import type { CacheableMarkers } from '../../types.js';
/**
 * Build a stable `prompt_cache_key` from the regions the agent marked as
 * cacheable. Returns `undefined` if no markers apply (request goes out
 * without a cache key — OpenAI still caches automatically above 1024
 * tokens, just without routing affinity).
 *
 * Exported for unit testing.
 */
export declare function buildPromptCacheKey(messages: unknown[], tools: unknown[] | undefined, cache: CacheableMarkers | undefined): string | undefined;
//# sourceMappingURL=prompt-cache.d.ts.map