Thank you for the excellent questions!
On cross-vendor standardization: Based on current adoption, AG-UI is evolving toward broader standardization. The protocol now has integrations across multiple major frameworks - Microsoft Agent Framework (Python & .NET), LangGraph, CrewAI, Google ADK, Pydantic AI, and others - as well as frontend platforms like CopilotKit. It's moving beyond a framework-driven approach toward becoming a shared standard.
On versioning: The event-based architecture provides natural extension points - new event types can be added without breaking existing clients (they ignore unknown events), and payloads can be versioned independently. As adoption grows, the protocol would benefit from explicit versioning semantics similar to OpenAPI's evolution.