/**
 * Zoe SDK — Session persistence
 *
 * Provides composable persistence backends for storing conversation history.
 * Built-in "file" and "memory" backends are registered by default. Custom
 * backends (Redis, SQLite, etc.) can be registered via `registerBackend()`.
 *
 * Legacy `SessionStore`-based API is preserved for backward compatibility.
 */
import type { Message, PersistenceBackend, PersistenceConfig, ProviderType, SessionData, SessionStore } from "./types.js";
/**
 * File-backed persistence backend. Each session is stored as a JSON file
 * at `{basePath}/{sessionId}.json`.
 */
export declare class FilePersistenceBackend implements PersistenceBackend {
    readonly __persistenceBackend: true;
    private basePath;
    constructor(basePath: string);
    private filePath;
    private ensureDir;
    save(id: string, data: SessionData): Promise<void>;
    load(id: string): Promise<SessionData | null>;
    delete(id: string): Promise<void>;
    list(): Promise<string[]>;
    private loadFromDisk;
}
/**
 * In-memory persistence backend backed by a Map. Useful for testing.
 */
export declare class MemoryPersistenceBackend implements PersistenceBackend {
    readonly __persistenceBackend: true;
    private store;
    save(id: string, data: SessionData): Promise<void>;
    load(id: string): Promise<SessionData | null>;
    delete(id: string): Promise<void>;
    list(): Promise<string[]>;
}
export type BackendFactory = (config: PersistenceConfig) => PersistenceBackend;
/**
 * Register a custom persistence backend factory.
 *
 * @param type    Unique backend identifier (e.g., "redis", "sqlite")
 * @param factory Factory function that creates a `PersistenceBackend` from config
 */
export declare function registerBackend(type: string, factory: BackendFactory): void;
/**
 * Create a persistence backend from a config object.
 * Uses the `type` field to look up the registered factory.
 *
 * @throws Error if `type` is not registered
 */
export declare function createPersistenceBackend(config: PersistenceConfig): PersistenceBackend;
/**
 * Persist a session's messages to the backend.
 *
 * Single source of truth for the save step shared by all adapters (SDK, CLI,
 * Server). The backend owns `createdAt` (assigns it on first save, preserves
 * it on overwrite — see FilePersistenceBackend / MemoryPersistenceBackend) and
 * merges optional `provider`/`model`/`metadata` fields, so callers only pass
 * what they know. Adapters that don't track provider/model (the SDK) omit them
 * and the persisted values are left untouched.
 */
export declare function persistSession(backend: PersistenceBackend, sessionId: string, messages: Message[], opts?: {
    provider?: ProviderType;
    model?: string;
    metadata?: Record<string, unknown>;
}): Promise<void>;
/**
 * @deprecated Use `createPersistenceBackend({ type: "file", path })` instead.
 */
export declare function createSessionStore(path?: string): SessionStore;
/**
 * @deprecated Use `createPersistenceBackend({ type: "memory" })` instead.
 */
export declare function createMemoryStore(): SessionStore;