simulateStreamingMiddleware()

simulateStreamingMiddleware is a middleware function that simulates streaming behavior with responses from non-streaming language models. This is useful when you want to maintain a consistent streaming interface even when using models that only provide complete responses.

import { simulateStreamingMiddleware } from 'ai';

const middleware = simulateStreamingMiddleware();

Import

import { simulateStreamingMiddleware } from "ai"

API Signature

Parameters

This middleware doesn't accept any parameters.

Returns

Returns a middleware object that:

• Takes a complete response from a language model
• Converts it into a simulated stream of chunks
• Properly handles various response components including:
  • Text content
  • Reasoning (as string or array of objects)
  • Tool calls
  • Metadata and usage information
  • Warnings

Usage Example

import { streamText } from 'ai';
import { wrapLanguageModel } from 'ai';
import { simulateStreamingMiddleware } from 'ai';

// Example with a non-streaming model
const result = streamText({
  model: wrapLanguageModel({
    model: nonStreamingModel,
    middleware: simulateStreamingMiddleware(),
  }),
  prompt: 'Your prompt here',
});

// Now you can use the streaming interface
for await (const chunk of result.fullStream) {
  // Process streaming chunks
}

How It Works

The middleware:

1. Awaits the complete response from the language model
2. Creates a ReadableStream that emits chunks in the correct sequence
3. Simulates streaming by breaking down the response into appropriate chunk types
4. Preserves all metadata, reasoning, tool calls, and other response properties