[FEATURE] request.signal.onabort is never triggered

[lixinyang123]

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

Before submitting

• I have checked that there isn't already a similar feature request
• This is a single feature (not multiple features in one request)

[sommeeeer]

Seems to work on my end. Did you enable the flag?

[lixinyang123]

Yes, this is my wrangler.jsonc .

{
  "$schema": "node_modules/wrangler/config-schema.json",
  "name": "karen",
  "main": ".open-next/worker.js",
  "compatibility_date": "2025-05-30",
  "compatibility_flags": ["nodejs_compat", "enable_request_signal"],
  "assets": {
    "binding": "ASSETS",
    "directory": ".open-next/assets",
  },
  "observability": {
    "enabled": true,
  }
}

When I use next dev --turbopack, the following code is triggered correctly:

request.signal.addEventListener("abort", () => {
  controller.close();
});

However, when I use opennextjs-cloudflare build && wrangler dev , it does not respond. Am I missing some details?

dependencies

"next": "^15.3.2",
"@opennextjs/cloudflare": "^1.1.0",
"wrangler": "^4.18.0"

[sommeeeer]

I tried with your versions and wrangler.jsonc. Seems to work fine here in wrangler dev. Does it work if you deploy it tho?

[lixinyang123]

Hi, @sommeeeer

After upgrading next to 15.3.3, abort was successfully triggered.

Thanks！

[sommeeeer]

After upgrading next to 15.3.3, abort was successfully triggered.

I dont think the Next version has anything to do with this. Anyhow, im glad its working now!

[lixinyang123]

Hi, @sommeeeer

Sorry, I mistakenly used next dev as wrangler dev.

I've created a demo to reproduce this error.
https://github.com/lixinyang123/opennext-request_signal-demo

You can run npm run dev and npm run preview to compare the log outputs.

When using npm run preview, closing the webpage does not trigger abort event.

[sommeeeer]

hey @lixinyang123 your actually right. Took another look at this, my initial demo was not really demonstrating this the correct way, so I was looking at the wrong thing.

My guesses is that this is probably expected behavior cause request.signal.onabort is part of the Fetch API/Workers API, and would not work in OpenNext since most common wrappers (except the cloudflare adapter) doesn't get access to this API on the incoming request/event. It wouldn't work the way the request cycle goes on in OpenNext either. It seems to be the case for OpenNext when ran locally aswell.

I tested a bare minimum worker with request.signal.onabort and it works fine there in wrangler dev. Here is the code I used. However, in a route handler like the one you provided, request.signal.onabort is not getting emitted in OpenNext, but it does in next start and next dev.

What I did find out is that there is a hacky way to solve this for this adapter. Be aware that this should most likely be solved a different way. First you need this as your route handler:

export async function GET() {
    const cfCtx = getCloudflareContext();
    const stream = new ReadableStream({
        async start(controller) {
        cfCtx.originalRequest.signal.addEventListener("abort", async () => {
            console.log("closing");
            controller.close();
        });
            while (!cfCtx.originalRequest.signal.aborted) {
// the rest of your code....

Then you build your project with npx opennextjs-cloudflare build. Then you edit your file in .open-next/cloudflare/init.js to use this on line 11-14:

async function runWithCloudflareRequestContext(request, env, ctx, handler) {
  init(request, env);
  return cloudflareContextALS.run({ env, ctx, cf: request.cf, originalRequest: request }, handler);
}
// now you can `npx opennextjs-cloudflare preview`

[lixinyang123]

Thanks !!!
I'll try this.

[lixinyang123]

Hi, @sommeeeer

The abort was successfully triggered.
Will OpenNext solve this issue?
I feel like this is always a compromise.


[sommeeeer]

We would have to wait for the maintainers of this repo to take a look at this.

[vicb]

@lixinyang123 Could you please update the PR description with a summary of your findings/discussion with @sommeeeer ?

If I understand correctly, the abort event is not fired on NextRequest while it is on the request passed to the cloudflare fetch handler?