Multi-Agent Handoffs

Agents can hand off control to other agents during a conversation. This lets you build systems where specialized agents collaborate to handle complex tasks.

How It Works

1. An agent declares which agents it can hand off to via the handoffs array
2. You provide the full agent definitions in the agents map when calling run()
3. When the LLM decides to hand off, the SDK swaps the active agent and continues

Example

import { z } from "zod";
import { defineAgent, defineTool, run } from "one-agent-sdk";

const searchTool = defineTool({
  name: "search",
  description: "Search the web",
  parameters: z.object({ query: z.string() }),
  handler: async ({ query }) => JSON.stringify({ results: [`Result for: ${query}`] }),
});

const calculatorTool = defineTool({
  name: "calculate",
  description: "Evaluate a math expression",
  parameters: z.object({ expression: z.string() }),
  handler: async ({ expression }) => String(eval(expression)),
});

const researcher = defineAgent({
  name: "researcher",
  description: "Research agent that can search the web",
  prompt: "You are a research assistant. Hand off to the math agent for calculations.",
  tools: [searchTool],
  handoffs: ["math"],
});

const mathAgent = defineAgent({
  name: "math",
  description: "Math agent that can evaluate expressions",
  prompt: "You are a math assistant. Hand off to the researcher for web searches.",
  tools: [calculatorTool],
  handoffs: ["researcher"],
});

const { stream } = await run(
  "What is the population of Tokyo? Then calculate 15% of that.",
  {
    provider: "claude",
    agent: researcher,
    agents: { researcher, math: mathAgent },
  },
);

for await (const chunk of stream) {
  switch (chunk.type) {
    case "text":
      process.stdout.write(chunk.text);
      break;
    case "handoff":
      console.log(`\n[handoff] ${chunk.fromAgent} -> ${chunk.toAgent}`);
      break;
  }
}

Provider Implementation

Handoffs are implemented differently by each provider, but behave the same from your perspective:

• Claude — delegates to the Claude Agent SDK's built-in agent support
• Codex / Kimi — handoffs are synthetic transfer_to_{name} function tools that swap the system prompt

The agents Map

The agents map passed to run() must include all agents that could be reached through handoffs:

await run(prompt, {
  provider: "claude",
  agent: entryAgent,       // The starting agent
  agents: {                // All reachable agents
    entry: entryAgent,
    specialist: specialistAgent,
    reviewer: reviewerAgent,
  },
});

Agent names in the handoffs array must match keys in the agents map.