No error/end-callback triggered for streams on ERR_NETWORK_CHANGED

We are using long-running server-streams where the server pushes updates to the frontend. If the user's network connections change (e.g. due to entering / leaving a VPN), these long-running streams immediately stop - so far so good.

The Browser shows these streams as "failed" inside the network tab:

In addition to that, the console tab also shows the failed request:

Note though that the HTTP Status is 200.

The issue: grpc-web does not propagate the error to our application. I'd expect both the "error" and "end"-callbacks to be triggered. Maybe even the "status"-callback. (Or, at least, the "end"-callback). They are not. As a consequence, these background-streams silently stop, and we can't inform the user or restart the streams.

Simplified code example:

this._alertServiceClient = new AlertServicePublicClient(/*...*/);

// ...

const req: Empty = new Empty();
this._alertStream = this._alertServiceClient.streamAlertChanges(req);

// None of these callbacks gets called if the stream stops with ERR_NETWORK_CHANGED:
this._alertStream.on('data', (response: AlertChanges) => {
  console.log('DATA', status); 
});
this._alertStream.on('error', (err: RpcError) => {
  console.log('ERROR', err); 
});
this._alertStream.on('end', () => {
  console.log('END'); 
});
this._alertStream.on('status', (status) => {
  console.log('STATUS', status); 
});

this._store.dispatch(AlertChangesStarted());

Setup: We are using Google Chrome, but it also happens for other browsers. The backend starts with an nginX-server, that forwards all grpc-web calls to an enovy proxy. Envoy then translates to grpc and forwards to individual backend services.

grpc / grpc-web

No error/end-callback triggered for streams on ERR_NETWORK_CHANGED #1363