Two competing effects -stretching and activity-induced condensation determines chain size and conformation as a whole. On the one hand, connectivity brings a unique process into the system -local stretching. On the other -stretched segments can act as active agents themselves, with the ability to aggregate. We claim that the collapsed state of the long active polymer chain occurs within the same physical reasons as MIPS in active gas , but at lower Pe due to intrinsically low translational entropy of monomer units. For comparison, we carried out several test calculations in a gas system with N = 1 and showed that at a similar density, MIPS is not observed; in order for MIPS to appear, both the concentration and Pe must be significantly increased -we observed separation at Pe=300 and concentration N/V = 0.5 (see SI1). Connectivity of active particles provides higher collision probability and increases spatial correlation time between monomer units. Similarity between MIPS of active gas system and collapse of active polymer arises as the appearance of bimodal distribution of monomer units local density in the collapsed state (Figure blue curve). Here, one small peak at low density stands for freely moving stretched fragments -there are only two neighbors in the vicinity of each monomer unit.