response:mocked not getting fired

[grgmo]

I'm not 100% sure if this is a bug or not.

Just to give a context of what I have got working so far -

react-native -> 0.81.1
msw -> 2.7.6
@react-native-community/cli

Works on both integration and e2e using same mocks. I also get life-cycle events ok.

I'm currently migrating from react-native cli -> expo cli

Not surprisingly both integration and e2e tests stopped working, which I've managed to fix.

So all is well but only thing I'm struggling to understand is life-cycle events. I've now stopped getting response:mocked event.

So I've done more digging and have found that on expo app

< 2.4.4 -> response:mocked event fires

> 2.4.3 -> response:mocked event DO NOT get fired

This is not a big deal, but if I could patch it somehow.

Looking through the code, it looks like this.interceptor.on("response"...) does not get fired

msw/src/node/SetupServerCommonApi.ts

Line 110 in e0a4643

this.emitter.emit(

So I'm guessing @mswjs/interceptors is not firing this event somewhere?

[kettanaito]

Hi, @grgmo. This was a bug that I believe has since been fixed. Please update msw and let me know if you're still experiencing it! A minimal reproduction in that case would be great.

[Adit-Jain-srm]

The response:mocked lifecycle event not firing after migrating from React Native CLI to Expo CLI is likely due to how Expo handles network requests differently.

Root cause: Expo's newer networking layer uses a different fetch implementation that may bypass MSW's interceptor registration. In the RN CLI, you were likely using the native XMLHttpRequest path which MSW intercepts correctly.

Things to check:

1. Verify MSW is intercepting at all — add a broader listener:

server.events.on('request:start', ({ request }) => {
  console.log('MSW saw:', request.method, request.url)
})

If this fires but response:mocked doesn't, the handler is matching but the response event isn't emitting.

2. Check your MSW setup location — with Expo CLI, the setup timing matters. Make sure MSW is started BEFORE any network requests happen:

// In your test setup or app entry
await server.listen({ onUnhandledRequest: 'warn' })

3. Expo's fetch polyfill — Expo may override globalThis.fetch. Try explicitly setting:

import { setupServer } from 'msw/native'  // not 'msw/node'

4. Known issue with MSW 2.x + Expo: There's a timing race where Expo's network layer initializes before MSW can patch it. Try adding a delay or using beforeAll in your test setup.

@grgmo Does request:start fire? That'll tell us if it's an interception issue or just the lifecycle event specifically.