import type { ONIModel, ONIModelMessage } from "../models/types.js";
export interface CompactionBudgetSnapshot {
    estimatedTokens: number;
    percentUsed: number;
    threshold: number;
    maxTokens: number;
}
export interface CompactionCheck extends CompactionBudgetSnapshot {
    needed: boolean;
}
export interface CompactorConfig {
    /** Model used to generate the summary (typically a fast/cheap model) */
    summaryModel: ONIModel;
    /**
     * Usage fraction at which compaction triggers.
     * Research: performance degrades non-linearly above 65%.
     * @default 0.68
     */
    threshold?: number;
    /**
     * Maximum token budget for the context window.
     * @default 200_000
     */
    maxTokens?: number;
    /**
     * Approximate characters per token for estimation.
     * @default 4
     */
    charsPerToken?: number;
    /**
     * Additional instructions included in the summarization prompt.
     */
    compactInstructions?: string;
}
export declare class ContextCompactor {
    private readonly summaryModel;
    private readonly threshold;
    private readonly maxTokens;
    private readonly charsPerToken;
    private readonly compactInstructions?;
    private _lastSummary;
    /** Promise-chain lock: serializes concurrent calls to compact(). */
    private _lockChain;
    constructor(config: CompactorConfig);
    /**
     * Estimate token count from total character length of all messages.
     * Uses ceiling to avoid underestimation.
     */
    estimateTokens(messages: ONIModelMessage[]): number;
    /**
     * Returns true when estimated usage exceeds the compaction threshold.
     */
    shouldCompact(messages: ONIModelMessage[]): boolean;
    /**
     * Check if compaction is needed and return details.
     */
    checkCompaction(messages: ONIModelMessage[]): CompactionCheck;
    /**
     * Current usage as a fraction of maxTokens (0–1+).
     */
    usageFraction(messages: ONIModelMessage[]): number;
    getThreshold(): number;
    getMaxTokens(): number;
    getBudgetSnapshot(messages: ONIModelMessage[]): CompactionBudgetSnapshot;
    /**
     * Returns the text of the last compaction summary, or null if compaction
     * has not been run in this session.
     */
    getLastSummary(): string | null;
    /**
     * Extracts open threads / unresolved tasks from the last summary.
     * Looks for lines containing open-ended markers (TODO, WIP, pending, unresolved,
     * open, in progress) and returns them as a deduplicated string array.
     * Returns [] if no summary has been produced.
     */
    getOpenThreads(): string[];
    /**
     * Two-stage compaction:
     * 1. Clear old tool results (less lossy)
     * 2. Full summarization if still over threshold
     *
     * Returns the compacted message array.
     */
    compact(messages: ONIModelMessage[], opts?: {
        skipInitialCheck?: boolean;
    }): Promise<ONIModelMessage[]>;
    private _runCompaction;
    /**
     * Remove tool-role messages from the older portion of the conversation,
     * keeping the most recent `keepRecent` messages intact.
     */
    private clearOldToolResults;
    /**
     * Build a history text from all messages and ask the summary model
     * to produce a compact summary wrapped in <summary> tags.
     */
    private summarize;
    /**
     * Fallback when the summary model fails — keep the most recent messages
     * that fit within the token budget and prepend a truncation notice.
     */
    private fallbackTruncation;
    /**
     * Get the character length of a message's content.
     */
    private contentLength;
}
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