import type { Message } from '../types/messages.js';
export interface CompactionSummaryCacheOptions {
    /** Maximum distinct summaries retained in memory (default: 32). Must be a positive integer. */
    capacity?: number | undefined;
    /** Time a successful summary remains reusable (default: 1 hour). Must be finite and > 0. */
    ttlMs?: number | undefined;
}
/** Non-semantic summarizer results that must never become durable cache hits. */
export declare const PLACEHOLDER_SUMMARIES: Readonly<{
    empty: "(empty)";
    emptySummary: "(empty summary)";
}>;
export declare function isPlaceholderSummary(value: string): boolean;
/**
 * Small, process-local cache for isolated compaction summaries.
 *
 * Auto-compaction and overflow recovery can race or retry against the same
 * pre-compaction history. Without a shared cache each path pays for the same
 * secondary-model request. The cache is deliberately bounded and TTL-based:
 * long-running agents cannot accumulate one entry per compaction forever.
 */
export declare class CompactionSummaryCache {
    private readonly entries;
    private readonly pending;
    private readonly ttlMs;
    private generation;
    constructor(opts?: CompactionSummaryCacheOptions);
    get(key: string): string | undefined;
    set(key: string, value: string): void;
    /** Clear entries and invalidate pending creators so their results cannot repopulate the cache. */
    clear(): void;
    /** Reuse both completed results and an identical call already in flight. */
    getOrCreate(key: string, create: () => Promise<string>): Promise<string>;
}
/** Process-wide default with a 32-entry capacity and 1-hour TTL. */
export declare const defaultCompactionSummaryCache: CompactionSummaryCache;
/** Stable key for a summary request; transient estimator and provider metadata are excluded. */
export declare function compactionSummaryKey(model: string, prompt: string, messages: readonly Message[]): string;
//# sourceMappingURL=compaction-summary-cache.d.ts.map