Why doesn't SetHealth update through GAS?

Direct SetAttribute bypasses replication and the GameplayEffect lifecycle. Apply changes via UGameplayEffect with a Modifier Magnitude; PostGameplayEffectExecute clamps and replicates.

What's PostGameplayEffectExecute for?

Override on UAttributeSet to clamp values after a GameplayEffect modifies them. Health clamped to 0..MaxHealth, etc. Direct SetAttribute calls don't trigger this.

Instant vs Duration GE?

Instant for damage hits. Duration for buffs that persist. Periodic for DoTs. Pick based on whether the effect should be removable later.

Fix: Unreal GAS Attribute Not Modified

Quick answer: Apply changes via UGameplayEffect + ModifierMagnitude. Override PostGameplayEffectExecute for clamping. Don’t call SetAttribute directly.

You call AbilitySystem->SetNumericAttributeBase(HealthAttribute, NewHp). Server logs change. Clients don’t see it. Direct setters skip the GE pipeline that replicates.

The Symptom

Server-side attribute changed but the OnAttributeChanged delegate doesn’t fire on clients. UI stays stale.

The Fix

// Damage GE
UCLASS()
class UGE_Damage : public UGameplayEffect {
    GENERATED_BODY()
public:
    UGE_Damage() {
        DurationPolicy = EGameplayEffectDurationType::Instant;

        FGameplayModifierInfo Mod;
        Mod.Attribute = UMyAttributeSet::GetHealthAttribute();
        Mod.ModifierOp = EGameplayModOp::Additive;
        Mod.ModifierMagnitude = FScalableFloat(-10.f);
        Modifiers.Add(Mod);
    }
};

// Apply
auto Spec = ASC->MakeOutgoingSpec(UGE_Damage::StaticClass(), 1.f, ASC->MakeEffectContext());
ASC->ApplyGameplayEffectSpecToSelf(*Spec.Data);

// In UMyAttributeSet
void UMyAttributeSet::PostGameplayEffectExecute(const FGameplayEffectModCallbackData& Data) {
    Super::PostGameplayEffectExecute(Data);
    Health.SetCurrentValue(FMath::Clamp(Health.GetCurrentValue(), 0.f, GetMaxHealth()));
}

Spec-based application replicates through the GAS network layer. PostGameplayEffectExecute clamps after every change.

Verifying

Server damages. Clients receive replicated attribute, OnAttributeChange fires, UI updates. Without the GE: silence on clients.

“GE for changes. PostExecute for clamp. Replication just works.”

Related Issues

For replication condition, see replication scope. For Niagara user param, see user param.

GE applies. Replication free. Clamp on execute.