diff --git a/GamecraftModdingAPI/Events/DeterministicStepComposeEngineGroupsPatch.cs b/GamecraftModdingAPI/Events/DeterministicStepComposeEngineGroupsPatch.cs
new file mode 100644
index 0000000..b880257
--- /dev/null
+++ b/GamecraftModdingAPI/Events/DeterministicStepComposeEngineGroupsPatch.cs
@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Text;
+using System.Threading.Tasks;
+
+using Harmony;
+using Svelto.ECS;
+using RobocraftX.StateSync;
+
+using GamecraftModdingAPI.Utility;
+
+namespace GamecraftModdingAPI.Events
+{
+    /// <summary>
+    /// Patch of RobocraftX.StateSync.DeterministicStepCompositionRoot.ComposeEnginesGroups(...)
+    /// </summary>
+	[HarmonyPatch(typeof(DeterministicStepCompositionRoot), "ComposeEnginesGroups")]
+	//[HarmonyPatch]
+    class DeterministicStepComposeEngineGroupsPatch
+    {
+
+		public static readonly GameStateBuildEmitterEngine buildEngine = new GameStateBuildEmitterEngine();
+
+		public static readonly GameStateSimulationEmitterEngine simEngine = new GameStateSimulationEmitterEngine();
+        
+        public static void Prefix(ref StateSyncRegistrationHelper stateSyncReg)
+        {
+			stateSyncReg.buildModeInitializationEngines.Add(buildEngine);
+			stateSyncReg.simulationModeInitializationEngines.Add(simEngine);
+        }
+
+		public static MethodBase NopeTargetMethod()
+        {
+			return typeof(DeterministicStepCompositionRoot).GetMethods().First(m => m.Name == "ComposeEnginesGroups")
+                .MakeGenericMethod(typeof(object));
+        }
+    }
+}
diff --git a/GamecraftModdingAPI/Events/EventType.cs b/GamecraftModdingAPI/Events/EventType.cs
index 7383da2..468e214 100644
--- a/GamecraftModdingAPI/Events/EventType.cs
+++ b/GamecraftModdingAPI/Events/EventType.cs
@@ -17,6 +17,8 @@ namespace GamecraftModdingAPI.Events
         MenuSwitchedTo,
         Game,
         GameReloaded,
-        GameSwitchedTo
+        GameSwitchedTo,
+        SimulationSwitchedTo,
+        BuildSwitchedTo
     }
 }
diff --git a/GamecraftModdingAPI/Events/GameStateBuildEmitterEngine.cs b/GamecraftModdingAPI/Events/GameStateBuildEmitterEngine.cs
new file mode 100644
index 0000000..c9b267e
--- /dev/null
+++ b/GamecraftModdingAPI/Events/GameStateBuildEmitterEngine.cs
@@ -0,0 +1,44 @@
+using System;
+
+using Unity.Jobs;
+using RobocraftX.StateSync;
+using Svelto.ECS;
+
+using GamecraftModdingAPI.Utility;
+
+namespace GamecraftModdingAPI.Events
+{
+    /// <summary>
+    /// Event emitter engine for switching to to build mode.
+    /// </summary>
+	public class GameStateBuildEmitterEngine : IEventEmitterEngine, IInitializeOnBuildStart
+	{
+		public string Name { get; } = "GamecraftModdingAPIGameStateBuildEventEmitter" ;
+
+		public IEntitiesDB entitiesDB { set; private get; }
+
+		public object type { get; } = EventType.BuildSwitchedTo;
+
+		public bool isRemovable { get; } = false;
+
+		public IEntityFactory Factory { set; private get; }
+
+		public void Dispose() { }
+
+		public void Emit()
+		{
+			Logging.Log("Dispatching Build Switched To event");
+			if (Factory == null) { return; }
+			Factory.BuildEntity<ModEventEntityDescriptor>(ApiExclusiveGroups.eventID++, ApiExclusiveGroups.eventsExclusiveGroup)
+                .Init(new ModEventEntityStruct { type = type });
+		}
+
+		public JobHandle OnInitializeBuildMode()
+		{
+			Emit();
+			return default(JobHandle);
+		}
+
+		public void Ready() { }
+	}
+}
diff --git a/GamecraftModdingAPI/Events/GameStateSimulationEmitterEngine.cs b/GamecraftModdingAPI/Events/GameStateSimulationEmitterEngine.cs
new file mode 100644
index 0000000..7427dd0
--- /dev/null
+++ b/GamecraftModdingAPI/Events/GameStateSimulationEmitterEngine.cs
@@ -0,0 +1,44 @@
+using System;
+
+using Unity.Jobs;
+using RobocraftX.StateSync;
+using Svelto.ECS;
+
+using GamecraftModdingAPI.Utility;
+
+namespace GamecraftModdingAPI.Events
+{
+    /// <summary>
+    /// Event emitter engine for switching to simulation mode.
+    /// </summary>
+	public class GameStateSimulationEmitterEngine : IEventEmitterEngine, IInitializeOnSimulationStart
+	{
+		public string Name { get; } = "GamecraftModdingAPIGameStateSimulationEventEmitter" ;
+
+		public IEntitiesDB entitiesDB { set; private get; }
+
+		public object type { get; } = EventType.SimulationSwitchedTo;
+
+		public bool isRemovable { get; } = false;
+
+		public IEntityFactory Factory { set; private get; }
+
+		public void Dispose() { }
+
+		public void Emit()
+		{
+			Logging.Log("Dispatching Simulation Switched To event");
+			if (Factory == null) { return; }
+			Factory.BuildEntity<ModEventEntityDescriptor>(ApiExclusiveGroups.eventID++, ApiExclusiveGroups.eventsExclusiveGroup)
+			       .Init(new ModEventEntityStruct { type = type });
+		}
+
+		public JobHandle OnInitializeSimulationMode()
+		{
+			Emit();
+			return default(JobHandle);
+		}
+
+		public void Ready() { }
+	}
+}
diff --git a/GamecraftModdingAPI/Main.cs b/GamecraftModdingAPI/Main.cs
index 28b4dce..2c51872 100644
--- a/GamecraftModdingAPI/Main.cs
+++ b/GamecraftModdingAPI/Main.cs
@@ -56,6 +56,8 @@ namespace GamecraftModdingAPI
             EventManager.AddEventEmitter(new SimpleEventEmitterEngine(EventType.Game, "GamecraftModdingAPIGameActivatedEventEmitter", false));
             EventManager.AddEventEmitter(new SimpleEventEmitterEngine(EventType.GameReloaded, "GamecraftModdingAPIGameReloadedEventEmitter", false));
             EventManager.AddEventEmitter(new SimpleEventEmitterEngine(EventType.GameSwitchedTo, "GamecraftModdingAPIGameSwitchedToEventEmitter", false));
+			EventManager.AddEventEmitter(DeterministicStepComposeEngineGroupsPatch.buildEngine);
+			EventManager.AddEventEmitter(DeterministicStepComposeEngineGroupsPatch.simEngine);
             // init block implementors
             Logging.MetaDebugLog($"Initializing Blocks");
             Blocks.Movement.Init();
diff --git a/GamecraftModdingAPI/Tests/GamecraftModdingAPIPluginTest.cs b/GamecraftModdingAPI/Tests/GamecraftModdingAPIPluginTest.cs
index 3a47ad9..1d55602 100644
--- a/GamecraftModdingAPI/Tests/GamecraftModdingAPIPluginTest.cs
+++ b/GamecraftModdingAPI/Tests/GamecraftModdingAPIPluginTest.cs
@@ -68,6 +68,10 @@ namespace GamecraftModdingAPI.Tests
                 EventType.GameReloaded, "gamerel API debug"));
             EventManager.AddEventHandler(new SimpleEventHandlerEngine(() => { Logging.Log("Game Switched To event!"); }, () => { },
                 EventType.GameSwitchedTo, "gameswitch API debug"));
+			EventManager.AddEventHandler(new SimpleEventHandlerEngine(() => { Logging.Log("Game Mode Simulation Switched To event!"); }, () => { },
+			    EventType.SimulationSwitchedTo, "simulationswitch API debug"));
+			EventManager.AddEventHandler(new SimpleEventHandlerEngine(() => { Logging.Log("Game Mode Build Switched To event!"); }, () => { },
+                EventType.BuildSwitchedTo, "buildswitch API debug"));
 
             // debug/test commands
 			if (Dependency.Hell("ExtraCommands"))