feat(transport): add a headless boot path for the HTTP plugin hub

MCPForUnity/Editor/Helpers/HttpEndpointUtility.cs

@@ -47,10 +47,13 @@ public static void SaveBaseUrl(string userValue)
         }
 
         /// <summary>
-        /// Returns the normalized local HTTP base URL (always reads local pref).
+        /// Returns the normalized local HTTP base URL. UNITY_MCP_HTTP_PORT wins when set,
+        /// so a CI editor keeps its own port instead of the one a sibling last wrote.
         /// </summary>
         public static string GetLocalBaseUrl()
         {
+            if (McpHttpCiBoot.TryGetCiPort(out int ciPort)) return $"http://127.0.0.1:{ciPort}";
+
             string stored = EditorPrefs.GetString(LocalPrefKey, DefaultLocalBaseUrl);
             return NormalizeBaseUrl(stored, DefaultLocalBaseUrl, remoteScope: false);
         }
@@ -128,9 +131,12 @@ public static string GetRegisterToolsUrl()
 
         /// <summary>
         /// Returns true if the active HTTP transport scope is "remote".
+        /// Always false under UNITY_MCP_HTTP_PORT: the CI endpoint is local by construction.
         /// </summary>
         public static bool IsRemoteScope()
         {
+            if (McpHttpCiBoot.TryGetCiPort(out _)) return false;
+
             string scope = EditorConfigurationCache.Instance.HttpTransportScope;
             return string.Equals(scope, "remote", StringComparison.OrdinalIgnoreCase);
         }

MCPForUnity/Editor/McpHttpCiBoot.cs

@@ -0,0 +1,49 @@
+using System;
+using MCPForUnity.Editor.Helpers;
+using MCPForUnity.Editor.Services;
+using MCPForUnity.Editor.Services.Transport;
+using UnityEditor;
+
+namespace MCPForUnity.Editor
+{
+    // HTTP is a plugin-hub pull model: the editor dials ws://127.0.0.1:<port>/hub/plugin
+    // StartStdioForCi only listens, so an editor booted that way never registers
+    public static class McpHttpCiBoot
+    {
+        private const string PortEnv = "UNITY_MCP_HTTP_PORT";
+
+        // Never persisted: sibling checkouts share one EditorPrefs file, so the last writer wins
+        public static bool TryGetCiPort(out int port)
+        {
+            port = 0;
+            string raw = Environment.GetEnvironmentVariable(PortEnv);
+            return !string.IsNullOrWhiteSpace(raw)
+                   && int.TryParse(raw, out port)
+                   && port > 0
+                   && port <= 65535;
+        }
+
+        public static void StartHttpForCi()
+        {
+            if (!TryGetCiPort(out _))
+            {
+                McpLog.Error($"[MCPForUnity] StartHttpForCi: {PortEnv} not set or invalid; cannot start HTTP transport");
+                return;
+            }
+
+            // Defer the connect so MCPServiceLocator and friends are initialized.
+            EditorApplication.delayCall += async () =>
+            {
+                try
+                {
+                    if (!await MCPServiceLocator.TransportManager.StartAsync(TransportMode.Http))
+                        McpLog.Error("[MCPForUnity] StartHttpForCi: HTTP transport failed to start");
+                }
+                catch (Exception e)
+                {
+                    McpLog.Error($"[MCPForUnity] StartHttpForCi: HTTP transport threw on start: {e}");
+                }
+            };
+        }
+    }
+}