Abstract
The increasing adoption of artificial intelligence (AI) in English writing instruction has drawn growing attention to teachers' perceptions of AI-supported writing instruction (TPAI) in classroom contexts. However, existing research has predominantly focused on technological affordances and student outcomes, offering limited insight into teachers' instructional agency (IA) and professional support needs. This study aims to examine how English TPAI influences the pedagogical integration of AI-supported writing instruction (PIAI), with particular emphasis on the roles of IA and professional development (PD), as well as the moderating effect of institutional and ethical support (IES). A quantitative research design was employed using survey data collected from English teachers in formal educational institutions. Partial least squares structural equation modeling (PLS-SEM) was applied to test the hypothesized relationships among TPAI, IA, PD, IES, and PIAI. The results show that TPAI significantly enhances IA (β = 0.40, p < 0.01) and PD engagement (β = 0.65, p < 0.01). Both IA (β = 0.19, p < 0.05) and PD (β = 0.68, p < 0.01) positively influence PIAI, explaining 57% of the variance. IES significantly moderates the relationship between IA and PIAI (β = -0.18, p < 0.05). These findings underscore the importance of targeted PD and coherent IES structures in facilitating effective PIAI, and provide a teacher-centered perspective on how teacher preparedness and institutional context jointly shape the early adoption of AI in writing instruction.