import { type TaskResult } from "@sema-agent/core";
import type { Pool } from "mysql2/promise";
import type { Metrics } from "./observability/metrics.js";
import type { Logger } from "./observability/logger.js";
export type DegenerateClass = "a" | "b" | "unknown";
export interface DegenerateSignals {
    class: DegenerateClass;
    /** Assistant turns since the last user message, INCLUDING the degenerate one. */
    turnsSinceUser: number;
    /** Substantive (non-looping) assistant text before the degenerate turn, since the last user message. */
    priorChars: number;
    salvagedLen: number;
    /** `salvagedLen` minus the estimated looped tail = how much real answer the degenerate turn carries. */
    uniquePrefixLen: number;
    repeatedTailLen: number;
}
/**
 * Length of the longest periodic suffix of `text` (≥ {@link MIN_REPEATS} contiguous copies of some
 * unit ≤ {@link MAX_UNIT}). 0 when no qualifying loop is found. Bounded to the last {@link REP_WINDOW}
 * chars. This estimates where the degenerate repetition begins — a measurement aid, not a trimmer.
 */
export declare function repetitionTail(text: string): number;
/**
 * Classify a degenerate failure from its salvaged text + the substantive content of the assistant
 * turns that preceded it (since the last user message). Pure — unit-tested directly.
 */
export declare function classifyDegenerate(salvaged: string, priorChars: number, turnsSinceUser: number): DegenerateSignals;
/**
 * Build the fire-and-forget instrument. Returns a sync `(result) => void` so the hot result paths
 * (`recordTaskResult` / `recordDone`) stay unblocked; the session read + classification run in the
 * background and never throw into the response. No-op for non-degenerate results.
 */
export declare function makeDegenerateInstrument(pool: Pool, metrics?: Metrics, logger?: Logger): (result: TaskResult) => void;
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