AI SDK UI - Frontend React Hooks

Frontend React hooks for AI-powered user interfaces with Vercel AI SDK v5.

Version: AI SDK v5.0.116 (Stable) Framework: React 18+, Next.js 15+ Last Updated: 2025-12-22

Table of Contents

1. Quick Start
2. When to Load References
3. useChat Hook
4. useCompletion Hook
5. useObject Hook
6. Next.js Integration
7. Top UI Errors & Solutions
8. Streaming Best Practices
9. When to Use This Skill
10. Package Versions

---

Quick Start (5 Minutes)

Installation

bun add ai @ai-sdk/openai  # preferred
# or: bun add ai @ai-sdk/openai

Basic Chat Component (v5)

// app/chat/page.tsx
'use client';
import { useChat } from 'ai/react';
import { useState, FormEvent } from 'react';

export default function Chat() {
  const { messages, sendMessage, isLoading } = useChat({
    api: '/api/chat',
  });
  const [input, setInput] = useState('');

  const handleSubmit = (e: FormEvent) => {
    e.preventDefault();
    sendMessage({ content: input });
    setInput('');
  };

  return (
    <div>
      <div>
        {messages.map(m => (
          <div key={m.id}>
            <strong>{m.role}:</strong> {m.content}
          </div>
        ))}
      </div>
      <form onSubmit={handleSubmit}>
        <input
          value={input}
          onChange={(e) => setInput(e.target.value)}
          placeholder="Type a message..."
          disabled={isLoading}
        />
      </form>
    </div>
  );
}

API Route (Next.js App Router)

// app/api/chat/route.ts
import { streamText } from 'ai';
import { openai } from '@ai-sdk/openai';

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

  const result = streamText({
    model: openai('gpt-4-turbo'),
    messages,
  });

  return result.toDataStreamResponse();
}

Result: A functional chat interface with streaming AI responses in ~10 lines of frontend code.

---

When to Load References

For detailed implementation guides, API references, and advanced patterns, load the following reference files:

Reference File	Load When...
references/use-chat-migration.md	Migrating from v4 to v5, understanding breaking changes
references/streaming-patterns.md	UI streaming best practices, performance optimization
references/top-ui-errors.md	Debugging common UI errors, error prevention
references/nextjs-integration.md	Next.js setup patterns, App vs Pages Router differences
references/links-to-official-docs.md	Finding official Vercel AI SDK documentation
references/tool-calling-ui.md	Implementing tool/function calling in chat UI
references/file-attachments-guide.md	Adding file upload/attachment support to chat
references/message-persistence.md	Persisting chat history with localStorage
references/use-completion-full-reference.md	Complete useCompletion API and examples
references/use-object-full-reference.md	Complete useObject API with Zod schemas
references/nextjs-app-router-full.md	Full Next.js App Router implementation
references/nextjs-pages-router-full.md	Full Next.js Pages Router implementation

---

useChat Hook - Complete Reference

Basic Usage (v5 Pattern)

'use client';
import { useChat } from 'ai/react';
import { useState, FormEvent } from 'react';

export default function ChatComponent() {
  const { messages, sendMessage, isLoading, error } = useChat({
    api: '/api/chat',
  });
  const [input, setInput] = useState('');

  const handleSubmit = (e: FormEvent) => {
    e.preventDefault();
    if (!input.trim()) return;

    sendMessage({ content: input });
    setInput('');
  };

  return (
    <div className="flex flex-col h-screen">
      {/* Messages */}
      <div className="flex-1 overflow-y-auto p-4">
        {messages.map(message => (
          <div
            key={message.id}
            className={message.role === 'user' ? 'text-right' : 'text-left'}
          >
            <div className="inline-block p-2 rounded bg-gray-100">
              {message.content}
            </div>
          </div>
        ))}
        {isLoading && <div className="text-gray-500">AI is thinking...</div>}
      </div>

      {/* Input */}
      <form onSubmit={handleSubmit} className="p-4 border-t">
        <input
          value={input}
          onChange={(e) => setInput(e.target.value)}
          placeholder="Type a message..."
          disabled={isLoading}
          className="w-full p-2 border rounded"
        />
      </form>

      {/* Error */}
      {error && <div className="text-red-500 p-4">{error.message}</div>}
    </div>
  );
}

Full API Reference

const {
  // Messages
  messages,           // Message[] - Chat history
  setMessages,        // (messages: Message[]) => void - Update messages

  // Actions
  sendMessage,        // (message: { content: string }) => void - Send message (v5)
  reload,             // () => void - Reload last response
  stop,               // () => void - Stop current generation

  // State
  isLoading,          // boolean - Is AI responding?
  error,              // Error | undefined - Error if any

  // Data
  data,               // any[] - Custom data from stream
  metadata,           // object - Response metadata
} = useChat({
  // Required
  api: '/api/chat',   // API endpoint

  // Optional
  id: 'chat-1',       // Chat ID for persistence
  initialMessages: [], // Initial messages (controlled mode)

  // Callbacks
  onFinish: (message, options) => {},  // Called when response completes
  onError: (error) => {},              // Called on error

  // Configuration
  headers: {},        // Custom headers
  body: {},           // Additional body data
  credentials: 'same-origin', // Fetch credentials

  // Streaming
  streamProtocol: 'data', // 'data' | 'text' (default: 'data')
});

v4 → v5 Breaking Changes

CRITICAL: useChat no longer manages input state in v5!

v4 (OLD - DON'T USE):

const { messages, input, handleInputChange, handleSubmit, append } = useChat();

<form onSubmit={handleSubmit}>
  <input value={input} onChange={handleInputChange} />
</form>

v5 (NEW - CORRECT):

const { messages, sendMessage } = useChat();
const [input, setInput] = useState('');

<form onSubmit={(e) => {
  e.preventDefault();
  sendMessage({ content: input });
  setInput('');
}}>
  <input value={input} onChange={(e) => setInput(e.target.value)} />
</form>

Summary of v5 Changes:

1. Input management removed: input, handleInputChange, handleSubmit no longer exist
2. append() → sendMessage(): New method for sending messages
3. onResponse removed: Use onFinish instead
4. initialMessages → controlled mode: Use messages prop for full control
5. maxSteps removed: Handle on server-side only

See references/use-chat-migration.md for complete migration guide.

Advanced Features: useChat supports tool calling (display message.toolInvocations), file attachments (experimental_attachments), and message persistence (localStorage with id + initialMessages). See official docs for implementation examples.

---

useCompletion & useObject Hooks

useCompletion: For single-prompt completions (not multi-turn chat). Returns { completion, complete, isLoading }. Call complete(prompt) to generate. API route uses streamText().

useObject: Stream structured JSON with live updates using Zod schemas. Returns { object, submit, isLoading } where object is Partial<T> that updates progressively. API route uses streamObject().

See official docs for complete API references and examples.

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Next.js Integration

Complete working examples for both App Router and Pages Router with full chat UI components, API routes, and proper streaming setup.

📖 Load references/nextjs-integration.md for complete implementation code including:

• App Router: Full chat page with auto-scroll, loading states, error handling, and API route
• Pages Router: Complete chat implementation with proper streaming setup
• Key Differences: toDataStreamResponse() vs pipeDataStreamToResponse()

---

Top UI Errors & Solutions

See references/top-ui-errors.md for complete documentation. Quick reference:

1. useChat Failed to Parse Stream

Error: SyntaxError: Unexpected token in JSON at position X

Cause: API route not returning proper stream format.

Solution:

// ✅ CORRECT
return result.toDataStreamResponse();

// ❌ WRONG
return new Response(result.textStream);

2. useChat No Response

Cause: API route not streaming correctly.

Solution:

// App Router - use toDataStreamResponse()
export async function POST(req: Request) {
  const result = streamText({ /* ... */ });
  return result.toDataStreamResponse(); // ✅
}

// Pages Router - use pipeDataStreamToResponse()
export default async function handler(req, res) {
  const result = streamText({ /* ... */ });
  return result.pipeDataStreamToResponse(res); // ✅
}

3. Streaming Not Working When Deployed

Cause: Deployment platform buffering responses.

Solution: Vercel auto-detects streaming. Other platforms may need configuration.

4. Stale Body Values with useChat

Cause: body option captured at first render only.

Solution:

// ❌ WRONG - body captured once
const { userId } = useUser();
const { messages } = useChat({
  body: { userId },  // Stale!
});

// ✅ CORRECT - use controlled mode
const { userId } = useUser();
const { messages, sendMessage } = useChat();

sendMessage({
  content: input,
  data: { userId },  // Fresh on each send
});

5. React Maximum Update Depth

Cause: Infinite loop in useEffect.

Solution:

// ❌ WRONG
useEffect(() => {
  saveMessages(messages);
}, [messages, saveMessages]); // saveMessages triggers re-render!

// ✅ CORRECT
useEffect(() => {
  saveMessages(messages);
}, [messages]); // Only depend on messages

See references/top-ui-errors.md for 7 more common errors.

---

Streaming Best Practices

Performance

Always use streaming for better UX:

// ✅ GOOD - Streaming (shows tokens as they arrive)
const { messages } = useChat({ api: '/api/chat' });

// ❌ BAD - Non-streaming (user waits for full response)
const response = await fetch('/api/chat', { method: 'POST' });

UX Patterns

Show loading states:

{isLoading && <div>AI is typing...</div>}

Provide stop button:

{isLoading && <button onClick={stop}>Stop</button>}

Auto-scroll to latest message:

useEffect(() => {
  messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
}, [messages]);

Disable input while loading:

<input disabled={isLoading} />

See references/streaming-patterns.md for comprehensive best practices.

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When to Use This Skill

Use ai-sdk-ui When:

• Building React chat interfaces
• Implementing AI completions in UI
• Streaming AI responses to frontend
• Building Next.js AI applications
• Handling chat message state
• Displaying tool calls in UI
• Managing file attachments with AI
• Migrating from v4 to v5 (UI hooks)
• Encountering useChat/useCompletion errors

Don't Use When:

• Need backend AI functionality → Use ai-sdk-core instead
• Building non-React frontends (Svelte, Vue) → Check official docs
• Need Generative UI / RSC → See https://ai-sdk.dev/docs/ai-sdk-rsc
• Building native apps → Different SDK required

Related Skills:

• ai-sdk-core - Backend text generation, structured output, tools, agents
• Compose both for full-stack AI applications

---

Package Versions

Required:

{
  "dependencies": {
    "ai": "^5.0.116",
    "@ai-sdk/openai": "^2.0.88",
    "react": "^18.2.0",
    "zod": "^3.23.8",
    "isomorphic-dompurify": "^2.16.0"
  }
}

Next.js:

{
  "dependencies": {
    "next": "^14.0.0",
    "react": "^18.2.0",
    "react-dom": "^18.2.0"
  }
}

Version Notes:

• AI SDK v5.0.116+ (stable)
• React 18+ (React 19 supported)
• Next.js 14+ recommended (13.4+ works)
• Zod 3.23.8+ for schema validation

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Links to Official Documentation

Core UI Hooks:

• AI SDK UI Overview: https://ai-sdk.dev/docs/ai-sdk-ui/overview
• useChat: https://ai-sdk.dev/docs/ai-sdk-ui/chatbot
• useCompletion: https://ai-sdk.dev/docs/ai-sdk-ui/completion
• useObject: https://ai-sdk.dev/docs/ai-sdk-ui/object-generation

Advanced Topics (Link Only):

• Generative UI (RSC): https://ai-sdk.dev/docs/ai-sdk-rsc/overview
• Stream Protocols: https://ai-sdk.dev/docs/ai-sdk-ui/stream-protocols
• Message Metadata: https://ai-sdk.dev/docs/ai-sdk-ui/message-metadata

Next.js Integration:

• Next.js App Router: https://ai-sdk.dev/docs/getting-started/nextjs-app-router
• Next.js Pages Router: https://ai-sdk.dev/docs/getting-started/nextjs-pages-router

Migration & Troubleshooting:

• v4→v5 Migration: https://ai-sdk.dev/docs/migration-guides/migration-guide-5-0
• Troubleshooting: https://ai-sdk.dev/docs/troubleshooting
• Common Issues: https://ai-sdk.dev/docs/troubleshooting/common-issues

Vercel Deployment:

• Vercel Functions: https://vercel.com/docs/functions
• Streaming on Vercel: https://vercel.com/docs/functions/streaming

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Templates

This skill includes the following templates in templates/:

1. use-chat-basic.tsx - Basic chat with manual input (v5 pattern)
2. use-chat-tools.tsx - Chat with tool calling UI rendering
3. use-chat-attachments.tsx - File attachments support
4. use-completion-basic.tsx - Basic text completion
5. use-object-streaming.tsx - Streaming structured data
6. nextjs-chat-app-router.tsx - Next.js App Router complete example
7. nextjs-chat-pages-router.tsx - Next.js Pages Router complete example
8. nextjs-api-route.ts - API route for both App and Pages Router
9. message-persistence.tsx - Save/load chat history
10. custom-message-renderer.tsx - Custom message components with markdown
11. package.json - Dependencies template

Reference Documents

See references/ for:

• use-chat-migration.md - Complete v4→v5 migration guide
• streaming-patterns.md - UI streaming best practices
• top-ui-errors.md - 12 common UI errors with solutions
• nextjs-integration.md - Next.js setup patterns
• links-to-official-docs.md - Organized links to official docs

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Production Tested: WordPress Auditor (https://wordpress-auditor.webfonts.workers.dev) Last Updated: 2025-10-22