# RouteExecutor

Transitions between decoded route candidates while retaining compatible mounted work.

## Signatures

```ts
export interface RouteExecutor<A, E = never, R = never> {
    readonly transition: (transition: RouteTransition) => Effect.Effect<Fx.Fx<A, E, R | Scope.Scope | Router>, E | RouteDecodeError | RouteGuardError, R>;
}
```

## Why

Parameter-only updates can reuse a handler; route changes switch scopes deterministically.

## Ownership and lifetime

An executor is acquired by `makeRouteExecutor` in a Scope. That Scope owns its current handler and the
Layer, layout, and catch managers reused across calls to `transition`.

## Property: transition

Decodes and selects the first accepted candidate for one route transition.

## Property: transition: Why

Candidate schemas and guards run in their supplied order after path lookup has selected a matcher
shape. Decode failures, guard `None`, and guard failures fall through; selected identity controls
parameter reuse, and route changes switch the owned handler Scope.

## Property: transition: Ownership and lifetime

Calls are serialized by the executor's semaphore. Preparing a replacement occurs before commit;
rejection rolls back new Layer Scopes, while commit closes replaced handler and manager Scopes.