export interface Turn {
    index: number;
    bytes: string;
}
export interface TrimConfig {
    /** Keep the most recent N turns untouched. */
    recentFloor: number;
}
export interface TrimResult {
    kept: Turn[];
    summary: Turn;
    droppedCount: number;
}
/** Deterministic summary bytes derived from dropped turns. */
export declare function summarize(dropped: Turn[]): string;
/** Middle-drop: keep [0..pivot] as a placeholder floor and [tail - recentFloor..tail];
 *  drop the middle span and replace with a stable summary. */
export declare function trimMiddle(turns: Turn[], config: TrimConfig): TrimResult;
export interface KeepaliveConfig {
    intervalMs: number;
    retention: "long" | "short" | "none";
    enabled: boolean;
}
export declare class KeepaliveScheduler {
    private lastPingMs;
    private lastActivityMs;
    tick(now: number, config: KeepaliveConfig): "ping" | "shutoff" | "skip";
    markActivity(now: number): void;
}
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