Issues with AI SDK v5

I've been having some issues integrating resumable-stream into a non-Next.js setup.

And specifically, I've been wondering about the need to do this:

const result = streamText({
  model: google('gemini-2.0-flash-001'),
  messages: convertToModelMessages(messages),
});

const stream = result.toUIMessageStream();

const resumableStream = await streamContext.resumableStream(
  dbStream.id,
  () => stream.pipeThrough(new JsonToSseTransformStream()), // THIS!
);

Why is it required to pipe the stream through JsonToSseTransformStream before sending it to resumable-stream?

Shouldn't resumable-stream integrate better with AI SDK v5, and use UIMessageStream as its input? Or at least provide a compat layer.

Start with the resumableStream call and the JsonToSseTransformStream usage shown in the issue, then compare their expected inputs with the AI SDK v5 UIMessageStream. Define the desired compatibility behavior and how it should work in a non-Next.js setup; the issue does not name tests or files to update.