/**
 * Sentinel marking the end of the cacheable STABLE system-prompt prefix.
 *
 * Zero-width on purpose: engines that do not split the system prompt forward
 * it to the model verbatim, so anything visible here would leak into their
 * rendered prompt.
 */
export declare const SYSTEM_PROMPT_CACHE_SPLIT = "\u200B";
/**
 * Split an assembled system prompt into the stable prefix (which carries the
 * cache breakpoint) and the volatile remainder (resources, app extras, model
 * overlay, runtime context). Without a sentinel the whole prompt is stable.
 */
export declare function splitSystemPromptForCache(systemPrompt: string): {
    stable: string;
    volatile: string;
};
export type PromptCacheControl = {
    type: "ephemeral";
    ttl?: "1h";
};
/**
 * Cache control for the stable prefix (system prompt + tool definitions).
 *
 * Anthropic's default ephemeral entry lives 5 minutes. Measured hosted chunk
 * boundaries sit ~6 minutes apart on average with a quarter of them past 5
 * minutes, so the default expires between chunks and the whole prefix is
 * re-written at full price. A 1h entry costs 2x to write and 0.1x to read,
 * which can be useful for long hosted turns, but gateways may reject the
 * newer `ttl` field. Opt into it explicitly with
 * `AGENT_PROMPT_CACHE_TTL=1h`.
 */
export declare function stablePrefixCacheControl(): PromptCacheControl;
//# sourceMappingURL=prompt-cache.d.ts.map