/**
 * Per-conduit serial Promise queue. Each conduit has at most one tail entry.
 * Consumers may call .has(conduitId) to check whether a queue is already running
 * (e.g. to show a hourglass reaction), and .delete(conduitId) to discard a
 * pending tail (e.g. !cancel).
 */
export declare const conduitQueues: Map<string, Promise<void>>;
/**
 * Append fn to the conduit's serial queue.
 *
 * Returns true if a queue was already running for this conduit when enqueue()
 * was called (useful for showing backpressure indicators). Returns false if
 * this is the first entry for the conduit.
 *
 * The queue entry is automatically removed once fn resolves or rejects, so
 * the Map never accumulates stale entries for completed conduits.
 */
export declare function enqueue(conduitId: string, fn: () => Promise<void>): boolean;