Recently, a hybrid percolation transitions (HPT) that exhibits both a discontinuous transition and critical behavior at the same transition point has been observed in diverse complex systems. In spite of considerable effort to develop the theory of HPT, it is still incomplete, particularly when the transition is induced by cluster merging dynamics. Here, we aim to develop a theoretical framework of the HPT induced by such dynamics. We find that two correlation-length exponents are necessary for characterizing the giant cluster and finite clusters, respectively. Finite-size scaling method for the HPT is also introduced. The conventional formula of the fractal dimension in terms of the critical exponents is not valid. Neither the giant nor finite clusters are fractals but they have fractal boundaries.Percolation has long served as a simple model that undergoes a geometrical phase transition in non-equilibrium disordered systems [1]. As an occupation probability p is increased beyond a transition point p c , a macroscopicscale giant cluster emerges across the system. Theory of percolation transition was well established by the Kasteleyn-Fortuin formula [2]. This percolation theory has been used for understanding percolation-related diverse phenomena such as conductor-insulator transitions [3], the resilience of systems [4][5][6], the formation of public opinion [7,8], and the spread of disease in a population [9,10]. The percolation transition is known to be one of the most robust continuous transitions [1,11].Recently, however, many abrupt percolation transitions have been observed in complex systems [12][13][14][15][16][17][18], for instance, large-scale blackouts in power grid systems [19] and pandemics [20], in which the order parameter increases abruptly at a transition point. Among those transitions, an HPT has attracted substantial attention. The transitions in k-core percolation [21][22][23][24][25] and in the cascading failure model on interdependent networks [19,[26][27][28][29] are prototypical instances of the HPT. For these cases, the HPT is driven by cascade failures over the entire system as links are removed. The cluster size distribution (CSD) does not obey a power law. Instead, the avalanche size distribution follows a power law and shows critical behavior [29]. Consequently, the conventional formalism of percolation transition based on the CSD cannot be extended in an appropriate way to the HPT.Here, we aim to develop a theoretical framework of the critical phenomena of the HPT. To achieve this goal, we use a modified version [30] of the so-called half-restricted percolation model [31] in two and infinite dimensions. This model has potential applications to the transport or communication systems with global control equipments [30]. This model exhibits a HPT induced by cluster merging dynamics as links are added. The order parameter remains zero up to a transition point, at which it increases abruptly to a finite value, leading to a firstorder transition. As the order parameter abruptly increases,...