Getting uncaughtException: Error: aborted with SSE after client browser close the connection

Link to the code that reproduces this issue

https://codesandbox.io/p/sandbox/n-vlt865

To Reproduce

1- Create a route on the api folder inside the app directory like this:

export const runtime = "edge";

export async function POST() {
  console.log("Route: /api/sse triggered");

  const responseStream = new TransformStream();

  return new Response(responseStream.readable, {
    headers: {
      "Content-Type": "text/event-stream",
      Connection: "keep-alive",
      "Cache-Control": "no-cache, no-transform",
      "X-Accel-Buffering": "no",
      "Content-Encoding": "none",
      "Access-Control-Allow-Origin": "*",
    },
  });
}

2- Create a client to connect to the SSE route

'use client';
import {
  EventSourceMessage,
  EventStreamContentType,
  fetchEventSource,
} from '@microsoft/fetch-event-source';

class RetriableError extends Error {}
class FatalError extends Error {}

class SSEService extends EventTarget {
  constructor() {
    super();

    this.connect();
  }

  connect = async () => {
    await fetchEventSource('/api/sse', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        foo: 'bar',
      }),
      onmessage: this.onMessage,
      onclose: this.onClose,
      onopen: this.onOpen,
      onerror: this.onError,
      openWhenHidden: true,
    });
  };

  onMessage(msg: EventSourceMessage) {
    console.log(msg);
  }

  onClose() {
    console.log('closed');
    // if the server closes the connection unexpectedly, retry:
    throw new RetriableError();
  }

  async onOpen(response: Response) {
    console.log('open', response);
    if (
      response.ok &&
      response.headers.get('content-type') === EventStreamContentType
    ) {
      return; // everything's good
    } else if (
      response.status >= 400 &&
      response.status < 500 &&
      response.status !== 429
    ) {
      // client-side errors are usually non-retriable:
      throw new FatalError();
    } else {
      throw new RetriableError();
    }
  }

  onError(err: Error) {
    console.log('error', err);
    if (err instanceof FatalError) {
      throw err; // rethrow to stop the operation
    } else {
      // do nothing to automatically retry. You can also
      // return a specific retry interval here.
    }
  }
}

export default SSEService;

3- Use the client to connect inside a page

"use client";
import React, { useEffect, useRef } from "react";
import SSEService from "./services/SSEService";

export default function Home() {
  const ref = useRef<SSEService>();
  useEffect(() => {
    if (!ref.current) {
      ref.current = new SSEService();
    }
  }, []);

  return <div>page index</div>;
}

4- Refresh the page and you will get this error on the server console

 ⨯ uncaughtException: Error: aborted
    at connResetException (node:internal/errors:705:14)
    at abortIncoming (node:_http_server:642:17)
    at socketOnClose (node:_http_server:636:3)
    at Socket.emit (node:events:525:35)
    at TCP.<anonymous> (node:net:301:12)
    at TCP.callbackTrampoline (node:internal/async_hooks:130:17) {
  code: 'ECONNRESET'
}

Current vs. Expected behavior

Close gracefully the connection

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 22.6.0: Fri Sep 15 13:41:28 PDT 2023; root:xnu-8796.141.3.700.8~1/RELEASE_ARM64_T6020
Binaries:
  Node: 16.20.1
  npm: 8.19.4
  Yarn: 1.22.19
  pnpm: N/A
Relevant Packages:
  next: 13.5.3
  eslint-config-next: 13.5.3
  react: 18.2.0
  react-dom: 18.2.0
  typescript: 4.9.5
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

App Router

Additional context

No response

Start by running the linked CodeSandbox and reproducing the refresh or browser-close behavior against the App Router /api/sse POST route. Read the edge route and the SSEService client disconnect path, then confirm when the server emits ECONNRESET. Done means the connection closes without an uncaughtException while the SSE route continues to work.