/**
 * HandoffEventSink — pluggable event sink for Phase 4.
 *
 * Phase 4 does NOT extend `SessionEvent` with handoff variants (they land in a
 * later phase that wires the full `SessionHierarchyEvent` union referenced
 * by roadmap §1). In the meantime the flow functions invoke this sink so
 * consumers + tests can observe state transitions without a concrete event
 * bus. Every callback is optional; {@link NOOP_HANDOFF_SINK} is the
 * deny-by-default instance to pass when observation is not needed.
 */
import type { SessionId } from '../../types/ids/index.js';
import type { HandoffId } from '../../types/session/ids.js';
/** Fired when a source session transitions `idle → locked` for handoff. */
export interface HandoffLockedEvent {
    sessionId: SessionId;
    at: Date;
}
/**
 * Fired when a compensating rollback returns a source session
 * `locked → idle` (either CAS failure or downstream provisioning failure).
 */
export interface HandoffUnlockedEvent {
    sessionId: SessionId;
    at: Date;
}
/**
 * Fired once per handoff commit. For `single` the `handoffIds` array has one
 * entry; for `broadcast` it contains every recipient's assignment id.
 */
export interface HandoffCommittedEvent {
    sessionId: SessionId;
    newVersion: number;
    handoffIds: readonly HandoffId[];
    at: Date;
}
/**
 * Fired when a broadcast fan-out mid-flight rolls back. `partialState` carries
 * the per-stage counts of resources that were provisioned before the failure
 * was detected — consumers can correlate with their own observability signals
 * to verify the rollback is complete.
 */
export interface HandoffBroadcastRollbackEvent {
    sessionId: SessionId;
    broadcastId: string;
    reason: string;
    partialState: {
        assignmentsWritten: number;
        subsessionsCreated: number;
        worktreesProvisioned: number;
    };
    at: Date;
}
/**
 * Pluggable observer interface. All callbacks optional; consumers implement
 * only what they need (Convention #5 deny-by-default applies to event
 * consumers too — they must opt in explicitly).
 */
export interface HandoffEventSink {
    onLocked?(ev: HandoffLockedEvent): void;
    onUnlocked?(ev: HandoffUnlockedEvent): void;
    onCommitted?(ev: HandoffCommittedEvent): void;
    onBroadcastRollback?(ev: HandoffBroadcastRollbackEvent): void;
}
/** No-op sink — inject when the caller does not need handoff observability. */
export declare const NOOP_HANDOFF_SINK: HandoffEventSink;
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