  We revisit the exact thermodynamic description of the classical sine-Gordon
field theory, a notorious integrable model. We found that existing results in
the literature based on the soliton-gas picture did not correctly take into
account light, but extended, solitons and thus led to incorrect results. This
issue is regularized upon requantization: we derive the correct thermodynamics
by taking the semiclassical limit of the quantum model. Our results are then
extended to transport settings by means of Generalized Hydrodynamics.
