/** Latest-wins, idle-bound queue for safe Agent session changes. */
export interface IdleActivity {
    readonly status: 'idle' | 'running';
    whenIdle(): Promise<void>;
}
export declare class SessionSwitchQueue<T> {
    private readonly execute;
    private readonly failed;
    private pending;
    private pumping;
    private running;
    constructor(execute: (value: T) => Promise<void>, failed: (error: unknown) => void);
    /** Queue a request; a later request replaces any request still waiting. */
    request(activity: IdleActivity, value: T): 'queued' | 'started';
    /** Cancel only work that has not begun activation. */
    cancel(): boolean;
    /**
     * Whether a queued change is being activated right now. Between the idle
     * wait and the handoff the old session is still installed, so a submission
     * made in that window would start a turn the handoff then discards; callers
     * use this to refuse one instead of losing it.
     */
    get activating(): boolean;
    private pump;
}