---
title: Lifecycle and route interception
description: Understand results, queues, Host lifetime, and router adapters.
order: 20
toc:
  - id: result-contracts
    title: Result contracts
  - id: queue
    title: Queues and Hosts
  - id: dismissal
    title: Dismissal
  - id: navigation
    title: Route interception
---

## Result contracts {#result-contracts}

`openConfirm` uses `false` for cancellation, `openPrompt` uses `null`, and custom Modals, Sheets, and Drawers use `undefined` when no result is supplied. `close(value)` is checked against the generic passed to `openModal<Result>()`.

```tsx
import { openModal } from "@workspace/overlays/modal"

const productId = await openModal<string>({
  title: "Choose a product",
  content: ({ close }) => (
    <ProductPicker onSelect={(product) => close(product.id)} />
  ),
})
```

## Queues and Hosts {#queue}

Within one Scope, each feature has a lazily created channel and Base UI handle. Calls of the same kind enter a FIFO queue and the next request appears after the previous closing animation completes. Different features can remain visible together, so a Modal may open a Confirm.

Unmounting a Host settles its pending requests with their cancellation values. React Strict Mode's simulated unmount does not incorrectly cancel requests.

## Dismissal {#dismissal}

Custom content can call `dismiss()`. The close button, Escape key, and backdrop press enter the same cancellation path. Setting `dismissible: false` blocks external dismissal, while the content may still explicitly call `close(result)` or `dismiss()`.

## Route interception {#navigation}

`@workspace/overlays/navigation` depends only on Scope, not on a concrete overlay feature or router:

```tsx
import { OverlayNavigationGuard } from "@workspace/overlays/navigation"

const adapter: OverlayNavigationAdapter = {
  subscribe(listener) {
    return router.block((transition) => {
      listener({
        cancel: transition.reset,
        proceed: transition.retry,
      })
    })
  },
}

<OverlayNavigationGuard adapter={adapter} />
```

The default Guard examines the current and named local Scopes and finds the last-opened layer. It dismisses an allowed layer and cancels navigation. A layer with `dismissible: false` remains open and keeps blocking. It calls `proceed()` only when no layer is open.

The adapter's `proceed()` must continue the exact blocked attempt instead of starting a new navigation that triggers the blocker again. Pass a custom `interceptor` to replace the policy.