Worked on the spring-authorization-server repository to deliver an enhancement to the OAuth2 refresh token flow using Java and Spring Security. The update involved modifying the refresh token generator to accept the newly issued access token, allowing each refresh token to be directly linked to its corresponding access token. This approach ensured that updated authorization details were persisted after token generation, reducing the risk of token drift and improving the reliability of client refresh operations. Focused on authentication and OAuth2 protocols, the work reinforced security best practices and contributed to maintaining accurate token lifecycles across distributed services without addressing major bug fixes.