/**
 * OutputDelta — re-send only what changed, never the whole thing again.
 *
 * The problem: a debug loop reads the same file (or runs the same command) six times.
 * Between two of those calls maybe three lines moved, but the model pays for the entire
 * file or the entire 400-line `tsc` dump each time — and because tool results stay in the
 * transcript, it keeps paying for every copy on every subsequent turn.
 *
 * `ReadWorkspaceCache` already suppresses the *identical* case. This module covers the far
 * more common one: it changed, but barely.
 *
 * Two rules this module is built around:
 *
 *  1. The diff is computed against the exact text the model received. Not the file on
 *     disk, not the pre-squeeze source — the final emitted string. A diff against
 *     anything else describes a document the model never had, which is worse than
 *     re-sending the whole file.
 *  2. A delta is only emitted when it is decisively smaller than the full text. Below
 *     that margin, reconstructing from a diff is cognitive work with no token payoff, so
 *     the full text wins. See `shouldEmitDelta`.
 */
export interface Hunk {
    /** 1-indexed start line in the previous text. */
    oldStart: number;
    oldLines: number;
    /** 1-indexed start line in the new text. */
    newStart: number;
    newLines: number;
    /** Rendered lines, each prefixed with ' ', '-' or '+'. */
    lines: string[];
}
export interface DiffResult {
    hunks: Hunk[];
    added: number;
    removed: number;
    /** True when the two texts are byte-identical. */
    identical: boolean;
}
/** Line-level diff between the text the model already has and the text we would send now. */
export declare function computeDiff(previous: string, next: string): DiffResult | null;
/** Render hunks as a unified diff body (no ---/+++ file headers; the caller supplies context). */
export declare function renderDiff(diff: DiffResult): string;
export interface DeltaDecision {
    emit: boolean;
    /** The rendered diff body, present only when `emit` is true. */
    body?: string;
    added: number;
    removed: number;
    hunkCount: number;
    /** Why a delta was declined — surfaced in logs and receipts, never guessed at. */
    reason?: string;
}
/**
 * Decide whether to hand the model a delta instead of the full text.
 *
 * Declining is the safe direction: the caller falls back to sending everything, which is
 * always correct. So every uncertain case here resolves to `emit: false`.
 */
export declare function shouldEmitDelta(previous: string, next: string): DeltaDecision;
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