poorly understood despite emerging applications in hydrogen-powered energy systems. Now, multiscale damage analysis of Ni-based superalloys tested in a high-temperature hydrogen atmosphere uncovers degradation mechanisms that differ from those operating at near-room temperature.