Worked on the nextcloud/user_oidc repository to enhance the reliability of the OIDC logout process by addressing a bug in backchannel logout token validation. Focused on backend development using PHP, the solution involved updating the validation logic to account for cases where the 'sub' claim is missing from logout tokens, as permitted by the OIDC specification. This adjustment improved compatibility with OAuth providers that omit the 'sub' claim, reducing logout failures and ensuring smoother session termination for enterprise users. The work demonstrated careful defensive coding and contributed to the maintainability and interoperability of authentication and logout flows within the codebase.