Why does Cast to MyInterface fail in shipping but work in editor?

BP Cast to interface produces a hard reference to the interface, sometimes loading the wrong native class in cooked builds. Use Does Implement Interface (returns bool) and call methods via Interface Message nodes instead.

What's the Interface Message node?

Right-click in BP and search 'MyInterface'; pick the Message version of the function. Calls the implementation safely whether the target implements the interface in BP or C++. No cast required.

Should interfaces be C++ or BP?

For widely used interfaces, C++ — faster dispatch, stable across cooks. BP-only interfaces work but may behave differently when implemented across BP and C++ classes.

Fix: Unreal Blueprint Interface Cast Fails in Cooked Build

Quick answer: Replace BP “Cast to MyInterface” with “Does Implement Interface” check + Interface Message node call. Prefer C++ interfaces for stable dispatch in cooked builds.

Editor PIE: enemy responds to player’s OnInteract call. Shipping build: silence. Cast to BPI_Interactable returns false even though enemy clearly implements it.

The Symptom

Interface call only works in editor. Cooked build returns null/false from the cast. Implementation visible in the BP editor.

The Fix

Use Does Implement Interface + Message.

BP graph:
  Other -> Does Implement Interface(BPI_Interactable) -> Branch true:
    Other -> OnInteract (Message)   // no cast needed

The Message version dispatches to the implementation without a hard reference. Works for both BP and C++ implementers in cooked builds.

C++ Interface Pattern

UINTERFACE(BlueprintType)
class UInteractable : public UInterface { GENERATED_BODY() };
class IInteractable
{
    GENERATED_BODY()
public:
    UFUNCTION(BlueprintCallable, BlueprintNativeEvent)
    void OnInteract(AActor* Initiator);
};

BP classes can implement IInteractable; from anywhere, call IInteractable::Execute_OnInteract(Target, Initiator) safely.

Verifying

Cook for Shipping. Run on device. Interface calls land. If still failing, check the implementation class is actually cooked (DataAsset cooked correctly).

“Does Implement + Message. C++ interface for stability. Cooks deliver.”

Related Issues

For DataAsset cooked build, see DataAsset. For Blueprint async pending, see async task.

Message dispatch. Cooks honor.