import type { Channel } from '../types/graph.js';
/**
 * The last write wins.
 *
 * The right default for a scalar a node computes fresh each time. Under fan-out the winner is
 * whichever branch reduced last, so prefer an accumulating channel when several branches write the
 * same slot and the outcome matters.
 */
export declare function lastValue<T>(initial?: T): Channel<T>;
/** Concatenates every write, which is what a message history or an event log wants. */
export declare function appendList<T>(): Channel<T[]>;
/** Shallow-merges object writes, so two branches can each contribute their own keys. */
export declare function mergeObject<T extends Record<string, unknown>>(): Channel<T>;
/** Sums numeric writes, for a counter several branches increment. */
export declare function counter(initial?: number): Channel<number>;
/** Keeps distinct values in first-seen order. */
export declare function appendSet<T>(): Channel<T[]>;
/** Builds a channel from a plain reducer, for a rule none of the built-ins covers. */
export declare function reducerChannel<T>(reduce: (current: T | undefined, update: T) => T, initial?: () => T): Channel<T>;