/**
 * Conservative, streaming token estimator used to drive the live UI counter.
 *
 * Typical LLM tokenizers produce ~1 token per 4 characters of English text. We
 * deliberately use `chars / 5` so the estimate stays below the true count —
 * the real `tokenUsage` (which includes input and cache tokens we never see on
 * the wire) always exceeds this running estimate, letting the UI smoothly
 * count up to the final value without ever reversing.
 *
 * `onProgress` is throttled to only fire when the estimate has grown by at
 * least `MIN_DELTA` tokens, which avoids flooding `onJobUpdate` on very busy
 * streams.
 */
export interface TokenEstimator {
    /** Append assistant text. Triggers `onProgress` when the estimate grows enough. */
    addText(text: string): void;
    /** Current conservative token estimate. */
    current(): number;
}
export declare function createTokenEstimator(onProgress?: (estimatedTokens: number) => void): TokenEstimator;
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