Unity ScriptableObject Architecture

Use ScriptableObject assets to store shared data and decouple systems in Unity 6.3 LTS —
configuration, event channels, and registries that live as project assets instead of being
hard-wired into scenes or singletons. Targets Unity 6.3 LTS (6000.3).

When to use

• Use when you need designer-editable config (weapon stats, level data), to share one value
  between unrelated systems, to decouple senders from listeners via event channels, or to
  build a runtime registry of active objects — without a static/singleton manager.
• Use when the project has *.asset data files backed by : ScriptableObject classes.

When not to use: per-instance runtime state that differs per GameObject (that belongs on
a MonoBehaviour) — a ScriptableObject asset is shared by everyone who references it. Saving
player progress to disk → save-systems. Plain DTOs that never need to be an asset can just be
[System.Serializable] classes.

Core workflow

1. Define the class deriving from ScriptableObject and tag it with [CreateAssetMenu] so
   designers can create instances from the Assets menu.
2. Create one or more .asset instances in the Project window; each is a shared, named
   piece of data referenced by [SerializeField] fields.
3. Reference, don't copy. MonoBehaviours hold a reference to the asset; they all see the
   same data, so changing the asset changes every consumer.
4. For decoupling, model signals and shared variables as ScriptableObjects: a
   "FloatVariable" the HUD reads and the player writes; an "event channel" the player raises
   and many systems listen to. Neither side references the other.
5. Reset runtime mutations in OnEnable if the asset is mutated during play, because edits
   made in the Editor at runtime persist on the asset (a frequent source of "my values
   changed after I played").
6. Verify by inspecting the asset values during Play mode and confirming consumers react.

Patterns

1. Config/data asset

using UnityEngine;

[CreateAssetMenu(fileName = "WeaponData", menuName = "Game/Weapon Data", order = 0)]
public class WeaponData : ScriptableObject
{
    public string displayName = "Pistol";
    public int    damage = 10;
    public float  fireRate = 0.25f;
    public GameObject projectilePrefab;
}

public class Weapon : MonoBehaviour
{
    [SerializeField] private WeaponData data;   // assign the shared asset in the Inspector
    private void Fire() => Debug.Log($"{data.displayName} for {data.damage}");
}

2. Shared runtime variable (decouples producer from consumer)

[CreateAssetMenu(menuName = "Game/Float Variable")]
public class FloatVariable : ScriptableObject
{
    [SerializeField] private float initialValue;
    [System.NonSerialized] public float runtimeValue;   // not saved to the asset

    private void OnEnable() => runtimeValue = initialValue;  // reset each play session
}
// Player writes playerHealth.runtimeValue; the HUD reads it — neither references the other.

3. Creating an instance at runtime (not an asset on disk)

// For transient SO data you build in code (e.g. a generated config).
var temp = ScriptableObject.CreateInstance<WeaponData>();
temp.damage = 25;
// ...use temp...  Destroy(temp);   // clean up runtime-created instances

Pitfalls

• Editing an SO at runtime persists in the Editor — values you change during Play stay
  changed on the asset after you stop. Keep mutable runtime state in [NonSerialized] fields
  reset in OnEnable, or it will surprise you. (In a build, asset edits do not persist
  across launches.)
• Disabled Domain Reload skips your OnEnable reset — with Enter Play Mode Options
  enabled and Reload Domain off (a Unity 6.3 LTS fast-iteration setting), already-loaded SOs are
  not re-created when you press Play, so OnEnable never fires and runtimeValue keeps its
  value from the previous session. Reset explicitly from an ISerializationCallbackReceiver or
  a scene-load hook instead of relying on OnEnable alone.
• Expecting per-object state — every reference points to the same asset. If two enemies
  need different current HP, store HP on the MonoBehaviour, not the shared SO.
• No frame lifecycle — ScriptableObjects have OnEnable/OnDisable/OnDestroy but no
  Update. Don't expect per-frame callbacks.
• Using SOs as a save file — they're authoring assets, not runtime persistence; write
  progress with save-systems instead.
• Leaking CreateInstance objects — runtime-created instances are not garbage-collected
  like plain C# objects; Destroy them when done.

References

• For the event-channel pattern (a GameEvent SO + listeners, type-safe payloads) and
  runtime sets/registries (a shared list of active enemies), read
  references/event-channels.md.
• Primary docs: Unity Manual "ScriptableObject" (/Manual/class-ScriptableObject.html) and
  ScriptReference/ScriptableObject, ScriptReference/CreateAssetMenuAttribute.

Related skills

• unity-csharp-scripting — the MonoBehaviours that consume these assets.
• save-systems — persisting state to disk (what SOs are not for).
• card-game / rpg / survival-crafting — genres that lean on SO-driven data.