Open Generative UI

Let agents generate fully interactive HTML/CSS/JS UIs that stream live into the chat.

What is this?#

Open Generative UI lets the agent generate complete, sandboxed UI on the fly (HTML, CSS, and JavaScript) and stream it live into the chat. The user sees the interface build in real time: styles apply first, then HTML streams in progressively, and finally JavaScript expressions execute one by one.

Free course: See this pattern built end-to-end in Build Interactive Agents with Generative UI — a free DeepLearning.AI short course taught by CopilotKit's CEO covering the full Generative UI spectrum (Controlled, Declarative, and Open-Ended).

Key benefits:

No predefined components — the agent creates any UI it needs, on demand
Live streaming — HTML streams into a preview as it's generated
CDN libraries — the generated UI can load Chart.js, D3, Three.js, etc. via <script> tags
Secure sandboxing — content runs in an isolated iframe without same-origin access
Sandbox functions — optionally expose host functions to the generated UI for two-way communication

Minimal setup#

Turning on Open Generative UI takes one flag in the runtime plus a plain <CopilotChat /> on the frontend; the built-in activity renderer is auto-registered by CopilotKit, so no extra wiring is needed.

Enable it in the runtime#

Add OpenGenerativeUIMiddleware to your runtime configuration:

route.ts

      runtime: new CopilotRuntime({        // @ts-ignore -- see main route.ts        agents,        openGenerativeUI: {          agents: ["open-gen-ui", "open-gen-ui-advanced"],        },      }),

The OpenGenerativeUIMiddleware then converts the agent's streamed generateSandboxedUi tool call into open-generative-ui activity events, which the built-in OpenGenerativeUIActivityRenderer mounts inside a sandboxed iframe.

Drop `<CopilotChat />` into the page#

Wrap your app in CopilotKit and render <CopilotChat> — no extra props needed:

page.tsx

  // Minimal Open Generative UI frontend: the built-in activity renderer is  // registered by CopilotKitProvider, so a plain <CopilotChat /> is enough —  // no custom tool renderers, no activity-renderer registration.  // We DO pass `openGenerativeUI.designSkill` to swap in visualisation-tuned  // guidance in place of the default shadcn design skill.  return (    <CopilotKit      runtimeUrl="/api/copilotkit-ogui"      agent="open-gen-ui"      openGenerativeUI={{ designSkill: VISUALIZATION_DESIGN_SKILL }}    >      <div className="flex justify-center items-center h-screen w-full">        <div className="h-full w-full max-w-4xl flex flex-col p-3">          <Chat />        </div>      </div>    </CopilotKit>  );

That's it. Ask the agent "build me a simple greeting card" to see HTML stream into a sandboxed preview live.

Advanced: With app tool calling#

Sandbox functions let the generated UI call back into your host application — a generated settings panel can toggle your app's theme, a product card can push items into your cart, or a data view can ask the host to fetch data the iframe can't reach directly.

Runtime is unchanged#

The server-side flag is identical to the minimal cell; the advanced behaviour is a pure frontend addition.

route.ts

      runtime: new CopilotRuntime({        // @ts-ignore -- see main route.ts        agents,        openGenerativeUI: {          agents: ["open-gen-ui", "open-gen-ui-advanced"],        },      }),

Register sandbox functions on the provider#

Each sandbox function is a Zod-validated, host-side bridge the agent can invoke from inside the generated iframe via Websandbox.connection.remote.<name>(args). The handler runs in the host page and its description is appended to the agent's context, so the agent knows which bridges are available when generating HTML/JS.

page.tsx

import React from "react";import {  CopilotKit,  CopilotChat,  useConfigureSuggestions,} from "@copilotkit/react-core/v2";import { openGenUiSandboxFunctions } from "./sandbox-functions";import { openGenUiSuggestions } from "./suggestions";export default function OpenGenUiAdvancedDemo() {  return (    // Pass the sandbox-function array on the `openGenerativeUI` provider prop.    // The built-in `OpenGenerativeUIActivityRenderer` wires these as callable    // remotes inside the agent-authored iframe.    <CopilotKit      runtimeUrl="/api/copilotkit-ogui"      agent="open-gen-ui-advanced"      openGenerativeUI={{ sandboxFunctions: openGenUiSandboxFunctions }}    >      <div className="flex justify-center items-center h-screen w-full">        <div className="h-full w-full max-w-4xl">          <Chat />        </div>      </div>    </CopilotKit>import { z } from "zod";/** * Host-side functions that agent-authored, sandboxed UIs can invoke from * inside the iframe via `Websandbox.connection.remote.<name>(args)`. * * The names, descriptions, and Zod-derived JSON schemas below are injected * into the agent's context so the LLM knows which bridges exist when it * generates HTML/JS. Each handler runs on the HOST page and its return * value is awaited by the in-iframe caller. * * Keep the surface small and obvious — these are the demo's "app-side * tools" that the sandbox-generated UI can call. */export const openGenUiSandboxFunctions = [  {    name: "evaluateExpression",    description:      "Safely evaluate a basic arithmetic expression on the host page and return the numeric result. " +      "Supports +, -, *, /, parentheses, and decimal numbers. " +      "Use this from inside a calculator or spreadsheet UI.",    parameters: z.object({      expression: z        .string()        .describe("An arithmetic expression, e.g. '12 * (3 + 4.5)'"),    }),    handler: async ({ expression }: { expression: string }) => {      // Evaluate only arithmetic-safe expressions. Reject anything with      // identifiers or suspicious characters so we never exec arbitrary JS.      if (!/^[\d+\-*/().\s]+$/.test(expression)) {        return { ok: false, error: "Unsupported characters in expression." };      }      try {        // eslint-disable-next-line no-new-func        const value = Function(`"use strict"; return (${expression});`)();        if (typeof value !== "number" || !Number.isFinite(value)) {          return { ok: false, error: "Not a finite number." };        }        // eslint-disable-next-line no-console        console.log(          "[open-gen-ui/advanced] evaluateExpression",          expression,          "=",          value,        );        return { ok: true, value };      } catch (err) {        return {          ok: false,          error: err instanceof Error ? err.message : String(err),        };      }    },  },  {    name: "notifyHost",    description:      "Send a short notification message from the sandboxed UI to the host page. " +      "The host logs the message and returns a confirmation object.",    parameters: z.object({      message: z.string().describe("A short status message."),    }),    handler: async ({ message }: { message: string }) => {      // eslint-disable-next-line no-console      console.log("[open-gen-ui/advanced] notifyHost:", message);      return { ok: true, receivedAt: new Date().toISOString(), message };    },  },];

How the sandbox calls you back

Inside the generated UI, the agent writes JS that calls await Websandbox.connection.remote.notifyHost({ message: "hi" }). The call is proxied back to the host page, where your handler runs with the validated args.

Common use cases#

Theme toggling — generated UI controls your app's appearance
Cart / state management — product cards push items into host state
Navigation — generated UI triggers route changes in the host app
Data fetching — sandbox asks the host to fetch data the iframe can't reach directly

How streaming works#

The agent generates the tool call's parameters in an order optimized for the user experience:

placeholderMessages — shown immediately while generating
css — all styles first; the preview starts once CSS is complete
html — streams live into the preview as it's generated
jsFunctions — reusable helpers injected before expressions
jsExpressions — executed one by one; the user sees each take effect

The middleware parses the tool-call arguments incrementally and emits activity events as each parameter completes, so the preview updates progressively.

Using CDN libraries#

The sandboxed iframe can load external libraries from CDNs; just include <script> or <link> tags in the generated HTML <head>. Chart.js, D3, Three.js, and any other CDN-hosted library work out of the box.

<head>
  <script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
</head>
<body>
  <canvas id="myChart"></canvas>
</body>