import { type IStream } from '../../stream/index.js';
/**
 * Creates a "tethered" pair of streams from a single source.
 *
 * The pattern creates a split topology where each primary subscription
 * creates its own TetherSink that forwards events to both destinations:
 *
 * ```
 * Source ──┬── TetherSink₁ ──┬──> Primary Sink₁
 *          │                 └──┐
 *          │                    │
 *          ├── TetherSink₂ ──┬──> Primary Sink₂
 *          │                 └──┤
 *          │                    │
 *          └── TetherSink₃ ──┬──> Primary Sink₃
 *                            └──┤
 *                               ↓
 *                        Tether Multicast
 *                         /    |    \
 *                        v     v     v
 *                     tether tether tether
 *                     sub₁   sub₂   sub₃
 * ```
 *
 * Example flow for event 'x':
 * - Primary subscription 1: Source → TetherSink₁ → Primary Sink₁ + Tether
 * - Primary subscription 2: Source → TetherSink₂ → Primary Sink₂ + Tether
 * - Tether sees 'x' twice (once from each primary subscription)
 *
 * Key behaviors:
 * - Primary stream: Unicast (each subscriber gets independent source subscription)
 * - Tether stream: Multicast that aggregates events from ALL primary subscriptions
 * - Each primary subscription creates its own TetherSink
 * - Tether receives events from every primary subscription (may see duplicates)
 *
 * @returns [primary, tethered] stream tuple
 */
export declare const tether: <T>(source: IStream<T>) => [IStream<T>, IStream<T>];