import type { EvaluationPayload } from "./types";
export type LkgEntry = {
    /** Meta.generation stamped on the cached payload (0 if unversioned). */
    generation: number;
    payload: EvaluationPayload;
};
/**
 * Cache key for a (workspace+environment, context) pair. The frontend SDK key
 * is the client-side proxy for workspace+environment (the server resolves both
 * from it), and `contextSig` (encodeContexts) carries the evaluated context, so
 * `${sdkKey}:${contextSig}` is exactly the dimension along which an
 * eval-with-context response is unique — the same keying the per-URL ETag cache
 * uses, minus the host (LKG must be primary/secondary-agnostic).
 */
export declare function lkgKey(sdkKey: string, contextSig: string): string;
/** Read the cached entry for `key`, or undefined if absent/unreadable/corrupt. */
export declare function readLkg(key: string): LkgEntry | undefined;
/**
 * Persist `entry` as the last-known-good for `key`. Best-effort: a thrown quota
 * or serialization error is swallowed. Callers persist only what the client
 * actually installed (post reject-older guard), so the per-context entry is
 * already monotonic — an older live response is dropped by the guard before it
 * ever reaches here, satisfying "the watermark rule applies to the cache too".
 */
export declare function writeLkg(key: string, entry: LkgEntry): void;