Module '@stomp/stompjs' used by is not ESM

[BigMichi1]

since version 7.3.0 i'm getting this warning in my angular project:

Application bundle generation complete. [13.455 seconds] - 2026-02-25T14:36:12.419Z

▲ [WARNING] Module '@stomp/stompjs' used by 'src/app/log-viewer/services/log-websocket.service.ts' is not ESM

  CommonJS or AMD dependencies can cause optimization bailouts.
  For more information see: https://angular.dev/tools/cli/build#configuring-commonjs-dependencies

just like with older versions i have in my log-websocket.service.ts

import { Client, IMessage } from '@stomp/stompjs';

@Injectable({
  providedIn: 'root',
})
export class LogWebSocketService implements OnDestroy {
  connect(): void {
    if (this.client?.connected) {
      return;
    }

    this.connectionStatusSubject.next(this.reconnectAttempts > 0 ? ConnectionStatus.RECONNECTING : ConnectionStatus.CONNECTING);

    this.client = new Client({
      brokerURL: this.wsUrl,
 ...
}

[kum-deepak]

I do not use this library with Angular. Please share a minimal Angular project that demonstrates this issue. It will help me in resolving the issue.

I strongly suggest you try the rx-stomp library, an RxJS wrapper for Angular. Please see the guide at https://stomp-js.github.io/guide/rx-stomp/rx-stomp-with-angular.html and https://stomp-js.github.io/guide/rx-stomp/connection-status-rx-stomp.html

[BigMichi1]

Steps:

1. npm install -g @angular/cli
2. ng new stomp-test (Answer all questions with default)
3. nano src/app/app.ts
4. add import { Client } from '@stomp/stompjs';
5. add protected readonly client = new Client({}); after export class App {
6. run ng build

using rx-stomp results in the same warning

ng build
Initial chunk files | Names         |  Raw size | Estimated transfer size
main-7XASZ3TR.js    | main          | 242.69 kB |                65.78 kB
styles-5INURTSO.css | styles        |   0 bytes |                 0 bytes

                    | Initial total | 242.69 kB |                65.78 kB

Application bundle generation complete. [2.192 seconds] - 2026-02-26T09:57:48.418Z

▲ [WARNING] Module '@stomp/stompjs' used by 'node_modules/@stomp/rx-stomp/esm6/index.js' is not ESM

  CommonJS or AMD dependencies can cause optimization bailouts.
  For more information see: https://angular.dev/tools/cli/build#configuring-commonjs-dependencies


Output location: /home/cramer/ttt/stomp-test/dist/stomp-test

[kum-deepak]

The root cause was the "browser" condition in the exports field of package.json. The "browser" entry was taking priority over "import" for Angular/esbuild browser builds — causing bundlers to resolve @stomp/stompjs to the UMD bundle instead of the ESM output in esm6/. The "browser" entry has now been removed.

Published as v7.4.0-beta.2 — Please give it a try and report back if the warning persists in your setup.