Issue

Using any overload of ToDataSourceResult(Async) with a DataSourceRequest containing filter descriptors on an IQueryable provided by Entity Framework core 2.x, causes Entity Framework's "Query cache" to fill up for different filter values, leaking memory in the process. This is caused by using Expression.Constant in the generated expression trees for a DataSourceRequest's FilterDescriptors. Refer to https://github.com/dotnet/efcore/issues/14859 for more details about why this leaks memory.

Since Entity Framework's cache is always missed for new filter values, performance is also degraded due to this issue.

The issue is not present when using Entity Framework core 3 or greater. Apparently using Expression.Constant is not an issue on these version.

I have attached a minimal working example that illustrates the memory leak.

Fix

This issue can be fixed by changing FilterDescriptorExpressionBuilder.CreateValueExpression to not return a ConstantExpression, but a MemberExpression instead. Entity Framework 2.x will correctly parameterize the MemberExpression, causing the query cache to be hit correctly for queries that only differ in parameter values. It won't parameterize ConstantExpressions. Refer to https://stackoverflow.com/a/60516780/147993 for an example of generating a MemberExpression instead of a ConstantExpression.

Using the latest 2026.3.811 version produces the following errors:

• kendo.all.d.ts(12072,26): error TS2552: Build:Cannot find name 'SchedulerKendoKeydownEvent'. Did you mean 'SliderKendoKeydownEvent'?
• kendo.all.d.ts(14372,9): error TS2416: Build:Property 'options' in type 'ToggleButton' is not assignable to the same property in base type 'Button'.
• kendo.all.d.ts(14384,15): error TS2430: Build:Interface 'ToggleButtonOptions' incorrectly extends interface 'ButtonOptions'.

I am seeing that once a grid checkboxlist column filter exceeds about 1000 items the wait time appears to increase non-linearly (performance is worse than linear.)  For example, with 3,000 items the page freezes for about 30 seconds.  The data is fetched in under 50 milliseconds, so the vast majority of this time appears to be processing by Kendo.

Please see the attached for my configuration.

In the ThemeBuilder the controls do not use the latest version.

For instance while playing around with the ThemeBuilder I noticed that the primary button does not look primary like on the demos page.

Also it would be helpful to provide a page where you explain where every color is used.

When certain options of the editable Window are set through configuration, they are not being serialized correctly:

MinWidth
MinHeight
Events (Open, Close, etc.)

Bug report
For the Telerik Scheduler Timeline View, since the update from somewhere in between version 2022.3.1109 to 2024.2.154, a custom timeline view cannot be selected if the view name has dot(s) in its name (e.g. "kendo.ui.customTimelineView").

Reproduction of the problem

Add a custom Timeline View by extending the kendo.ui.TimelineView

Current behavior

Unlike older versions (I know that it worked with version <= 2022.3.1109, but don't know when exactly it was introduced)  now the ui blocks, when the custom select view button is clicked. Specifically, the problem is in kendo.scheduler.js at line 4554:

var viewElementToSelect = that.toolbar.find("[" + kendo.attr("name") + "=" + name + "]");

Expected behavior

In this code line, the find method does not work when the variable "name" contains something like "kendo.ui.CustomTimelineView". As a solution, I suggest escaping the name beforehand:

var nameEscaped = $.escapeSelector(name);
var viewElementToSelect = that.toolbar.find("[" + kendo.attr("name") + "=" + nameEscaped + "]");

I am working on a grid that has 3 requirements that seem to cause the bug:

• A FK column must have its lookup values loaded remotely
• The grid has sticky columns
• The grid is loaded inside a tab strip control

The combination of these 3 factors causes the grid not to load and results in a devtools console error. It's worth noting that removing any of the 3 bullet points above (e.g. NOT using sticky columns, NOT loading grid in tab control, or NOT have a remote FK column) allows the grid to load properly.

The error thrown in the DevTools console indicates that the grid's "tbody" property is not created at the time it is trying to call _setStickyStyles.

Before error is thrown (mouse is hovering over "tbody" property):

After error is thrown (look at console output):

I have upload a zip file containing a sample project that demonstrates the issue. When you launch the sample application, there are 2 links at the top of the page, "No Tabs" and "Tabs". The issue is reproducible on the "Tabs" page. Both pages use the same grid partial, but the "Tabs" page loads the partial through the tabstrip with a controller action. The "Tabs" page includes the 3 bullet points I indicated above that cause the problem.

The workaround I am using for now in my application is to NOT set the columns as sticky in my partial view. Instead, I set the sticky columns using the grid's API method "stickColumn" (https://www.telerik.com/kendo-jquery-ui/documentation/api/javascript/ui/grid/methods/stickcolumn) during the grid's dataBinding event (to ensure sticky columns are set AFTER grid initialization). This allows the grid to load and sets the sticky columns appropriately.

Thank you!

Consider the use of TextWriter async methods for the HTML Helpers, for example the WriteInitializationScript methods.  In certain scenarios the use of the synchronous methods causes an exception: System.InvalidOperationException: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.

This can be resolved by explicitly enabling synchronous operations

services.Configure<IISServerOptions>(options =>
    {
        options.AllowSynchronousIO = true;
    });

though synchronous operations have been disabled by default at framework level as of .NET 3.0.

Bug report

When a custom bundle is created the kendo.aspnetmvc script is not placed on the correct order. Thus, in some scenarios errors occur. For example if a custom kendo script is created using the following kendo-config.json and MultiColumnComboBox is used with ServerFiltering enabled and error will be thrown:

{
  "version": "2026.2.520",
  "components": [
    {
      "file": "kendo.aspnetmvc.js",
      "features": []
    },       
    {
      "file": "kendo.dropdownlist.js",
      "features": []
    },
    {
      "file": "kendo.multicolumncombobox.js",
      "features": []
    }
  ]
}

Reproduction of the problem

1. Run the attached sample. In the sample a custom bundle as explained above is used. TelerikAspNetCoreApp1.zip
2. Try to select values in the DropDownList or MultiColumnCombobox

Current behavior

The bundle builder allows kendo.aspnetmvc.js to run before the widgets whose UI for ASP.NET Core helpers it augments. The data in the components is not filtered and the following error is thrown:

Uncaught TypeError: kendo.ui.MultiColumnComboBox.requestData is not a function

Expected/desired behavior

The kendo.aspnetmvc.js schould be ordered correctly by the custom script builder, so errors to be avoided and the components to work as expected.

TicketID:

1716198

Environment

• Kendo/Telerik version: 2026.2.520
• Browser: [all ]

According the the documentation a user should be able to use the keyboard to navigate out of the spreadsheet as deescribed here. However, this does not happen.

Steps to reproduce:

1. Open the Dojo - https://dojo.telerik.com/IvdWHNwo/2
2. Navigate or click in the last cell in the last row
3. Click Tab key.

Current behavior: The focus remains in the same cell.

Expected behavior: Teh second input should be focused.

The issue is a regression starting with version 2024.4.1112

The MCP assistant server currently supports Visual Studio, Visual Studio Code and Cursor.

Provide official support for Claude Code as well:

Bug report

Editor components throw AmbiguousMatchException when bound with models that have property shadowing in inheritance hierarchies.

Reproduction of the problem

1. Create a model hierarchy where a derived class shadows a base class property with new keyword
2. Bind the Editor component with the shadowed property
3. Exception is thrown during reflection

Current behavior

(optional)
The components should handle property shadowing gracefully and generate the appropriate HTML input element.

Expected/desired behavior

AmbiguousMatchException is thrown when trying to bind the component to the shadowed property.

TicketID:

1699473

Environment

• Kendo UI version: 2025.3.825
• Browser: [all]

### Bug report

When building the scripts with NPM, there is syntax error "Unexpected number":

### Reproduction of the problem

Build the scripts (version 2025.3.812).

### Expected/desired behavior

The scripts must be built successfully.

### Workaround:

Remove the extra single quotes that wrap the version in the "rollup.mjs.config.mjs" and "rollup.modules.config.js" files:

• rollup.mjs.config.mjs

import glob from 'glob';
import path from 'path';
import { nodeResolve } from '@rollup/plugin-node-resolve';
import polyfill from 'rollup-plugin-polyfill';
import alias from '@rollup/plugin-alias';

...

const version = '2025.3.812';

• rollup.modules.config.mjs

import glob from "glob";
import path from "path";
import { nodeResolve } from "@rollup/plugin-node-resolve";
import polyfill from "rollup-plugin-polyfill";
import alias from "@rollup/plugin-alias";

...

const version = '2025.3.812';

### Environment

* **Kendo UI version: 2025.3.812