manage_scene: tolerant params + optional buildIndex; add writer IO logs; keep direct write path

Author: dsarno

UnityMcpBridge/Editor/MCPForUnityBridge.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.IO;
 using System.Linq;
 using System.Net;
@@ -25,6 +26,14 @@ public static partial class MCPForUnityBridge
         private static readonly object startStopLock = new();
         private static readonly object clientsLock = new();
         private static readonly System.Collections.Generic.HashSet<TcpClient> activeClients = new();
+        // Single-writer outbox for framed responses
+        private class Outbound
+        {
+            public byte[] Payload;
+            public string Tag;
+            public int? ReqId;
+        }
+        private static readonly BlockingCollection<Outbound> _outbox = new(new ConcurrentQueue<Outbound>());
         private static CancellationTokenSource cts;
         private static Task listenerTask;
         private static int processingCommands = 0;
@@ -44,6 +53,10 @@ private static Dictionary<
         private const ulong MaxFrameBytes = 64UL * 1024 * 1024; // 64 MiB hard cap for framed payloads
         private const int FrameIOTimeoutMs = 30000; // Per-read timeout to avoid stalled clients
 
+        // IO diagnostics
+        private static long _ioSeq = 0;
+        private static void IoInfo(string s) { McpLog.Info(s, always: false); }
+
         // Debug helpers
         private static bool IsDebugEnabled()
         {
@@ -112,6 +125,35 @@ static MCPForUnityBridge()
         {
             // Record the main thread ID for safe thread checks
             try { mainThreadId = Thread.CurrentThread.ManagedThreadId; } catch { mainThreadId = 0; }
+            // Start single writer thread for framed responses
+            try
+            {
+                var writerThread = new Thread(() =>
+                {
+                    foreach (var item in _outbox.GetConsumingEnumerable())
+                    {
+                        try
+                        {
+                            long seq = Interlocked.Increment(ref _ioSeq);
+                            IoInfo($"[IO] ➜ write start seq={seq} tag={item.Tag} len={(item.Payload?.Length ?? 0)} reqId={(item.ReqId?.ToString() ?? "?")}");
+                            var sw = System.Diagnostics.Stopwatch.StartNew();
+                            // Note: We currently have a per-connection 'stream' in the client handler. For simplicity,
+                            // writes are performed inline there. This outbox provides single-writer semantics; if a shared
+                            // stream is introduced, redirect here accordingly.
+                            // No-op: actual write happens in client loop using WriteFrameAsync
+                            sw.Stop();
+                            IoInfo($"[IO] ✓ write end   tag={item.Tag} len={(item.Payload?.Length ?? 0)} reqId={(item.ReqId?.ToString() ?? "?")} durMs={sw.Elapsed.TotalMilliseconds:F1}");
+                        }
+                        catch (Exception ex)
+                        {
+                            IoInfo($"[IO] ✗ write FAIL  tag={item.Tag} reqId={(item.ReqId?.ToString() ?? "?")} {ex.GetType().Name}: {ex.Message}");
+                        }
+                    }
+                }) { IsBackground = true, Name = "MCP-Writer" };
+                writerThread.Start();
+            }
+            catch { }
+
             // Skip bridge in headless/batch environments (CI/builds) unless explicitly allowed via env
             // CI override: set UNITY_MCP_ALLOW_BATCH=1 to allow the bridge in batch mode
             if (Application.isBatchMode && string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("UNITY_MCP_ALLOW_BATCH")))
@@ -579,8 +621,32 @@ private static async Task HandleClientAsync(TcpClient client, CancellationToken
                         {
                             try { MCPForUnity.Editor.Helpers.McpLog.Info("[MCP] sending framed response", always: false); } catch { }
                         }
-                        byte[] responseBytes = System.Text.Encoding.UTF8.GetBytes(response);
-                        await WriteFrameAsync(stream, responseBytes);
+                        // Crash-proof and self-reporting writer logs (direct write to this client's stream)
+                        long seq = System.Threading.Interlocked.Increment(ref _ioSeq);
+                        byte[] responseBytes;
+                        try
+                        {
+                            responseBytes = System.Text.Encoding.UTF8.GetBytes(response);
+                            IoInfo($"[IO] ➜ write start seq={seq} tag=response len={responseBytes.Length} reqId=?");
+                        }
+                        catch (Exception ex)
+                        {
+                            IoInfo($"[IO] ✗ serialize FAIL tag=response reqId=? {ex.GetType().Name}: {ex.Message}");
+                            throw;
+                        }
+
+                        var swDirect = System.Diagnostics.Stopwatch.StartNew();
+                        try
+                        {
+                            await WriteFrameAsync(stream, responseBytes);
+                            swDirect.Stop();
+                            IoInfo($"[IO] ✓ write end   tag=response len={responseBytes.Length} reqId=? durMs={swDirect.Elapsed.TotalMilliseconds:F1}");
+                        }
+                        catch (Exception ex)
+                        {
+                            IoInfo($"[IO] ✗ write FAIL  tag=response reqId=? {ex.GetType().Name}: {ex.Message}");
+                            throw;
+                        }
                     }
                     catch (Exception ex)
                     {

UnityMcpBridge/Editor/Tools/ManageScene.cs

@@ -16,16 +16,46 @@ namespace MCPForUnity.Editor.Tools
     /// </summary>
     public static class ManageScene
     {
+        private sealed class SceneCommand
+        {
+            public string action { get; set; } = string.Empty;
+            public string name { get; set; } = string.Empty;
+            public string path { get; set; } = string.Empty;
+            public int? buildIndex { get; set; }
+        }
+
+        private static SceneCommand ToSceneCommand(JObject p)
+        {
+            if (p == null) return new SceneCommand();
+            int? BI(JToken t)
+            {
+                if (t == null || t.Type == JTokenType.Null) return null;
+                var s = t.ToString().Trim();
+                if (s.Length == 0) return null;
+                if (int.TryParse(s, out var i)) return i;
+                if (double.TryParse(s, out var d)) return (int)d;
+                return t.Type == JTokenType.Integer ? t.Value<int>() : (int?)null;
+            }
+            return new SceneCommand
+            {
+                action = (p["action"]?.ToString() ?? string.Empty).Trim().ToLowerInvariant(),
+                name = p["name"]?.ToString() ?? string.Empty,
+                path = p["path"]?.ToString() ?? string.Empty,
+                buildIndex = BI(p["buildIndex"] ?? p["build_index"])
+            };
+        }
+
         /// <summary>
         /// Main handler for scene management actions.
         /// </summary>
         public static object HandleCommand(JObject @params)
         {
             try { McpLog.Info("[ManageScene] HandleCommand: start", always: false); } catch { }
-            string action = @params["action"]?.ToString().ToLower();
-            string name = @params["name"]?.ToString();
-            string path = @params["path"]?.ToString(); // Relative to Assets/
-            int? buildIndex = @params["buildIndex"]?.ToObject<int?>();
+            var cmd = ToSceneCommand(@params);
+            string action = cmd.action;
+            string name = string.IsNullOrEmpty(cmd.name) ? null : cmd.name;
+            string path = string.IsNullOrEmpty(cmd.path) ? null : cmd.path; // Relative to Assets/
+            int? buildIndex = cmd.buildIndex;
             // bool loadAdditive = @params["loadAdditive"]?.ToObject<bool>() ?? false; // Example for future extension
 
             // Ensure path is relative to Assets/, removing any leading "Assets/"

UnityMcpBridge/UnityMcpServer~/src/tools/manage_scene.py

@@ -14,9 +14,9 @@ def register_manage_scene_tools(mcp: FastMCP):
     def manage_scene(
         ctx: Context,
         action: str,
-        name: str,
-        path: str,
-        build_index: Any,
+        name: str = "",
+        path: str = "",
+        build_index: Any = None,
     ) -> Dict[str, Any]:
         """Manages Unity scenes (load, save, create, get hierarchy, etc.).
 
@@ -47,15 +47,15 @@ def _coerce_int(value, default=None):
                 except Exception:
                     return default
 
-            build_index = _coerce_int(build_index, default=0)
+            coerced_build_index = _coerce_int(build_index, default=None)
 
-            params = {
-                "action": action,
-                "name": name,
-                "path": path,
-                "buildIndex": build_index
-            }
-            params = {k: v for k, v in params.items() if v is not None}
+            params = {"action": action}
+            if name:
+                params["name"] = name
+            if path:
+                params["path"] = path
+            if coerced_build_index is not None:
+                params["buildIndex"] = coerced_build_index
 
             # Use centralized retry helper
             response = send_command_with_retry("manage_scene", params)