From ca10689bb6b79dc7a27f76fe31ee3ee7484d3099 Mon Sep 17 00:00:00 2001
From: "j.foucher" <j.foucher@polymorph.fr>
Date: Thu, 5 Mar 2026 15:16:10 +0100
Subject: [PATCH] Fix thread-safety crash in LipSync anim node: TMap race
 condition

GetCurrentBlendshapes() was copying CurrentBlendshapes on the anim worker
thread while the game thread mutated it (TSet::UnhashElements crash).
Use a snapshot pattern: game thread copies to ThreadSafeBlendshapes under
FCriticalSection at end of TickComponent, anim node reads the snapshot.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../Private/PS_AI_ConvAgent_LipSyncComponent.cpp | 10 ++++++++++
 .../Public/PS_AI_ConvAgent_LipSyncComponent.h    | 16 +++++++++++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Private/PS_AI_ConvAgent_LipSyncComponent.cpp b/Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Private/PS_AI_ConvAgent_LipSyncComponent.cpp
index 4a17a8a..cd75601 100644
--- a/Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Private/PS_AI_ConvAgent_LipSyncComponent.cpp
+++ b/Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Private/PS_AI_ConvAgent_LipSyncComponent.cpp
@@ -1109,6 +1109,12 @@ void UPS_AI_ConvAgent_LipSyncComponent::TickComponent(float DeltaTime, ELevelTic
 		}
 	}
 
+	// Snapshot for thread-safe anim node read (GetCurrentBlendshapes)
+	{
+		FScopeLock Lock(&BlendshapeLock);
+		ThreadSafeBlendshapes = CurrentBlendshapes;
+	}
+
 	// Auto-apply morph targets if a target mesh is set
 	if (TargetMesh)
 	{
@@ -1201,6 +1207,10 @@ void UPS_AI_ConvAgent_LipSyncComponent::ResetToNeutral()
 
 	// Clear blendshapes so the mouth returns to fully neutral
 	CurrentBlendshapes.Reset();
+	{
+		FScopeLock Lock(&BlendshapeLock);
+		ThreadSafeBlendshapes.Reset();
+	}
 	PreviousBlendshapes.Reset();
 	LastConsumedVisemes.Reset();
 }
diff --git a/Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Public/PS_AI_ConvAgent_LipSyncComponent.h b/Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Public/PS_AI_ConvAgent_LipSyncComponent.h
index 6fe3807..c66d949 100644
--- a/Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Public/PS_AI_ConvAgent_LipSyncComponent.h
+++ b/Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Public/PS_AI_ConvAgent_LipSyncComponent.h
@@ -170,9 +170,14 @@ public:
 	UFUNCTION(BlueprintCallable, Category = "PS AI ConvAgent|LipSync")
 	TMap<FName, float> GetCurrentVisemes() const { return SmoothedVisemes; }
 
-	/** Get current ARKit blendshape weights (MetaHuman compatible: jawOpen, mouthFunnel, mouthClose, etc.). */
+	/** Get current ARKit blendshape weights (MetaHuman compatible: jawOpen, mouthFunnel, mouthClose, etc.).
+	 *  Thread-safe: returns a snapshot updated each tick. Safe to call from anim worker threads. */
 	UFUNCTION(BlueprintCallable, Category = "PS AI ConvAgent|LipSync")
-	TMap<FName, float> GetCurrentBlendshapes() const { return CurrentBlendshapes; }
+	TMap<FName, float> GetCurrentBlendshapes() const
+	{
+		FScopeLock Lock(&BlendshapeLock);
+		return ThreadSafeBlendshapes;
+	}
 
 	/** True when the agent is currently producing speech audio.
 	 *  When false, lip sync releases mouth curves to let emotion curves through. */
@@ -268,9 +273,14 @@ private:
 	// Smoothed viseme weights (interpolated each tick, exposed via GetCurrentVisemes)
 	TMap<FName, float> SmoothedVisemes;
 
-	// ARKit blendshape weights derived from SmoothedVisemes (exposed via GetCurrentBlendshapes)
+	// ARKit blendshape weights derived from SmoothedVisemes (game-thread working copy)
 	TMap<FName, float> CurrentBlendshapes;
 
+	// Thread-safe snapshot of CurrentBlendshapes, updated each tick under BlendshapeLock.
+	// Read by the anim worker thread via GetCurrentBlendshapes().
+	TMap<FName, float> ThreadSafeBlendshapes;
+	mutable FCriticalSection BlendshapeLock;
+
 	// Previous frame's blendshape values for additional output smoothing
 	TMap<FName, float> PreviousBlendshapes;