Worked on stabilizing Firestore-backed session persistence in the google/adk-python repository by addressing a crash caused by temporary or non-serializable state keys. The solution involved filtering out temporary keys from Firestore writes, ensuring that only valid session data is persisted and aligning Firestore’s behavior with other delta-based backends. This approach reinforced data integrity across multi-tool sessions and prevented future crashes related to invalid state data. The work was implemented using Python and focused on backend development, Firestore integration, and unit testing. A dedicated test was added to verify that temporary state keys are excluded from persistence, improving overall session reliability.