Subagents

Put an agent in another agent's tools to let the model delegate to it. This is on the npm beta channel (@nylorun/agents@0.5.0-beta and the matching Runtime / Harness set).

import { Agent } from "@nylorun/agents";
import { z } from "zod";

const researcher = Agent({
  id: "researcher",
  description:
    "Investigates an order's history. Returns a short summary with the ids it relied on.",
  instructions:
    "Investigate one question about one order. Be exhaustive, then be brief.",
  tools: [searchOrders, readTicket],
  outputSchema: z.object({
    summary: z.string(),
    evidence: z.array(z.string()),
  }),
});

const support = Agent({
  id: "support",
  instructions:
    "For anything needing more than two lookups, delegate to researcher with a complete, self-contained task.",
  tools: [lookupOrder, refundOrder, researcher],
});

The tool is named after the child's id and takes { task: string }. The child's description (required) is what the parent's model reads. The child starts with a fresh context: it sees its own instructions and the task, nothing of the parent's conversation, and only its final text (or outputSchema result) comes back.

connectAgents({ agents: [support] }) serves both. Children share the session's sandbox, keep their own tools, hooks, skills, and MCP servers, and start with empty ctx.state. Tools can read ctx.agent ({ id, path, delegationId }). Several delegation calls in one model response run in parallel.

An empty answer, a failure (with the child's last text marked as evidence), or a cancelled child reaches the parent's model as a failed tool result, never as success. Runtime emits delegation.started and delegation.completed. session.history({ agent }) filters by delegationId (one child invocation) or by path such as support/researcher (every concurrent child that shares that path).

This version is one level deep and non-interactive: a delegated agent cannot use agents as tools, its tools cannot declare approval (keep those on the parent), and ctx.ask, ctx.approve, ctx.sleep, or ctx.waitFor inside it fail with delegation.interaction-unsupported. Delegation is not an approval boundary; approvals live on tools.

Delegate when the parent should keep the answer. When a specialist should own the rest of the conversation, switch capabilities with a before("step") patch instead.

See Compatibility for the beta pin set.

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