/**
 * Branded OG-placeholder URL construction — the DEFAULT cover-image fallback
 * for entity cards (onboarding guides, blog/case-study/release/etc.) that have
 * no image.
 *
 * ALL of the logic lives here, in the lib. A consumer hands over its runtime
 * `endpoints` object and NOTHING else — base resolution AND the `?title=…`
 * concatenation happen inside `buildOgPlaceholderUrl`. For the entity-card +
 * onboarding-detail surfaces this is the single entry point — no card builds an
 * og-placeholder URL itself (that was the bug this replaced: each embedder
 * wired a per-surface callback that concatenated the URL, and a host that
 * forgot it rendered a blank slot with no request). (Other server-side OG paths
 * such as the hub's blog og:image generator construct their own URLs and are
 * out of this module's scope.)
 *
 * The base API URL is taken from the endpoints the host already configures:
 *   1. explicit `endpoints.ogPlaceholderUrl`
 *   2. derived from the sibling `endpoints.imageProxyUrlPrefix` (same API base)
 *   3. same-origin relative `/api/og-placeholder`
 * The base may already carry pre-existing query params; they're preserved and
 * `title` (+ dimensions) are layered on top. Per-platform brand colors are NOT
 * baked into this URL — the `/api/og-placeholder` route resolves them
 * server-side from the platform. Most hosts leave `ogPlaceholderUrl` unset and
 * let the base derive from `imageProxyUrlPrefix`.
 */
/** The slice of `ChatRuntime.endpoints` this module needs. */
export interface OgPlaceholderEndpoints {
    /** Explicit base URL for the og-placeholder route. May already carry query
     *  params — they're preserved. Per-platform colors are NOT baked here; the
     *  route resolves them server-side from the platform. */
    ogPlaceholderUrl?: string;
    /** Sibling image route under the SAME API base. When `ogPlaceholderUrl` is
     *  unset, the base is derived from this by swapping the trailing
     *  `/image-proxy` segment for `/og-placeholder` — so a host that already
     *  proxies images gets the placeholder for free, with zero extra wiring. */
    imageProxyUrlPrefix?: string;
}
export interface BuildOgPlaceholderOptions {
    /** Site name shown under the title. Skipped when empty. */
    site?: string;
    /** `'wide'` (1200×630, the route default — no `w`/`h` emitted) or
     *  `'square'` (1024×1024, for compact 56×56 chat-inline slots). */
    aspect?: 'wide' | 'square';
    /** Explicit pixel overrides (win over `aspect`). */
    width?: number;
    height?: number;
}
/**
 * Build the branded og-placeholder image URL from the host's `endpoints` + a
 * title. This is the single entry point for entity-card + onboarding-detail
 * cover fallbacks: it resolves the route base from `endpoints` AND concatenates
 * `title` (+ dimensions), so those consumers never construct a URL themselves.
 *
 * Pure string construction — SSR- and browser-safe. Always returns a usable
 * URL (relative default at worst), so a missing/unknown image degrades
 * gracefully via the `<img onError>` recovery in the card components.
 */
export declare function buildOgPlaceholderUrl(endpoints: OgPlaceholderEndpoints | null | undefined, title: string, options?: BuildOgPlaceholderOptions): string;
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