/**
 * `AgentsClient` — observer for QAR's `agent.spawn` envelopes.
 *
 * Each envelope reports a sub-agent spawn: `child_agent_id` /
 * `parent_agent_id` / `spawn_protocol` (`bulletin` or `direct`).
 * Surfacing this stream lets consumers like Studio render a
 * multi-agent run's topology live without scraping a side-channel.
 *
 * Filter helpers narrow by parent agent (rendering one tree branch) or by
 * spawn protocol (bulletin-only vs direct-only views).
 */
import type { AgentSpawnEnvelope } from '../qar/envelopes.js';
import type { SpawnProtocol } from '../qar/payloads.js';
import { KindObserverClient } from './observers.js';
import type { EventSubscription } from './observers.js';
export interface AgentSpawnFilter {
    /** Match against `payload.parent_agent_id` — useful for tree-branch views. */
    readonly parent_agent_id?: string;
    /** Match against `payload.spawn_protocol` — `'bulletin'` or `'direct'`. */
    readonly spawn_protocol?: SpawnProtocol;
}
export type AgentSpawnHandler = (env: AgentSpawnEnvelope) => void;
export declare class AgentsClient extends KindObserverClient<'agent.spawn', AgentSpawnEnvelope> {
    /**
     * Register a handler invoked for every inbound `agent.spawn` envelope.
     *
     * Same multi-handler / fan-out / throw-swallowing semantics as the other
     * observer surfaces.
     */
    onSpawn(handler: AgentSpawnHandler): EventSubscription;
    onSpawn(filter: AgentSpawnFilter, handler: AgentSpawnHandler): EventSubscription;
}
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