/ue-input-system

name: ue-input-system
description: "Use this skill when implementing player input with Unreal Engine's Enhanced Input system. Also use when the user mentions 'Enhanced Input', 'input', 'input action', 'InputAction', 'mapping context', 'InputMappingContext', 'input binding', 'key binding', 'input trigger', 'input modifier', 'gamepad', or 'keyboard'. Covers ETriggerEvent, built-in triggers (Hold, Tap, Pulse, ChordAction, Combo), built-in modifiers (DeadZone, Scalar, Negate, SwizzleAxis), and custom trigger/modifier authoring. See references/input-action-reference.md for the full catalogue. For UI input modes, see ue-ui-umg-slate."
metadata:
  version: 1.0.0

UE Enhanced Input System

You are an expert in Unreal Engine's Enhanced Input system.

Context Check

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

• `EnhancedInput` plugin is listed as enabled
• Target platforms (affects which modifiers are needed per platform)
• Whether CommonUI is in use (it manages input mode switching automatically)
• Whether the project still uses legacy input (migration may be needed)

Information Gathering

Ask the developer: what actions are needed and their value types (Bool/Axis1D/Axis2D/Axis3D), which platforms, any complex input requirements (hold-to-charge, double-tap, combos, chord shortcuts), and whether multiple input modes are required (gameplay vs UI vs vehicle).

---

Enhanced Input Setup

Plugin and Module

`.uproject`: add `{ "Name": "EnhancedInput", "Enabled": true }` to Plugins.

`Build.cs`: add `"EnhancedInput"` to `PublicDependencyModuleNames`.

`DefaultInput.ini`:

[/Script/Engine.InputSettings]
DefaultPlayerInputClass=/Script/EnhancedInput.EnhancedPlayerInput
DefaultInputComponentClass=/Script/EnhancedInput.EnhancedInputComponent

UInputAction Asset

`UInputAction : UDataAsset`. Create one per logical player action. Key properties (from `InputAction.h`):

EInputActionValueType ValueType = EInputActionValueType::Boolean;
// Boolean | Axis1D (float) | Axis2D (FVector2D) | Axis3D (FVector)

EInputActionAccumulationBehavior AccumulationBehavior
    = EInputActionAccumulationBehavior::TakeHighestAbsoluteValue;
// TakeHighestAbsoluteValue — highest magnitude wins across all mappings to this action
// Cumulative — all mapping values sum (W + S cancel each other for WASD)

bool bConsumeInput = true;  // blocks lower-priority Enhanced Input mappings to same keys

TArray<TObjectPtr<UInputTrigger>> Triggers;   // applied AFTER per-mapping triggers
TArray<TObjectPtr<UInputModifier>> Modifiers; // applied AFTER per-mapping modifiers

UInputMappingContext Asset

`UInputMappingContext : UDataAsset`. Maps physical keys to actions.

• `DefaultKeyMappings.Mappings` — `TArray<FEnhancedActionKeyMapping>` of key-to-action entries
• `MappingProfileOverrides` — per-profile key overrides for player remapping support
• `RegistrationTrackingMode`: `Untracked` (default, first Remove wins) or `CountRegistrations` (IMC stays until Remove called N times, safe when multiple systems share it)

---

Binding Actions in C++

SetupPlayerInputComponent

// MyCharacter.h — declare assets and handlers
UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "Input")
TObjectPtr<UInputMappingContext> DefaultMappingContext;
UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "Input")
TObjectPtr<UInputAction> MoveAction;
UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "Input")
TObjectPtr<UInputAction> JumpAction;

void Move(const FInputActionValue& Value);
void StartJump();
void StopJump();

// MyCharacter.cpp
#include "EnhancedInputComponent.h"
#include "EnhancedInputSubsystems.h"

void AMyCharacter::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
{
    Super::SetupPlayerInputComponent(PlayerInputComponent);
    UEnhancedInputComponent* EIC = Cast<UEnhancedInputComponent>(PlayerInputComponent);
    if (!EIC) { return; }

    EIC->BindAction(MoveAction, ETriggerEvent::Triggered, this, &AMyCharacter::Move);
    EIC->BindAction(JumpAction, ETriggerEvent::Started,   this, &AMyCharacter::StartJump);
    EIC->BindAction(JumpAction, ETriggerEvent::Completed, this, &AMyCharacter::StopJump);
}

void AMyCharacter::BeginPlay()
{
    Super::BeginPlay();
    if (APlayerController* PC = Cast<APlayerController>(GetController()))
    {
        if (auto* Sub = ULocalPlayer::GetSubsystem<UEnhancedInputLocalPlayerSubsystem>(
                PC->GetLocalPlayer()))
        {
            Sub->AddMappingContext(DefaultMappingContext, 0); // priority 0 = lowest
        }
    }
}

Callback Signatures

`BindAction` accepts four delegate signatures:

// No params — press/release without value needed
void AMyCharacter::StartJump() { Jump(); }

// FInputActionValue — for axis values
void AMyCharacter::Move(const FInputActionValue& Value)
{
    const FVector2D Input = Value.Get<FVector2D>();
    AddMovementInput(GetActorForwardVector(), Input.Y);
    AddMovementInput(GetActorRightVector(),   Input.X);
}

// FInputActionInstance — when elapsed/triggered time is needed
void AMyCharacter::OnChargeAttack(const FInputActionInstance& Instance)
{
    const float HeldFor = Instance.GetElapsedTime();    // Started + Ongoing + Triggered
    const float ActiveFor = Instance.GetTriggeredTime(); // Triggered only
}

// Lambda variant
EIC->BindActionValueLambda(InteractAction, ETriggerEvent::Triggered,
    [this](const FInputActionValue& Value) { TryInteract(); });

Storing and removing a binding:

FEnhancedInputActionEventBinding& B =
    EIC->BindAction(DebugAction, ETriggerEvent::Started, this, &AMyCharacter::DebugToggle);
uint32 Handle = B.GetHandle();
// ...
EIC->RemoveBindingByHandle(Handle);        // remove one binding
EIC->ClearBindingsForObject(this);         // remove all bindings for an object

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Trigger Events (ETriggerEvent)

Bitmask enum from `InputTriggers.h`:

| Event | State Transition | Use for | |---|---|