export interface BlobPutResult {
    hash: string;
    path: string;
    get ref(): string;
}
/**
 * Content-addressed blob store for externalizing large binary data (images) from session JSONL files.
 *
 * Files are stored at `<dir>/<sha256-hex>` with no extension. The SHA-256 hash is computed
 * over the raw binary data (not base64). Content-addressing makes writes idempotent and
 * provides automatic deduplication across sessions.
 */
export declare class BlobStore {
    readonly dir: string;
    constructor(dir: string);
    /**
     * Write binary data to the blob store.
     * @returns SHA-256 hex hash of the data
     */
    put(data: Buffer): Promise<BlobPutResult>;
    /**
     * Synchronous variant of {@link put}. Use on persistence hot paths where the caller
     * cannot afford the microtask hops of the async version (e.g. OOM-safe session writes).
     * Returns once the bytes are in the kernel page cache.
     */
    putSync(data: Buffer): BlobPutResult;
    /** Read blob by hash, returns Buffer or null if not found. */
    get(hash: string): Promise<Buffer | null>;
    /** Check if a blob exists. */
    has(hash: string): Promise<boolean>;
}
/** Check if a data string is a blob reference. */
export declare function isBlobRef(data: string): boolean;
/** Extract the SHA-256 hash from a blob reference string. */
export declare function parseBlobRef(data: string): string | null;
/** Identify provider transport image data URLs so persistence can externalize and restore them losslessly. */
export declare function isImageDataUrl(data: string): boolean;
/**
 * Externalize a provider image data URL to the blob store, returning a blob reference.
 * The full data URL string is preserved so transport-native history can be reconstructed on resume.
 */
export declare function externalizeImageDataUrl(blobStore: BlobStore, dataUrl: string): Promise<string>;
/** Synchronous variant of {@link externalizeImageDataUrl}. */
export declare function externalizeImageDataUrlSync(blobStore: BlobStore, dataUrl: string): string;
/**
 * Externalize an image's base64 data to the blob store, returning a blob reference.
 * If the data is already a blob reference, returns it unchanged.
 */
export declare function externalizeImageData(blobStore: BlobStore, base64Data: string): Promise<string>;
/** Synchronous variant of {@link externalizeImageData}. */
export declare function externalizeImageDataSync(blobStore: BlobStore, base64Data: string): string;
/**
 * Resolve an externalized provider image data URL back to its original string.
 * If the data is not a blob reference, returns it unchanged.
 * If the blob is missing, logs a warning and returns the reference as-is.
 */
export declare function resolveImageDataUrl(blobStore: BlobStore, data: string): Promise<string>;
/**
 * Resolve a blob reference back to base64 data.
 * If the data is not a blob reference, returns it unchanged.
 * If the blob is missing, logs a warning and returns a placeholder.
 */
export declare function resolveImageData(blobStore: BlobStore, data: string): Promise<string>;