In ASP.NET Core MVC projects, Bootstrap 5 Input Group renders incorrectly due to ASP Tag Helper including hidden __Invariant field in the HTML. Specifically, the right border of the right-most input-group field is not rounded if ASP Helper inserts a hidden input[name="__Invariant"] after the field. This happens when the right-most field is the last part in the input-group and the right-most field's Tag Helper generates a hidden __Invariant input.

<div class="input-group">
    <span class="input-group-text">Test</span>
    <input class="form-control" asp-for="NullableDateTime" />
</div>

Update could be made to VS.Web.CG.Mvc's Bootstrap 5 site.css template so that appropriate CSS reset rules are included to resolve the issue.

Relevant links:
https://stackoverflow.com/questions/79481827/strange-invariant-hidden-element-inserted-into-markup