/**
 * `ArtifactsClient` — observer for QAR's `artifact.add` envelopes.
 *
 * Artifacts are durable outputs from a task or sub-agent: files,
 * structured records, references the consumer can fetch later. The wire
 * payload is `JsonObject`-shaped today; consumers narrow against their
 * agent's known artifact schema. The filter helper below matches against
 * the two fields QAR's runtime exposes consistently (`kind`, `agent_id`).
 *
 * Observer-only **today**, bidirectional on the wire. QAR's
 * `BIDIRECTIONAL_KINDS` whitelist accepts `artifact.add` in either
 * direction; the SDK aligns its taxonomy in `envelopes.ts` accordingly.
 * The current SDK surface does not expose a client emitter — tool
 * handlers that need to write artifacts route them through the agent
 * loop on the QAR side. A future addition may surface
 * `ArtifactsClient.emit(...)` without a wire-contract change.
 */
import type { ArtifactAddEnvelope } from '../qar/envelopes.js';
import { KindObserverClient } from './observers.js';
import type { EventSubscription } from './observers.js';
/**
 * Best-effort filter for `artifact.add` envelopes. Each field, when set,
 * must equal the same-named field in the envelope payload.
 */
export interface ArtifactFilter {
    /** Match against `payload.kind` (artifact schema discriminator). */
    readonly kind?: string;
    /** Match against `payload.agent_id` (the agent that produced the artifact). */
    readonly agent_id?: string;
}
export type ArtifactHandler = (env: ArtifactAddEnvelope) => void;
export declare class ArtifactsClient extends KindObserverClient<'artifact.add', ArtifactAddEnvelope> {
    /**
     * Register a handler invoked for every inbound `artifact.add` envelope.
     *
     * Same multi-handler / fan-out / throw-swallowing semantics as the other
     * observer surfaces. The two-arg overload accepts an `ArtifactFilter`;
     * only envelopes whose payload matches every set field invoke the handler.
     */
    onArtifact(handler: ArtifactHandler): EventSubscription;
    onArtifact(filter: ArtifactFilter, handler: ArtifactHandler): EventSubscription;
}
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