Debugging Gameplay Tags in the Runtime Environment

You will use console commands and the visual debugger to track real-time tag changes and troubleshoot failed ability activation requests.

In this lesson, you will learn how to leverage Unreal Engine’s runtime inspection tools to track dynamic tag changes and diagnose why an ability refuses to fire.

When working with complex Gameplay Ability System (GAS) logic, tags often propagate, block, or expire in ways that are difficult to visualize in code. If an ability fails to activate despite meeting its cost requirements, the culprit is almost always a "blocked" tag or a missing "required" tag state.

Using Console Commands

The most immediate way to inspect the state of an actor is the showdebug abilitysystem console command. Once enabled (by pressing ~ and typing showdebug abilitysystem while possessing your character), you will see an overlay displaying the current OwnedTags and BlockedTags.

If you suspect an ability is failing to activate, keep an eye on the "Active Abilities" section. If the ability is grayed out or missing from the list, check the "Ability Tags" section to see if a BlockTags requirement is currently being satisfied by an active effect.

The Gameplay Debugger

For more complex scenarios, press apostrophe (') to open the Gameplay Debugger (ensure you have the GameplayDebugger module enabled in your build). Press 4 to switch to the Ability System category. This provides a clean breakdown of:

Owned Tags: What the actor currently possesses.
Active Effects: The source of those tags.
Ability Activation Requirements: A history log of recent attempts to activate abilities and why they failed (e.g., Ability.Activate failed: Blocked by tag X).

Real-Time Tracking

If you need to log tag changes programmatically to filter through the output log, you can hook into the AbilitySystemComponent delegate:

AbilitySystemComponent->RegisterGameplayTagEvent(
    MySpecificTag, 
    EGameplayTagEventType::NewOrRemoved
).AddLambda([](const FGameplayTag Tag, int32 NewCount) {
    UE_LOG(LogTemp, Warning, TEXT("Tag %s changed to count: %d"), *Tag.ToString(), NewCount);
});

By observing these logs alongside the visual debugger, you can identify exactly which GameplayEffect is applying a blocking tag at the moment of failure, allowing you to trace the logical leak back to its origin.

Key Takeaway: Use showdebug abilitysystem for a high-level view of tag state, and rely on the Gameplay Debugger’s activation logs to pinpoint the exact constraint preventing your ability from executing.