Handling remote-load errors in Angular Module Federation v2 with Rspack

When a Module Federation v2 remote fails to load — network blip, bad deploy, expired tab — the default behaviour is an unhandled exception somewhere deep in your shell app. Here’s how to intercept that and render a fallback component instead, in an Nx + Angular + Rspack setup. If you have no clue how to set up module federation v2 with rspack and angular, I wrote up my own start-to-finish setup log — Setting up Angular with Module Federation 2.0, Nx, and rspack — and the eight ways it broke — with the exact error codes hit along the way. Manfred Steyer’s Nx and Angular with Rspack and Module Federation is also a great reference for the broader setup.

you can scaffold new nx workspace using this command npx create-nx-workspace@latest --preset=apps

My example is using 19.0.0-alpha.13 for packages @ng-rsbuild/plugin-angular and @ng-rsbuild/plugin-nx because the latest version of these package seems broken.

errorLoadRemote#

This is a plugin provided by Module federation v2 to intercept error from loading the remote so that we can handle the error gracefully.

We can use this to provide error component when we failed to load the remote. First we need to have an error component such as below

// shell/src/app/error.component.ts
import {Component} from '@angular/core';

@Component({
    selector: 'app-error',
    template: `
        <h1>Error Loading remote component!</h1>
    `,
    standalone: true
})
export class ErrorComponent{
}

Then we can use this component in Module federation such as below

// shell/src/main.ts
import { FederationRuntimePlugin, init } from '@module-federation/enhanced/runtime';
import { ErrorComponent } from './app/error.component';

const fallbackPlugin: () => FederationRuntimePlugin = function () {
 return {
   name: 'fallback-plugin',
   errorLoadRemote(args) {
     return ErrorComponent;
   },
 };
};

Why errorLoadRemote beats a global error handler#

Angular’s ErrorHandler catches the exception but by the time it fires, the router outlet is already broken — you end up with a blank area and a stack trace in the console, not a graceful fallback. errorLoadRemote intercepts at the Module Federation runtime layer, before Angular ever tries to mount the component, and the value you return is the component Angular uses. The outlet renders a real component; the user sees a real message.

It’s also per-remote by design. The args parameter carries the remote name and the specific error — if you need different fallbacks per microfrontend (e.g. a lightweight inline message for a header widget, a full-page error for a checkout flow), you branch on args.from and return different components. A global ErrorHandler can’t do that without reaching for private Angular internals.

References#

• Nx and Angular with Rspack and Module Federation — Manfred Steyer’s setup guide
• Module Federation runtime plugin API