Unexpected result on the client when an exception is thrown in experimental_transform (streamText).

[s-h-a-d-o-w]

This might be a bug but I wanted to confirm that it's not just because of lack of understanding on my part.

When an error is thrown in experimental_transform, the behavior on the server is as I would expect, it results in a 500 code:

[Error: failed to pipe response] {
  [cause]: TypeError: Cannot read properties of undefined (reading 'at')
      at Object.transform (src\app\api\chat\route.ts:95:43)
  > 95 |             // [REDACTED] Code that throws is irrelevant.
}
 POST /api/chat 500 in 2356ms

But the client actually receives a 200 response:

page.tsx:438 
 POST http://localhost:3000/api/chat net::ERR_INCOMPLETE_CHUNKED_ENCODING 200 (OK)

And the error provided by useChat is TypeError: network error - which seems wrong, since the network is just fine.

(Also: onError isn't triggered in result.toUIMessageStreamResponse.)