/** Cached token data persisted to disk. */
export interface TokenCacheData {
    readonly idToken: string;
    readonly refreshToken: string;
    readonly userId: string;
    /** ISO 8601 timestamp of token expiry. */
    readonly expiresAt: string;
    /** Firebase project ID (avoids fetching web config on cache hit). */
    readonly projectId: string;
}
/** Resolve the token cache file path from user input or default. */
export declare function resolveTokenCachePath(userPath?: string): string;
/**
 * Read cached tokens. Tries OS keychain first, falls back to file.
 * Returns null if cache is missing, corrupt, or malformed.
 */
export declare function readTokenCache(cachePath: string): Promise<TokenCacheData | null>;
/**
 * Write token data to cache. Stores in OS keychain when available,
 * falls back to file with restricted permissions.
 */
export declare function writeTokenCache(cachePath: string, data: TokenCacheData): Promise<void>;
/** Delete the token cache from all storage backends. */
export declare function invalidateTokenCache(cachePath?: string): Promise<void>;
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