Browser support

The target is Baseline newly available. Newer features are used behind feature detection, with a small fallback where the library depends on them. No polyfills ship in the bundle.

What your browser does natively

This browser

Who covers what

Feature	Native	Fallback
`closedby="any"`	Light dismiss	`lightDismiss()`, inside `enhanceDialog()` and `<surface-drawer>`
Exit transitions out of the top layer	`overlay` and `transition-behavior: allow-discrete`	`routeCloseRequests()` and `closeAnimated()` via `data-closing`
Entry transitions	`@starting-style`	None. The drawer appears without sliding in.
Invoker commands (`commandfor`)	Opens and closes from HTML	Not included. Load a polyfill (below).
`<details>` open/close animation	`::details-content` and `interpolate-size`	`<surface-accordion>` animates with Web Animations
`:state()`	`surface-drawer:state(open)`	None. Style `dialog[open]` instead.
`:modal`	Modal detection	Treats any open dialog as modal.

Invoker commands polyfill

Load invokers-polyfill only where it is missing:

if (!("commandForElement" in HTMLButtonElement.prototype)) {
  import("invokers-polyfill")
}

Deliberate deviations from platform guidance are recorded as ADRs.