/**
 * Fixed-capacity ring buffer.
 *
 * When the buffer is full, the oldest item is overwritten.
 * No array allocations on overflow (unlike slice-based approaches).
 *
 * Used for task output line storage — bounded memory, O(1) append.
 */
export declare class RingBuffer<T> {
    private readonly items;
    private head;
    private count;
    readonly capacity: number;
    constructor(capacity: number);
    /**
     * Append an item. If at capacity, overwrites the oldest item.
     */
    push(item: T): void;
    /**
     * Number of items currently in the buffer.
     */
    get length(): number;
    /**
     * Whether the buffer is at capacity.
     */
    get isFull(): boolean;
    /**
     * Get all items in order (oldest first).
     * Returns a new array — safe to mutate.
     */
    toArray(): T[];
    /**
     * Get the last N items (newest first → reversed to oldest first).
     */
    last(n: number): T[];
    /**
     * Clear all items.
     */
    clear(): void;
}
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