Generate the session ID from the server

We also make the identifying hashes longer

Author: msanatan

MCPForUnity/Editor/Helpers/ProjectIdentityUtility.cs

@@ -94,7 +94,7 @@ private static string ComputeProjectHash(string dataPath)
                 {
                     sb.Append(b.ToString("x2"));
                 }
-                return sb.ToString(0, Math.Min(8, sb.Length));
+                return sb.ToString(0, Math.Min(16, sb.Length));
             }
             catch
             {
@@ -122,6 +122,32 @@ private static string ComputeProjectName(string dataPath)
             }
         }
 
+        /// <summary>
+        /// Persists a server-assigned session id.
+        /// Safe to call from background threads.
+        /// </summary>
+        public static void SetSessionId(string sessionId)
+        {
+            if (string.IsNullOrEmpty(sessionId))
+            {
+                return;
+            }
+
+            EditorApplication.delayCall += () =>
+            {
+                try
+                {
+                    string projectHash = GetProjectHash();
+                    string projectSpecificKey = $"{SessionPrefKey}_{projectHash}";
+                    EditorPrefs.SetString(projectSpecificKey, sessionId);
+                }
+                catch (Exception ex)
+                {
+                    McpLog.Warn($"Failed to persist session ID: {ex.Message}");
+                }
+            };
+        }
+
         /// <summary>
         /// Retrieves a persistent session id for the plugin, creating one if absent.
         /// The session id is unique per project (scoped by project hash).

MCPForUnity/Editor/Services/Transport/Transports/WebSocketTransportClient.cs

@@ -42,6 +42,9 @@ public class WebSocketTransportClient : IMcpTransportClient, IDisposable
 
         private Uri _endpointUri;
         private string _sessionId;
+        private string _projectHash;
+        private string _projectName;
+        private string _unityVersion;
         private TimeSpan _keepAliveInterval = DefaultKeepAliveInterval;
         private TimeSpan _socketKeepAliveInterval = DefaultKeepAliveInterval;
         private volatile bool _isConnected;
@@ -54,19 +57,25 @@ public class WebSocketTransportClient : IMcpTransportClient, IDisposable
 
         public async Task<bool> StartAsync()
         {
+            // Capture identity values on the main thread before any async context switching
+            _projectName = ProjectIdentityUtility.GetProjectName();
+            _projectHash = ProjectIdentityUtility.GetProjectHash();
+            _unityVersion = Application.unityVersion;
+
             await StopAsync();
 
             _lifecycleCts = new CancellationTokenSource();
             _endpointUri = BuildWebSocketUri(HttpEndpointUtility.GetBaseUrl());
-            _sessionId = ProjectIdentityUtility.GetOrCreateSessionId();
+            _sessionId = null;
 
             if (!await EstablishConnectionAsync(_lifecycleCts.Token))
             {
                 await StopAsync();
                 return false;
             }
 
-            _state = TransportState.Connected(TransportDisplayName, sessionId: _sessionId, details: _endpointUri.ToString());
+            // State is connected but session ID might be pending until 'registered' message
+            _state = TransportState.Connected(TransportDisplayName, sessionId: "pending", details: _endpointUri.ToString());
             _isConnected = true;
             return true;
         }
@@ -281,6 +290,9 @@ private async Task HandleMessageAsync(string message, CancellationToken token)
                 case "welcome":
                     ApplyWelcome(payload);
                     break;
+                case "registered":
+                    HandleRegistered(payload);
+                    break;
                 case "execute":
                     await HandleExecuteAsync(payload, token).ConfigureAwait(false);
                     break;
@@ -311,6 +323,18 @@ private void ApplyWelcome(JObject payload)
             }
         }
 
+        private void HandleRegistered(JObject payload)
+        {
+            string newSessionId = payload.Value<string>("session_id");
+            if (!string.IsNullOrEmpty(newSessionId))
+            {
+                _sessionId = newSessionId;
+                ProjectIdentityUtility.SetSessionId(_sessionId);
+                _state = TransportState.Connected(TransportDisplayName, sessionId: _sessionId, details: _endpointUri.ToString());
+                McpLog.Info($"[WebSocket] Registered with session ID: {_sessionId}");
+            }
+        }
+
         private async Task HandleExecuteAsync(JObject payload, CancellationToken token)
         {
             string commandId = payload.Value<string>("id");
@@ -409,10 +433,10 @@ private async Task SendRegisterAsync(CancellationToken token)
             var registerPayload = new JObject
             {
                 ["type"] = "register",
-                ["session_id"] = _sessionId,
-                ["project_name"] = ProjectIdentityUtility.GetProjectName(),
-                ["project_hash"] = ProjectIdentityUtility.GetProjectHash(),
-                ["unity_version"] = Application.unityVersion
+                // session_id is now server-authoritative; omitted here or sent as null
+                ["project_name"] = _projectName,
+                ["project_hash"] = _projectHash,
+                ["unity_version"] = _unityVersion
             };
 
             await SendJsonAsync(registerPayload, token).ConfigureAwait(false);

Server/src/transport/plugin_hub.py

@@ -149,15 +149,21 @@ async def _handle_register(self, websocket: WebSocket, payload: Dict[str, Any])
             await websocket.close(code=1011)
             raise RuntimeError("PluginHub not configured")
 
-        session_id = payload.get("session_id")
         project_name = payload.get("project_name", "Unknown Project")
         project_hash = payload.get("project_hash")
         unity_version = payload.get("unity_version", "Unknown")
 
-        if not session_id or not project_hash:
+        if not project_hash:
             await websocket.close(code=4400)
             raise ValueError(
-                "Plugin registration missing session_id or project_hash")
+                "Plugin registration missing project_hash")
+
+        session_id = str(uuid.uuid4())
+        # Inform the plugin of its assigned session ID
+        await websocket.send_json({
+            "type": "registered",
+            "session_id": session_id
+        })
 
         session = await registry.register(session_id, project_name, project_hash, unity_version)
         async with lock: