The model system portrays an isomerization reaction containing two electronic states |g⟩ and |e⟩ and two photonic Fock states |0⟩ and |1⟩ with a spin-boson bath for the nuclear DOFs to mediate electronic transitions. Due to the use of the Jaynes-Cummings Hamiltonian in the single-excited subspace, the ground state is "uncoupled" from the excited states via direct light-matter interaction; however, due to the cavity loss, the Lindblad decay mediates population transfer from |g, 1⟩ → |g, 0⟩ with a rate of Γ. Fig. ,b show the potential energy surfaces of the three states with light-matter coupling A 0 set to 0.0 eV (Fig. ) and 0.136 eV (Fig. ) with a cavity frequency of ω c = 1.632 eV. Fig. ,d present the polariton population dynamics in the adiabatic-Fock basis with loss rates of Γ = 0 meV (Fig. ) and Γ = 1 meV (Fig. ). The numerically exact results are obtained using the discrete variable representation (DVR) basis 114 for the nuclear DOF and Fock states for the photonic basis. As shown in Fig. , the L-MFE dynamics (dotted line) capture the essential physics of the problem but deviate from the exact simulations (solid) at a longer time, which is a known problem of the mean-field Ehrenfest approach and is not the main point of this discussion. The dynamics portrayed with a loss rate of Γ = 0.0 meV (Fig. ) reduce exactly to the dynamics of a closed quantum system with zero population residing in the uncoupled ground state, at any time t . At increased cavity loss of Γ = 1 meV (Fig. ), the system slowly populates the ground polaritonic states by funneling population from |g, 1⟩ to |g, 0⟩. This gives rise to plateaus in the ground state population curve when the majority of the population is present in the |e, 1⟩ state during the coherent population transfer processes, most pronounced at short times t < 1.0 ps. Fig. ,f provides a direct application of this method to an ab initio on-the-fly dynamics study of the isomerization of azomethane (a direct extension to the results shown in Fig. ). The polaritonic potential energy surfaces can relaxing. This almost completely removes the isomerization pathway previously available to the system, effectively turning off the isomerization process for increased cavity loss rate.