import type { PrefixCacheConfig, PrefixCacheTurnResult } from "./types.js";
/** Length of the longest common character prefix between two strings. */
export declare function commonPrefixLength(a: string, b: string): number;
/**
 * Deterministic simulator of OpenAI-style automatic prompt caching.
 *
 * Caching is scoped to `sessionId` and matches the longest common prefix with
 * the previous request in that session. A prefix must reach `minCacheTokens`
 * to be served from cache at all (OpenAI's real threshold is ~1024 tokens).
 */
export declare class PrefixCacheSimulator {
    private readonly config;
    private lastPrompt;
    constructor(config: PrefixCacheConfig);
    /** Account one provider request. `outputTokens` does not affect cache, only reporting. */
    account(promptText: string, outputTokens: number): PrefixCacheTurnResult;
}
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