/**
 * Building blocks for the read-only sub-clients that surface QAR's
 * `bulletin.post`, `artifact.add`, `state.update`, and `agent.spawn`
 * envelopes to opt-in consumers.
 *
 * These sub-clients are observers — they tap inbound envelopes alongside the
 * `TaskSubscription` chain (so the same envelope still drives the canonical
 * `AsyncIterable<TaskEvent>` from `client.tasks.start()`). Multiple handlers
 * per kind are allowed and run in registration order; throws are swallowed
 * so a misbehaving consumer never crashes the WS loop.
 */
import type { Envelope, EnvelopeKind } from '../qar/envelopes.js';
/**
 * Token returned by the four `client.{bulletin,artifacts,state,agents}.on*`
 * methods. `close()` deregisters the handler; subsequent envelopes do not
 * invoke it. Idempotent.
 *
 * Distinct from `Subscription` (`unsubscribe()`) on `ToolClient` — the four
 * read-only event surfaces use `close()` to mirror QAR's spawn-lifecycle
 * vocabulary (see `docs/sdk2/event-surfaces.md`).
 */
export interface EventSubscription {
    close(): void;
}
/**
 * Shared base for the four kind-filtered observer sub-clients. Holds the
 * handler registry; `attach`/`detach` are called by `QodoClient` on
 * `connect`/`disconnect`. Registrations made before `connect()` are honored
 * once the WS opens — consumers can wire handlers eagerly during construction.
 */
export declare abstract class KindObserverClient<K extends EnvelopeKind, E extends Envelope & {
    readonly kind: K;
}> {
    private readonly kind;
    private port;
    private connection;
    private readonly registrations;
    protected constructor(kind: K);
    /**
     * Called by the port from `close()` / `fail()`. The connection is already
     * tearing itself down (it cleared its own subscription set), so do NOT
     * call `unsubscribe` here — just clear the sub-client's pointers so a
     * later `attach()` against a fresh connection starts cleanly. Guards on
     * identity in case a stale port from a prior attach cycle fires after
     * the sub-client already moved on.
     */
    private onPortUnbound;
    /**
     * Register a handler. The optional `matches` predicate runs per envelope —
     * sub-classes pass their filter shape through it. Returns an
     * `EventSubscription` whose `close()` is idempotent.
     */
    protected register(handler: (env: E) => void, matches?: (env: E) => boolean): EventSubscription;
    private dispatch;
    private logHandlerError;
}
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