Why does Property Access throw a threading warning?

AnimBP runs on a worker thread by default. Property Access invocations of game-thread-only getters or BlueprintCallable functions trigger the warning. Mark functions [BlueprintThreadSafe] or copy the value into a thread-safe variable in NativeUpdateAnimation.

What's NativeUpdateAnimation?

C++ override on UAnimInstance that runs on the game thread before the worker pose. Safe place to read game-thread state and copy into thread-safe member variables.

Disable parallel anim?

USkeletalMeshComponent → bRunParallelAnimation = false. Loses worker-thread perf but eliminates threading constraints. Last resort.

Fix: Unreal Anim BP Property Access Thread Error

Quick answer: Move game-thread reads into NativeUpdateAnimation (C++) or BlueprintUpdateAnimation (BP). Cache values into AnimInstance member variables; AnimGraph reads those.

Property Access pulling Character->GetVelocity() in a state machine condition fires a threading warning when parallel animation is on.

The Fix

// AnimInstance C++
UCLASS()
class UMyAnimInstance : public UAnimInstance {
    GENERATED_BODY()

    UPROPERTY(BlueprintReadOnly)
    float Speed;

    UPROPERTY(BlueprintReadOnly)
    bool bIsFalling;

    virtual void NativeUpdateAnimation(float Dt) override {
        Super::NativeUpdateAnimation(Dt);
        auto* C = Cast<ACharacter>(TryGetPawnOwner());
        if (!C) return;
        Speed       = C->GetVelocity().Size2D();
        bIsFalling  = C->GetCharacterMovement()->IsFalling();
    }
};

// AnimGraph reads Speed / bIsFalling: thread-safe member access.

NativeUpdateAnimation runs on game thread. Members are POD. AnimGraph thread reads them safely, no warnings.

Verifying

Threading warning gone. Animation transitions still react to character state.

“Cache on game thread. Read on worker. Quiet.”

Related Issues

For Anim BP cached pose, see cached pose. For state alias, see state alias.

Cache. Read. No race.