This study examines algorithmic collaborations and co-authorship in first-language (L1) education, drawing on empirical data from the Futures Day postdigital intervention project. Data sources, including screen and audio recordings, capture engagements between upper secondary students and AI tools to co-create speculative fiction about future societies, humans, and technology. The analysis employs posthumanist concepts such as diffraction and intra-action to analyze relational movements between humans and AI in creative writing processes. Findings show that fostering Futures Literacy (FL) through AI collaborations and speculative storytelling challenges conventional literacy practices. Generative AI and human creativity become entangled, reshaping notions of authorship and text production in school settings. The study contests binary views of human vis-à-vis AI-generated texts, advocating for literacy as a process of intra-action rather than a fixed human ability. This shift reframes reading and writing in L1 education, embracing transformation, digitally born texts, and creative possibilities in the GenAI era.