diff --git a/UPGRADING.md b/UPGRADING.md
index 9ebdc4a..39fde1e 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -53,6 +53,11 @@ The `OpenIDProvider` and sub-interfaces like `Authorizer` and `Exchanger` got a
 
 We also provide a new optional interface: [`LogAuthRequest`](https://pkg.go.dev/github.com/zitadel/oidc/v3/pkg/op#LogAuthRequest). If an `AuthRequest` implements this interface, it is completely passed into the logger after an error. Its `LogValue()` will be used by `slog` to print desired fields. This allows omitting sensitive fields you wish not no print. If the interface is not implemented, no `AuthRequest` details will ever be printed.
 
+#### Server interface
+
+We've added a new [`Server`](https://pkg.go.dev/github.com/zitadel/oidc/v3/pkg/op#Server) interface. This interface is experimental and subject to change. See [issue 440](https://github.com/zitadel/oidc/issues/440) for the motivation and discussion around this new interface.
+Usage of the new interface is not required, but may be used for advanced scenarios when working with the `Storage` interface isn't the optimal solution for your app (like we experienced in [Zitadel](https://github.com/zitadel/zitadel)).
+
 #### AuthRequestError
 
 `AuthRequestError` now takes the complete `Authorizer` as final argument, instead of only the encoder.