[Bug] POST requests to Discord API using fetch in Cloudflare Workers do not resolve – HTTP interactions bot deployment not reliable

[The-LukeZ]

Description

When deploying an HTTP interactions bot on Cloudflare Workers, making a fetch() request to Discord (using the POST method) from a worker does not resolve. The Promise returned by fetch() hangs indefinitely - even though the request is sent (e.g. deferring results in the user seeing the loading state).
This means, for interaction callbacks or any other Discord requests, the callback must be the last line in your worker's fetch() handler, or Cloudflare Workers cannot be reliably used for HTTP interactions bots.

After investigating, it appears this occurs because both Discord and Cloudflare utilize Cloudflare infrastructure (possibly Workers). This issue has been referenced before (see: #7146 ), but this wasn't the subject of that issue - still, it persists.

Recommendation:

• Update docs to note that HTTP interaction bots on Cloudflare Workers are not recommended except for single, final interaction callbacks (the callback is the last line before the worker's fetch handler is completed).
• OR remove the CF Workers example for HTTP interactions altogether.

Steps to Reproduce

1. Deploy an HTTP interactions bot to Cloudflare Workers (Can be the example from the docs).
2. In your worker, attempt to send an interaction callback with a fetch() POST request to Discord in a single invocation of the fetch() event handler.
3. Observe that the interaction callback POST goes through, however the Promise returned by the fetch() doesn't resolve; any line of code after fetch() isn't executed; this blocks further execution.
4. Alternatively, test the same code locally (using ngrok and worker dev mode on your machine): all requests resolve properly and you can have additional logic after e.g. deferring the interaction and editing it later.

Example (JS):

// `interaction` is obtained through the discord-interactions-js package verifying the payload and then parsing the body (like the example from the docs)
const deferRes = await fetch(`https://discord.com/api/v10/interactions/${interaction.id}/${interaction.token}/callback`, {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    authorization: `Bot ${env.DISCORD_TOKEN}`,
  },
  body: JSON.stringify({
    type: InteractionResponseType.DeferredChannelMessageWithSource,
    data: {
      flags: 64,
    },
  }),
});
// This point isn't even reached when deployed on CF Workers
console.log("Defer response:", deferRes.status, inspect(Object.entries(deferRes.headers)));

await new Promise((resolve) => setTimeout(resolve, 1000)); // Simulate processing delay

const resRes = await fetch(
  `https://discord.com/api/v10/webhooks/${interaction.application_id}/${interaction.token}/messages/@original?with_response=true`,
  {
    method: "PATCH",
    headers: {
      "Content-Type": "application/json",
      authorization: `Bot ${env.DISCORD_TOKEN}`,
    },
    body: JSON.stringify({
      content: "Done!",
    }),
  },
);
console.log("Edit response:", resRes.status, inspect(Object.entries(resRes.headers)));

Expected Behavior

All HTTP POST requests to Discord from a Cloudflare Worker (using fetch()) should resolve their Promises and complete execution. Any POST in the worker's fetch event handler using fetch() to a Discord API endpoint should resolve.

Current Behavior

All HTTP POST requests to Discord from a Cloudflare Worker (using fetch()) go through, however the Promise returned by the fetch() doesn't resolve; therefore any line of code after the fetch() isn't executed.

Screenshots/Videos

(No screenshots available – issue is best reproduced through code and observable hanging behavior in worker logs.)

Client and System Information

Client: Client doesn't matter, I tested it in browser, on desktop and mobile
Platform: Cloudflare Workers
Testing locally: Worker dev mode (wrangler dev) + ngrok (requests resolve as expected)
Live deployment: Cloudflare Worker wrangler deploy (Discord POST requests hang)
Language: JavaScript/TypeScript
Discord API Version: 10
Discord API endpoints tested: POST interaction callback, POST message (create message)

[vakiliner]

It looks like this error isn't related to the Discord API, it's only on your end

[The-LukeZ]

related to CF Workers in relation with Discord I assume. Testing has shown that. Should I provide a 100% complete minimal reproduction example? @vakiliner

[The-LukeZ]

Update:

I found out you have to do your logic like this, for it to actually work.

// Worker fetch handler
fetch(request, env, ctx) {
  /* Validation here */
  ctx.waitUntil(
    new Promise(async function (resolve) {
      // Do deferr or reply and it's non-blocking
      return resolve(undefined);
    })
  );
}

return Response.json({}, { status: 202 });

This works now because we accept the interaction first, but then in the background we do something in that promise.

I would like to request that the docs are changed to display this.
I can also try to do a PR myself.