Ue Game Features

UE Game Features and Modular Gameplay

You are an expert in Unreal Engine's Game Features plugin system and modular gameplay architecture.

Context Check

Read .agents/ue-project-context.md before proceeding. Determine:

• Whether the GameFeatures and ModularGameplay plugins are enabled
• Which actors register as component receivers (AddReceiver)
• Whether the project uses an init state system or experience-based loading
• Existing UGameFeatureAction subclasses or modular component base classes

Information Gathering

Ask the developer:

1. Are you creating a new Game Feature plugin or extending an existing one?
2. What components or abilities should the feature inject into gameplay actors?
3. Does the feature need async loading or runtime activation/deactivation?
4. Is there an experience/game mode composition system (Lyra-style)?
5. Do components need ordered initialization across features?

Game Feature Plugin Structure

A Game Feature plugin is a standard UE plugin with Type set to "GameFeature" in its .uplugin descriptor. This tells the engine to manage its lifecycle through the Game Features subsystem rather than loading it as a regular plugin.

.uplugin Descriptor

{
    "Type": "GameFeature",
    "BuiltInInitialFeatureState": "Active",  // or "Registered", "Installed"
    "Plugins": [
        { "Name": "GameFeatures", "Enabled": true },
        { "Name": "ModularGameplay", "Enabled": true }
    ]
}

BuiltInInitialFeatureState controls how far the plugin advances on startup. Use "Active" for always-on features, "Registered" for features activated by gameplay code, or "Installed" for downloadable content loaded on demand.

UGameFeatureData

Each Game Feature plugin contains a UGameFeatureData primary data asset (extends UPrimaryDataAsset) that defines what the feature does:

// From GameFeatureData.h
UPROPERTY(EditDefaultsOnly, Instanced, Category = "Game Feature | Actions")
TArray<TObjectPtr<UGameFeatureAction>> Actions;

UPROPERTY(EditAnywhere, Category = "Game Feature | Asset Manager")
TArray<FPrimaryAssetTypeInfo> PrimaryAssetTypesToScan;

Actions is the core — an instanced array of UGameFeatureAction subclasses that execute when the feature activates.

Directory Convention

Plugins/GameFeatures/
├── ShooterCore/
│   ├── ShooterCore.uplugin          (Type: GameFeature)
│   ├── Content/
│   │   └── ShooterCore.uasset       (UGameFeatureData)
│   └── Source/ShooterCoreRuntime/
└── DeathmatchRules/
    ├── DeathmatchRules.uplugin
    └── Content/DeathmatchRules.uasset

Plugin State Machine

Game Feature plugins transition through a well-defined state machine. Actions fire at specific transitions and runtime activation must target valid destination states.

EGameFeaturePluginState Lifecycle

Uninitialized → Terminal → UnknownStatus → StatusKnown
    → Installed → Registered → Loaded → Active

Each major state has transition states between them (e.g., Registering, Loading, Activating). You target a destination state and the subsystem walks the chain.

Destination States

URL protocols: file: for built-in disk plugins, installbundle: for downloadable features. Convert descriptor path to URL with UGameFeaturesSubsystem::GetPluginURL_FileProtocol(Path).

UGameFeatureAction

UGameFeatureAction (UCLASS(MinimalAPI, DefaultToInstanced, EditInlineNew, Abstract)) is the base class for all actions. DefaultToInstanced + EditInlineNew allow instances to be created inline within UGameFeatureData's Actions array.

Lifecycle Methods

// Registration phase
virtual void OnGameFeatureRegistering();
virtual void OnGameFeatureUnregistering();

// Loading phase
virtual void OnGameFeatureLoading();
virtual void OnGameFeatureUnloading();

// Activation — primary override point
virtual void OnGameFeatureActivating(FGameFeatureActivatingContext& Context);
virtual void OnGameFeatureActivating();  // legacy no-arg fallback

// Post-activation confirmation
virtual void OnGameFeatureActivated();

// Deactivation — supports async via context
virtual void OnGameFeatureDeactivating(FGameFeatureDeactivatingContext& Context);

OnGameFeatureActivating(Context) is the primary override. The base calls the legacy no-arg version for backward compatibility.

Async Deactivation

When deactivation requires async work, pause it via the context:

void UMyAction::OnGameFeatureDeactivating(FGameFeatureDeactivatingContext& Context)
{
    FSimpleDelegate ResumeDelegate = Context.PauseDeactivationUntilComplete(
        TEXT("MyAction_AsyncCleanup"));
    // Start async work — MUST invoke ResumeDelegate when done or deactivation hangs
    AsyncTask(ENamedThreads::GameThread, [ResumeDelegate]()
    {
        // ... cleanup ...
        ResumeDelegate.ExecuteIfBound();
    });
}

See references/game-feature-patterns.md for complete custom action subclass templates.

Built-in Actions

UGameFeatureAction_AddComponents

UCLASS(MinimalAPI, meta=(DisplayName="Add Components"), final). The most commonly used action — injects components into actors via UGameFrameworkComponentManager.

Configuration uses FGameFeatureComponentEntry:

UPROPERTY(EditAnywhere) TSoftClassPtr<AActor> ActorClass;
UPROPERTY(EditAnywhere) TSoftClassPtr<UActorComponent> ComponentClass;
UPROPERTY(EditAnywhere) uint8 bClientComponent : 1;
UPROPERTY(EditAnywhere) uint8 bServerComponent : 1;

Internally stores TSharedPtr<FComponentRequestHandle> — RAII removes components when the handle drops (feature deactivates). Set both bClientComponent and bServerComponent for components needed everywhere, server-only for gameplay logic, client-only for cosmetic.

Other Built-in Actions

UGameFeaturesSubsystem

UGameFeaturesSubsystem (UEngineSubsystem) manages all Game Feature plugin lifecycles:

UGameFeaturesSubsystem& GFS = UGameFeaturesSubsystem::Get();

Runtime Activation and Deactivation

FString PluginURL = UGameFeaturesSubsystem::GetPluginURL_FileProtocol(
    TEXT("/MyProject/Plugins/GameFeatures/MyFeature/MyFeature.uplugin"));

// Activate — callback receives const UE::GameFeatures::FResult&
GFS.LoadAndActivateGameFeaturePlugin(PluginURL,
    FGameFeaturePluginLoadComplete::CreateUObject(this, &UMyMgr::OnLoaded));

// Deactivate and unload
GFS.DeactivateGameFeaturePlugin(PluginURL);
GFS.UnloadGameFeaturePlugin(PluginURL, /*bKeepRegistered=*/ false);

// Or target a specific state:
GFS.ChangeGameFeatureTargetState(PluginURL, EGameFeatureTargetState::Registered,
    FGameFeaturePluginChangeStateComplete());

Query and Observe

bool bActive = GFS.IsGameFeaturePluginActive(PluginURL, /*bCheckForActivating=*/ false);
EGameFeaturePluginState State = GFS.GetPluginState(PluginURL);

// Global observer — implement IGameFeatureStateChangeObserver
GFS.AddObserver(MyObserver, UGameFeaturesSubsystem::EObserverPluginStateUpdateMode::CurrentAndFuture);
GFS.RemoveObserver(MyObserver);

IGameFeatureStateChangeObserver provides: OnGameFeatureRegistering(Data, PluginName, URL), OnGameFeatureActivating(Data, URL), OnGameFeatureDeactivating(Data, Context, URL).

Component Injection System