<p>This study explores the role of grit, perseverance, and sustained effort in second language writing and examines ChatGPT’s effectiveness in fostering them. Grit, along with positive traits like self-efficacy and motivation, is believed to impact language learning more than other subjects. To reduce language learning anxiety and promote positive emotions, ChatGPT was integrated into L2 writing classes. Using a sequential explanatory mixed-methods design, quantitative data from a single-subject quasi-experimental study were supported by qualitative data from phenomenological interviews. The study was conducted with 20 students learning a foreign language and taking a writing skill development course at a state university. All participants were informed about the study according to the Ethical Guidelines for Educational Research outlined by the British Educational Research Association before starting the application. The quantitative data were analyzed using IBM SPSS 27. The qualitative data were analyzed using MAXQDA. Results indicated quantitatively, no statistically significant mean change was observed in total L2 grit from pre- to posttest (small effect; paired t(19) = 1.13, p = .273; Cohen’s dz=0.25; 95% CI [ − 0.07, 0.24]). Qualitatively, students described clearer writing plans, more iterative revisions, and greater confidence—process indicators consistent with perseverance of effort and sustained interest. Taken together, the intervention appears to support persistence at the process level during writing, yet these gains did not translate into a substantive scale-level increase in overall grit within six weeks and with a small sample (n = 20). Students also reported improvements in writing skills. The study outlines a process-level account of how AI-supported scaffolding may foster persistence in L2 writing and highlights the need for longer-term, higher-powered evaluations.</p>