Profile

I am a PhD student in the Laboratory for Software Design and Analysis at Nara Institute of Science and Technology (NAIST). I study software quality assurance in the AI era, with a focus on refactoring and bug prediction.

Supported by NAIST Granite-AI, I investigate bug prediction in the AI era. My ACT-X project, starting in October 2026, will build on this work to develop a quality assurance framework for AI-generated tests. These complementary sources of support enable me to establish my research environment and share findings internationally.

From August 2026 to August 2027, I am a Visiting Research Student at Queen’s University, SAIL & MCIS Lab, in Canada.

Research Funding

JST ACT-X — Selected in FY2026

Project: AI駆動開発を支えるテスト品質保証基盤の創出
English translation: Establishing a Test Quality Assurance Foundation for AI-Driven Development
Research area: Cyberinfrastructure for AI Empowered Society
Period: October 2026–March 2029 (scheduled)
Selection announcement · JST selected projects (Japanese)

NAIST Granite-AI (JST BOOST)

NAIST’s program supporting innovative doctoral students in next-generation AI (NAIST Granite-AI)
Project: AIエージェント協働時代における品質保証基盤の構築
English translation: Building a Quality Assurance Foundation for the Era of Collaboration with AI Agents
Funding program: JST BOOST (JPMJBS2423)
Period: April 2026–March 2029
Research funding: JPY 900,000 per year
Program details (Japanese)

Major Publications

First Author

Peer-Reviewed International Journal Articles

• Agentic Refactoring: An Empirical Study of AI Coding Agents
  Kosei Horikawa, Hao Li, Yutaro Kashiwa, Bram Adams, Hajimu Iida, Ahmed E. Hassan
  ACM Transactions on Software Engineering and Methodology (TOSEM), 2026. Just Accepted. [Q1, IF6.2]

Peer-Reviewed Conference Papers

• How Does Test Code Differ From Production Code in Terms of Refactoring? An Empirical Study
  Kosei Horikawa, Yutaro Kashiwa, Bin Lin, Kenji Fujiwara, Hajimu Iida
  The 41st International Conference on Software Maintenance and Evolution (ICSME 2025 NIER Track). [CORE A]

Co-author

Peer-Reviewed Conference Papers

• Is Self-Admitted Technical Debt Tested? An Empirical Study of Coverage, Co-change, and Impact
  Suzuka Yoshimoto, Kosei Horikawa, Daniel Feitosa, Yutaro Kashiwa, Hajimu Iida
  The 20th ACM/IEEE International Symposium on Empirical Software Engineering and Measurement (ESEM 2026, Technical Track), 2026. Accepted. [CORE A]

• What Are Developers Actually Discussing When Visual Regression Tests Fail?
  Miku Watanabe, Kosei Horikawa, Brittany Reid, Yutaro Kashiwa, Hajimu Iida
  The 42nd IEEE International Conference on Software Maintenance and Evolution (ICSME 2026, Visions and Emerging Results Track), 2026. [CORE A]

• Do AI Agents Really Improve Code Readability?
  Kyogo Horikawa, Kosei Horikawa, Yutaro Kashiwa, Hidetake Uwano, Hajimu Iida
  The 23rd International Conference on Mining Software Repositories (MSR 2026 Mining Challenge Track). [CORE A]

• Testing with AI Agents: An Empirical Study of Test Generation Frequency, Quality, and Coverage
  Suzuka Yoshimoto, Shun Fujita, Kosei Horikawa, Daniel Feitosa, Yutaro Kashiwa, Hajimu Iida
  The 23rd International Conference on Mining Software Repositories (MSR 2026 Mining Challenge Track). [CORE A]

• An Empirical Investigation into Maintenance of Load Testing Scripts
  Ibuki Nakamura, Kosei Horikawa, Brittany Reid, Yutaro Kashiwa, Hajimu Iida
  The ACM/IEEE International Symposium on Empirical Software Engineering and Measurement (ESEM 2025 ERVT Track). [CORE A]

Preprints

• AgentLogs: A Dataset for Opening the Black Box of GitHub’s Cloud Agent
  Jonan Richards, Kosei Horikawa, Youmei Fan, Yutaro Kashiwa, Mairieli Wessel
  arXiv preprint arXiv:2608.29204, 2026.

Awards

• Best International Poster Award — Software Engineering Symposium (SES 2025)
  Presentation: Understanding Refactoring in Test Code: An Empirical Study
  Lab news

Education

• April 2026–Present: PhD Program, Graduate School of Science and Technology, NAIST
• April 2024–March 2026: Master’s Program, Graduate School of Science and Technology, NAIST (Master of Engineering)
• Completed in 2024: Advanced Course in Systems Innovation Engineering, Information Systems Course, NIT, Nara College
• Graduated in 2022: Department of Information Engineering, NIT, Nara College

International Research Experience

• August 2026–August 2027: Visiting Research Student, Queen’s University, SAIL & MCIS Lab, Canada
• September–November 2025: Visiting Student, Queen’s University, SAIL & MCIS Lab, Canada
• June–July 2025: Visiting Student, Hangzhou Dianzi University, China
• September–November 2024: Visiting Student, Radboud University, Netherlands

Industry Experience

• March–April 2025: Part-time QA Engineer, Recruit Co., Ltd.
• November–December 2024: QA Engineer Intern, Recruit Co., Ltd.

Outside Research

I enjoy basketball, reading, and traveling.