This article investigates hashtag-centered action during the 227 controversy on Weibo following the 2020 blocking of Archive of Our Own (AO3) in China, focusing on Chinese Boys’ Love (BL) fans’ participation in this episode of digitally mediated contention. Through participant observation, interviews, and secondary source analysis, it traces BL fans’ development of sophisticated algorithmic imaginaries: shared understandings of how platform algorithms function and can be contested. The study reveals three-layered algorithmic imaginaries: participatory visibility, commercial manipulation, and institutional authority. These imaginaries circulated across adjacent user communities, showing how algorithmic knowledge accumulates and adapts within China’s co-regulated platform environment. The analysis advances scholarship on digital contention by demonstrating how, under authoritarian constraints, everyday users collectively negotiate algorithmic power, making hashtags as infrastructures for learning and tactical adaptation.