You spent six months building the perfect dashboard. You agonized over the information architecture. You debated the color of the “Export” button. You optimized the load time of the Analytics tab.
And nobody uses it.
They log in. They ignore your navigation. They go straight to the little sparkle icon in the bottom right corner and type: “Show me Q3 revenue compared to last year.”
The user doesn’t want your interface. They want your data. And in 2026, the interface is just an obstacle between them and the answer.
The Navigation Tax
For the last decade, SaaS was built on a premise: The Developer predicts the User’s intent. We built “User Flows.” We assumed: First they click here, then they filter by date, then they sort by price.
But User Flows are a tax. They force the user to translate their goal (“I want to see risky accounts”) into your language (“Click Users -> Filter -> Risk > 50”).
AI Agents broke this model. Agents don’t navigate. They act. And now, with the rise of Generative UI (GenUI), they don’t just return text. They return the screen.
The Rise of Vercel’s “Component Streaming”
Tools like Vercel’s AI SDK introduced a radical concept: Streaming Component Systems.
The LLM doesn’t just output markdown. It outputs a function call: renderFlightCard({ flightId: '123' }).
The frontend intercepts this and renders a fully interactive React component.
This is magic. It means the UI is no longer “Static Layout.” The UI is “Just-in-Time.”
- If the user asks for data, render a Table.
- If the user asks for a trend, render a Chart.
- If the user asks to cancel, render a Confirmation Modal.
The “Dashboard” is gone. The application is now a blank canvas that the Agent paints on demand.
The Hallucinated Interface
But there is a catch. When you let an Agent build the UI, you are ceding control of your Brand and your UX to a probabilistic model.
I saw this firsthand last week. A fintech startup deployed a GenUI assistant. I asked it: “How do I delete my account?”
The agent didn’t send me a link to the settings page.
It hallucinated a Red Button right there in the chat.
It labeled it “Nuke It”.
And it bound the onClick handler to… nothing. It was a dead button.
This is the nightmare of GenUI.
- Visual Hallucination: The agent invents components that don’t exist in your Design System.
- Functional Hallucination: The agent renders a real component but feeds it garbage props.
- Brand Suicide: The agent renders your “Premium” feature in “Error State” red.
You Can’t Snapshot a Ghost
How do you test this? Cypress and Playwright are designed for Static Routes.
- “Go to
/dashboard. Check if#headerexists.”
But in GenUI, /dashboard doesn’t exist. The UI is ephemeral. It exists only for that specific user, for that specific prompt, at that specific second.
You cannot snapshot test a ghost.
The Generative Sandbox
To survive the shift to GenUI, we need a new kind of verification. We need Component Sandboxing for Agents.
This is the newest pattern we see on PrevHQ. Engineering teams are treating their Agents as “Junior Frontend Developers.”
Before the Agent is allowed to render UI to a user, it must pass the Registry Exam.
- The Prompt: We feed the agent a scenario. “User wants to upgrade plan.”
- The Render: The agent generates the JSON tree for the UI.
- The PrevHQ Sandbox: We instantly hydrate this JSON into a real React runtime in an isolated environment.
- The Check: We run visual assertions.
- Does it use a component from the official registry? (Pass)
- Are the props valid types? (Pass)
- Does the button actually link to a valid route? (Pass)
Constraint is Freedom
The goal isn’t to stop the agent from building UI. It’s to give it LEGOs, not Clay.
By forcing the agent to build within a sandboxed, verified environment, you get the best of both worlds. You get the magic of a “Just-in-Time” interface. But you get the reliability of a Static App.
The Dashboard is dead. Long live the ephemeral interface. Just make sure you verify it before it renders.
FAQ: Testing Generative UI Components
Q: What is Generative UI (GenUI)?
A: UI created at runtime. Instead of developers building static pages, an AI Agent chooses which UI components (Charts, Forms, Buttons) to show the user based on their specific query. The UI is “generated” on the fly.
Q: How do I test generative UI?
A: Runtime Schema Validation. You cannot use static snapshots. You must intercept the agent’s output (usually JSON) and validate it against a strict schema (e.g., Zod) to ensure it matches your Component Registry’s expected props. Then, render it in a sandbox (like PrevHQ) to check for visual regressions.
Q: Does this replace my Design System?
A: No, it enforces it. GenUI relies heavily on a robust Design System. The Agent needs a “Menu” of pre-built, accessible components to choose from. If your Design System is weak, the Agent will hallucinate broken UI.
Q: What tools support GenUI?
A: Vercel AI SDK is the leader. Its streamUI and useObject hooks allow you to stream structured component data from LLMs directly to the frontend. PrevHQ integrates with these workflows to provide a preview environment for the generated output.