/**
 * compaction.ts — Dual-phase conversation compaction.
 *
 * Phase 1 (prune): Remove tool outputs older than N turns to free context
 * window without losing conversation structure.
 * Phase 2 (summary): Rely on the upstream LLM to summarize (handled by
 * pi-coding-agent's built-in compaction).
 */
/** Default number of conversation turns to keep fully intact during pruning. */
export declare const DEFAULT_KEEP_TURNS = 5;
/** Minimum number of turns that can be kept — protects against overly aggressive pruning. */
export declare const MIN_KEEP_TURNS = 2;
/** Result of a compaction operation with token reduction metrics. */
export interface CompactResult {
    originalTokens: number;
    compactedTokens: number;
    reductionPercent: number;
    turnCount: number;
}
/** Minimal message shape needed for compaction — works with any message-like object. */
export interface CompactableMessage {
    role: "user" | "assistant" | "toolResult";
    content: string | unknown[];
    toolName?: string;
}
/**
 * Prune old tool outputs from a conversation while keeping the last N turns intact.
 *
 * Walks messages in reverse. Each assistant message counts as one turn boundary.
 * Keeps the last `keepLastNTurns` turns fully intact (all message roles).
 * For older turns, removes tool result messages while preserving user and assistant messages.
 * Never removes user messages regardless of their position.
 */
export declare function pruneOldToolOutputs(messages: readonly CompactableMessage[], keepLastNTurns: number): CompactableMessage[];
/**
 * Estimate the reduction achieved by compaction.
 */
export declare function estimateReduction(original: readonly CompactableMessage[], compacted: readonly CompactableMessage[]): CompactResult;
/** Check whether a conversation exceeds a given token threshold. */
export declare function shouldCompact(messages: readonly CompactableMessage[], thresholdTokens: number): boolean;