What is generative UI, and how do you add it to an app you already have?
Published 13 October 2026
Generative UI is an interface the AI puts together for each request: someone asks a question, and the answer comes back as real components, such as a chart, a form or an order tracker, filled with their own data. Rendel is a Generative UI SDK for Flutter and web apps that does this inside the app you already have.
From a reply to a screen
A chatbot answers “where did my money go this month?” with a paragraph. A generative interface answers with the spending chart and the three largest payments, drawn in the app's own style, with a button to set a budget.
The model does not draw anything itself. It chooses which components to show and with what data, and the app draws them. That is what keeps the answer looking like the rest of the product.
Three ways to build it
Teams usually choose between letting the model write markup, sending a description that a renderer turns into components, or picking from a fixed catalog of components the app already knows how to draw.
| Approach | What the model sends | What to watch |
|---|---|---|
| Generated markup or code | HTML or code, written per answer | Hard to keep on brand, and hard to review what will run |
| An open render protocol | A description of a layout, drawn by a renderer you host | You build and maintain the renderer, the actions and the safety around them |
| A component catalog | The name of a component and its data | Only as rich as the catalog; Rendel's is drawn natively and included on every plan |
What it needs in a real app
Showing a screen is the easy half. In a bank or a shop, people want the assistant to do things: freeze a card, return an item, move money. That needs your app's own actions behind the components, and a rule for when something is allowed to change.
In Rendel, reads run at once and every change waits for a confirmation card that Rendel's server builds from your action, never from the model's wording. The action runs with the signed-in user's own token, so your API's checks still decide.
Native, and never a component an old build cannot draw
Every component is drawn by Flutter or by your web page itself; nothing is a web view. Each build of your app tells Rendel which components it can draw, and the model is only offered those, so an older version never receives a screen it cannot show.
Questions
Is generative UI the same as a chatbot?
No. A chatbot answers in text. Generative UI answers with components built for the request, filled with the person's own data, and can be paired with actions that do the task.
Does the model see my users' data?
It sees your actions' names, descriptions and parameter types, the app state you choose to pass, and the conversation. Emails and card numbers that users type are masked before the model sees them.
Which platforms does Rendel support?
Flutter and the web today. Swift, Kotlin and React Native are planned and not shipped.