Example: AI SDK `useChat` Hook with Mastra Server

This example shows how to integrate Mastra’s memory with the Vercel AI SDK’s useChat hook when using a Mastra Server deployment. The key is connecting your Next.js app to the Mastra Server via the MastraClient SDK.

Architecture Overview

When using a Mastra Server, you have two options:

Option 1: Via API Route (Recommended for production)

Your React frontend uses the useChat hook to manage UI state
Your API route uses MastraClient to communicate with the Mastra Server
The Mastra Server handles agent execution, memory, and tools

Benefits:

Keeps your Mastra Server URL and API keys secure on the backend
Allows you to add additional authentication/authorization logic
Enables request transformation and response handling
Better for multi-tenant applications

Option 2: Direct Connection (Good for development/prototyping)

Your React frontend uses the useChat hook to manage UI state
The useChat hook connects directly to the Mastra Server’s stream endpoint
The Mastra Server handles agent execution, memory, and tools

Preventing Message Duplication with `useChat`

The default behavior of useChat sends the entire chat history with each request. Since Mastra’s memory automatically retrieves history based on threadId, sending the full history from the client leads to duplicate messages in the context window and storage.

Solution: Configure useChat to send only the latest message along with your threadId and resourceId.

components/Chat.tsx


import { useChat } from "ai/react";
 
export function Chat({ threadId, resourceId }) {
  const { messages, input, handleInputChange, handleSubmit } = useChat({
    api: "/api/chat", // Your backend endpoint
    // Pass only the latest message and custom IDs
    experimental_prepareRequestBody: (request) => {
      // Ensure messages array is not empty and get the last message
      const lastMessage = request.messages.length > 0 ? request.messages[request.messages.length - 1] : null;
 
      // Return the structured body for your API route
      return {
        message: lastMessage, // Send only the most recent message content/role
        threadId,
        resourceId,
      };
    },
    // Optional: Initial messages if loading history from backend
    // initialMessages: loadedMessages,
  });
 
  // ... rest of your chat UI component
  return (
    <div>
      {/* Render messages */}
      <form onSubmit={handleSubmit}>
        <input value={input} onChange={handleInputChange} placeholder="Send a message..." />
        <button type="submit">Send</button>
      </form>
    </div>
  );
}

app/api/chat/route.ts


import { MastraClient } from "@mastra/client-js";
import { CoreMessage } from "@mastra/core";
 
// Initialize the Mastra client to connect to your server
const mastraClient = new MastraClient({
  baseUrl: process.env.MASTRA_SERVER_URL || "http://localhost:4111",
  // Optional: Add API key if your server requires authentication
  headers: {
    "x-api-key": process.env.MASTRA_API_KEY,
  },
});
 
export async function POST(request: Request) {
  // Get data structured by experimental_prepareRequestBody
  const { message, threadId, resourceId }: { message: CoreMessage | null; threadId: string; resourceId: string } = await request.json();
 
  // Handle cases where message might be null (e.g., initial load or error)
  if (!message || !message.content) {
    return new Response("Missing message content", { status: 400 });
  }
 
  // Get the agent from your Mastra Server
  const agent = mastraClient.getAgent("ChatAgent"); // Use your agent's ID
 
  // Stream the response with memory context
  const response = await agent.stream({
    messages: [{ role: message.role || "user", content: message.content }],
    threadId,
    resourceId,
  });
 
  // Return the streaming response to the frontend
  return new Response(response.body);
}

Alternative: Direct Server Route

If you’ve deployed your Mastra Server with a custom route handler for chat, you can also connect directly:

components/Chat.tsx


import { useChat } from "ai/react";
 
export function Chat({ threadId, resourceId, agentId = "ChatAgent" }) {
  const { messages, input, handleInputChange, handleSubmit } = useChat({
    // Connect directly to your Mastra Server's stream endpoint
    api: `${process.env.NEXT_PUBLIC_MASTRA_SERVER_URL}/api/agents/${agentId}/stream`,
    experimental_prepareRequestBody: (request) => {
      const lastMessage = request.messages.length > 0 ? request.messages[request.messages.length - 1] : null;
      // The Mastra Server expects the full messages array, not just a single message
      return {
        messages: lastMessage ? [lastMessage] : [],
        threadId,
        resourceId,
      };
    },
    headers: {
      // Include authentication if required
      "x-api-key": process.env.NEXT_PUBLIC_MASTRA_API_KEY,
    },
  });
 
  // ... rest of component
}

Environment Variables

Make sure to configure your environment variables:

.env.local


MASTRA_SERVER_URL=http://localhost:4111  # Your Mastra Server URL
MASTRA_API_KEY=your-api-key             # If authentication is enabled
 
# For direct client connection (if using the alternative approach)
NEXT_PUBLIC_MASTRA_SERVER_URL=http://localhost:4111
NEXT_PUBLIC_MASTRA_API_KEY=your-api-key

See the AI SDK documentation on message persistence for more background.

Basic Thread Management UI

While this page focuses on useChat, you can also build UIs for managing threads (listing, creating, selecting). This typically involves backend API endpoints that interact with Mastra’s memory functions like memory.getThreadsByResourceId() and memory.createThread().

components/ThreadList.tsx


import React, { useState, useEffect } from 'react';
 
// Assume API functions exist: fetchThreads, createNewThread
async function fetchThreads(userId: string): Promise<{ id: string; title: string }[]> { /* ... */ }
async function createNewThread(userId: string): Promise<{ id: string; title: string }> { /* ... */ }
 
function ThreadList({ userId, currentThreadId, onSelectThread }) {
  const [threads, setThreads] = useState([]);
  // ... loading and error states ...
 
  useEffect(() => {
    // Fetch threads for userId
  }, [userId]);
 
  const handleCreateThread = async () => {
    // Call createNewThread API, update state, select new thread
  };
 
  // ... render UI with list of threads and New Conversation button ...
  return (
     <div>
       <h2>Conversations</h2>
       <button onClick={handleCreateThread}>New Conversation</button>
       <ul>
         {threads.map(thread => (
           <li key={thread.id}>
             <button onClick={() => onSelectThread(thread.id)} disabled={thread.id === currentThreadId}>
               {thread.title || `Chat ${thread.id.substring(0, 8)}...`}
             </button>
           </li>
         ))}
       </ul>
     </div>
  );
}
 
// Example Usage in a Parent Chat Component
function ChatApp() {
  const userId = "user_123";
  const [currentThreadId, setCurrentThreadId] = useState<string | null>(null);
 
  return (
    <div style={{ display: 'flex' }}>
      <ThreadList
        userId={userId}
        currentThreadId={currentThreadId}
        onSelectThread={setCurrentThreadId}
      />
      <div style={{ flexGrow: 1 }}>
        {currentThreadId ? (
          <Chat threadId={currentThreadId} resourceId={userId} agentId="your-agent-id" /> // Your useChat component
        ) : (
          <div>Select or start a conversation.</div>
        )}
      </div>
    </div>
  );
}

Key Differences: Mastra Server vs Direct Integration

When using Mastra Server:

Your Next.js app acts as a client to the Mastra Server
Use MastraClient to communicate with the server
Agent configuration, memory, and tools are managed on the server
Better for production deployments and multi-client scenarios

When using direct integration (from the AI SDK docs):

Agent runs directly in your Next.js server
You manage agent configuration and dependencies locally
Simpler for development but requires more setup

Troubleshooting

Common Issues:

Connection refused: Ensure your Mastra Server is running and accessible
Authentication errors: Check your API key configuration
Message duplication: Verify you’re only sending the latest message
Missing thread history: Ensure threadId and resourceId are passed correctly
CORS errors (direct connection): Configure your Mastra Server to allow requests from your frontend origin

MastraClient Overview: Learn more about the Mastra Client SDK
Mastra Server: How to deploy and configure a Mastra Server
Memory Overview: Core concepts of resourceId and threadId
AI SDK Integration: General useChat documentation

Example: AI SDK useChat Hook with Mastra Server