A Langevin canonical framework for a chiral two--level system coupled to a bath of harmonic oscillators is developed within a coupling scheme different to the well known spin-boson model. Thermal equilibrium values are reached at asymptotic times by
solving the corresponding set of non--linear coupled equations in a Markovian regime. In particular, phase difference thermal values (or, equivalently, the so--called coherence factor) and heat capacity through energy fluctuations are obtained and discussed in terms of tunneling rates and asymmetries.
