1.2 — Multi-Agent Orchestration

CCAR-F Domain 1 · Task 1.2

What You Need to Know

Multi-agent orchestration is several Claude agents working together on one complex task. A coordinator agent receives the task and splits it up. Subagents each handle one specialised task. In the hub-and-spoke pattern, the coordinator is the hub and the subagents are the spokes. The coordinator's split of a task into subtopics is its decomposition.

Hub-and-Spoke Architecture

The coordinator receives the initial task and decomposes it. It decides which subagents to invoke and passes context to them. It aggregates their results, handles errors, and routes information between them. Each subagent receives instructions from the coordinator and returns results to it.

All communication flows through the coordinator. Subagents never communicate directly with each other.

One hub gives three things:

1. Observability: you can log and monitor every message in one place.
2. Consistent error handling: the coordinator applies uniform error recovery policies.
3. Controlled information flow: the coordinator decides what context each subagent receives.

Key Concept: Routing all inter-subagent communication through the coordinator is the foundational architectural constraint of hub-and-spoke orchestration.

The Critical Isolation Principle

Isolation is the most misunderstood idea in multi-agent systems. Subagents do not automatically inherit the coordinator's conversation history. A new subagent starts with only what the coordinator explicitly includes in its prompt. It has no access to:

• The coordinator's system prompt (unless explicitly included)
• Previous messages in the coordinator's conversation
• Results from other subagents (unless the coordinator passes them)
• Any "shared memory" or global state

Subagents also do not share memory between invocations. Every piece of information a subagent needs goes in its prompt, explicitly.

Coordinator Responsibilities

1. Dynamic subagent selection. Analyse what a query requires and select only the subagents it needs.
2. Research scope partitioning. Partition the research scope to minimise duplication. Assign each agent distinct subtopics or source types.
3. Iterative refinement loops. Evaluate the synthesis output for gaps. If incomplete, re-delegate with targeted queries.
4. Centralised communication routing. All subagent communication routes through the coordinator.

The Narrow Decomposition Failure

Overly narrow task decomposition by the coordinator leads to incomplete coverage of broad research topics. Each subagent researches only what it is assigned. A subtopic nobody is assigned never gets researched.

When subagents execute their assigned tasks correctly but coverage is missing, the root cause is what the coordinator assigned them. The fault sits in the coordinator's decomposition, not any downstream agent.

In the exam

The exam tests one orchestration pattern: hub-and-spoke, with a coordinator at the centre. It tests all four coordinator responsibilities. Direct subagent-to-subagent communication is the wrong answer. The exam leans hard on the isolation confusion.

When a report misses entire categories, check the decomposition before blaming the subagents.

Exam Traps

• Blaming downstream subagents for coverage gaps when the coordinator's task decomposition was too narrow
• Assuming subagents share memory or inherit the coordinator's conversation history
• Proposing direct inter-subagent communication as an efficiency improvement
• Routing every query through the full subagent pipeline