Unify simulate/timeline controls + BeforeStop event + AI auto-possess safety net

- Remove the Simulate toolbar button (both Legacy + UMG widgets). Play /
  Pause / Restart / Stop now live exclusively on the Timeline panel, and
  the panel is visible by default (no more toggle button on the toolbar).
  Keeps a global Play button on the Legacy toolbar that opens the level
  outside the editor.

- Move the grace-period / deferred-stop logic out of the TimelineSubsystem
  and into APS_Editor_PlayerController::RequestStopSimulation. This lets
  the timeline Stop button AND the UMG topbar simulate buttons share the
  same event sequence: OnEditorBeforeSimulateStop fires immediately (after
  RestoreBaseline), then a 500ms BT grace period, then StopSimulation
  fires OnEditorSimulateStop and cuts AI. New event
  OnEditorBeforeSimulateStop added to the editable interface with full
  timing docs.

- Drop the early-return in TimelineSubsystem::Play when Tracks.Num()==0 —
  the timeline Play button is now the only way to start the sim, so it
  must drive StartSimulation unconditionally.

- StartSimulation now force-calls SpawnDefaultController() on any pawn
  that enters sim without a Controller but has an AIControllerClass set,
  so AutoPossessAI=Disabled or race-lost possessions don't leave the BT
  unreachable.

- Route the UMG topbar Play / Simulate buttons and the "simulate" command
  through RequestStopSimulation too, so every path emits the full event
  sequence consistently.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Unreal/Plugins/PS_Editor/Source/PS_Editor/GameMode/PS_Editor_PlayerController.cpp

@@ -9,6 +9,7 @@
 #include "PS_Editor_SplineActor.h"
 #include "PS_Editor_SplineEditable.h"
 #include "PS_Editor_PointPlaceable.h"
+#include "PS_Editor_EditableInterface.h"
 #include "Engine/LevelStreamingDynamic.h"
 #include "GameFramework/Character.h"
 #include "GameFramework/CharacterMovementComponent.h"
@@ -237,6 +238,16 @@ void APS_Editor_PlayerController::CloseEditor()
 
 void APS_Editor_PlayerController::StartSimulation()
 {
+	// If a RequestStopSimulation is in flight, cancel it — user wants to resume.
+	if (UWorld* World = GetWorld())
+	{
+		if (PendingStopSimulationHandle.IsValid())
+		{
+			World->GetTimerManager().ClearTimer(PendingStopSimulationHandle);
+			PendingStopSimulationHandle.Invalidate();
+		}
+	}
+
 	if (bSimulating) return;
 	bSimulating = true;
 
@@ -286,7 +297,18 @@ void APS_Editor_PlayerController::StartSimulation()
 					}
 				}
 
-				if (AAIController* AIC = Cast<AAIController>(P->GetController()))
+				AController* RawCtrl = P->GetController();
+
+				// Safety net: if auto-possession never fired (e.g. AutoPossessAI=Disabled, or
+				// pawn got its tick frozen before possession completed), spawn the default
+				// AIController now so the BT can run during simulation.
+				if (!RawCtrl && P->AIControllerClass)
+				{
+					P->SpawnDefaultController();
+					RawCtrl = P->GetController();
+				}
+
+				if (AAIController* AIC = Cast<AAIController>(RawCtrl))
 				{
 					AIC->SetActorTickEnabled(true);
 					if (UBrainComponent* Brain = AIC->GetBrainComponent())
@@ -298,11 +320,35 @@ void APS_Editor_PlayerController::StartSimulation()
 		}
 	}
 
+	// Broadcast OnEditorSimulateStart to every spawned actor that implements the editable
+	// interface — fired AFTER AI has been enabled so BP handlers can query the AI state.
+	if (SpawnManager)
+	{
+		for (const TWeakObjectPtr<AActor>& Weak : SpawnManager->GetSpawnedActors())
+		{
+			AActor* Actor = Weak.Get();
+			if (Actor && Actor->GetClass()->ImplementsInterface(UPS_Editor_EditableInterface::StaticClass()))
+			{
+				IPS_Editor_EditableInterface::Execute_OnEditorSimulateStart(Actor);
+			}
+		}
+	}
+
 	UE_LOG(LogTemp, Log, TEXT("PS_Editor: Simulation started (%d actors saved)"), SimulationSavedTransforms.Num());
 }
 
 void APS_Editor_PlayerController::SetSimulationPaused(bool bPaused)
 {
+	// Resuming? Cancel any in-flight deferred stop (user chose to keep going).
+	if (!bPaused && PendingStopSimulationHandle.IsValid())
+	{
+		if (UWorld* World = GetWorld())
+		{
+			World->GetTimerManager().ClearTimer(PendingStopSimulationHandle);
+			PendingStopSimulationHandle.Invalidate();
+		}
+	}
+
 	// Toggle AI tick + BT on every spawned pawn without touching bSimulating or the saved
 	// transforms — the timeline's Pause uses this so characters freeze instead of snapping
 	// back to their pre-play positions.
@@ -332,9 +378,73 @@ void APS_Editor_PlayerController::SetSimulationPaused(bool bPaused)
 	}
 }
 
+void APS_Editor_PlayerController::RequestStopSimulation()
+{
+	if (!bSimulating) return;
+
+	// If a request is already scheduled, do nothing (debounce double-clicks on Stop).
+	if (UWorld* World = GetWorld())
+	{
+		if (PendingStopSimulationHandle.IsValid()) return;
+	}
+
+	// Fire OnEditorBeforeSimulateStop immediately on every actor so BP handlers can react
+	// while the BT is still live. Then schedule the real cut for ~500ms later.
+	if (SpawnManager)
+	{
+		for (const TWeakObjectPtr<AActor>& Weak : SpawnManager->GetSpawnedActors())
+		{
+			AActor* Actor = Weak.Get();
+			if (Actor && Actor->GetClass()->ImplementsInterface(UPS_Editor_EditableInterface::StaticClass()))
+			{
+				IPS_Editor_EditableInterface::Execute_OnEditorBeforeSimulateStop(Actor);
+			}
+		}
+	}
+
+	if (UWorld* World = GetWorld())
+	{
+		TWeakObjectPtr<APS_Editor_PlayerController> WeakThis(this);
+		World->GetTimerManager().SetTimer(PendingStopSimulationHandle,
+			[WeakThis]()
+			{
+				if (APS_Editor_PlayerController* Self = WeakThis.Get())
+				{
+					if (Self->IsSimulating())
+					{
+						Self->StopSimulation();
+					}
+					Self->PendingStopSimulationHandle.Invalidate();
+				}
+			},
+			0.5f, false);
+	}
+	else
+	{
+		// No world timer available (shouldn't happen in practice) — fall back to sync stop.
+		StopSimulation();
+	}
+}
+
 void APS_Editor_PlayerController::StopSimulation()
 {
 	if (!bSimulating) return;
+
+	// Broadcast OnEditorSimulateStop to every spawned actor BEFORE we actually cut AI or
+	// restore transforms. At this point bSimulating is still true and the BT is still
+	// live — BP handlers can read world state, stop audio, log telemetry, etc.
+	if (SpawnManager)
+	{
+		for (const TWeakObjectPtr<AActor>& Weak : SpawnManager->GetSpawnedActors())
+		{
+			AActor* Actor = Weak.Get();
+			if (Actor && Actor->GetClass()->ImplementsInterface(UPS_Editor_EditableInterface::StaticClass()))
+			{
+				IPS_Editor_EditableInterface::Execute_OnEditorSimulateStop(Actor);
+			}
+		}
+	}
+
 	bSimulating = false;
 
 	// Disable AI logic and re-apply rotation/movement overrides on all spawned pawns

Unreal/Plugins/PS_Editor/Source/PS_Editor/GameMode/PS_Editor_PlayerController.h

@@ -62,14 +62,24 @@ public:
 
 	// ---- Simulate Mode ----
 
-	/** Start simulation: enable AI, store actor positions, disable saving. */
+	/** Start simulation: enable AI, store actor positions, disable saving.
+	 *  Cancels any in-flight deferred RequestStopSimulation. */
 	UFUNCTION(BlueprintCallable, Category = "ASTERION|PS_Editor")
 	void StartSimulation();
 
-	/** Stop simulation: disable AI, restore actor positions, re-enable saving. */
+	/** Stop simulation: disable AI, restore actor positions, re-enable saving.
+	 *  Synchronous — fires OnEditorSimulateStop and cuts AI immediately. Callers that want
+	 *  a BT grace period (with OnEditorBeforeSimulateStop) should use RequestStopSimulation. */
 	UFUNCTION(BlueprintCallable, Category = "ASTERION|PS_Editor")
 	void StopSimulation();
 
+	/** Request a deferred stop: fires OnEditorBeforeSimulateStop immediately, then schedules
+	 *  the real StopSimulation after a grace period (500ms by default) so BT has time to
+	 *  react to whatever the BP handler does in OnEditorBeforeSimulateStop.
+	 *  Timeline Stop and the Simulate toolbar button both go through this. */
+	UFUNCTION(BlueprintCallable, Category = "ASTERION|PS_Editor")
+	void RequestStopSimulation();
+
 	/** True while simulation is running. */
 	UFUNCTION(BlueprintCallable, Category = "ASTERION|PS_Editor")
 	bool IsSimulating() const { return bSimulating; }
@@ -165,6 +175,9 @@ private:
 	/** Saved transforms for all spawned actors before simulation, to restore on stop. */
 	TMap<TWeakObjectPtr<AActor>, FTransform> SimulationSavedTransforms;
 
+	/** Timer handle for the deferred StopSimulation used by RequestStopSimulation. */
+	FTimerHandle PendingStopSimulationHandle;
+
 	/** Currently loaded sublevel instance. */
 	UPROPERTY()
 	TObjectPtr<ULevelStreamingDynamic> CurrentSublevel;

Unreal/Plugins/PS_Editor/Source/PS_Editor/Spawn/PS_Editor_EditableInterface.h

@@ -84,6 +84,55 @@ public:
 	UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "ASTERION|PS_Editor")
 	void OnEditorModeChanged(bool bIsEditing);
 
+	/**
+	 * Fired on every spawned actor once when the simulation starts — either via the
+	 * Simulate button or the timeline Play button (which calls StartSimulation under
+	 * the hood). Use this to kick off behaviour that should only happen while AI is live
+	 * (spawn FX, reset state counters, unlock input, etc.).
+	 */
+	UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "ASTERION|PS_Editor")
+	void OnEditorSimulateStart();
+
+	/**
+	 * Fired on every spawned actor once when the simulation is about to stop — either via
+	 * the Simulate button, the Stop button, or after a natural end. Called BEFORE AI tick
+	 * is actually cut and BEFORE transforms are restored, so the BT is still live and you
+	 * can still read / write state. Use this for cleanup (stop audio, save telemetry, etc.).
+	 *
+	 * Timing: fires at the "AI cut" moment, AFTER any grace period the timeline applied
+	 * (typically 500ms after Stop was clicked). BT is still live but about to be disabled.
+	 */
+	UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "ASTERION|PS_Editor")
+	void OnEditorSimulateStop();
+
+	/**
+	 * Fired synchronously on the Stop sequence, AFTER the timeline has restored the
+	 * pre-animation baseline onto every track (so properties are back to their initial
+	 * values and OnEditorPropertyChanged has already fired for each of them) but BEFORE
+	 * the grace period that leads up to the actual AI cut.
+	 *
+	 * Use this hook to trigger transition animations, resume BT branches, stop in-flight
+	 * actions — whatever reacts to the baseline being restored. You have ~500ms before
+	 * OnEditorSimulateStop fires and the AI tick is disabled, so anything you start here
+	 * has time to play out on-screen.
+	 *
+	 * Timing sequence:
+	 *   t=0     Stop() starts
+	 *           RestoreBaseline → ImportText + OnEditorPropertyChanged per track
+	 *           >>> OnEditorBeforeSimulateStop fires here <<<
+	 *           Grace period scheduled (500ms)
+	 *   t=500   OnEditorSimulateStop fires → AI tick cut → transforms restored
+	 *
+	 * Fires for ALL stop paths that go through RequestStopSimulation:
+	 *   - Timeline Stop / Restart (baseline restored first, then this event)
+	 *   - Simulate toolbar button when at least one timeline track exists
+	 *   - Simulate toolbar button without any timeline track (no baseline restore, but
+	 *     event still fires + grace period still granted)
+	 * Does NOT fire for direct StopSimulation calls (rare — e.g. forced editor close).
+	 */
+	UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "ASTERION|PS_Editor")
+	void OnEditorBeforeSimulateStop();
+
 	/**
 	 * Called every frame while in editor mode.
 	 * Use this to update visuals dynamically based on property changes, animate helpers, etc.

Unreal/Plugins/PS_Editor/Source/PS_Editor/Timeline/PS_Editor_TimelineSubsystem.cpp

@@ -3,6 +3,7 @@
 #include "PS_Editor_EditableComponent.h"
 #include "PS_Editor_EditableInterface.h"
 #include "PS_Editor_PlayerController.h"
+#include "PS_Editor_SpawnManager.h"
 #include "Engine/World.h"
 #include "Components/ActorComponent.h"
 #include "GameFramework/Actor.h"
@@ -87,23 +88,16 @@ bool UPS_Editor_TimelineSubsystem::IsTickable() const
 
 void UPS_Editor_TimelineSubsystem::Play()
 {
-	if (Data.Tracks.Num() == 0) return;
+	// NOTE: do NOT early-return when Data.Tracks.Num() == 0 — the timeline Play button is
+	// the only user-facing way to start simulation now (the old toolbar Simulate button was
+	// removed), so it must drive StartSimulation unconditionally. An empty timeline still
+	// runs the sim lifecycle (Start/BeforeStop/Stop events fire), it just doesn't animate
+	// any property.
 	if (CurrentTime >= Data.Duration)
 	{
 		CurrentTime = 0.f;
 	}
 
-	// Cancel any pending deferred StopSimulation (user hit Play again during the BT grace
-	// period after a previous Stop — don't cut the AI now).
-	if (UWorld* World = GetWorld())
-	{
-		if (PendingStopSimulationHandle.IsValid())
-		{
-			World->GetTimerManager().ClearTimer(PendingStopSimulationHandle);
-			PendingStopSimulationHandle.Invalidate();
-		}
-	}
-
 	// Make sure every track has a captured baseline. New tracks typically get their baseline
 	// at creation time (in AddOrUpdateKeyAtCurrentTime), tracks loaded from a scenario get
 	// theirs at SetData — this call is a safety net for anything that slipped through.
@@ -152,37 +146,19 @@ void UPS_Editor_TimelineSubsystem::Stop()
 	LastAppliedValues.Empty();
 	LastAppliedValues.SetNum(Data.Tracks.Num());
 
-	// Restore pre-play baseline values onto the actors BEFORE stopping simulation, so the
+	// Restore pre-play baseline values onto the actors BEFORE asking the PC to stop sim.
-	// BT sees the restored values (via OnEditorPropertyChanged / OnRep) and has a chance
+	// This fires OnEditorPropertyChanged per track so the BT sees the restored values
-	// to transition to a neutral state during the grace period below.
+	// while it's still live (during the grace period that RequestStopSimulation sets up).
 	RestoreBaseline();
 
-	// Defer the actual AI cut by a few frames so the BT can react to the restored values.
+	// Delegate to the PlayerController: it fires OnEditorBeforeSimulateStop, waits for its
-	// If Play() is called again during this window, the timer is cancelled there.
+	// grace period, then runs the actual StopSimulation (which in turn fires the final
+	// OnEditorSimulateStop and cuts AI). Same sequence the Simulate toolbar button uses.
 	if (APS_Editor_PlayerController* EditorPC = FindEditorPC(GetWorld()))
 	{
 		if (EditorPC->IsSimulating())
 		{
-			if (UWorld* World = GetWorld())
+			EditorPC->RequestStopSimulation();
-			{
-				TWeakObjectPtr<APS_Editor_PlayerController> WeakPC(EditorPC);
-				World->GetTimerManager().SetTimer(PendingStopSimulationHandle,
-					[WeakPC]()
-					{
-						if (APS_Editor_PlayerController* PC = WeakPC.Get())
-						{
-							if (PC->IsSimulating())
-							{
-								PC->StopSimulation();
-							}
-						}
-					},
-					0.1f, false);
-			}
-			else
-			{
-				EditorPC->StopSimulation();
-			}
 		}
 	}
 

Unreal/Plugins/PS_Editor/Source/PS_Editor/Timeline/PS_Editor_TimelineSubsystem.h

@@ -156,10 +156,6 @@ private:
 	 *  and Clear reset it. */
 	TMap<TPair<FGuid, FName>, FString> PrePlayBaseline;
 
-	/** Deferred StopSimulation timer — set by Stop() so the BT gets a few frames to react
-	 *  to the restored baseline before AI tick is cut. Cancelled if Play() is called again. */
-	FTimerHandle PendingStopSimulationHandle;
-
 	/** Map of stable IDs for every actor that participates in the timeline / scene registry. */
 	TMap<TWeakObjectPtr<AActor>, FGuid> ActorIds;
 

Unreal/Plugins/PS_Editor/Source/PS_Editor/UI/Widgets/PS_Editor_MainWidget.cpp

@@ -1079,74 +1079,6 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildSceneButtons()
 				+ SHorizontalBox::Slot()
 				.AutoWidth()
 				.Padding(4.0f, 0.0f, 0.0f, 0.0f)
-				[
-					SNew(SButton)
-					.ButtonStyle(StyleFlatButton.Get())
-					.ToolTipText(FText::FromString(TEXT("Start/stop simulation. If a timeline exists, also plays/pauses it in sync.")))
-					.OnClicked_Lambda([this]() -> FReply
-					{
-						APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer());
-						if (!EditorPC) return FReply::Handled();
-
-						UPS_Editor_TimelineSubsystem* TS = GetTimelineSubsystemFromWidget(this);
-
-						// If there's a timeline with at least one track, route through the timeline
-						// so simulate + animation are always in lockstep (Simulate is effectively
-						// the Play/Pause button of the timeline).
-						if (TS && TS->GetNumTracks() > 0)
-						{
-							if (TS->IsPlaying())
-							{
-								TS->Pause();
-							}
-							else
-							{
-								TS->Play();
-							}
-						}
-						else
-						{
-							// No animation to sync with — just toggle simulation directly.
-							if (EditorPC->IsSimulating())
-							{
-								EditorPC->StopSimulation();
-							}
-							else
-							{
-								EditorPC->StartSimulation();
-							}
-						}
-						return FReply::Handled();
-					})
-					[
-						SAssignNew(SimulateButtonText, STextBlock)
-						.Text(FText::FromString(TEXT("Simulate")))
-						.Font(FCoreStyle::GetDefaultFontStyle("Bold", 10))
-						.ColorAndOpacity(FLinearColor(1.0f, 0.6f, 0.0f))
-					]
-				]
-				+ SHorizontalBox::Slot()
-				.AutoWidth()
-				.Padding(4.0f, 0.0f, 0.0f, 0.0f)
-				[
-					SNew(SButton)
-					.ButtonStyle(StyleFlatButton.Get())
-					.ToolTipText(FText::FromString(TEXT("Show/hide the timeline panel")))
-					.OnClicked_Lambda([this]() -> FReply
-					{
-						ToggleTimelineVisible();
-						return FReply::Handled();
-					})
-					[
-						SNew(STextBlock)
-						.Text(FText::FromString(TEXT("Timeline")))
-						.Font(FCoreStyle::GetDefaultFontStyle("Bold", 10))
-						.ColorAndOpacity(FLinearColor(0.6f, 0.8f, 1.0f))
-					]
-				]
-				+ SHorizontalBox::Slot()
-				.AutoWidth()
-				.Padding(4.0f, 0.0f, 0.0f, 0.0f)
 				[
 					SNew(SButton)
 					.ButtonStyle(StyleFlatButton.Get())
@@ -1816,30 +1748,7 @@ void UPS_Editor_MainWidget::NativeTick(const FGeometry& MyGeometry, float InDelt
 		}
 	}
 
-	// Update simulate button text / color. Keep the label "Simulate" / "Stop" regardless of
+	// (Simulate toolbar button removed — Play/Pause/Restart/Stop live in the timeline panel.)
-	// the timeline state so it doesn't clash with the dedicated Play button in the timeline
-	// panel — a second "Play" on the toolbar was confusing. The button still drives the
-	// timeline under the hood (see BuildToolbar lambda).
-	if (SimulateButtonText.IsValid())
-	{
-		if (APS_Editor_PlayerController* SimPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
-		{
-			UPS_Editor_TimelineSubsystem* TS = GetTimelineSubsystemFromWidget(this);
-			const bool bTimelinePlaying = TS && TS->GetNumTracks() > 0 && TS->IsPlaying();
-			const bool bActive = SimPC->IsSimulating() || bTimelinePlaying;
-
-			if (bActive)
-			{
-				SimulateButtonText->SetText(FText::FromString(TEXT("Stop")));
-				SimulateButtonText->SetColorAndOpacity(FLinearColor(1.0f, 0.3f, 0.2f));
-			}
-			else
-			{
-				SimulateButtonText->SetText(FText::FromString(TEXT("Simulate")));
-				SimulateButtonText->SetColorAndOpacity(FLinearColor(1.0f, 0.6f, 0.0f));
-			}
-		}
-	}
 
 	RefreshPropertiesFromSelection();
 	RefreshOutliner();
@@ -3570,7 +3479,7 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildTimelinePanel()
 	const FSlateFontInfo Bold = FPS_Editor_UIStyle::BodyFontBold(S);
 
 	return SAssignNew(TimelinePanel, SBorder)
-		.Visibility(EVisibility::Collapsed)
+		.Visibility(EVisibility::Visible)
 		.BorderImage(BrushGlassStrong.Get())
 		.Padding(FMargin(12.0f, 8.0f))
 		[
@@ -4266,7 +4175,9 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildTopbar()
 						{
 							if (APS_Editor_PlayerController* PC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
 							{
-								if (PC->IsSimulating()) PC->StopSimulation();
+								// Route through RequestStopSimulation so OnEditorBeforeSimulateStop
+								// fires + BT gets its grace period before AI is cut.
+								if (PC->IsSimulating()) PC->RequestStopSimulation();
 								else PC->StartSimulation();
 							}
 							return FReply::Handled();
@@ -4307,7 +4218,9 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildTopbar()
 						{
 							if (APS_Editor_PlayerController* PC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
 							{
-								if (PC->IsSimulating()) PC->StopSimulation();
+								// Route through RequestStopSimulation so OnEditorBeforeSimulateStop
+								// fires + BT gets its grace period before AI is cut.
+								if (PC->IsSimulating()) PC->RequestStopSimulation();
 								else PC->StartSimulation();
 							}
 							return FReply::Handled();
@@ -4390,18 +4303,6 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildTopbar()
 					FPS_Editor_UIStyle::MakeIconFollowForeground(S, EPS_Editor_Icon::Sidebar, 14.0f)
 				]
 			]
-			// Timeline toggle
-			+ SHorizontalBox::Slot().AutoWidth().VAlign(VAlign_Center).Padding(2.0f, 0.0f)
-			[
-				SNew(SButton)
-				.ButtonStyle(StyleFlatButton.Get())
-				.ContentPadding(FMargin(6.0f, 3.0f))
-				.ToolTipText(FText::FromString(TEXT("Toggle timeline")))
-				.OnClicked_Lambda([this]() -> FReply { ToggleTimelineVisible(); return FReply::Handled(); })
-				[
-					FPS_Editor_UIStyle::MakeIconFollowForeground(S, EPS_Editor_Icon::PanelBottom, 14.0f)
-				]
-			]
 			// Inspector (panel right) toggle
 			+ SHorizontalBox::Slot().AutoWidth().VAlign(VAlign_Center).Padding(2.0f, 0.0f)
 			[
@@ -4953,7 +4854,8 @@ void UPS_Editor_MainWidget::ExecuteCommand(const FString& CommandId)
 	{
 		if (PC)
 		{
-			if (PC->IsSimulating()) PC->StopSimulation(); else PC->StartSimulation();
+			// Route through RequestStopSimulation so OnEditorBeforeSimulateStop fires + BT grace.
+			if (PC->IsSimulating()) PC->RequestStopSimulation(); else PC->StartSimulation();
 		}
 	}
 	else if (CommandId == TEXT("timeline")) { ToggleTimelineVisible(); }

Unreal/Plugins/PS_Editor/Source/PS_Editor/UI/Widgets/PS_Editor_MainWidget.h

@@ -155,9 +155,6 @@ private:
 	TSharedPtr<SWidget> SplineDeletePointButton;
 	TSharedPtr<SWidget> ChildEditButton;
 
-	// Simulate button
-	TSharedPtr<STextBlock> SimulateButtonText;
-
 	// Timeline panel
 	TSharedPtr<SWidget> TimelinePanel;
 	TSharedPtr<class SSlider> TimelineSlider;
@@ -165,7 +162,7 @@ private:
 	TSharedPtr<STextBlock> TimelinePlayButtonText;
 	TSharedPtr<SEditableTextBox> TimelineDurationBox;
 	TSharedPtr<SVerticalBox> TimelineTracksContainer;
-	bool bTimelineVisible = false;
+	bool bTimelineVisible = true;
 	FDelegateHandle TimelineChangedHandle;
 	/** Currently selected timeline key (updated on click). -1 means no selection. */
 	int32 SelectedTimelineTrackIdx = -1;

Unreal/Plugins/PS_Editor/Source/PS_Editor/UI/Widgets/PS_Editor_MainWidget_Legacy.cpp

@@ -179,7 +179,7 @@ TSharedRef<SWidget> UPS_Editor_MainWidget_Legacy::RebuildWidget()
 				BuildOutliner()
 			]
 		]
-		// Timeline panel (hidden by default; toggled via toolbar button)
+		// Timeline panel (always visible — toolbar toggle removed)
 		+ SOverlay::Slot()
 		.HAlign(HAlign_Fill)
 		.VAlign(VAlign_Bottom)
@@ -907,72 +907,6 @@ TSharedRef<SWidget> UPS_Editor_MainWidget_Legacy::BuildSceneButtons()
 				+ SHorizontalBox::Slot()
 				.AutoWidth()
 				.Padding(4.0f, 0.0f, 0.0f, 0.0f)
-				[
-					SNew(SButton)
-					.ToolTipText(FText::FromString(TEXT("Start/stop simulation. If a timeline exists, also plays/pauses it in sync.")))
-					.OnClicked_Lambda([this]() -> FReply
-					{
-						APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer());
-						if (!EditorPC) return FReply::Handled();
-
-						UPS_Editor_TimelineSubsystem* TS = GetTimelineSubsystemFromWidget(this);
-
-						// If there's a timeline with at least one track, route through the timeline
-						// so simulate + animation are always in lockstep (Simulate is effectively
-						// the Play/Pause button of the timeline).
-						if (TS && TS->GetNumTracks() > 0)
-						{
-							if (TS->IsPlaying())
-							{
-								TS->Pause();
-							}
-							else
-							{
-								TS->Play();
-							}
-						}
-						else
-						{
-							// No animation to sync with — just toggle simulation directly.
-							if (EditorPC->IsSimulating())
-							{
-								EditorPC->StopSimulation();
-							}
-							else
-							{
-								EditorPC->StartSimulation();
-							}
-						}
-						return FReply::Handled();
-					})
-					[
-						SAssignNew(SimulateButtonText, STextBlock)
-						.Text(FText::FromString(TEXT("Simulate")))
-						.Font(FCoreStyle::GetDefaultFontStyle("Bold", 10))
-						.ColorAndOpacity(FLinearColor(1.0f, 0.6f, 0.0f))
-					]
-				]
-				+ SHorizontalBox::Slot()
-				.AutoWidth()
-				.Padding(4.0f, 0.0f, 0.0f, 0.0f)
-				[
-					SNew(SButton)
-					.ToolTipText(FText::FromString(TEXT("Show/hide the timeline panel")))
-					.OnClicked_Lambda([this]() -> FReply
-					{
-						ToggleTimelineVisible();
-						return FReply::Handled();
-					})
-					[
-						SNew(STextBlock)
-						.Text(FText::FromString(TEXT("Timeline")))
-						.Font(FCoreStyle::GetDefaultFontStyle("Bold", 10))
-						.ColorAndOpacity(FLinearColor(0.6f, 0.8f, 1.0f))
-					]
-				]
-				+ SHorizontalBox::Slot()
-				.AutoWidth()
-				.Padding(4.0f, 0.0f, 0.0f, 0.0f)
 				[
 					SNew(SButton)
 					.OnClicked_Lambda([this]() -> FReply
@@ -1566,30 +1500,7 @@ void UPS_Editor_MainWidget_Legacy::NativeTick(const FGeometry& MyGeometry, float
 		}
 	}
 
-	// Update simulate button text / color. Keep the label "Simulate" / "Stop" regardless of
+	// (Simulate toolbar button removed — Play/Pause/Restart/Stop live in the timeline panel.)
-	// the timeline state so it doesn't clash with the dedicated Play button in the timeline
-	// panel — a second "Play" on the toolbar was confusing. The button still drives the
-	// timeline under the hood (see BuildToolbar lambda).
-	if (SimulateButtonText.IsValid())
-	{
-		if (APS_Editor_PlayerController* SimPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
-		{
-			UPS_Editor_TimelineSubsystem* TS = GetTimelineSubsystemFromWidget(this);
-			const bool bTimelinePlaying = TS && TS->GetNumTracks() > 0 && TS->IsPlaying();
-			const bool bActive = SimPC->IsSimulating() || bTimelinePlaying;
-
-			if (bActive)
-			{
-				SimulateButtonText->SetText(FText::FromString(TEXT("Stop")));
-				SimulateButtonText->SetColorAndOpacity(FLinearColor(1.0f, 0.3f, 0.2f));
-			}
-			else
-			{
-				SimulateButtonText->SetText(FText::FromString(TEXT("Simulate")));
-				SimulateButtonText->SetColorAndOpacity(FLinearColor(1.0f, 0.6f, 0.0f));
-			}
-		}
-	}
 
 	RefreshPropertiesFromSelection();
 	RefreshOutliner();
@@ -3231,7 +3142,7 @@ TSharedRef<SWidget> UPS_Editor_MainWidget_Legacy::BuildTimelinePanel()
 	const FSlateFontInfo Bold = FCoreStyle::GetDefaultFontStyle("Bold", 10);
 
 	return SAssignNew(TimelinePanel, SBorder)
-		.Visibility(EVisibility::Collapsed)
+		.Visibility(EVisibility::Visible)
 		.BorderImage(FCoreStyle::Get().GetBrush("WhiteBrush"))
 		.BorderBackgroundColor(FLinearColor(0.05f, 0.05f, 0.05f, 0.95f))
 		.Padding(FMargin(12.0f, 8.0f))

Unreal/Plugins/PS_Editor/Source/PS_Editor/UI/Widgets/PS_Editor_MainWidget_Legacy.h

@@ -128,9 +128,6 @@ private:
 	TSharedPtr<SWidget> SplineDeletePointButton;
 	TSharedPtr<SWidget> ChildEditButton;
 
-	// Simulate button
-	TSharedPtr<STextBlock> SimulateButtonText;
-
 	// Timeline panel
 	TSharedPtr<SWidget> TimelinePanel;
 	TSharedPtr<class SSlider> TimelineSlider;
@@ -138,7 +135,7 @@ private:
 	TSharedPtr<STextBlock> TimelinePlayButtonText;
 	TSharedPtr<SEditableTextBox> TimelineDurationBox;
 	TSharedPtr<SVerticalBox> TimelineTracksContainer;
-	bool bTimelineVisible = false;
+	bool bTimelineVisible = true;
 	FDelegateHandle TimelineChangedHandle;
 	/** Currently selected timeline key (updated on click). -1 means no selection. */
 	int32 SelectedTimelineTrackIdx = -1;

Unreal/Plugins/PS_Editor/Source/PS_Editor/UI/Widgets/PS_Editor_MainWidget_UMG.cpp

@@ -99,7 +99,8 @@ void UPS_Editor_MainWidget_UMG::StopSimulation()
 {
 	if (APS_Editor_PlayerController* PC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
 	{
-		PC->StopSimulation();
+		// Route through RequestStopSimulation so OnEditorBeforeSimulateStop fires + BT grace.
+		PC->RequestStopSimulation();
 		OnSimulateChanged.Broadcast();
 	}
 }