/**
* Fire-and-forget delivery for telemetry/analytics. Tries (in order):
*
*   1. `fetchLater()` — WICG Pending Beacon API, Chromium 135+. Deferred
*      delivery; the browser sends the request even if the page unloads.
*   2. `fetch(url, { keepalive: true })` — survives unload up to 64 KiB
*      total in-flight per origin. Errors visible if you await the promise.
*   3. `navigator.sendBeacon(url, body)` — same 64 KiB cap, POST-only,
*      no response.
*
* Browser-only — no Node fallback. The first available primitive wins.
*
* @example
* ```ts
* import { beacon } from "misina/beacon"
*
* beacon("/telemetry", { event: "page_view", ts: Date.now() })
* ```
*/
export interface BeaconOptions {
	/** HTTP method. Default: 'POST'. sendBeacon ignores this and always POSTs. */
	method?: string;
	/** Headers. Note: sendBeacon ignores headers entirely. */
	headers?: Record<string, string>;
	/**
	* Earliest delivery time in ms relative to now. Honored by fetchLater
	* only; falls through to immediate dispatch on the other backends.
	*/
	activateAfter?: number;
}
export type BeaconResult = {
	ok: true;
	via: "fetchLater" | "fetch-keepalive" | "sendBeacon";
} | {
	ok: false;
	reason: "no-backend" | "send-rejected";
};
export declare function beacon(url: string, body: BodyInit | Record<string, unknown> | undefined, options?: BeaconOptions): BeaconResult;