unity-input-system

Imported from gamedev-skills/awesome-gamedev-agent-skills (skills/unity/unity-input-system/SKILL.md) via skills.sh. Install upstream with npx skills add gamedev-skills/awesome-gamedev-agent-skills --skill unity-input-system. Copyright stays with the author.

Unity Input System (new)

Read input through Unity's Input System package (com.unity.inputsystem 1.x; Unity 6.3 LTS ships 1.20) — action-based, device-agnostic, rebindable. Targets Unity 6.3 LTS. This is the modern replacement for the legacy Input.GetAxis/Input.GetKey Input Manager.

When to use

• Use when setting up movement/jump/fire input, defining an .inputactions asset with action maps and control schemes, wiring a PlayerInput component, reading a Vector2 stick/WASD value, or handling gamepad + keyboard + touch from one set of actions.
• Use when Packages/manifest.json contains com.unity.inputsystem or the project has an *.inputactions asset.

When not to use: rebindable-control architecture across engines → input-systems (this skill is the Unity-specific API). Moving the character once you have the input vector → unity-physics / unity-csharp-scripting.

Core workflow

1. Check Active Input Handling (Project Settings → Player). The package only receives input when this is Input System Package (New) or Both. Both is required if any old Input.GetAxis code remains.
2. Find or create the .inputactions asset. New Unity 6 projects usually already have one assigned as the project-wide actions (Project Settings → Input System Package; the template file is InputSystem_Actions.inputactions) — reuse it rather than adding a second asset. Add an action map (e.g. Gameplay), add actions (Move = Value/Vector2, Jump = Button, Fire = Button), and bind them to controls and composite bindings (WASD = 2D Vector composite).
3. Choose how to read it:
   • PlayerInput component (designer-friendly) — drop it on the player, point it at the asset, pick a Behavior (Send Messages / Broadcast / Invoke Unity Events / Invoke C# Events). Best for single/local-coop players.
   • Project-wide actions in code (InputSystem.actions.FindAction("Move")) — no asset reference to wire up, and the actions are already enabled.
   • Direct in code (InputActionReference / InputActionAsset) — most control; you Enable() actions and read them. Best for systems and tools.
4. Enable the actions/maps you read. PlayerInput enables its default map automatically and project-wide actions start enabled; actions from any other asset must be .Enable()d (and disabled on teardown).
5. Switch action maps for context (gameplay ↔ UI/menu) instead of guarding every handler.
6. Verify with the Input Debugger (Window → Analysis → Input Debugger) to confirm devices and that actions fire.

Patterns

1. PlayerInput with "Send Messages" (handlers on the same GameObject)

using UnityEngine;
using UnityEngine.InputSystem;

// PlayerInput (Behavior = Send Messages) calls On<ActionName>(InputValue) by name.
public class PlayerInputReceiver : MonoBehaviour
{
    private Vector2 _move;

    private void OnMove(InputValue value) => _move = value.Get<Vector2>();   // Move action
    private void OnJump(InputValue value) { if (value.isPressed) Jump(); }   // Button action

    private void Update() { /* drive movement from _move */ }
    private void Jump() { }
}

2. Reading an action directly in code (polling a value)

using UnityEngine;
using UnityEngine.InputSystem;

public class DirectMover : MonoBehaviour
{
    [SerializeField] private InputActionReference moveAction;  // assign the Move action

    private void OnEnable()  => moveAction.action.Enable();    // REQUIRED or it reads zero
    private void OnDisable() => moveAction.action.Disable();

    private void Update()
    {
        Vector2 move = moveAction.action.ReadValue<Vector2>(); // continuous value
        transform.Translate(new Vector3(move.x, 0, move.y) * (5f * Time.deltaTime));
    }
}

3. Project-wide actions (no asset reference)

using UnityEngine;
using UnityEngine.InputSystem;

public class ProjectWideMover : MonoBehaviour
{
    private InputAction _move, _jump;

    private void Awake()
    {
        // Looked up once; project-wide actions are preloaded and enabled by default.
        _move = InputSystem.actions.FindAction("Move");
        _jump = InputSystem.actions.FindAction("Jump");
    }

    private void Update()
    {
        Vector2 move = _move.ReadValue<Vector2>();
        if (_jump.WasPressedThisFrame()) { /* jump */ }
    }
}

4. Event callbacks + switching action maps (gameplay ↔ UI)

[SerializeField] private InputActionAsset actions;

private void OnEnable()
{
    actions.FindAction("Gameplay/Fire").performed += OnFire;  // edge event: fires once
    actions.FindActionMap("Gameplay").Enable();
}
private void OnDisable() => actions.FindAction("Gameplay/Fire").performed -= OnFire;

private void OnFire(InputAction.CallbackContext ctx) => Shoot();  // ctx.ReadValue<T>() if needed

private void OpenPauseMenu()                       // change context, don't sprinkle if-checks
{
    actions.FindActionMap("Gameplay").Disable();
    actions.FindActionMap("UI").Enable();
}
private void Shoot() { }

Pitfalls

• No input at all → either Active Input Handling is still Input Manager (Old), or you forgot to Enable() the action/map. PlayerInput and project-wide actions start enabled; actions from other assets do not.
• Gameplay actions fire while a menu is open → project-wide actions enable every action map at startup, including when PlayerInput uses that asset. In Start, disable the maps you do not want (InputSystem.actions.FindActionMap("UI").Disable()) and enable only the current one.
• FindAction returns null → the name (or Map/Action path) does not exist in that asset. Check the spelling in the Actions Editor; with project-wide actions, make sure the asset you edited is the one assigned in Project Settings → Input System Package.
• InvalidOperationException about the old input backend → some script still calls Input.GetAxis/Input.GetKey while Active Input Handling is New. Port it or set Both.
• Buttons read as 0 with ReadValue → button presses are edge events; use the performed callback (or WasPressedThisFrame()), not per-frame ReadValue for triggers.
• Send Messages handlers never fire → the receiving script must be on the same GameObject as the PlayerInput; Broadcast Messages reaches children too.
• Leaking subscriptions → unsubscribe (-=) in OnDisable; re-subscribing in OnEnable without unsubscribing doubles up handlers.
• Touch/gamepad not detected → enable the matching control scheme and confirm the device in the Input Debugger; the Vector2 composite needs all four bindings set.

References

• For interactive control rebinding (PerformInteractiveRebinding), saving/loading bindings as JSON, and local multiplayer with PlayerInputManager, read references/rebinding.md.
• Primary docs: Unity Manual "Input System" (https://docs.unity3d.com/Manual/com.unity.inputsystem.html) and the package manual (https://docs.unity3d.com/Packages/com.unity.inputsystem@1.20/manual/index.html), including "About project-wide actions".

Related skills

• input-systems — engine-agnostic input architecture (rebinding, buffering, multi-device).
• unity-csharp-scripting — the MonoBehaviour these handlers live in.
• unity-physics — applying the input vector to a Rigidbody.