export declare const STICKY_SESSION_HEADER = "x-llm-relay-session";
export declare const STICKY_PROVENANCE_HEADER = "x-llm-relay-sticky";
export type SessionRequestHeaders = Readonly<Record<string, string | string[] | undefined>>;
export interface SessionPin {
    readonly targetSpec: string;
    readonly pinnedAt: number;
    lastUsedAt: number;
    useCount: number;
}
export interface StickySessionManagerOptions {
    ttlMs?: number;
    maxSessions?: number;
}
export declare const DEFAULT_STICKY_TTL_MS: number;
export declare const DEFAULT_STICKY_MAX_SESSIONS = 1000;
/** Ephemeral, metadata-only sliding-TTL session affinity. */
export declare class StickySessionManager {
    private readonly pins;
    private readonly ttlMs;
    private readonly maxSessions;
    constructor(options?: StickySessionManagerOptions);
    getPin(key: string, now?: number): string | null;
    setPin(key: string, targetSpec: string, now?: number): void;
    deletePin(key: string): void;
    clear(): void;
    private prune;
}
/**
 * Derive a session key without retaining request content.
 *
 * The only explicit base header is relay-owned and opt-in. No client session header is accepted
 * until this repository has evidence that the client actually emits it. Claude Code's documented
 * agent id is a qualifier only: it keeps a child from overwriting its parent's affinity.
 */
export declare function deriveSessionKey(headers: SessionRequestHeaders | undefined, reqJson: unknown): string | null;