# Runtime API

!!! note "Summary"
    The **Runtime API** runs designer-authored logic and reads Visual Script state from C#. Use it to connect existing systems to Events, variables, saving, pooling, audio, and cached component lookups.

## Available runtime systems

<div class="grid cards" markdown>

- **[Events](events.md)** — run Event components or host Instructions and Conditions on your own component.
- **[Variables](variables.md)** — read, write, subscribe to, and find variable containers.
- **[Components](components.md)** — cache component lookups and add missing components.
- **[Save and Load](save-load.md)** — call `SaveLoadManager` and observe its lifecycle.
- **[Pooling](pooling.md)** — reuse game objects through `PoolManager`.
- **[Audio](audio.md)** — play, stop, inspect, and mix sounds.

</div>

## Start with RunnerInstructions

`RunnerInstructions` adds a designer-authored Instructions list to your component. This example runs the list when `Finish` is called:

```cs
using UnityEngine;
using VisualScript.Runtime;

public class MyComponent : MonoBehaviour
{
    [SerializeField] private RunnerInstructions m_OnComplete = new RunnerInstructions();

    private void Finish()
    {
        using Args args = Args.Get(this.gameObject, this.gameObject);
        this.m_OnComplete.Run(args).Fire(null, this);
    }
}
```

The `m_OnComplete` field exposes a configurable response to `Finish`. Designers can change that response without changing `MyComponent`.

`RunnerConditions` does the same for checks.

## Lifecycle and caching boundaries

These boundaries affect when you access managers and how long you keep runtime objects:

| Boundary | Consequence |
| :--- | :--- |
| `Args` instances are pooled | Get one with `Args.Get`, dispose it, and never store the reference. See [Args](../args.md). |
| Singletons initialize on demand | The first manager access may cost more than later calls. Avoid first access in a hot path. |
| The application may be exiting | Check `AppManager.IsExiting` before teardown work to avoid quit-only errors. |
| Edit mode differs from Play mode | Repositories re-read, [component lookups aren't cached](components.md), and breakpoints don't affect builds. |

## Where to go next

- **[Events and Runners](events.md)** — expose and execute designer-authored behavior.
- **[Variables](variables.md)** — read and write designer-authored state.
- **[Args](../args.md)** — manage Source, Target, parameters, and pooled context.
- **[Extending Visual Script](../extending/index.md)** — add new types to editor dropdowns.