/**
 * EventBus — central pub/sub for ProviderRuntimeEvents.
 *
 * Today the engine's primitives (checkpoint-store, hook-runner,
 * walkthrough-writer, artifact-store, monitor-manager, etc.) each have
 * their own ad-hoc trigger surface — checkpointing is called explicitly
 * from the tool broker, hook-runner is dispatched from tool-broker too,
 * walkthrough-writer fires from a session-end callback chain, and so on.
 * Every consumer of the agent stream wires itself in differently.
 *
 * The EventBus consolidates that. Drivers publish every emitted event to
 * a single bus; primitives subscribe to the events they care about. Adding
 * a new primitive becomes "register a subscriber"; adding a new event
 * type doesn't require touching any subscriber wiring.
 *
 * Pattern adapted from t3code's event subscription model. Stream-shaped
 * (Stream.Stream<ProviderRuntimeEvent>) is the right type long-term, but
 * we ship the Set-based pub/sub today so existing primitives can subscribe
 * without taking a dependency on Effect throughout.
 *
 * This commit builds the bus + a worked integration example
 * (CheckpointStore subscribing to tool.call.started for write tools).
 * The full A–E migration is mechanical from here and lands incrementally;
 * each primitive's subscribe-and-act file is a 30-line follow-up.
 */
import type { ProviderRuntimeEvent, ProviderRuntimeEventType } from "./contracts/provider-runtime.js";
export type EventBusSubscriber = (event: ProviderRuntimeEvent) => void | Promise<void>;
export interface EventBusFilter {
    /** Match only events of these types. Empty/missing = match all. */
    types?: readonly ProviderRuntimeEventType[];
    /** Match only events for this session id. Missing = match all. */
    sessionId?: string;
    /** Match only events from this harness id. Missing = match all. */
    harnessId?: string;
    /** Custom predicate. Runs after the type/session/harness filters. */
    predicate?: (event: ProviderRuntimeEvent) => boolean;
}
export interface EventBusSubscription {
    unsubscribe(): void;
}
export interface EventBusStats {
    subscriberCount: number;
    publishedCount: number;
    droppedDueToErrorCount: number;
}
/**
 * Single in-process EventBus. Subscribe with subscribe()/subscribeFiltered();
 * publish with publish(). Unsubscribe via the returned handle.
 */
export declare class EventBus {
    private readonly subscribers;
    private published;
    private droppedDueToError;
    subscribe(subscriber: EventBusSubscriber): EventBusSubscription;
    subscribeFiltered(subscriber: EventBusSubscriber, filter: EventBusFilter | undefined): EventBusSubscription;
    publish(event: ProviderRuntimeEvent): void;
    stats(): EventBusStats;
    clear(): void;
}