Unity MCP

using System; using System.CodeDom.Compiler; using System.Linq; using System.Collections.Generic; using Microsoft.CSharp; using UnityEditor; using UnityEngine; using System.Threading.Tasks; using Cysharp.Threading.Tasks; namespace UnityMCP { /// <summary> /// Executes arbitrary C# code in Unity Editor context /// This enables AI assistants to perform ANY Unity operation without predefined tools /// Threading pattern from CoplayDev/unity-mcp - uses EditorApplication.update for main thread dispatch /// </summary> public static class CSharpExecutor { private static readonly System.Collections.Concurrent.ConcurrentQueue<PendingExecution> executionQueue = new System.Collections.Concurrent.ConcurrentQueue<PendingExecution>(); private static bool isProcessorRegistered = false; private static readonly object registrationLock = new object(); private static int mainThreadId = -1; // Will be set by InitializeOnLoad private class PendingExecution { public string Code; public TaskCompletionSource<ExecutionResult> Tcs; } /// <summary> /// Initialize on Unity's main thread to capture correct thread ID /// This is called by Unity before any other code runs /// </summary> [UnityEditor.InitializeOnLoadMethod] private static void InitializeOnMainThread() { // Capture Unity's main thread ID mainThreadId = System.Threading.Thread.CurrentThread.ManagedThreadId; RegisterUpdateProcessor(); } private static void RegisterUpdateProcessor() { lock (registrationLock) { if (!isProcessorRegistered) { UnityEditor.EditorApplication.update += ProcessExecutionQueue; isProcessorRegistered = true; } } } private static void ProcessExecutionQueue() { // Process all pending executions on Unity's main thread while (executionQueue.TryDequeue(out var pending)) { try { var result = ExecuteOnMainThread(pending.Code); pending.Tcs.TrySetResult(result); } catch (Exception ex) { UnityEngine.Debug.LogError($"[Unity MCP] Code execution failed: {ex.Message}"); var errorResult = new ExecutionResult { Success = false, Error = $"Execution failed: {ex.Message}", Logs = new System.Collections.Generic.List<string>(), Warnings = new System.Collections.Generic.List<string>(), Errors = new System.Collections.Generic.List<string> { ex.Message } }; pending.Tcs.TrySetResult(errorResult); } } } /// <summary> /// Execute C# code with full access to UnityEngine and UnityEditor APIs /// </summary> /// <param name="code">The C# code to execute</param> /// <returns>Execution result or "Success" if void</returns> public static object ExecuteCode(string code) { if (string.IsNullOrWhiteSpace(code)) { throw new ArgumentException("Code cannot be empty"); } // Wrap code in a static method string wrappedCode = $@" using UnityEngine; using UnityEditor; using System; using System.Linq; using System.Collections; using System.Collections.Generic; using UnityEngine.SceneManagement; using UnityEditor.SceneManagement; public class CodeExecutor {{ public static object Execute() {{ {code} return ""Success""; }} }} "; var options = new CompilerParameters { GenerateInMemory = true, GenerateExecutable = false, IncludeDebugInformation = false }; // Add assemblies - only Unity assemblies, CSharpCodeProvider includes mscorlib automatically options.ReferencedAssemblies.Add(typeof(UnityEngine.Object).Assembly.Location); options.ReferencedAssemblies.Add(typeof(UnityEditor.Editor).Assembly.Location); // Add System.Core for LINQ support var linqAssembly = typeof(System.Linq.Enumerable).Assembly.Location; if (!string.IsNullOrEmpty(linqAssembly)) options.ReferencedAssemblies.Add(linqAssembly); // Compile and execute using (var provider = new CSharpCodeProvider()) { var results = provider.CompileAssemblyFromSource(options, wrappedCode); // Check for compilation errors if (results.Errors.HasErrors) { var errors = string.Join("\n", results.Errors.Cast<CompilerError>() .Select(e => $"Line {e.Line}: {e.ErrorText}")); throw new Exception($"Compilation failed:\n{errors}"); } // Execute the compiled code var assembly = results.CompiledAssembly; var type = assembly.GetType("CodeExecutor"); var method = type.GetMethod("Execute"); try { return method.Invoke(null, null); } catch (Exception e) { // Unwrap TargetInvocationException to get the real error var innerException = e.InnerException ?? e; throw new Exception($"Runtime error: {innerException.Message}\n{innerException.StackTrace}"); } } } /// <summary> /// Execute code with comprehensive error handling and logging /// Automatically handles threading - safe to call from any thread /// Uses EditorApplication.update queue pattern from CoplayDev/unity-mcp /// </summary> public static ExecutionResult ExecuteWithResult(string code) { // Check if Unity is compiling if (UnityEditor.EditorApplication.isCompiling) { return new ExecutionResult { Success = false, Error = "Unity is compiling, please wait...", Logs = new System.Collections.Generic.List<string>(), Warnings = new System.Collections.Generic.List<string>(), Errors = new System.Collections.Generic.List<string> { "Compilation in progress" } }; } // If already on Unity's main thread, execute directly (avoid deadlock) var currentThreadId = System.Threading.Thread.CurrentThread.ManagedThreadId; if (currentThreadId == mainThreadId) { return ExecuteOnMainThread(code); } // From background thread: Queue execution and wait for completion // Pattern from CoplayDev/unity-mcp - EditorApplication.update processes queue every frame var tcs = new TaskCompletionSource<ExecutionResult>( TaskCreationOptions.RunContinuationsAsynchronously); // Prevent deadlocks executionQueue.Enqueue(new PendingExecution { Code = code, Tcs = tcs }); // Block background thread waiting for completion with timeout if (tcs.Task.Wait(System.TimeSpan.FromSeconds(30))) { return tcs.Task.Result; } else { return new ExecutionResult { Success = false, Error = "Execution timed out after 30 seconds", Logs = new System.Collections.Generic.List<string>(), Warnings = new System.Collections.Generic.List<string>(), Errors = new System.Collections.Generic.List<string> { "Timeout" } }; } } /// <summary> /// Async version using UniTask for Unity editor operations /// Use this when you're already in an async context and want to leverage UniTask /// </summary> public static async UniTask<ExecutionResult> ExecuteAsync(string code) { // Check if Unity is compiling if (UnityEditor.EditorApplication.isCompiling) { return new ExecutionResult { Success = false, Error = "Unity is compiling, please wait...", Logs = new System.Collections.Generic.List<string>(), Warnings = new System.Collections.Generic.List<string>(), Errors = new System.Collections.Generic.List<string> { "Compilation in progress" } }; } // Switch to Unity's main thread using UniTask await UniTask.SwitchToMainThread(); // Execute on main thread return ExecuteOnMainThread(code); } private static ExecutionResult ExecuteOnMainThread(string code) { var result = new ExecutionResult { Success = false, Logs = new System.Collections.Generic.List<string>(), Warnings = new System.Collections.Generic.List<string>(), Errors = new System.Collections.Generic.List<string>() }; // Capture logs during execution Application.logMessageReceived += LogHandler; try { var startTime = System.DateTime.Now; result.Result = ExecuteCode(code); result.Success = true; result.ExecutionTime = (System.DateTime.Now - startTime).TotalMilliseconds; } catch (Exception e) { result.Success = false; result.Errors.Add(e.Message); result.Error = e.Message; } finally { Application.logMessageReceived -= LogHandler; } return result; void LogHandler(string message, string stackTrace, LogType type) { switch (type) { case LogType.Log: result.Logs.Add(message); break; case LogType.Warning: result.Warnings.Add(message); break; case LogType.Error: case LogType.Exception: result.Errors.Add($"{message}\n{stackTrace}"); break; } } } } /// <summary> /// Result of C# code execution /// </summary> [System.Serializable] public class ExecutionResult { public bool Success; public object Result; public string Error; public System.Collections.Generic.List<string> Logs; public System.Collections.Generic.List<string> Warnings; public System.Collections.Generic.List<string> Errors; public double ExecutionTime; // milliseconds } }