Worked on the apache/logging-log4j2 repository to address a concurrency issue in the ThrowableStackTraceRenderer component. Focused on resolving a concurrency-induced ArrayIndexOutOfBoundsException by capturing stack trace elements at the point of metadata creation, thereby preventing runtime modifications during stack trace rendering. Applied Java concurrency and exception handling techniques to ensure thread safety and maintain binary compatibility. Enhanced the reliability of logging in high-concurrency environments by adding targeted regression tests that simulate concurrent mutation scenarios. The work emphasized robust unit testing and careful logging practices, ultimately reducing the risk of runtime failures for users relying on log4j2 in production systems.