  The paper is concerned with identification of the key mechanisms controlling
deflagration-to-detonation transition in stellar medium. The issue of thermal
runaway triggered by positive feedback between the advancing flame and the
flame-driven precompression is discussed in the framework of a one-dimensional
flame-folding model. The paper is an extension of the authors' previous study
dealing with the non-stoichiometric fusion, $fuel \to products$, kinetics
(Phys.Rev.E, 103(2021)) over physically more relevant, $fuel+fuel \to
products$, kinetics. Despite this change the runaway effect endures. The
transition occurs prior to merging of the flame with the flame-supported
precursor shock, i.e. the pretransition flame does not reach the threshold of
Chapman-Jouguet deflagration.
