This research evaluates the impact of Cami, an AI-powered tool, integration across SAMR (Substitution, Augmentation, Modification, and Redefinition) stages (Cami AI-SAMR) in EFL (English as a Foreign Language) writing instruction. By examining student achievement and perceptions, it explores how AI technology redefines language learning and teaching in diverse educational settings. Through a mixed-method approach with an explanatory sequential research design, this study investigates the quantitative effects of Cami AI-SAMR implementation on student performance and gauges the qualitative responses of 126 EFL university students to its effectiveness and perceptions. The findings show that Cami AI-SAMR implementation significantly impacted EFL students' writing achievement. Then, the majority of students also had positive perceptions due to the Cami AI's efficacy in supporting EFL writing learning. These findings provide valuable insights into the transformative potential of Cami AI technology in enhancing EFL pedagogy through the SAMR framework, addressing the diverse needs of students, and reshaping the language education landscape. This research contributes to the ongoing discourse on AI integration in education and offers recommendations for optimizing AI-powered EFL instruction for better learning outcomes and experiences.