The various types of interactions that students carry out when engaged in scientific argumentation function together to move forward developing ideas and support sensemaking. As such, incorporating argumentation in classroom instruction holds promise for supporting students in developing and acting with an epistemic agency, being positioned, and taking up, opportunities to inform their classroom community's knowledge construction work. To foster science classrooms in which students take on active roles, argue to learn, and engage in authentic meaning-making, the field needs better understandings of how students are supported in developing, and acting with, epistemic agency. We contend that focusing on critique--specifically, examining circumstances where students partake in this type of exchange with peers when engaged in argumentation--is a productive starting point. In this study, we characterized manifestations of epistemic agency as captured through instances of student critique during argumentation discussions in three middle school classrooms. Specifically, we used social network analysis to illuminate interactional patterns related to critique, and discourse analysis to highlight language moves individuals carried out when student critique was observed. Our findings point to there being multiple, sometimes conflating, approaches to addressing tensions inherent to helping students develop and act with epistemic agency. Our findings also suggest we can learn from critiquing practices that all students bring and employ in the classroom. This latter point is especially important when desiring to create and foster equitable learning environments, where all students' ways of knowing and doing science are appreciated, recognized, and used to support sensemaking.