Hub-and-Spoke Coordinator Topology

When one agent has to research five sources, review ten files, or juggle a dozen tools, its attention gets diluted and its context window fills with noise. The hub-and-spoke (coordinator) topology fixes this by splitting the work: a central coordinator agent decomposes the task and delegates each slice to a focused specialist subagent.

• The hub (coordinator) owns the plan: it decomposes, delegates, aggregates, routes, and handles errors.
• Each spoke (subagent) is a narrow specialist with its own role, system prompt, and a least-privilege tool set.

This is the backbone of the Multi-Agent Research System pattern, and a high-value topic in Domain 1 (Agent Architecture & Orchestration, 27% of the exam).

A coordinator is not just a router. On the exam, the correct answer almost always shows the hub doing all five of these jobs:

• Decompose — break the goal into independent or sequential sub-tasks.
• Delegate — hand each sub-task to the right specialist.
• Aggregate — merge subagent results into one coherent answer.
• Route — decide which specialist (or none) a sub-task needs.
• Handle errors — recover transient faults, escalate the non-recoverable, and keep partial results.

If a design makes the coordinator a thin pass-through that just forwards text, it is doing too little. If a subagent tries to plan the whole job, it is doing too much.