/**
 * Version Upgrade Notification
 *
 * Checks npm registry for newer versions and displays an unobtrusive notice
 * with changelog highlights. Non-blocking — spawns a detached child process
 * on cache miss so CLI startup is never delayed.
 *
 * Cache: .data/.version-check.json (24h TTL)
 * Notice: shown once per new version (tracks notifiedVersion)
 */
/**
 * Compare two semver strings, ignoring build metadata.
 * Returns 1 if a > b, -1 if a < b, 0 if equal.
 */
export declare function compareSemver(a: string, b: string): number;
/**
 * Spawn a detached background process that fetches the latest version
 * and changelog, then writes the cache file. The parent process does
 * not wait for this — CLI exits immediately.
 *
 * The detached child does a direct HTTPS request to registry.npmjs.org
 * rather than shelling out to `npm view`. Under launchd / sandboxed PATH,
 * `npm` is frequently absent and the previous code silently exited
 * without ever updating the cache (Bug 3 in v1.27.0).
 */
export declare function refreshUpdateCache(): void;
/**
 * Show update notice to stderr if a newer version is available.
 *
 * Returns silently if:
 * - No cache exists (background refresh hasn't completed yet)
 * - Current version is up to date
 * - Already notified for this version
 * - Running in MCP STDIO mode
 */
export declare function showUpdateNotice(): void;
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