During April 2026, Petr Marinec focused on security hardening for the google/adk-python repository, addressing a vulnerability in the Vertex AI Session Service. He implemented a Python-based solution that quotes and escapes user_id literals in list filters, mitigating injection risks and improving backend reliability. Petr developed a reusable helper function for safe filter construction and expanded unit test coverage to validate handling of special characters. His work emphasized backend development, API integration, and security, prioritizing risk reduction and maintainability over new features. The depth of his contribution strengthened the repository’s security posture and ensured robust, reliable integration with Vertex AI.