Worked on stabilizing authentication flows in the keycloak/keycloak repository by addressing a critical bug related to realm session limits. Using Java and backend development skills, implemented logic to clamp negative session calculations to zero, preventing server crashes and 500 errors when session limits were exceeded during login. Enhanced reliability by adding a dedicated regression test to ensure the issue could not recur, covering scenarios involving realm limits, client limits, and cross-client sessions. Focused on robust testing practices to reduce authentication-related incidents in production, ultimately improving user login reliability and maintaining system stability during periods of high usage.