Once the token expires there is no way to renew it other than to create a new instance of the Client. Given that HttpClient is created by the Client and Credentials are required for the Client creation I figured that in most scenarios non-modifiable Credential provider should work (assuming Client is not kept in memory for over 10-15 min). I agree, though, that this class should be upgraded to support Token renewal, but we need to think about the workflow first.