Kouji Kiyokawa upgraded authentication flows in the cakephp/docs repository by modernizing the Authentication Plugin to version 3.0. He refactored the DefaultPasswordHasher usage to align with the new Authentication\PasswordHasher\DefaultPasswordHasher namespace, ensuring that documentation samples remain compatible with the latest CakePHP standards. This work involved updating the composer constraint from ^2.0 to ^3.0, which streamlines future upgrades and reduces maintenance overhead for downstream projects. Using CakePHP and PHP, Kouji focused on backend development, delivering a targeted feature that addresses evolving security requirements and keeps documentation aligned with current authentication practices. The work was concise and technically focused.