LangSmith Deployment, previously known as LangGraph Platform, introduced custom authentication and resource-level access control for Python deployments, enhancing integration with existing authentication systems and providing granular access patterns for LangGraph applications. This new feature allows for the integration of custom authentication providers and role-based access control (RBAC), ensuring that only authorized users can access specific resources within applications. The system utilizes authentication handlers to validate credentials and identify users, while authorization handlers manage access control, embedding metadata in resources to enforce ownership and access restrictions. The platform supports fine-grained control over various operations, such as threads and assistants, enabling the implementation of custom logic for different resource types. Currently, this feature is available for Python deployments, with plans to extend support to JavaScript in the near future. Users are encouraged to explore the available resources, including video tutorials, guides, and reference documentation, to effectively implement custom authentication in their deployments.