import type { AgentChatAttachment } from "../agent/types.js";
import { type OwnedAttachmentHydrationBudget } from "./owned-attachment.js";
export declare function canonicalImageReferenceUrl(value: string): string;
export declare class PriorThreadImageHistoryReadError extends Error {
    readonly code = "prior_attachment_history_unreadable";
    constructor();
}
export interface PriorThreadImageHistory {
    attachments: AgentChatAttachment[];
    contextNote?: string;
}
export interface PriorThreadImageHistoryCacheScope {
    ownerEmail: string;
    orgId?: string | null;
    threadId: string;
}
export declare const PRIOR_THREAD_IMAGE_CACHE_TTL_MS: number;
export declare const MAX_PRIOR_THREAD_IMAGE_CACHE_ENTRIES = 16;
export declare const MAX_PRIOR_THREAD_IMAGE_CACHE_ENCODED_BYTES: number;
export declare function retainedStructuredHistoryImageUrls(history: unknown): ReadonlySet<string>;
/**
 * Rehydrate only recent image references from an already-authorized thread.
 * URL ownership and download limits are enforced by hydrateOwnedImageUrl.
 */
export declare function hydratePriorThreadImages(threadData: string, options?: {
    cacheScope?: PriorThreadImageHistoryCacheScope;
    excludeUrls?: ReadonlySet<string>;
    budget?: OwnedAttachmentHydrationBudget;
}): Promise<PriorThreadImageHistory>;