> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cascadeflow.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# @cascadeflow/vercel-ai

> Vercel AI SDK middleware integration for cascade routing with streaming, multi-turn chat, and tool execution.

Middleware integration for the Vercel AI SDK. Adds cascade routing to AI SDK applications with streaming support.

## Install

```bash theme={null}
npm install @cascadeflow/vercel-ai
```

## createChatHandler

Creates a request handler for AI SDK chat endpoints.

```typescript theme={null}
import { createChatHandler } from '@cascadeflow/vercel-ai';
import { CascadeAgent } from '@cascadeflow/core';

const agent = new CascadeAgent({
  models: [
    { name: 'gpt-4o-mini', provider: 'openai', cost: 0.000375 },
    { name: 'gpt-4o', provider: 'openai', cost: 0.00625 },
  ],
});

const handler = createChatHandler(agent, {
  protocol: 'data',
  tools,
  toolHandlers,
  maxSteps: 5,
});
```

## Options

```typescript theme={null}
interface ChatHandlerOptions {
  protocol: 'data' | 'ui';             // AI SDK stream protocol
  tools?: ToolDefinition[];             // Tool definitions
  toolHandlers?: Record<string, Function>; // Server-side tool execution
  toolExecutor?: Function;              // Universal tool executor
  maxSteps?: number;                    // Multi-step tool loop limit
  forceDirect?: boolean;                // Skip cascade, use verifier
  allowOverrides?: string[];            // Request-level override keys
  overrideSecret?: string;              // Shared secret for overrides
}
```

## Features

* AI SDK v4 `data` stream and v5/v6 UI streams
* `useChat` multi-turn support
* `parts` message format (AI SDK v6)
* Tool call streaming visibility
* Server-side tool execution loops
* Multi-step controls
* Cascade decision stream parts
* Request-level overrides with allowlist