/**
 * `reduce`: N → 1. One agent synthesises the results of a fan-out.
 */
import type { Agent } from "./../agent.ts";
import { type Result, type WorkflowResult } from "./../result.ts";
import type { WorkflowOptions } from "./options.ts";
/** The synthesiser, the branches it folds, and the instruction that frames them. */
export type ReduceOptions = WorkflowOptions & {
    /** The agent doing the synthesis. */
    agent: Agent;
    /** What is being synthesised - typically a {@link fanOut}'s results. */
    results: Result[];
    /** The instruction, placed **before** the branches. */
    input: string;
    /**
     * Turns the branches into the prompt the reducer receives.
     *
     * Defaults to {@link formatBranches}. Override it when the branches are not
     * prose - a list of files, a diff - and the default headings would get in
     * the way.
     */
    format?: (results: readonly Result[], input: string) => string;
};
/**
 * Hands every branch to one agent and asks it for a single answer.
 *
 * **Failed branches are shown, not dropped.** A synthesis built from six
 * branches when two of them crashed, with nothing saying so, is a confident
 * lie - and it is the caller who is then unable to tell a thin answer from a
 * thin body of evidence. The reducer sees the failures, labelled, and can say
 * its coverage was incomplete. Pass only the successes if that is really what
 * you want: filtering an array needs no option.
 *
 * The returned `Result` is the synthesis itself; `steps` holds the branches it
 * was given followed by that synthesis, so the usage of the whole N→1 is
 * `sumUsage(result.steps.map(s => s.usage), wallMs)`.
 *
 * Lifetime is passed down but cannot change the shape of this combinator: one
 * agent, one turn, one spawn either way. It only matters here as an option a
 * caller may already be threading through a larger workflow.
 */
export declare function reduce(options: ReduceOptions): Promise<WorkflowResult>;
/**
 * The default rendering: the instruction, then one numbered section per
 * branch, failures kept and marked.
 */
export declare function formatBranches(results: readonly Result[], input: string): string;
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