Worked on the envoyproxy/envoy repository, focusing on backend development and API stability using C++. Addressed a critical race condition in the OAuth2 filter that could result in a use-after-free crash when asynchronous token change callbacks occurred after filter teardown. The solution involved canceling the token client during filter destruction, effectively preventing dangling-pointer access and aligning the fix with CVE-2026-48090. This work required a deep understanding of asynchronous programming and memory management in C++. No new features were added during this period, but the targeted bug fix improved the security and reliability of the OAuth2 authentication flow.