## OPAQUE · constant

A symbol that controls how Aberdeen handles an object in copy operations and proxy wrapping.

The **presence** of this symbol (regardless of its value) prevents deep-copying: the object is
stored and passed by reference in `clone` and `copy`.

The **value** of the symbol controls proxy wrapping when the object is read from reactive state:
- **Truthy** (e.g. `true`): the object is fully opaque — it is not wrapped in a proxy, so its
  properties are not observable. Use this for objects that break when proxied (e.g. class instances
  with internal slots, Promises) or that must be invisible to Aberdeen's reactive system.
- **Falsy** (e.g. `false`): the object is still wrapped in a proxy, so reads on its properties
  create reactive dependencies as normal — only deep-copying is suppressed.

**Value:** `unique symbol`