Abstract
This mixed-methods study explores how English as a Foreign Language (EFL) students and their teachers think about and actually use ChatGPT in academic writing, and how this relates to academic integrity. A unique contribution of the study is its use of observed behavioral data, capturing students' real-time interactions with ChatGPT rather than relying solely on self-reports. 60 female Saudi EFL students wrote a timed argumentative essay in a computer lab where they were allowed to use ChatGPT. Screen recordings captured all their prompts and AI outputs. These texts were later compared with students' final essays using copy ratio and Levenshtein distance to show how much they copied or revised. Students also completed pre- and post-task surveys about their ChatGPT use and integrity beliefs, and 20 teachers rated how acceptable eight ChatGPT functions were for academic writing. Short interviews were conducted with a sample of students. Findings showed that students viewed ChatGPT more positively than teachers and spent about one third of the writing time using it, mainly for editing and brainstorming. Cluster analysis identified three user types: constructive, hybrid, and substitutive, with about one-fifth of students relying heavily on AI text. Higher copying was linked to weaker integrity beliefs, while more revision and clearer policy awareness were linked to stronger ethical views. The study calls for clearer AI policies, process-based assessment, and practical AI literacy training.