/**
 * Update-check utility.
 *
 * Quietly pings npm once per day, caches the latest published version in
 * `~/.blockrun/version-check.json`, and exposes a sync helper the CLI
 * uses to nudge users when they're behind. The check is non-blocking:
 * fire-and-forget at startup, render the notice on the *next* run if the
 * network was slow the first time. Users never wait on it.
 *
 * Respects two opt-outs:
 *   - `FRANKLIN_NO_UPDATE_CHECK=1` — explicit user preference
 *   - CI-like environments (`CI`, `GITHUB_ACTIONS`, `GITLAB_CI`, etc.)
 *
 * Cache format is intentionally small and forward-compatible: new fields
 * may be added, old fields are tolerated on read.
 */
/**
 * Compare two semver strings (stripping a leading `v` and any pre-release
 * tag after a hyphen — we don't publish prereleases). Returns:
 *   1  if a > b
 *  -1  if a < b
 *   0  if equal or unparseable
 */
export declare function compareSemver(a: string, b: string): number;
/**
 * Refresh the cache in the background if it's stale. Never throws, never
 * awaited by callers — result lands before next startup.
 */
export declare function kickoffVersionCheck(): void;
export interface UpdateInfo {
    current: string;
    latest: string;
}
/**
 * Sync check against the cached latest. Returns update info if the cache
 * knows of a newer version, null otherwise. Safe to call before the first
 * background check settles — returns null (we don't speculate).
 */
export declare function getAvailableUpdate(): UpdateInfo | null;
/**
 * Authoritative check that forces a fresh fetch (up to FETCH_TIMEOUT_MS).
 * Use for on-demand diagnostics like `franklin doctor` where the user
 * explicitly asked "am I up to date?" and a 24h-stale cache is the wrong
 * answer. Verified 2026-05-11: between two same-day releases (3.15.91 →
 * 3.15.92), the daily cache made `franklin doctor` show green for a user
 * who was actually 4 versions behind (3.15.88), because they ran doctor
 * in the brief gap between npm publish and the next cache refresh.
 *
 * Falls back to the cached value if the fetch fails (offline, slow npm,
 * etc.) — same behavior as the cached check, just refreshed when
 * possible.
 */
export declare function getAvailableUpdateFresh(): Promise<UpdateInfo | null>;