ai-sdk-ui（AI SDK UI 浏览器）

AI SDK UI - Frontend React Hooks

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

Version: AI SDK v5.0.76+ (Stable) Framework: React 18+, Next.js 14+ Last Updated: 2025-10-22

Quick Start (5 Minutes)

Installation

npm install 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.

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.

Tool Calling in UI

When your API uses tools, useChat automatically handles tool invocations in the message stream:

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

export default function ChatWithTools() {
  const { messages } = useChat({ api: '/api/chat' });

  return (
    <div>
      {messages.map(message => (
        <div key={message.id}>
          {/* Text content */}
          {message.content && <p>{message.content}</p>}

          {/* Tool invocations */}
          {message.toolInvocations?.map((tool, idx) => (
            <div key={idx} className="bg-blue-50 p-2 rounded my-2">
              <div className="font-bold">Tool: {tool.toolName}</div>
              <div className="text-sm">
                <strong>Args:</strong> {JSON.stringify(tool.args, null, 2)}
              </div>
              {tool.result && (
                <div className="text-sm">
                  <strong>Result:</strong> {JSON.stringify(tool.result, null, 2)}
                </div>
              )}
            </div>
          ))}
        </div>
      ))}
    </div>
  );
}

File Attachments

Upload files (images, PDFs, etc.) alongside messages:

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

export default function ChatWithAttachments() {
  const { messages, sendMessage, isLoading } = useChat({ api: '/api/chat' });
  const [input, setInput] = useState('');
  const [files, setFiles] = useState<FileList | null>(null);

  const handleSubmit = (e: FormEvent) => {
    e.preventDefault();

    sendMessage({
      content: input,
      experimental_attachments: files
        ? Array.from(files).map(file => ({
            name: file.name,
            contentType: file.type,
            url: URL.createObjectURL(file),
          }))
        : undefined,
    });

    setInput('');
    setFiles(null);
  };

  return (
    <div>
      {/* Messages */}
      {messages.map(m => (
        <div key={m.id}>
          {m.content}
          {m.experimental_attachments?.map((att, idx) => (
            <div key={idx}>
              <img src={att.url} alt={att.name} />
            </div>
          ))}
        </div>
      ))}

      {/* Input */}
      <form onSubmit={handleSubmit}>
        <input
          type="file"
          multiple
          onChange={(e) => setFiles(e.target.files)}
          accept="image/*"
        />
        <input
          value={input}
          onChange={(e) => setInput(e.target.value)}
        />
        <button type="submit" disabled={isLoading}>Send</button>
      </form>
    </div>
  );
}

Message Persistence

Save and load chat history to localStorage:

'use client';
import { useChat } from 'ai/react';
import { useEffect } from 'react';

export default function PersistentChat() {
  const chatId = 'my-chat-1';

  const { messages, setMessages, sendMessage } = useChat({
    api: '/api/chat',
    id: chatId,
    initialMessages: loadMessages(chatId),
  });

  // Save messages whenever they change
  useEffect(() => {
    saveMessages(chatId, messages);
  }, [messages, chatId]);

  return (
    <div>
      {messages.map(m => (
        <div key={m.id}>{m.role}: {m.content}</div>
      ))}
      {/* Input form... */}
    </div>
  );
}

// Helper functions
function loadMessages(chatId: string) {
  const stored = localStorage.getItem(`chat-${chatId}`);
  return stored ? JSON.parse(stored) : [];
}

function saveMessages(chatId: string, messages: any[]) {
  localStorage.setItem(`chat-${chatId}`, JSON.stringify(messages));
}

useCompletion Hook - Complete Reference

Basic Usage

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

export default function Completion() {
  const { completion, complete, isLoading, error } = useCompletion({
    api: '/api/completion',
  });
  const [input, setInput] = useState('');

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

  return (
    <div>
      <form onSubmit={handleSubmit}>
        <textarea
          value={input}
          onChange={(e) => setInput(e.target.value)}
          placeholder="Enter a prompt..."
          rows={4}
          className="w-full p-2 border rounded"
        />
        <button type="submit" disabled={isLoading}>
          {isLoading ? 'Generating...' : 'Generate'}
        </button>
      </form>

      {completion && (
        <div className="mt-4 p-4 bg-gray-50 rounded">
          <h3>Result:</h3>
          <p>{completion}</p>
        </div>
      )}

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

Full API Reference

const {
  completion,         // string - Current completion text
  complete,           // (prompt: string) => void - Trigger completion
  setCompletion,      // (completion: string) => void - Update completion
  isLoading,          // boolean - Is generating?
  error,              // Error | undefined - Error if any
  stop,               // () => void - Stop generation
} = useCompletion({
  api: '/api/completion',
  id: 'completion-1',

  // Callbacks
  onFinish: (prompt, completion) => {},
  onError: (error) => {},

  // Configuration
  headers: {},
  body: {},
});

API Route for useCompletion

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

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

  const result = streamText({
    model: openai('gpt-3.5-turbo'),
    prompt,
    maxOutputTokens: 500,
  });

  return result.toDataStreamResponse();
}

useObject Hook - Complete Reference

Basic Usage

Stream structured data (e.g., forms, JSON objects) with live updates:

'use client';
import { useObject } from 'ai/react';
import { z } from 'zod';

const recipeSchema = z.object({
  recipe: z.object({
    name: z.string(),
    ingredients: z.array(z.string()),
    instructions: z.array(z.string()),
  }),
});

export default function RecipeGenerator() {
  const { object, submit, isLoading, error } = useObject({
    api: '/api/recipe',
    schema: recipeSchema,
  });

  return (
    <div>
      <button onClick={() => submit('pasta carbonara')} disabled={isLoading}>
        Generate Recipe
      </button>

      {isLoading && <div>Generating recipe...</div>}

      {object?.recipe && (
        <div className="mt-4">
          <h2 className="text-2xl font-bold">{object.recipe.name}</h2>

          <h3 className="text-xl mt-4">Ingredients:</h3>
          <ul>
            {object.recipe.ingredients?.map((ingredient, idx) => (
              <li key={idx}>{ingredient}</li>
            ))}
          </ul>

          <h3 className="text-xl mt-4">Instructions:</h3>
          <ol>
            {object.recipe.instructions?.map((step, idx) => (
              <li key={idx}>{step}</li>
            ))}
          </ol>
        </div>
      )}

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

Full API Reference

const {
  object,             // Partial<T> - Partial object (updates as stream progresses)
  submit,             // (input: string) => void - Trigger generation
  isLoading,          // boolean - Is generating?
  error,              // Error | undefined - Error if any
  stop,               // () => void - Stop generation
} = useObject({
  api: '/api/object',
  schema: zodSchema,  // Zod schema

  // Callbacks
  onFinish: (object) => {},
  onError: (error) => {},
});

API Route for useObject

// app/api/recipe/route.ts
import { streamObject } from 'ai';
import { openai } from '@ai-sdk/openai';
import { z } from 'zod';

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

  const result = streamObject({
    model: openai('gpt-4'),
    schema: z.object({
      recipe: z.object({
        name: z.string(),
        ingredients: z.array(z.string()),
        instructions: z.array(z.string()),
      }),
    }),
    prompt: `Generate a recipe for ${prompt}`,
  });

  return result.toTextStreamResponse();
}

Next.js Integration

App Router Complete Example

Directory Structure:

app/
├── api/
│   └── chat/
│       └── route.ts      # Chat API endpoint
├── chat/
│   └── page.tsx          # Chat page
└── layout.tsx

Chat Page:

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

export default function ChatPage() {
  const { messages, sendMessage, isLoading, error } = useChat({
    api: '/api/chat',
  });
  const [input, setInput] = useState('');
  const messagesEndRef = useRef<HTMLDivElement>(null);

  // Auto-scroll to bottom
  useEffect(() => {
    messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
  }, [messages]);

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

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

  return (
    <div className="flex flex-col h-screen max-w-2xl mx-auto">
      {/* Messages */}
      <div className="flex-1 overflow-y-auto p-4 space-y-4">
        {messages.map(message => (
          <div
            key={message.id}
            className={`flex ${
              message.role === 'user' ? 'justify-end' : 'justify-start'
            }`}
          >
            <div
              className={`max-w-[70%] p-3 rounded-lg ${
                message.role === 'user'
                  ? 'bg-blue-500 text-white'
                  : 'bg-gray-200 text-gray-900'
              }`}
            >
              {message.content}
            </div>
          </div>
        ))}
        {isLoading && (
          <div className="flex justify-start">
            <div className="bg-gray-200 p-3 rounded-lg">
              <div className="flex space-x-2">
                <div className="w-2 h-2 bg-gray-500 rounded-full animate-bounce"></div>
                <div className="w-2 h-2 bg-gray-500 rounded-full animate-bounce delay-100"></div>
                <div className="w-2 h-2 bg-gray-500 rounded-full animate-bounce delay-200"></div>
              </div>
            </div>
          </div>
        )}
        <div ref={messagesEndRef} />
      </div>

      {/* Error */}
      {error && (
        <div className="p-4 bg-red-50 border-t border-red-200 text-red-700">
          Error: {error.message}
        </div>
      )}

      {/* Input */}
      <form onSubmit={handleSubmit} className="p-4 border-t">
        <div className="flex space-x-2">
          <input
            value={input}
            onChange={(e) => setInput(e.target.value)}
            placeholder="Type a message..."
            disabled={isLoading}
            className="flex-1 p-2 border rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500"
          />
          <button
            type="submit"
            disabled={isLoading || !input.trim()}
            className="px-4 py-2 bg-blue-500 text-white rounded-lg disabled:bg-gray-300 disabled:cursor-not-allowed"
          >
            Send
          </button>
        </div>
      </form>
    </div>
  );
}

API Route:

// 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,
    system: 'You are a helpful AI assistant.',
    maxOutputTokens: 1000,
  });

  return result.toDataStreamResponse();
}

Pages Router Complete Example

Directory Structure:

pages/
├── api/
│   └── chat.ts           # Chat API endpoint
└── chat.tsx              # Chat page

Chat Page:

// pages/chat.tsx
import { useChat } from 'ai/react';
import { useState, FormEvent } from 'react';

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

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

  return (
    <div className="container mx-auto p-4">
      <h1 className="text-2xl font-bold mb-4">AI Chat</h1>

      <div className="border rounded p-4 h-96 overflow-y-auto mb-4">
        {messages.map(m => (
          <div key={m.id} className="mb-4">
            <strong>{m.role === 'user' ? 'You' : 'AI'}:</strong> {m.content}
          </div>
        ))}
      </div>

      <form onSubmit={handleSubmit} className="flex space-x-2">
        <input
          value={input}
          onChange={(e) => setInput(e.target.value)}
          placeholder="Type a message..."
          disabled={isLoading}
          className="flex-1 p-2 border rounded"
        />
        <button
          type="submit"
          disabled={isLoading}
          className="px-4 py-2 bg-blue-500 text-white rounded"
        >
          Send
        </button>
      </form>
    </div>
  );
}

API Route:

// pages/api/chat.ts
import type { NextApiRequest, NextApiResponse } from 'next';
import { streamText } from 'ai';
import { openai } from '@ai-sdk/openai';

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse
) {
  const { messages } = req.body;

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

  // Pages Router uses pipeDataStreamToResponse
  return result.pipeDataStreamToResponse(res);
}

Key Difference: App Router uses toDataStreamResponse(), Pages Router uses 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.

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": "^5.0.76",
    "@ai-sdk/openai": "^2.0.53",
    "react": "^18.2.0",
    "zod": "^3.23.8"
  }
}

Next.js:

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

Version Notes:

• AI SDK v5.0.76+ (stable)
• React 18+ (React 19 supported)
• Next.js 14+ recommended (13.4+ works)
• Zod 3.23.8+ for schema validation

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

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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