Constant KEY_PREFIX_APP 

pub const KEY_PREFIX_APP: &'static str;

Core traits and types.

Always available regardless of feature flags. Includes:

• Agent - The fundamental trait for all agents
• Tool / Toolset - For extending agents with capabilities
• Session / State - For managing conversation context
• Event - For streaming agent responses
• AdkError / Result - Unified error handling Key prefix for application-scoped state (persists across sessions).