Response to “Comment on ‘Rethinking the evidence for a liquid–liquid transition in water: What decompression experiments reveal’” [J. Chem. Phys. 164, 024506 (2026)]

Ultrafast decompression experiments on deeply supercooled water have been interpreted as showing long-lived coexistence of high- and low-density liquids. We reassess this interpretation by separating the timescales of pressure release, structural relaxation, crystallization, and heat exchange. The experimental trajectories are adiabatic, and under these conditions, the two fitted wide-angle x-ray scattering components cannot represent equilibrium HDL and LDL persisting along a common thermodynamic path. We show instead that the spectra are consistent with a responsive liquid fraction evolving during decompression together with a structurally lagged, HDA-like fraction produced by heterogeneous heating. This framework also rationalizes the fluence dependence and clarifies the distinct information contained in the small-angle x-ray scattering response. The analysis identifies which observables can provide decisive evidence for a first-order liquid-liquid transition and constrain the location of its critical point.