/**
 * Earliest sign that a session is about to spawn subagents: its model is
 * streaming spawning tool calls. Main-thread sessions feed their streamed
 * assistant events here and, whenever the expected number of spawns grows,
 * let the worker pool start a worker those spawns will need
 * (`prewarmSubagentWorker`), so it boots while the arguments are still
 * streaming instead of after dispatch.
 *
 * Spawning calls: a `task` call (one spawn from its first event, then one per
 * `tasks[]` item whose opening brace has streamed), and an `eval` call once its streamed code
 * mentions `agent(` or `workpool(` (the eval subagent helpers; most cells never
 * spawn, so the name alone is no signal; counted as one spawn).
 */
import type { AssistantMessageEvent } from "@oh-my-pi/pi-ai";
/** Per-message counter of spawns its streaming tool calls are about to make; see the module doc. */
export declare class SubagentSpawnSignal {
    #private;
    /**
     * Feed one streamed assistant event; returns the number of spawns the message's tool
     * calls are expected to make whenever it grows, else `undefined`.
     */
    observe(event: AssistantMessageEvent): number | undefined;
}