Regards,
Rumen
Progress Telerik

Hi Frank,

Thank you for the update and for confirming the versions you are using.

Yes, the versions you listed are the latest ones:

• Telerik UI for ASP.NET AJAX: 2026.1.225.462
• Kendo UI for jQuery: 2026.1.212

Regarding the "Uncaught ReferenceError: kendo is not defined" error - this is expected if the page includes Kendo culture scripts (or any custom code) that directly references the global window.kendo object. In the Telerik UI for ASP.NET AJAX templates, Kendo is encapsulated and exposed through $telerik._kendo, so window.kendo is not available by default.

To resolve this, please create an alias to the correct Kendo instance after the RadScriptManager is loaded and before you load and execute the culture scripts:

<telerik:RadScriptManager ID="RadScriptManager1" runat="server">
</telerik:RadScriptManager>

<telerik:RadCodeBlock runat="server">
    <script>
        // create an alias for the kendo pointing to $telerik._kendo
        let kendo = $telerik._kendo;
    </script>
    <script type="text/javascript" src="/scripts/kendoui/2026.1.212/js/cultures/kendo.culture.<% =CurrentUICultureTwoLetterISOLanguageName %>.min.js"></script>
    <script type="text/javascript">
        kendo.culture(‘<% =CurrentUICultureTwoLetterISOLanguageName %>’);
    </script>
</telerik:RadCodeBlock>

This way, the culture scripts (and the kendo.culture(...) call) will work as expected, while still keeping the encapsulated Kendo instance used by the Telerik controls.

If you still see the error after applying the above, please send us:

• The full markup of the page (especially the ScriptManager/RadScriptManager and any RadCodeBlock/ScriptBlock sections)
• A screenshot of the browser console showing the exact error and the line that throws it
• Confirmation whether the culture scripts are loaded on the same page where the HtmlChart is initialized

Regards,
Rumen
Progress Telerik