This session presents a design-based research (DBR) study of an AI-integrated financial literacy project in required EFL classes at a Japanese university. In the initial 2025 design cycle, students learned the basics of financial planning through a case-study approach. The initial instruction was technology-free, but students were granted unrestricted access to AI tools for the final task. Although pre- and post-survey data showed improvements in financial knowledge, behavior, and attitudes, classroom observation revealed that many students were reproducing AI-generated content without critical reflection. In response, the 2026 design cycle will include a gated AI model utilizing the PAIR framework (Prompt, Assess, Iterate, Reflect) and Task-Based Language Learning. During the pre-task phase, students will develop content and target language knowledge through a guided case study. AI is then introduced as a mediated learning tool to evaluate, revise, and justify its use in additional case studies that students will complete in small groups. This session shows how a DBR approach can support the structured integration of AI in EFL contexts to promote language development, critical thinking, and technological literacy.