openui-forge-vercel

name	openui-forge-vercel
description	OpenUI generative UI with Vercel AI SDK. streamText, toUIMessageStreamResponse, and tools support.
version	1.0.0
author	OthmanAdi

OpenUI Forge — Vercel AI SDK

Build generative UI apps with OpenUI + Vercel AI SDK. Native streaming with streamText and toUIMessageStreamResponse().

Activation Triggers

• "openui vercel", "openui vercel ai", "openui ai sdk"
• "generative ui vercel", "vercel ai streaming ui"
• "useChat openui", "streamText openui"

Prerequisites

• Node.js >= 18, React >= 18.3.1 (19+ recommended)
• OPENAI_API_KEY environment variable set
• Next.js project (App Router)

Quick Start

1. Install dependencies:

npm install @openuidev/react-ui @openuidev/react-headless @openuidev/react-lang lucide-react zod ai @ai-sdk/openai

2. Add the CSS import to app/layout.tsx:

import "@openuidev/react-ui/components.css";

3. Create the API route and frontend page below
4. Run npm run dev and test

Full Code

Backend: app/api/chat/route.ts

import { openuiChatLibrary } from "@openuidev/react-ui/genui-lib";
import { streamText } from "ai";
import { openai } from "@ai-sdk/openai";

export async function POST(req: Request) {
  const { messages } = await req.json();

  const systemPrompt = openuiChatLibrary.prompt({
    preamble: "You are a helpful assistant that generates interactive UIs.",
    additionalRules: ["Always use Stack as root when combining multiple components."],
  });

  const result = streamText({
    model: openai(process.env.OPENAI_MODEL ?? "gpt-5.5"),
    system: systemPrompt,
    messages,
  });

  return result.toUIMessageStreamResponse();
}

Backend with Tools: app/api/chat/route.ts

import { openuiChatLibrary } from "@openuidev/react-ui/genui-lib";
import { streamText, tool, stepCountIs } from "ai";
import { openai } from "@ai-sdk/openai";
import { z } from "zod";

export async function POST(req: Request) {
  const { messages } = await req.json();

  const systemPrompt = openuiChatLibrary.prompt({
    preamble: "You are a helpful assistant that generates interactive UIs. Use tools to fetch data before rendering.",
  });

  const result = streamText({
    model: openai(process.env.OPENAI_MODEL ?? "gpt-5.5"),
    system: systemPrompt,
    messages,
    tools: {
      getWeather: tool({
        description: "Get current weather for a city",
        inputSchema: z.object({
          city: z.string().describe("City name"),
        }),
        execute: async ({ city }) => {
          return { city, temp: 22, condition: "sunny" };
        },
      }),
    },
    // AI SDK v5+: stopWhen replaces the removed `maxSteps` option.
    stopWhen: stepCountIs(3),
  });

  return result.toUIMessageStreamResponse();
}

Frontend (with processMessage): app/chat/page.tsx

"use client";
import { FullScreen } from "@openuidev/react-ui";
import { openuiChatLibrary } from "@openuidev/react-ui/genui-lib";

async function processMessage(messages: { role: string; content: string }[]) {
  const res = await fetch("/api/chat", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ messages }),
  });
  if (!res.body) throw new Error("No response body");
  return res.body;
}

export default function ChatPage() {
  return (
    <FullScreen
      componentLibrary={openuiChatLibrary}
      processMessage={processMessage}
    />
  );
}

Component Creation

import { defineComponent } from "@openuidev/react-lang";
import { z } from "zod";

export const WeatherCard = defineComponent({
  name: "WeatherCard",
  description: "Displays weather information for a location",
  props: z.object({
    city: z.string().describe("City name"),
    temp: z.number().describe("Temperature in Celsius"),
    condition: z.enum(["sunny", "cloudy", "rainy", "snowy"]).describe("Weather condition"),
  }),
  component: ({ props }) => (
    <div style={{ padding: 16, borderRadius: 12, background: "#f0f9ff" }}>
      <h3>{props.city}</h3>
      <div style={{ fontSize: 32 }}>{props.temp}C</div>
      <div>{props.condition}</div>
    </div>
  ),
});

System Prompt Generation

npx @openuidev/cli generate ./src/lib/library.ts --out src/generated/system-prompt.txt

Or at runtime via openuiChatLibrary.prompt() as shown in the route.

Validation Checklist

• OPENAI_API_KEY is set in .env.local
• ai and @ai-sdk/openai packages installed
• Route uses streamText and returns result.toUIMessageStreamResponse()
• Frontend uses processMessage returning response.body (the Vercel AI SDK stream is consumed natively, no streamProtocol needed)
• componentLibrary={openuiChatLibrary} prop passed to FullScreen
• CSS import in root layout
• If using tools: stopWhen: stepCountIs(n) is set (AI SDK v5+ replacement for the removed maxSteps), tool results feed back to model
• Tools declared with inputSchema: (v5+ rename of parameters:)

Error Patterns

Error	Cause	Fix
ai module not found	Missing Vercel AI SDK	npm install ai @ai-sdk/openai
Stream format mismatch	Trying to use openAIReadableStreamAdapter with Vercel AI's UI message stream	Drop streamProtocol. Use processMessage returning response.body — the AI SDK stream is consumed natively
Type error on maxSteps	maxSteps removed in AI SDK v5+	Import stepCountIs from ai and use stopWhen: stepCountIs(3)
Type error on tool parameters	Renamed to inputSchema in AI SDK v5+	Rename parameters: to inputSchema: in every tool({...}) definition
Blank response	Wrong export from @ai-sdk/openai	Use openai("gpt-5.5") not new OpenAI()
Props silently ignored	Passing messages/onSend/isLoading props to FullScreen	FullScreen does not accept these — use processMessage instead