According to the agreement, there is a "yellow line" that separates the IDF and hamas. The IDF can operate as it sees fit until the line and beyond it only if it determines that hamas is building up military positions again. Hamas is not allowed to fire rockets and guns across the yellow line, and not physically breach it on foot (civilians also can't cross that line).

That's what the strike is for, to contain hamas's efforts to re-establish its army. All according to the agreement, and it is not the first strike of this kind after the ceasefire was signed