EventSource.close does not trigger onabort

Description

When using EventSource.close on client side, request.signal.onabort event is not triggered. This prevents proper handling of client disconnection in server-sent events (SSE).

According to the Cloudflare Workers changelog (2025-05-22 Changelog), this issue has been addressed in Cloudflare Workers, allowing proper handling of request cancellation. However, the same functionality does not work in OpenNext.

Code Example

Below is a sample code snippet demonstrating the issue:

import { sleep } from "@/lib/utils";
import { NextRequest, NextResponse } from "next/server";

export async function GET(request: NextRequest) {
  const stream = new ReadableStream({
    async start(controller) {
      request.signal.addEventListener("abort", () => {
        controller.close();
      });

      while (!request.signal.aborted) {
        controller.enqueue(
          new TextEncoder().encode(
            `data: ${JSON.stringify([1,2,3])}\n\n`,
          ),
        );

        await sleep(10 * 1000);
      }
    },
  });

  return new NextResponse(stream, {
    headers: {
      "Content-Type": "text/event-stream",
      "Cache-Control": "no-cache",
      Connection: "keep-alive",
    },
  });
}

@opennextjs/cloudflare version

1.1.0

Additional context

No response

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