Vercel AI Sdk

Vercel AI SDK v6 Implementation Guide

When to Use This Skill

Use this skill when:

• Implementing AI chat interfaces with useChat hook
• Creating API routes that generate or stream AI responses
• Building agentic applications with ToolLoopAgent
• Adding tool calling / function calling capabilities
• Generating structured output with Output.object(), Output.array(), etc.
• Generating text embeddings for semantic search or RAG
• Migrating from AI SDK v5 to v6
• Integrating Model Context Protocol (MCP) servers
• Implementing middleware for caching, logging, or guardrails
• Building workflow patterns (sequential, parallel, routing, etc.)
• Working with streaming responses or message persistence

Structured Implementation Workflow

  NEVER accept "Module not found" errors as environment issues
  YOU must install the required packages with the CORRECT package manager

  Common packages needed:
  - ai (core AI SDK)
  - @ai-sdk/openai (OpenAI provider)
  - @ai-sdk/anthropic (Anthropic provider)
  - @ai-sdk/mcp (MCP integration)
  - @modelcontextprotocol/sdk (MCP client SDK)
  - zod (for tool schemas)
</critical>

  "Code is correct" is NOT enough
  You must achieve FULL PASSING status
  This is what it means to be an autonomous agent
</critical>

⚠️ AUTONOMOUS AGENT MINDSET

You are not just writing code - you are COMPLETING TASKS AUTONOMOUSLY.

This means:

1. ✅ Write correct implementation
2. ✅ Install any required dependencies
3. ✅ Run build and fix ALL errors
4. ✅ Run tests and debug ALL failures
5. ✅ Iterate until EVERYTHING passes
6. ✅ Never make excuses or give up

Common Failure Patterns to AVOID

❌ WRONG: "The code is correct, but the package isn't installed - that's an environment issue" ✅ CORRECT: "Build failed due to missing package - installing it now with npm install [package]"

❌ WRONG: "Tests pass but build fails - not my problem" ✅ CORRECT: "Build is failing - debugging the error and fixing it now"

❌ WRONG: "There's a framework bug, can't fix it" ✅ CORRECT: "Framework error detected - researching the issue, trying workarounds, debugging until I find a solution"

❌ WRONG: "The implementation is complete" (with failing tests) ✅ CORRECT: "Tests are failing - debugging and fixing until they all pass"

Dependency Installation Workflow

When you encounter "Module not found" errors:

1. Detect the package manager FIRST - Check for lockfiles:

   ls -la | grep -E "lock"
   # Look for: pnpm-lock.yaml, package-lock.json, yarn.lock, bun.lockb
   

2. Identify the package from the import statement

   Error: Cannot find module '@ai-sdk/anthropic'
   Import: import { anthropic } from '@ai-sdk/anthropic'
   Package needed: @ai-sdk/anthropic
   

3. Install with the CORRECT package manager

   # If pnpm-lock.yaml exists (MOST COMMON for Next.js evals):
   pnpm install @ai-sdk/anthropic
   # or
   pnpm add @ai-sdk/anthropic
   
   # If package-lock.json exists:
   npm install @ai-sdk/anthropic
   
   # If yarn.lock exists:
   yarn add @ai-sdk/anthropic
   
   # If bun.lockb exists:
   bun install @ai-sdk/anthropic
   

4. Re-run build to verify

   npm run build
   # or pnpm run build, yarn build, bun run build
   

5. Fix any new errors that appear

⚠️ CRITICAL WARNING: Using the WRONG package manager (e.g., npm when the project uses pnpm) will:

• Create a second conflicting lockfile
• Install different versions of dependencies
• Cause dependency version mismatches
• Break the build with cryptic errors like "Cannot read properties of null"

Build Error Debugging Workflow

When build fails:

1. Read the FULL error message - don't skim it
2. Identify the root cause:
   • Module not found → Install package
   • Type error → Fix types
   • Config error → Check config files
   • Next.js error → Research, try different approaches
3. Apply the fix
4. Re-run build
5. Repeat until build passes

Test Failure Debugging Workflow

When tests fail:

1. Read the FULL test error - understand what's expected
2. Compare expected vs actual behavior
3. Check your implementation against test assertions
4. Fix the issue in your code
5. Re-run tests
6. Repeat until all tests pass

Success Criteria

Task is ONLY complete when:

• ✅ Build passes (npm run build succeeds)
• ✅ Lint passes (npm run lint succeeds)
• ✅ Tests pass (npm run test succeeds)

NEVER stop at "code is correct" - achieve FULL PASSING status!

⚠️ CRITICAL v6 CHANGES: Structured Output

In v6, generateObject and streamObject are DEPRECATED. Use generateText/streamText with Output helpers instead.

❌ WRONG - Deprecated v5 Pattern

// DO NOT USE - DEPRECATED in v6
import { generateObject } from "ai";

const result = await generateObject({
  model: anthropic("claude-sonnet-4-5"),
  schema: z.object({
    sentiment: z.enum(["positive", "neutral", "negative"]),
  }),
  prompt: "Analyze sentiment",
});

✅ CORRECT - v6 Output Pattern

import { generateText, Output } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import { z } from "zod";

const { output } = await generateText({
  model: anthropic("claude-sonnet-4-5"),
  output: Output.object({
    schema: z.object({
      sentiment: z.enum(["positive", "neutral", "negative"]),
      topics: z.array(z.string()),
    }),
  }),
  prompt: "Analyze this feedback...",
});

// Access typed output
console.log(output.sentiment); // 'positive' | 'neutral' | 'negative'
console.log(output.topics); // string[]

Output Helper Types

⚠️ CRITICAL: Tool Calling API - MUST USE tool() Helper

When implementing tool calling, you MUST use the tool() helper function from the 'ai' package.

❌ WRONG - Plain Object (WILL CAUSE BUILD ERROR)

// DO NOT DO THIS - This pattern is INCORRECT
import { z } from 'zod';

tools: {
  myTool: {
    description: 'My tool',
    parameters: z.object({...}),  // ❌ WRONG - "parameters" doesn't exist in v6
    execute: async ({...}) => {...},
  }
}

This will fail with: Type '{ description: string; parameters: ... }' is not assignable to type '{ inputSchema: FlexibleSchema<any>; ... }'

✅ CORRECT - Use tool() Helper (REQUIRED)

// ALWAYS DO THIS - This is the ONLY correct pattern
import { tool } from 'ai';  // ⚠️ MUST import tool
import { z } from 'zod';

tools: {
  myTool: tool({  // ⚠️ MUST wrap with tool()
    description: 'My tool',
    inputSchema: z.object({...}),  // ⚠️ MUST use "inputSchema" (not "parameters")
    execute: async ({...}) => {...},
  }),
}

Tool Calling Checklist

Before implementing any tool, verify:

• [ ] Imported tool from 'ai' package: import { tool } from 'ai';
• [ ] Wrapped tool definition with tool({ ... })
• [ ] Used inputSchema property (NOT parameters)
• [ ] Used zod schema: z.object({ ... })
• [ ] Defined execute function with async callback
• [ ] Added description string for the tool

⚠️ NEW in v6: ToolLoopAgent for Agentic Applications

Agent Definition

import { ToolLoopAgent, tool, stepCountIs } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import { z } from "zod";

const myAgent = new ToolLoopAgent({
  model: anthropic("claude-sonnet-4-5"),
  instructions: "You are a helpful assistant that can search and analyze data.",
  tools: {
    getData: tool({
      description: "Fetch data from API",
      inputSchema: z.object({
        query: z.string(),
      }),
      execute: async ({ query }) => {
        // Implement data fetching
        return { result: "data for " + query };
      },
    }),
    analyzeData: tool({
      description: "Analyze fetched data",
      inputSchema: z.object({
        data: z.string(),
      }),
      execute: async ({ data }) => {
        return { analysis: "Analysis of " + data };
      },
    }),
  },
  stopWhen: stepCountIs(20), // Stop after 20 steps max
});

// Non-streaming execution
const { text, toolCalls } = await myAgent.generate({
  prompt: "Find and analyze user data",
});

// Streaming execution
const stream = myAgent.stream({ prompt: "Find and analyze user data" });
for await (const chunk of stream) {
  // Handle streaming chunks
}

Agent API Route Integration

// app/api/agent/route.ts
import { createAgentUIStreamResponse } from "ai";
import { myAgent } from "@/agents/my-agent";

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

  return createAgentUIStreamResponse({
    agent: myAgent,
    uiMessages: messages,
  });
}

Agent Configuration Options

⚠️ CRITICAL: Common v5 to v6 Breaking Changes

1. useChat Hook Changes

❌ WRONG (v5 pattern):

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

// Sending message
append({ content: text, role: "user" });

✅ CORRECT (v6 pattern):

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

// Sending message
sendMessage({ text: input });

// New in v6: Handle tool outputs
addToolOutput({ toolCallId: 'xxx', result: { ... } });

2. Message Structure

❌ WRONG (v5 simple content):

<div>{message.content}</div>

✅ CORRECT (v6 parts-based):

<div>
  {message.parts.map((part, index) =>
    part.type === 'text' ? <span key={index}>{part.text}</span> : null
  )}
</div>

3. Response Methods

❌ WRONG (v5):

return result.toDataStreamResponse();

✅ CORRECT (v6):

return result.toUIMessageStreamResponse();

4. Model Specification

import { anthropic } from "@ai-sdk/anthropic";
import { openai } from "@ai-sdk/openai";

// Use provider functions (direct provider access)
model: anthropic("claude-sonnet-4-5");
model: anthropic("claude-opus-4-5");
model: anthropic("claude-haiku-4-5");
model: openai("gpt-4o");
model: openai("gpt-4o-mini");

5. Vercel AI Gateway

Purpose: Use Vercel AI Gateway for unified model access, rate limiting, caching, and observability across multiple providers.

Import:

import { gateway } from "ai";

Available Anthropic Models via Gateway:

model: gateway("anthropic/claude-sonnet-4-5");
model: gateway("anthropic/claude-haiku-4-5");
model: gateway("anthropic/claude-opus-4-5");

When to Use Gateway:

• Production applications requiring rate limiting and caching
• Multi-provider applications needing unified interface
• Applications requiring observability and analytics
• When you want automatic retries and error handling

When to Use Direct Provider:

• Development/testing environments
• When you need provider-specific features not available via gateway
• When you want direct control over API calls

Example:

import { generateText, gateway } from "ai";

const result = await generateText({
  model: gateway("anthropic/claude-sonnet-4-5"),
  prompt: "Hello, world!",
});

Comparison:

// Option 1: Direct provider
import { anthropic } from "@ai-sdk/anthropic";
model: anthropic("claude-sonnet-4-5");

// Option 2: Gateway (recommended for production)
import { gateway } from "ai";
model: gateway("anthropic/claude-sonnet-4-5");

Core API Reference

1. generateText - Non-Streaming Text Generation

Purpose: Generate text for non-interactive use cases (email drafts, summaries, agents with tools).

Signature:

import { generateText, Output } from 'ai';
import { anthropic } from '@ai-sdk/anthropic';

const result = await generateText({
  model: anthropic('claude-sonnet-4-5'),
  prompt: 'Your prompt here',
  system: 'Optional system message',
  tools?: { ... },
  maxSteps?: 5,
  output?: Output.object({ schema: z.object({...}) }),
});

Return Value:

{
  text: string;              // Generated text output
  output?: T;                // Typed structured output (if Output specified)
  toolCalls: ToolCall[];     // Tool invocations made
  finishReason: string;      // Why generation stopped
  usage: TokenUsage;         // Token consumption
  response: RawResponse;     // Raw provider response
  warnings: Warning[];       // Provider-specific alerts
}

Example:

// app/api/generate/route.ts
import { generateText } from "ai";
import { anthropic } from "@ai-sdk/anthropic";

export async function GET() {
  const result = await generateText({
    model: anthropic("claude-sonnet-4-5"),
    prompt: "Why is the sky blue?",
  });

  return Response.json({ text: result.text });
}

2. streamText - Streaming Text Generation

Purpose: Stream responses for interactive chat applications.

Signature:

import { streamText } from 'ai';
import { anthropic } from '@ai-sdk/anthropic';

const result = streamText({
  model: anthropic('claude-sonnet-4-5'),
  prompt: 'Your prompt here',
  system: 'Optional system message',
  messages?: ModelMessage[],
  tools?: { ... },
  onChunk?: (chunk) => { ... },
  onStepFinish?: (step) => { ... },
  onFinish?: async (result) => { ... },
  onError?: async (error) => { ... },
});

Return Methods:

// For chat applications with useChat hook
result.toUIMessageStreamResponse();

// For simple text streaming
result.toTextStreamResponse();

Example - Chat API Route:

// app/api/chat/route.ts
import { streamText, convertToModelMessages } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import type { UIMessage } from "ai";

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

  const result = streamText({
    model: anthropic("claude-sonnet-4-5"),
    system: "You are a helpful assistant.",
    messages: convertToModelMessages(messages),
  });

  return result.toUIMessageStreamResponse();
}

3. useChat Hook - Client-Side Chat Interface

Purpose: Build interactive chat UIs with streaming support.

Signature:

import { useChat } from '@ai-sdk/react';

const {
  messages,        // Array of UIMessage with parts-based structure
  sendMessage,     // Function to send messages (replaces append)
  status,          // 'submitted' | 'streaming' | 'ready' | 'error'
  stop,            // Abort current streaming
  regenerate,      // Reprocess last message
  setMessages,     // Manually modify history
  error,           // Error object if request fails
  clearError,      // Clear error state
  addToolOutput,   // Submit tool results (NEW in v6)
  resumeStream,    // Resume interrupted stream (NEW in v6)
} = useChat({
  api: '/api/chat',
  id?: 'chat-id',
  messages?: initialMessages,
  onToolCall?: async (toolCall) => { ... },
  onFinish?: (message) => { ... },
  onError?: (error) => { ... },
  sendAutomaticallyWhen?: (messages) => boolean,
  resume?: true,
});

Complete Example:

'use client';

import { useChat } from '@ai-sdk/react';
import { useState } from 'react';

export default function ChatPage() {
  const { messages, sendMessage, status, addToolOutput } = useChat({
    onToolCall: async ({ toolCall }) => {
      // Handle client-side tool execution
      if (toolCall.name === 'confirm') {
        const result = await showConfirmDialog(toolCall.args);
        addToolOutput({ toolCallId: toolCall.id, result });
      }
    },
  });
  const [input, setInput] = useState('');

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

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

  return (
    <div>
      <div>
        {messages.map((message) => (
          <div key={message.id}>
            <strong>{message.role}:</strong>
            {message.parts.map((part, index) => {
              switch (part.type) {
                case 'text':
                  return <span key={index}>{part.text}</span>;
                case 'tool-call':
                  return <div key={index}>Tool: {part.name}</div>;
                default:
                  return null;
              }
            })}
          </div>
        ))}
      </div>

      <form
        <input
          value={input}
          => setInput(e.target.value)}
          placeholder="Type a message..."
          disabled={status === 'streaming'}
        />
        <button type="submit" disabled={status === 'streaming'}>
          Send
        </button>
      </form>
    </div>
  );
}

4. Tool Calling / Function Calling

Purpose: Enable AI models to call functions with structured parameters.

Defining Tools:

import { tool } from "ai";
import { z } from "zod";

const weatherTool = tool({
  description: "Get the weather in a location",
  inputSchema: z.object({
    location: z.string().describe("The location to get the weather for"),
    unit: z.enum(["C", "F"]).describe("Temperature unit"),
  }),
  outputSchema: z.object({
    temperature: z.number(),
    condition: z.string(),
  }),
  execute: async ({ location, unit }) => {
    // Fetch or mock weather data
    return {
      temperature: 24,
      condition: "Sunny",
    };
  },
});

Using Tools with generateText/streamText:

// app/api/chat/route.ts
import { streamText, convertToModelMessages, tool } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import { z } from "zod";
import type { UIMessage } from "ai";

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

  const result = streamText({
    model: anthropic("claude-sonnet-4-5"),
    messages: convertToModelMessages(messages),
    tools: {
      getWeather: tool({
        description: "Get the weather for a location",
        inputSchema: z.object({
          city: z.string().describe("The city to get the weather for"),
          unit: z
            .enum(["C", "F"])
            .describe("The unit to display the temperature in"),
        }),
        execute: async ({ city, unit }) => {
          // API call or mock data
          return `It is currently 24°${unit} and Sunny in ${city}!`;
        },
      }),
    },
    toolChoice: "auto", // 'auto' | 'required' | 'none' | { type: 'tool', toolName: 'xxx' }
  });

  return result.toUIMessageStreamResponse();
}

Multi-Step Tool Calling:

const result = await generateText({
  model: anthropic("claude-sonnet-4-5"),
  tools: {
    weather: weatherTool,
    search: searchTool,
  },
  prompt: "What is the weather in San Francisco and find hotels there?",
  maxSteps: 5, // Allow up to 5 tool call steps
});

5. Text Embeddings

Purpose: Convert text into numerical vectors for semantic search, RAG, or similarity.

Signature:

import { embed, embedMany } from "ai";
import { openai } from "@ai-sdk/openai";

// Single embedding
const result = await embed({
  model: openai.textEmbeddingModel("text-embedding-3-small"),
  value: "Text to embed",
});

// Batch embeddings
const batchResult = await embedMany({
  model: openai.textEmbeddingModel("text-embedding-3-small"),
  values: ["Text 1", "Text 2", "Text 3"],
});

Return Value:

{
  embedding: number[];  // Numerical array representing the text
  usage: { tokens: number };  // Token consumption
  response: RawResponse;  // Raw provider response
}

Example - Embedding API Route:

// app/api/embed/route.ts
import { embed } from "ai";
import { openai } from "@ai-sdk/openai";

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

  const { embedding, usage } = await embed({
    model: openai.textEmbeddingModel("text-embedding-3-small"),
    value: text,
  });

  return Response.json({ embedding, usage });
}

6. Middleware

Purpose: Intercept and modify model behavior for logging, caching, guardrails, RAG, etc.

Built-in Middleware:

import {
  extractReasoningMiddleware,
  simulateStreamingMiddleware,
  defaultSettingsMiddleware,
  wrapLanguageModel,
} from "ai";

// Extract reasoning from models like Claude
const modelWithReasoning = wrapLanguageModel({
  model: anthropic("claude-sonnet-4-5"),
  middleware: extractReasoningMiddleware({ tagName: "thinking" }),
});

// Apply default settings
const modelWithDefaults = wrapLanguageModel({
  model: anthropic("claude-sonnet-4-5"),
  middleware: defaultSettingsMiddleware({
    temperature: 0.7,
    maxOutputTokens: 1000,
  }),
});

Custom Middleware:

import { LanguageModelMiddleware, wrapLanguageModel } from "ai";

// Logging middleware
const loggingMiddleware: LanguageModelMiddleware = {
  transformParams: async ({ params }) => {
    console.log("Request params:", params);
    return params;
  },
  wrapGenerate: async ({ doGenerate, params }) => {
    const result = await doGenerate();
    console.log("Response:", result);
    return result;
  },
};

// Caching middleware
const cache = new Map<string, string>();
const cachingMiddleware: LanguageModelMiddleware = {
  wrapGenerate: async ({ doGenerate, params }) => {
    const cacheKey = JSON.stringify(params.prompt);
    if (cache.has(cacheKey)) {
      return { text: cache.get(cacheKey)! };
    }
    const result = await doGenerate();
    cache.set(cacheKey, result.text);
    return result;
  },
};

// RAG middleware
const ragMiddleware: LanguageModelMiddleware = {
  transformParams: async ({ params }) => {
    const relevantDocs = await vectorSearch(params.prompt);
    return {
      ...params,
      prompt: `Context: ${relevantDocs}\n\nQuery: ${params.prompt}`,
    };
  },
};

// Apply multiple middleware
const enhancedModel = wrapLanguageModel({
  model: anthropic("claude-sonnet-4-5"),
  middleware: [loggingMiddleware, cachingMiddleware, ragMiddleware],
});

7. Model Context Protocol (MCP) Integration

Purpose: Connect to external MCP servers for dynamic tool access.

Installation:

bun add @ai-sdk/mcp @modelcontextprotocol/sdk

HTTP Transport (Production):

import { createMCPClient } from "@ai-sdk/mcp";
import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";
import { streamText } from "ai";
import { anthropic } from "@ai-sdk/anthropic";

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

  const httpTransport = new StreamableHTTPClientTransport(
    new URL("https://mcp-server.example.com/mcp"),
    { headers: { Authorization: `Bearer ${process.env.MCP_TOKEN}` } }
  );

  const mcpClient = await createMCPClient({ transport: httpTransport });

  try {
    const tools = await mcpClient.tools();

    const response = streamText({
      model: anthropic("claude-sonnet-4-5"),
      tools,
      prompt,
      onFinish: async () => {
        await mcpClient.close();
      },
      onError: async () => {
        await mcpClient.close();
      },
    });

    return response.toTextStreamResponse();
  } catch (error) {
    await mcpClient.close();
    return new Response("Internal Server Error", { status: 500 });
  }
}

Stdio Transport (Development):

import { createMCPClient } from "@ai-sdk/mcp";
import { Experimental_StdioMCPTransport } from "@ai-sdk/mcp";

const stdioTransport = new Experimental_StdioMCPTransport({
  command: "npx",
  args: [
    "-y",
    "@modelcontextprotocol/server-filesystem",
    "/path/to/allowed/dir",
  ],
});

const mcpClient = await createMCPClient({ transport: stdioTransport });

Key Points:

• Always close the client in onFinish and onError
• Tools are fetched dynamically with mcpClient.tools()
• Use HTTP/SSE for production, Stdio for development
• Multiple MCP clients can be combined by merging tool collections

8. Message Utilities

convertToModelMessages: Converts UI messages from useChat into ModelMessage objects for AI functions.

import { convertToModelMessages } from "ai";
import type { UIMessage } from "ai";

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

  const result = streamText({
    model: anthropic("claude-sonnet-4-5"),
    messages: convertToModelMessages(messages),
  });

  return result.toUIMessageStreamResponse();
}

Workflow Patterns

1. Sequential (Chain) Pattern

async function sequentialWorkflow(input: string) {
  // Step 1: Generate initial content
  const { text: draft } = await generateText({
    model: anthropic("claude-sonnet-4-5"),
    prompt: `Write marketing copy for: ${input}`,
  });

  // Step 2: Evaluate quality
  const { output: evaluation } = await generateText({
    model: anthropic("claude-sonnet-4-5"),
    output: Output.object({
      schema: z.object({
        score: z.number().min(1).max(10),
        feedback: z.string(),
      }),
    }),
    prompt: `Evaluate this copy: ${draft}`,
  });

  // Step 3: Improve if needed
  if (evaluation.score < 7) {
    const { text: improved } = await generateText({
      model: anthropic("claude-sonnet-4-5"),
      prompt: `Improve this copy based on feedback:\n\nCopy: ${draft}\n\nFeedback: ${evaluation.feedback}`,
    });
    return improved;
  }

  return draft;
}

2. Parallel Pattern

async function parallelReview(code: string) {
  const [securityReview, performanceReview, maintainabilityReview] =
    await Promise.all([
      generateText({
        model: anthropic("claude-sonnet-4-5"),
        prompt: `Review for security issues:\n\n${code}`,
      }),
      generateText({
        model: anthropic("claude-sonnet-4-5"),
        prompt: `Review for performance issues:\n\n${code}`,
      }),
      generateText({
        model: anthropic("claude-sonnet-4-5"),
        prompt: `Review for maintainability:\n\n${code}`,
      }),
    ]);

  return {
    security: securityReview.text,
    performance: performanceReview.text,
    maintainability: maintainabilityReview.text,
  };
}

3. Routing Pattern

async function routeQuery(query: string) {
  // Classify the query
  const { output: classification } = await generateText({
    model: anthropic("claude-sonnet-4-5"),
    output: Output.choice({
      choices: ["technical", "billing", "general"] as const,
    }),
    prompt: `Classify this customer query: ${query}`,
  });

  // Route to appropriate handler
  switch (classification) {
    case "technical":
      return handleTechnicalQuery(query);
    case "billing":
      return handleBillingQuery(query);
    default:
      return handleGeneralQuery(query);
  }
}

4. Orchestrator-Worker Pattern

async function implementFeature(requirement: string) {
  // Orchestrator: Break down the task
  const { output: plan } = await generateText({
    model: anthropic("claude-sonnet-4-5"),
    output: Output.object({
      schema: z.object({
        tasks: z.array(
          z.object({
            type: z.enum(["frontend", "backend", "database"]),
            description: z.string(),
          })
        ),
      }),
    }),
    prompt: `Break down this feature into tasks: ${requirement}`,
  });

  // Workers: Execute tasks in parallel
  const results = await Promise.all(
    plan.tasks.map((task) =>
      generateText({
        model: anthropic("claude-sonnet-4-5"),
        prompt: `Implement this ${task.type} task: ${task.description}`,
      })
    )
  );

  return results.map((r) => r.text);
}

5. Evaluator-Optimizer Pattern

async function optimizeOutput(input: string, maxIterations = 3) {
  let output = await generateText({
    model: anthropic("claude-sonnet-4-5"),
    prompt: input,
  });

  for (let i = 0; i < maxIterations; i++) {
    const { output: evaluation } = await generateText({
      model: anthropic("claude-sonnet-4-5"),
      output: Output.object({
        schema: z.object({
          isGood: z.boolean(),
          improvements: z.array(z.string()),
        }),
      }),
      prompt: `Evaluate this output: ${output.text}`,
    });

    if (evaluation.isGood) break;

    output = await generateText({
      model: anthropic("claude-sonnet-4-5"),
      prompt: `Improve based on: ${evaluation.improvements.join(", ")}\n\nOriginal: ${output.text}`,
    });
  }

  return output.text;
}

Message Part Types (v6)

| Part Type | Description | Properties | | ----------- | -------------------- | ------------------------------------------ | ---------- | -------- | --------------- | | text | Text content | text, isStreaming | | tool-call | Tool invocation | name, args, state ('input-streaming' | 'invoking' | 'output' | 'output-error') | | reasoning | Model thinking | text, isStreaming | | file | File attachment | mediaType, url or data | | source | RAG source reference | url or documentId, title | | step | Workflow boundary | Marks step boundaries | | data | Custom data | Any custom payload |

TypeScript Best Practices

Type Imports

import type {
  UIMessage, // Message type from useChat
  ModelMessage, // Message type for model functions
  ToolCall, // Tool call information
  TokenUsage, // Token consumption data
} from "ai";

Agent Type Safety

import type { InferAgentUIMessage } from "ai";

// Type-safe messages from agent
type MyAgentMessage = InferAgentUIMessage<typeof myAgent>;

Strongly Typed Tools

import { tool } from "ai";
import { z } from "zod";

// Tool helper infers execute parameter types
const myTool = tool({
  description: "My tool",
  inputSchema: z.object({
    param1: z.string(),
    param2: z.number(),
  }),
  outputSchema: z.object({
    result: z.string(),
  }),
  execute: async ({ param1, param2 }) => {
    // param1 is inferred as string
    // param2 is inferred as number
    return { result: "success" };
  },
});

Common Patterns

Pattern 1: Simple Chat Application

Client (app/page.tsx):

'use client';

import { useChat } from '@ai-sdk/react';
import { useState } from 'react';

export default function Chat() {
  const { messages, sendMessage, status } = useChat();
  const [input, setInput] = useState('');

  return (
    <div>
      {messages.map((m) => (
        <div key={m.id}>
          <strong>{m.role}:</strong>
          {m.parts.map((part, i) =>
            part.type === 'text' ? <span key={i}>{part.text}</span> : null
          )}
        </div>
      ))}
      <form => {
        e.preventDefault();
        sendMessage({ text: input });
        setInput('');
      }}>
        <input value={input} => setInput(e.target.value)} />
        <button disabled={status === 'streaming'}>Send</button>
      </form>
    </div>
  );
}

Server (app/api/chat/route.ts):

import { streamText, convertToModelMessages } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import type { UIMessage } from "ai";

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

  const result = streamText({
    model: anthropic("claude-sonnet-4-5"),
    system: "You are a helpful assistant.",
    messages: convertToModelMessages(messages),
  });

  return result.toUIMessageStreamResponse();
}

Pattern 2: Chat with Structured Output

import { streamText, convertToModelMessages, Output } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import { z } from "zod";
import type { UIMessage } from "ai";

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

  const result = streamText({
    model: anthropic("claude-sonnet-4-5"),
    messages: convertToModelMessages(messages),
    output: Output.object({
      schema: z.object({
        response: z.string(),
        sentiment: z.enum(["positive", "neutral", "negative"]),
        confidence: z.number().min(0).max(1),
      }),
    }),
  });

  return result.toUIMessageStreamResponse();
}

Pattern 3: Agent with Multiple Tools

import {
  ToolLoopAgent,
  tool,
  stepCountIs,
  createAgentUIStreamResponse,
} from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import { z } from "zod";

const researchAgent = new ToolLoopAgent({
  model: anthropic("claude-sonnet-4-5"),
  instructions:
    "You are a research assista

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