Unfortunately, a clear theoretical understanding of cavity-modified ground-state chemical reactivity remains missing, despite recent theoretical progress. Recent theoretical efforts have been focused on using existing rate constant theories to investigate the possible VSC modifications for the rate constant because the cavity mode is in the Infrared (IR) range of frequency (similar to regular nuclear vibrations). These explorations include the Grote-Hynes (GH) theory, the quantum Transition State Theory (q-TST), the Pollak-Grabert-Hänggi (PGH) theory, and numerically computing the flux-side correlation function using ring polymer molecular dynamics (RPMD). These approaches often cannot predict the correct resonant frequency that matches the quantum vibration frequency ω 0 measured from the optical spectra. If one describes the rate constant using classical theory, the maximum modification of the rate constant occurs when ω c ≈ ω b , where ω b is the top of the barrier frequency (imaginary frequency of the Transition State). The PGH theory, or a semi-classical version of the q-TST rate theory, 13 finds that the cavity-frequency dependent rate modification is related to either the top of the barrier frequency ω b , the classical bottom of the well frequency ω cl 0 , or a broad frequency distribution between these two frequencies. The difficulties of using existing rate theory to explain the VSC resonance behavior strongly suggest that the VSC mechanism does not belong to a known chemical mechanism or can be accurately described by a known analytic rate expression. Further, the RPMD simulations of the VSC modification also suggest that the rate constant modification effect will maximize at ω c ≈ ω b , raising the question of how quantum is the resonance behavior in VSC because RPMD in principle quantizes a DOF that includes all zero point energy and possible tunneling effect. This presents a challenge for trajectory-based quantum dynamics methods to correctly capture the resonance behavior of VSC, as well as an open question of whether the reso-nance VSC behavior is intrinsic quantum and thus can not be obtained from trajectory-based simulations.