Here, we show how these problems can be addressed by combining YARP, a graph-based reaction exploration scheme, with a cluster model of a reactive interface. Ethylene oligomerization on silica-supported single site Ga 3+ catalysts is used as a benchmark system for this approach based on the fact that some reaction data exists for this system while it still exhibits several unaccounted for product pathways. In particular, it has been previously observed that single site Ga 3+ performs oligomerization chemistry via the classic Cossee-Arlman mechanism with reasonably high selectivity to short linear alpha-olefins; whereas, side products, such as light alkanes and coke, have also been detected. Here, YARP not only (re)discovers the 1-butene-centered Cossee-Arlman catalytic cycle, but also discovers TSs responsible for side reactions, such as the formation of isomers of 1-butene, odd-number oligomers, alkanes, and coke. Moreover, this represents the largest heterogeneous cataytic system (more than 50 atoms, with an open-ended pool of reactants) to be characterized using a quantum chemistry based automated reaction method. The reactions that are discovered by YARP are generalized based on mechanisms, including carbon-backbone lengthening, oligomer liberation, and hydrogen transfer to form alkanes. The kinetic significance of the TSs are further analyzed based on the energy surfaces of three representative catalytic cycles comprising 36 elementary steps.