/**
 * RepetitionDetector — catches text-degeneration loops during streaming.
 *
 * Weaker models sometimes get stuck (typically after an unrecoverable tool
 * error) and stream the same sentence/paragraph forever until the output-token
 * cap — burning tokens and hanging the UI. The tool-loop detector in the agent
 * handles repeated *tool calls*; this is its sibling for repeated *text*.
 *
 * Strategy: over the recent tail of accumulated output, look for any word
 * n-gram that recurs an excessive number of times. This catches both a single
 * repeated sentence and a repeated multi-sentence block (the n-gram spans the
 * cycle). Cheap (bounded tail + throttled checks) and conservative — a 10-word
 * exact sequence recurring 5× is virtually never legitimate output.
 */
export interface RepetitionDetectorOptions {
    /** Window size in words for the repeated-unit probe. */
    ngramWords?: number;
    /** Trip when any n-gram occurs at least this many times. */
    maxRepeats?: number;
    /** Don't check until at least this many chars have accumulated. */
    minChars?: number;
    /** Only examine the last N chars (bounds cost; loops live in the tail). */
    tailChars?: number;
    /** Re-check only after this many new chars (throttle). */
    checkEveryChars?: number;
}
export declare class RepetitionDetector {
    private text;
    private lastCheckedLen;
    private readonly ngramWords;
    private readonly maxRepeats;
    private readonly minChars;
    private readonly tailChars;
    private readonly checkEveryChars;
    constructor(opts?: RepetitionDetectorOptions);
    /**
     * Feed a streamed text chunk. Returns true the first time a degeneration
     * loop is detected (the caller should then stop the stream).
     */
    feed(chunk: string): boolean;
    private check;
}