/**
 * SSR-safe environment guards. The library must be import-safe outside a
 * browser (Next.js server components, Jest/Vitest in node, agent pipelines
 * running pre-flight validation server-side) — the research-validated
 * failure mode is touching browser globals at import time (Mapbox GL's
 * six-years-open #4593). Two rules keep us clean:
 *
 *   1. No module evaluates a browser global at import time. Class
 *      declarations `extends HTMLElementBase` (below) instead of
 *      `extends HTMLElement`, and element registration goes through
 *      `defineElement`, which no-ops outside a browser.
 *   2. Everything that genuinely needs a DOM (rendering, observers,
 *      sandbox iframes) touches it inside methods/functions only.
 *
 * Outside a browser the custom elements are inert-but-importable: the
 * classes exist (so types, registries, validation, expression compilation,
 * and IR snapshots all work), they just never register or upgrade.
 */
export declare const isBrowser: boolean;
/**
 * Base class for the om-* custom elements. In a browser this IS
 * HTMLElement; in node it's an empty class so the module can evaluate.
 * Constructing an element outside a browser is not supported (nothing
 * registers them there), so the stub never needs real behavior.
 */
export declare const HTMLElementBase: typeof HTMLElement;
/**
 * `customElements.define`, guarded twice: no-op outside a browser, and
 * idempotent under double-import (a second `define` of the same name
 * throws — a real hazard when a CDN tag and a bundled import coexist).
 */
export declare function defineElement(name: string, ctor: CustomElementConstructor): void;
/**
 * Parses a manifest HTML string into a Document — used by the string-input
 * surfaces (`OmMap.validate(html)`, `snapshotIR(html)`). Neither needs a
 * *browser* (no rendering, no custom-element upgrade — they read tags and
 * attributes), but they do need a DOM implementation for DOMParser. In
 * plain node, that means a test DOM: vitest/jest with the happy-dom or
 * jsdom environment both provide it.
 */
export declare function parseHtmlDocument(html: string): Document;