/**
 * Work out what a regenerate should send, separately from sending it.
 *
 * TORUK Core defines regenerate in terms of its edit path
 * (`useMessageActions.handleRefresh` calls `handleEditSubmit` with unchanged
 * content): find the user turn the answer belongs to, drop everything from there
 * on, and re-send that question with the preceding conversation as history.
 *
 * The decision is pure, so it is tested on its own — the parts with edge cases
 * are which turn owns the answer, what counts as context, and not duplicating the
 * question when the caller re-adds it.
 */
import type { MessageType } from '@/widget/types';
/** What the engine accepts as prior context (`IMessage` in the server's interface). */
export type PredictionHistoryMessage = {
    message: string;
    type: 'userMessage' | 'apiMessage';
};
export type RegeneratePlan = {
    /** The question to send again. */
    question: string;
    /** The transcript with the superseded exchange removed, ending before the question. */
    prefix: MessageType[];
    /** Conversation context for the new answer. */
    history: PredictionHistoryMessage[];
    /** Transcript index of the user turn being replaced — the point the conversation forks at. */
    userIndex: number;
};
/**
 * Plan a regenerate of the assistant turn at `assistantIndex`, or return null when
 * there is nothing to regenerate — the index is not an assistant turn, or no user
 * turn precedes it, or that turn has no text to re-send.
 *
 * The prefix stops *before* the user turn because the caller's submit path re-adds
 * the question; including it here would duplicate it.
 */
export declare function planRegenerate(messages: readonly MessageType[], assistantIndex: number): RegeneratePlan | null;
/**
 * Plan an edit of the user turn at `userIndex`, resending it as `newContent`.
 *
 * The same shape as a regenerate, and for the same reason Core implements one in terms of the
 * other: replacing a turn and re-answering it are the same operation on the transcript, differing
 * only in whether the question changes.
 *
 * Returns null when the index is not a user turn or the replacement is blank — an empty edit is a
 * cancel, not a turn.
 */
export declare function planEdit(messages: readonly MessageType[], userIndex: number, newContent: string): RegeneratePlan | null;