import type { SessionTrace, TurnUsage } from '../types/telemetry.js';
type TurnUsageInput = Omit<TurnUsage, 'cumulativeInputTokens' | 'cumulativeOutputTokens' | 'cumulativeTotalTokens' | 'contextUtilization'>;
/**
 * Append-only per-session token totals. `record()` is synchronous O(1).
 */
export declare class TokenAccumulator {
    private readonly contextWindow?;
    private _turns;
    private _cumInput;
    private _cumOutput;
    private _cumTotal;
    private _peakUtil;
    private _cumCacheRead;
    private _cumCacheWrite;
    constructor(contextWindow?: number | undefined);
    /** Rehydrate cumulative totals from persisted session state (cross-turn). */
    restoreCumulative(saved: {
        inputTokens: number;
        outputTokens: number;
        totalTokens: number;
        cacheReadTokens?: number;
        cacheWriteTokens?: number;
    }): void;
    record(usage: TurnUsageInput): TurnUsage;
    get cumulative(): {
        inputTokens: number;
        outputTokens: number;
        totalTokens: number;
        cacheReadTokens: number;
        cacheWriteTokens: number;
    };
    get peakUtilization(): number;
    get turns(): TurnUsage[];
    toSessionTraceFields(): Partial<SessionTrace>;
}
export {};