Fig. presents k/k 0 (blue dots and curve) as a function of Ω R in the range when the strong coupling condition is achieved. The results are obtained from HEOM simulations (blue dots), as well as from the FGR analytic expression (blue curve) based on Eq. 8 and Eq. 16. The results clearly show a non-linear relation of the rate constant with the Rabi splitting. In particular, at a large Rabi splitting, the maximum suppression of k/k 0 converges to the value of the bare double rate (k → k D ). As shown in Fig. , the cavity ultimately removes the effects the RPV mode has on the reaction rate by splitting the spectral density and shifting it away from the frequency of ω 0 . The trend of k/k 0 closely resembles the experimental trend (e.g., Fig. in Ref. 4), and the FGR analytic expression closely agrees with the HEOM results, especially for a large value of Ω R . The fundamental scaling in Eq. 18 is also observed, with details provided in the Supplemental Note 6.