Developed an extension hook for the LightningCLI in the Lightning-AI/pytorch-lightning repository, enabling a post-instantiation extension point for user customization and plugin workflows. Focused on CLI development and software design patterns, the work introduced the after_instantiate_classes hook, allowing users to modify or extend class initialization behavior without altering core logic. The implementation was aligned with an existing CLI enhancement proposal to ensure traceability and facilitate future extensibility. Using Python, the developer concentrated on architectural improvements rather than bug fixes, laying a foundation for more flexible plugin-based configurations and advanced user workflows within the LightningCLI ecosystem.