/**
 * compaction-snapshot.ts — Upstream Pi compaction observation shape.
 *
 * Runtime truth (#325): subagent sessions compact via Pi `AgentSession`
 * auto-compaction. This module maps `compaction_end` events (incl. 0.81
 * `usage` / `estimatedTokensAfter` / retry fields) into a stable snapshot
 * stored on `AgentRecord.lastCompaction`.
 */
import type { LifetimeUsage } from "./usage.js";
export type CompactionReason = "manual" | "threshold" | "overflow";
/** Observed metrics from the most recent upstream compaction attempt. */
export interface CompactionSnapshot {
    reason: CompactionReason;
    tokensBefore: number;
    tokensAfter?: number;
    reductionPercent?: number;
    firstKeptEntryId?: string;
    /** Summarization LLM usage charged during compaction (Pi 0.81+). */
    usage?: LifetimeUsage;
    aborted?: boolean;
    willRetry?: boolean;
    errorMessage?: string;
}
export interface UpstreamCompactionEndEvent {
    reason: CompactionReason;
    aborted: boolean;
    willRetry?: boolean;
    errorMessage?: string;
    result?: {
        tokensBefore?: number;
        estimatedTokensAfter?: number;
        firstKeptEntryId?: string;
        usage?: {
            input?: number;
            output?: number;
            cacheWrite?: number;
        };
    };
}
/** Map a Pi `compaction_end` event into an orchestrator snapshot. */
export declare function buildCompactionSnapshot(event: UpstreamCompactionEndEvent): CompactionSnapshot;