The key idea:
Do not put reusable business capability logic inside the interface.
Build the backend AI assistant capability once.
Then expose it through the right interface: web app, Teams, Power Apps, chatbot, workflow automation, API, mobile app, or future agent.
That gives you consistency, security, governance, testability, reuse, maintainability, and scalability.
The chat window is not the architecture.
The backend capability is the asset.