> ## Documentation Index
> Fetch the complete documentation index at: https://docs.langstate.com/llms.txt
> Use this file to discover all available pages before exploring further.

# SUP versus MVC

> Compare a state-update-presentation loop with the Model-View-Controller pattern.

<Note>
  **Design note.** This comparison is architectural vocabulary, not a claim that LangState replaces MVC frameworks.
</Note>

SUP and MVC both separate state from presentation, but they emphasize different boundaries.

| Concern             | SUP                                               | MVC                                                    |
| ------------------- | ------------------------------------------------- | ------------------------------------------------------ |
| State               | Explicit artifact shared across turns             | Model containing domain data and behavior              |
| Input handling      | Updater interprets input into state changes       | Controller handles requests and coordinates model/view |
| Output              | Presenter projects current state                  | View renders model data                                |
| Typical loop        | Iterative, possibly uncertain natural interaction | Request/response or event-driven application flow      |
| Key evaluation seam | Expected state transition versus presentation     | Controller/model behavior versus view output           |

SUP can live inside an MVC application. A controller can authenticate a request and invoke an updater; the model or service layer can own canonical persistence; a view can render presenter output. Choose ownership based on the host application rather than forcing a one-to-one class mapping.