/**
 * Deterministic pre-dispatch history truncation.
 *
 * Runs inside the shared context preflight, so one implementation bounds input
 * cost on every dispatch path: native Anthropic, the translated/SDK fallback
 * that serves Vertex, and native or bridged Codex.
 *
 * Deliberately provider-free. Summarizing history would add an outbound model
 * call to the very requests this exists to make cheaper, so reduction is pure
 * removal of the oldest complete units.
 */
import type { ProxyHistoryEstimate, ProxyHistoryTruncationResult } from "../types/index.js";
/**
 * Remove the oldest complete units until the estimate reaches `targetTokens`.
 *
 * Returns the body unchanged when there is nothing safe to remove. The newest
 * unit is always retained: it carries the turn being answered.
 */
export declare function truncateHistoryForBudget<T extends object>(args: {
    body: T;
    inputTokensEstimate: number;
    targetTokens: number;
    estimate: ProxyHistoryEstimate;
}): ProxyHistoryTruncationResult<T>;