/**
 * Anthropic prompt-caching strategies.
 *
 * Ported from Hermes agent/prompt_caching.py. Provides two injection
 * strategies that place `cache_control` breakpoints on Anthropic
 * Messages.create kwargs to reduce input-token costs on multi-turn
 * conversations:
 *
 * - `system_and_3`: mark every system block + last 3 user-message ends
 *   at the 5-minute TTL tier.
 * - `prefix_and_2`: mark the first system block at the 1-hour TTL tier
 *   (stable prefix) + last 2 user-message ends at the 5-minute TTL tier
 *   (rolling window).
 * - `none`: no-op — pass kwargs through unchanged.
 *
 * All functions are pure (mutate the input object — callers own the
 * lifecycle) and carry no class state.
 *
 * @see https://docs.anthropic.com/en/docs/build-with-claude/prompt-caching
 * @task T9269
 * @epic T9261
 */
/**
 * Anthropic cache breakpoint TTL options.
 *
 * The Anthropic API accepts string duration values:
 * - `'5m'` = 5-minute rolling window (default ephemeral tier).
 * - `'1h'` = 1-hour stable prefix (long-cache tier).
 *
 * @see https://docs.anthropic.com/en/docs/build-with-claude/prompt-caching
 */
export type CacheTtl = '5m' | '1h';
/**
 * The three supported prompt-caching injection strategies.
 *
 * - `system_and_3`: system block(s) + last 3 user messages, all at 5-minute TTL.
 * - `prefix_and_2`: first system block at 1-hour TTL + last 2 user messages at 5-minute TTL.
 * - `none`: no cache breakpoints injected.
 */
export type PromptCachingStrategy = 'system_and_3' | 'prefix_and_2' | 'none';
/**
 * Cache control marker as Anthropic accepts on content blocks and system blocks.
 *
 * @see https://docs.anthropic.com/en/docs/build-with-claude/prompt-caching
 */
export interface CacheControlMarker {
    /** Must be `'ephemeral'` per the Anthropic API. */
    type: 'ephemeral';
    /**
     * Optional TTL duration string.
     * `'5m'` = 5-minute tier (default when omitted).
     * `'1h'` = 1-hour tier (long-cache stable prefix).
     */
    ttl?: CacheTtl;
}
/**
 * Minimal shape of an Anthropic system block — must carry at least
 * `type` and optionally `text` and `cache_control`.
 */
export interface AnthropicSystemBlock {
    type: string;
    text?: string;
    cache_control?: CacheControlMarker;
}
/**
 * Minimal shape of an Anthropic message — role + content (string or block array).
 * The `content` field is widened to `Array<Record<string, unknown>>` after
 * string→block normalisation inside the injector.
 */
export interface AnthropicMessage {
    role: 'user' | 'assistant';
    content: string | Array<Record<string, unknown>>;
}
/**
 * Minimal kwargs shape accepted by `injectCacheBreakpoints`.
 *
 * Represents a partial Anthropic Messages.create parameters object that
 * contains at least `messages` and optionally a `system` block array.
 */
export interface AnthropicKwargs {
    system?: AnthropicSystemBlock[];
    messages: AnthropicMessage[];
}
/**
 * Inject Anthropic cache breakpoints into a Messages.create kwargs object
 * according to the chosen strategy.
 *
 * Mutates `kwargs` in-place — call this immediately before passing the object
 * to the Anthropic SDK so no copies need to be made on the hot path.
 *
 * Strategy details:
 * - `system_and_3`: every system block + the last 3 user messages receive
 *   `{ type: 'ephemeral', ttl: '5m' }`.
 * - `prefix_and_2`: the **first** system block receives
 *   `{ type: 'ephemeral', ttl: '1h' }` (stable long-cache prefix); the last
 *   2 user messages receive `{ type: 'ephemeral', ttl: '5m' }` (rolling
 *   window).
 * - `none`: kwargs returned unchanged.
 *
 * @param kwargs - Anthropic Messages.create kwargs to mutate.
 * @param strategy - Which caching strategy to apply.
 * @returns The same `kwargs` reference (mutated).
 *
 * @task T9269
 */
export declare function injectCacheBreakpoints<T extends AnthropicKwargs>(kwargs: T, strategy: PromptCachingStrategy): T;
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