'AI-Learner Partnership': Psychological mechanisms and developmental trajectories of EFL learners' writing agency in GenAI-assisted courses.

This study explores how EFL learners construct, negotiate, and develop writing agency through engagement with generative artificial intelligence (GenAI) in second language writing courses. GenAI is conceptualized as a cultural mediational means within an integrated sociocultural and positive psychological framework. Eleven Chinese EFL university students were followed over a 16-week semester as they completed multiple academic writing tasks with GenAI support. Drawing on a qualitative multi-method design, data were collected through semi-structured interviews, screen recordings of writing sessions, and reflective journals. The analysis identified three interrelated, non-linear phases in learners' agency development: initial exploration (characterized by novelty-driven engagement, dependency on AI output, and emergent self-efficacy), strategic adaptation (marked by more selective, task-contingent tool use and the strengthening of writing-specific psychological capital), and deliberate appropriation (signaled by personalized integration of GenAI into writing workflows and the emergence of a more agentic techno-authorial identity). Across these phases, cognitive processes, affective experiences, positive psychological resources, and task design features jointly shaped how learners mobilized technological affordances to enact writing agency. The findings suggest that writing agency in human-AI collaborative writing is a dynamic, context-sensitive accomplishment rather than a fixed individual trait. By connecting sociocultural accounts of mediated action with positive psychological resources, the study offers a process-oriented account of how EFL learners negotiate assistance, authorship, and autonomy in GenAI-supported academic writing.