/**
 * The hosted engine's answer to "is this session actually doing something right
 * now?", asked by the shared session broker's idle reaper.
 *
 * Why the reaper has to ask instead of working it out: every liveness signal
 * the broker records is emitted by a turn running IN the broker's own process,
 * a message appended, an agent bound, an input queued, a participant
 * heartbeat. A hosted turn emits none of them. Its transcript lives on the
 * hosted record (so the broker's `messageCount` stays 0, which puts the session
 * in the 10-minute idle-empty window instead of the 24-hour one), and the
 * intake tick that would otherwise refresh its heartbeat is itself blocked
 * awaiting that very turn. The reaper was reading a record that had gone quiet
 * and concluding the work had stopped, when the work was the reason it was
 * quiet.
 */
import type { HostedSessionRecord } from './types.js';
/**
 * How long after the hosted engine last touched a session the probe keeps
 * vouching for it.
 *
 * Matches the broker's own default idle-empty window: inside this window the
 * probe and the reaper would reach the same verdict anyway, so the probe only
 * changes an outcome where it has a positive reason to (a running turn, or an
 * engine-side touch the broker never saw).
 */
export declare const DEFAULT_HOSTED_LIVENESS_FRESHNESS_MS: number;
/** The slice of HostedSessionManager this probe needs. */
export interface HostedSessionLivenessLookup {
    get(sessionId: string): HostedSessionRecord | null;
}
/** The shape the probe reads off a broker record; structural so no import cycle forms. */
export interface ProbedSession {
    readonly id: string;
    readonly kind: string;
}
export interface HostedSessionLivenessProbeOptions {
    readonly now?: () => number;
    readonly freshnessMs?: number;
}
/**
 * Build the probe the broker installs via `setExternalLivenessProbe`.
 *
 * Answers true only for sessions this engine actually owns, a non-hosted
 * session, or a hosted id the engine has no record of, is not this probe's to
 * vouch for, and it says so rather than blanket-exempting everything and
 * quietly disabling the reaper.
 */
export declare function createHostedSessionLivenessProbe(lookup: HostedSessionLivenessLookup, options?: HostedSessionLivenessProbeOptions): (session: ProbedSession) => boolean;
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