Progress® Kendo UI® for Angular Feedback Portal
Back to Feed
Request a Feature Report a Bug
Completed
Last Updated: 11 Aug 2026 12:29 by Michael
Michael
Created on: 28 Jul 2026 15:04
Category: Kendo UI for Angular
Type: Bug Report
0
Treeview doesn't get updated in Angular 21

Hi,

This works with Angular 20, must be a change related to that.

If I assign data to the TreeView synchronously, it works, but e.g. in a setTimeout, it doesn't any more. (I assign the full array, change detection is set to eager.)

Reproduction can be found here: https://codesandbox.io/p/devbox/mutable-glade-39twhs?workspaceId=ws_P4gPDf6RC2r5W8xExWQehV

Best regards,
Michael

2 comments
Michael
Posted on: 11 Aug 2026 12:29

Hi Martin,

thank you for your detailed explanation!

My example was somewhat unfortunate, because we do use Zone in our project, still the Treeview components don't update. Our code works with the same Kendo version but with Angular 20. (Using Zone in both cases, Eager CD strategy.)

Sadly I was not able to create a minimal reproduction, but what's interesting: calling detectChanges on the Treeview manually doesn't do anything, but calling detectChanges on the change detector injected in TreeViewGroupComponent does work. But in production code, everything works out of the box, only unoptimized code is affected.

I assume you cannot do anything without the minimal reproduction, but this bug is only one of the Kendo-related bugs we are facing after the Angular update, something seems to be off with Angular 21-22, but only Kendo components are affected?

Best regards,
Michael

 

ADMIN
Martin Bechev
Posted on: 04 Aug 2026 09:07

Hi Michael,

Thank you for the prepared demo.

The zoneless change detection is enabled by default from Angular v21. Since Kendo Angular components still do not provide full support for it, the developer needs to:

1. Install the zone.js package and then import it in the angular.json polyfills array.

2. Provide provideZoneChangeDetection({ eventCoalescing: true }) in the app.config.ts file (or directly in main.ts).

The steps can also be found in this article:

https://www.telerik.com/kendo-angular-ui/components/knowledge-base/cannot-read-properties-of-undefined-grid

We are currently actively working on providing support for zoneless, but at this point we cannot commit to an exact date when this will be available for the TreeView.
Some smaller components already have the proper configuration to support zoneless, but bigger ones require some more time to refactor and adjust the code. Until full zoneless support is provided, please use the approach suggested above.

Here is the updated demo:

https://codesandbox.io/p/sandbox/kendo-angular-treeview-cd-problem-forked-kx5s2k

Do let us know how it goes.

Regards,
Martin Bechev
Progress Telerik

Love the Telerik and Kendo UI products and believe more people should try them? Invite a fellow developer to become a Progress customer and each of you can get a $50 Amazon gift voucher.

Create an account Log In
View
Type
Status
Category