VSTest is Removing its Newtonsoft.Json Dependency

VSTest is removing its Newtonsoft.Json dependency starting in .NET 11 Preview 4 and Visual Studio 18.8, replacing it with System.Text.Json on .NET and JSONite on .NET Framework. This is a security-driven change to eliminate vulnerable package versions from the SDK. Most projects are unaffected, but those relying on Newtonsoft.Json leaking through VSTest will see build or runtime failures. Fixes are straightforward — typically adding a single PackageReference. Affected scenarios include missing references, ExcludeAssets misconfigurations, and test adapter/data collector extensions that implicitly depended on VSTest's copy. A minor public API change removes JToken from VSTest's communication API.