Support useEvent (async context) in cloudflare workers

[ManasMadrecha]

Environment

Nitro 2.8.0
Nodejs: 20 (on my windows 11), but, in production, using Cloudflare pages preset while building my app.

Reproduction

Using useEvent() directly instead of explicitly passing in event gives this error: 500 Nitro request context is not available. Note: This is an experimental feature and might be broken on non-Node.js environments.

Describe the bug

Of course, Cloudflare is not node environment, so the error is logical and clearly states this. But, is there any way can we have this feature in non-node environment? I mean is it actually possible? Else I will simply have to keep passing event in each function in the utils folder. Thanks.

Additional context

• https://nitro.unjs.io/guide/utils#experimental-composition-api
• https://developers.cloudflare.com/workers/runtime-apis/nodejs/asynclocalstorage/

Currently, the Nitro docs say:

This feature is currently supported for Node.js and Bun runtimes and also coming soon to other presets that support AsyncLocalStorage interface.

Also, these are the docs for Async Local Storage option in Cloudflare. https://developers.cloudflare.com/workers/runtime-apis/nodejs/asynclocalstorage/#caveats. Do these caveats prevent Nitro from adding this feature in Cloudflare Pages preset?

Logs

No response

[pi0]

Hi. Support is on the way! (https://github.com/unjs/unenv?tab=readme-ov-file#cloudflare - to be integrated soon with Nitro!)

[DaniFoldi]

Hi @pi0,

Is there an update you could provide about this?
I saw #2777, which is also still open - is there something that the preset needs to add, perhaps? Or is enabling nodejs_compat enough?

[pi0]

This is how you can currently enable async context for cloudflare worker deployments:

nitro.config:

export default defineNitroConfig({
  compatibilityDate: '2025-01-01',
  experimental: {
    asyncContext: true,
  },
  unenv: {
    external: ["node:async_hooks"],
  },
});

wrangler.toml:

compatibility_flags = [ "nodejs_als" ]

---

#2949 + cloudflare/workers-sdk#7442 will allow Nitro to enable support out of the box.