diff --git a/src/GraphQL.Client/GraphQLHttpClient.cs b/src/GraphQL.Client/GraphQLHttpClient.cs
index 21485f01..eb8835f5 100644
--- a/src/GraphQL.Client/GraphQLHttpClient.cs
+++ b/src/GraphQL.Client/GraphQLHttpClient.cs
@@ -65,7 +65,7 @@ public GraphQLHttpClient(GraphQLHttpClientOptions options, IGraphQLWebsocketJson
             if (!HttpClient.DefaultRequestHeaders.UserAgent.Any())
                 HttpClient.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue(GetType().Assembly.GetName().Name, GetType().Assembly.GetName().Version.ToString()));
 
-            _lazyHttpWebSocket = new Lazy<GraphQLHttpWebSocket>(() => new GraphQLHttpWebSocket(Options.EndPoint.GetWebSocketUri(), this));
+            _lazyHttpWebSocket = new Lazy<GraphQLHttpWebSocket>(() => new GraphQLHttpWebSocket(Options.WebSocketEndPoint ?? Options.EndPoint.GetWebSocketUri(), this));
         }
 
         #endregion
diff --git a/src/GraphQL.Client/GraphQLHttpClientOptions.cs b/src/GraphQL.Client/GraphQLHttpClientOptions.cs
index 6e2c3a46..c727a661 100644
--- a/src/GraphQL.Client/GraphQLHttpClientOptions.cs
+++ b/src/GraphQL.Client/GraphQLHttpClientOptions.cs
@@ -12,10 +12,15 @@ namespace GraphQL.Client.Http
     public class GraphQLHttpClientOptions
     {
         /// <summary>
-        /// The GraphQL EndPoint to be used
+        /// The GraphQL EndPoint to be used for HTTP connections
         /// </summary>
         public Uri EndPoint { get; set; }
 
+        /// <summary>
+        /// The GraphQL EndPoint to be used for WebSocket connection
+        /// </summary>
+        public Uri WebSocketEndPoint { get; set; }
+
         /// <summary>
         /// The <see cref="System.Net.Http.HttpMessageHandler"/> that is going to be used
         /// </summary>
@@ -47,6 +52,11 @@ public class GraphQLHttpClientOptions
         public Func<GraphQLRequest, GraphQLHttpClient, Task<GraphQLHttpRequest>> PreprocessRequest { get; set; } = (request, client) =>
             Task.FromResult(request is GraphQLHttpRequest graphQLHttpRequest ? graphQLHttpRequest : new GraphQLHttpRequest(request));
 
+        /// <summary>
+        /// Subscription request preprocessing function. Can be used i.e. to inject authorization info into a GraphQL subscription request payload.
+        /// </summary>
+        public Func<GraphQLRequest, GraphQLHttpClient, Task<GraphQLHttpRequest>> PreprocessSubscriptionRequest { get; set; }
+
         /// <summary>
         /// This callback is called after successfully establishing a websocket connection but before any regular request is made. 
         /// </summary>
diff --git a/src/GraphQL.Client/GraphQLHttpRequest.cs b/src/GraphQL.Client/GraphQLHttpRequest.cs
index 00f90d4a..eb3aac14 100644
--- a/src/GraphQL.Client/GraphQLHttpRequest.cs
+++ b/src/GraphQL.Client/GraphQLHttpRequest.cs
@@ -16,7 +16,7 @@ public GraphQLHttpRequest(string query, object? variables = null, string? operat
         {
         }
 
-        public GraphQLHttpRequest(GraphQLRequest other): base(other.Query, other.Variables, other.OperationName)
+        public GraphQLHttpRequest(GraphQLRequest other): base(other)
         {
         }
 
diff --git a/src/GraphQL.Client/Websocket/GraphQLHttpWebSocket.cs b/src/GraphQL.Client/Websocket/GraphQLHttpWebSocket.cs
index aba35e8f..488db435 100644
--- a/src/GraphQL.Client/Websocket/GraphQLHttpWebSocket.cs
+++ b/src/GraphQL.Client/Websocket/GraphQLHttpWebSocket.cs
@@ -98,12 +98,11 @@ public IObservable<GraphQLResponse<TResponse>> CreateSubscriptionStream<TRespons
                     Observable.Create<GraphQLResponse<TResponse>>(async observer =>
                     {
                         Debug.WriteLine($"Create observable thread id: {Thread.CurrentThread.ManagedThreadId}");
-                        await _client.Options.PreprocessRequest(request, _client);
                         var startRequest = new GraphQLWebSocketRequest
                         {
                             Id = Guid.NewGuid().ToString("N"),
                             Type = GraphQLWebSocketMessageType.GQL_START,
-                            Payload = request
+                            Payload = await (_client.Options.PreprocessSubscriptionRequest?.Invoke(request, _client) ?? _client.Options.PreprocessRequest(request, _client))
                         };
                         var closeRequest = new GraphQLWebSocketRequest
                         {
@@ -136,6 +135,7 @@ public IObservable<GraphQLResponse<TResponse>> CreateSubscriptionStream<TRespons
                                         var typedResponse =
                                             _client.JsonSerializer.DeserializeToWebsocketResponse<TResponse>(
                                                 response.MessageBytes);
+                                        Debug.WriteLine($"payload => {System.Text.Encoding.UTF8.GetString(response.MessageBytes)}");
                                         o.OnNext(typedResponse.Payload);
 
                                         // in case of a GraphQL error, terminate the sequence after the response has been posted
@@ -194,10 +194,12 @@ public IObservable<GraphQLResponse<TResponse>> CreateSubscriptionStream<TRespons
                         }
                         catch (Exception e)
                         {
-                            Console.WriteLine(e);
+                            Debug.WriteLine(e);
                             throw;
                         }
 
+                        // TODO: wait for "connection_ack" response
+
                         Debug.WriteLine($"sending initial message on subscription {startRequest.Id}");
                         // send subscription request
                         try
@@ -206,7 +208,7 @@ public IObservable<GraphQLResponse<TResponse>> CreateSubscriptionStream<TRespons
                         }
                         catch (Exception e)
                         {
-                            Console.WriteLine(e);
+                            Debug.WriteLine(e);
                             throw;
                         }
 
@@ -255,14 +257,18 @@ public IObservable<GraphQLResponse<TResponse>> CreateSubscriptionStream<TRespons
                 // unwrap and push results or throw wrapped exceptions
                 .SelectMany(t =>
                 {
-                    Debug.WriteLine($"unwrap exception thread id: {Thread.CurrentThread.ManagedThreadId}");
                     // if the result contains an exception, throw it on the observable
                     if (t.Item2 != null)
+                    {
+                        Debug.WriteLine($"unwrap exception thread id: {Thread.CurrentThread.ManagedThreadId} => {t.Item2}");
                         return Observable.Throw<GraphQLResponse<TResponse>>(t.Item2);
-
-                    return t.Item1 == null
-                        ? Observable.Empty<GraphQLResponse<TResponse>>()
-                        : Observable.Return(t.Item1);
+                    }
+                    if (t.Item1 == null)
+                    {
+                        Debug.WriteLine($"empty item thread id: {Thread.CurrentThread.ManagedThreadId}");
+                        return Observable.Empty<GraphQLResponse<TResponse>>();
+                    }
+                    return Observable.Return(t.Item1);
                 })
                 // transform to hot observable and auto-connect
                 .Publish().RefCount();
@@ -319,7 +325,7 @@ public Task<GraphQLResponse<TResponse>> SendRequest<TResponse>(GraphQLRequest re
                     }
                     catch (Exception e)
                     {
-                        Console.WriteLine(e);
+                        Debug.WriteLine(e);
                         throw;
                     }
 
@@ -408,7 +414,7 @@ public Task InitializeWebSocket()
 #else
                 _clientWebSocket = new ClientWebSocket();
                 _clientWebSocket.Options.AddSubProtocol("graphql-ws");
-                if(!System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform(System.Runtime.InteropServices.OSPlatform.Create("WEBASSEMBLY")))
+                if(!System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform(System.Runtime.InteropServices.OSPlatform.Create("BROWSER")))
                 {
                     // the following properties are not supported in Blazor WebAssembly and throw a PlatformNotSupportedException error when accessed
                     _clientWebSocket.Options.ClientCertificates = ((HttpClientHandler)Options.HttpMessageHandler).ClientCertificates;
diff --git a/src/GraphQL.Primitives/GraphQLRequest.cs b/src/GraphQL.Primitives/GraphQLRequest.cs
index 72033552..19c7fded 100644
--- a/src/GraphQL.Primitives/GraphQLRequest.cs
+++ b/src/GraphQL.Primitives/GraphQLRequest.cs
@@ -49,6 +49,14 @@ public GraphQLRequest(string query, object? variables = null, string? operationN
             OperationName = operationName;
         }
 
+        public GraphQLRequest(IEnumerable<KeyValuePair<string, object>> values)
+        {
+            foreach(var kv in values)
+            {
+                Add(kv.Key, kv.Value);
+            }
+        }
+
         /// <summary>
         /// Returns a value that indicates whether this instance is equal to a specified object
         /// </summary>
@@ -86,7 +94,7 @@ public override int GetHashCode()
         {
             unchecked
             {
-                var hashCode = Query.GetHashCode();
+                var hashCode = Query?.GetHashCode() ?? 0;
                 hashCode = (hashCode * 397) ^ OperationName?.GetHashCode() ?? 0;
                 hashCode = (hashCode * 397) ^ Variables?.GetHashCode() ?? 0;
                 return hashCode;