# RefSubject.RefSubjectTypeId

Runtime symbol identifying writable RefSubject values.

## Signatures

```ts
export declare const RefSubjectTypeId: unique symbol;
```

```ts
export type RefSubjectTypeId = typeof RefSubjectTypeId;
```

## Why

Provides stable runtime identity for RefSubject values without relying on classes or a renderer.

## Ownership and lifetime

This declaration performs no acquisition and retains no resources. Implementations preserve
source errors, services, and lifetime.