This dissertation joins ongoing debates surrounding generative AI in writing studies by examining how AI unsettles the field’s long-standing relationship between writing and writing technology. From a rhetorical perspective, I argue that generative AI functions not only as a mediator of writing but also as a communicative and rhetorically capable agent. Unlike earlier writing technologies, which primarily served as medium through which writers composed and communicated, generative AI introduces a shift from writing on the screen, to attending to what happens behind and beyond the screen, to writing to and with an interlocutory machine. This shift reconfigures rhetorical agency and rhetorical situation and challenges existing understandings of digital rhetoric. Drawing on discourse analysis, rhetorical criticism, and secondary scholarship in writing studies, digital rhetoric, human–machine communication (HMC), and posthuman theory, this dissertation argues that AI’s communicative capacity and machine subjectivity introduce operational rhetorical agency into writing. This agency does not depend on human intention or consciousness; rather, it derives from AI’s rhetorical presence that is evident in how it produces discourse, responds to prompts, offers rhetorical options, and shapes invention, revision, decision-making, and agency. This shift challenges traditional understandings of rhetorical situation and requires writing studies to reconsider how agency is distributed and how meaning-making emerges when human writers compose with machine-generated language. To theorize this new writing dynamic, the dissertation proposes a cyborg lens for understanding AI-mediated writing. Cyborg writing names a dynamic and hybrid rhetorical situation in which humans and machines collaborate in meaning-making, while agency, authorship, and responsibility remain negotiated, relational, and distributed. Within this situation, meaning-making emerges through human–machine interaction and assemblage. The dissertation concludes by drawing pedagogical implications for AI-mediated writing instruction from administrative leadership, curriculum design, instructor training, teaching materials, and classroom experience. Ultimately, this project argues that AI does not mark the end of writing; rather, it revitalizes writing by making human rhetorical judgment, critical reflection, and rhetorical agency more urgent.