ue-gameplay-ability-system

Subclass UGameplayAbility and override ActivateAbility, calling CommitAbility to consume cost and cooldown, then EndAbility when finished. Grant it server-side with ASC->GiveAbility and activate via TryActivateAbilityByClass. Set cost and cooldown Gameplay Effect classes in the Blueprint subclass.

Declare FGameplayAttributeData properties in a UAttributeSet subclass and use the ATTRIBUTE_ACCESSORS macro to generate getters and setters. Register the set as a subobject on the ASC's owning actor, and modify values only through Gameplay Effects so replication and prediction work.

For multiplayer player characters, put the ASC on the PlayerState so ability state survives respawn, and have the Pawn implement IAbilitySystemInterface returning it. For AI or simple actors, place the ASC directly on the Pawn and call InitAbilityActorInfo(this, this).

Common causes are a wrong ASC replication mode (Mixed is required for player-owned ASCs), missing UAbilitySystemGlobals::InitGlobalData() at startup, or writing attribute fields directly instead of applying Gameplay Effects. Also verify the ability uses a compatible net execution policy like LocalPredicted.

GAS is heavyweight and best suited to games with many interacting abilities and stats. For a couple of simple actions, plain actor components are simpler and avoid the plugin setup, attribute plumbing, and replication configuration overhead.