# onFinish not called when stream is aborted

## Issue

When using `toUIMessageStreamResponse` with an `onFinish` callback, the callback may not execute when the stream is aborted. This happens because the abort handler immediately terminates the response, preventing the `onFinish` callback from being triggered.

```tsx
// Server-side code where onFinish isn't called on abort
export async function POST(req: Request) {
  const { messages } = await req.json();

  const result = streamText({
    model: __MODEL__,
    messages: convertToModelMessages(messages),
    abortSignal: req.signal,
  });

  return result.toUIMessageStreamResponse({
    onFinish: async ({ isAborted }) => {
      // This isn't called when the stream is aborted!
      if (isAborted) {
        console.log('Stream was aborted');
        // Handle abort-specific cleanup
      } else {
        console.log('Stream completed normally');
        // Handle normal completion
      }
    },
  });
}
```

## Background

When a stream is aborted, the response is immediately terminated. Without proper handling, the `onFinish` callback has no chance to execute, preventing important cleanup operations like saving partial results or logging abort events.

## Solution

Add `consumeStream` to the `toUIMessageStreamResponse` configuration. This ensures that abort events are properly captured and forwarded to the `onFinish` callback, allowing it to execute even when the stream is aborted.

```tsx
// other imports...
import { consumeStream } from 'ai';

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

  const result = streamText({
    model: __MODEL__,
    messages: convertToModelMessages(messages),
    abortSignal: req.signal,
  });

  return result.toUIMessageStreamResponse({
    onFinish: async ({ isAborted }) => {
      // Now this WILL be called even when aborted!
      if (isAborted) {
        console.log('Stream was aborted');
        // Handle abort-specific cleanup
      } else {
        console.log('Stream completed normally');
        // Handle normal completion
      }
    },
    consumeSseStream: consumeStream, // This enables onFinish to be called on abort
  });
}
```


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