The discovery of V1309 Sco, a contact binary with rapidly decreasing orbital period followed by an outburst, established a connection between astrophysically critical, catastrophic phases of binary star evolution and a group of transients characterized by their red color and the luminosity in the gap between classical novae and
supernovae. However, many properties of these transients, including their connection to the binary evolution theory, remain largely unexplained. I will present an exploration of the dynamics of outflows from mass-losing binary stars and the associated variety of transients. Using my simulation results, I will interpret the
unprecedentedly detailed pre-merger data on V1309 Sco and argue that these transients can provide a fresh observational input into some open problems of binary star evolution.