Multi Agent Patterns

Iron Law

CHOOSE ARCHITECTURE PATTERN BEFORE DISPATCHING AGENTS — dispatching without a chosen pattern (Supervisor, Swarm, or Hierarchical) produces uncontrolled context bloat and coordination failures

Explanation: Multi-agent systems consume ~15× the tokens of single-agent systems. Choosing the wrong pattern or dispatching without a plan creates bottlenecks that negate every parallelization benefit.

Multi-Agent Architecture Patterns

Reference skill for designing multi-agent systems. Covers when to use multi-agent architectures, which pattern to choose, how to handle context isolation, and how to prevent the most common failure modes.

Primary audience: Developers building LangGraph/LangChain agents, Google ADK agents, or Claude Code agent orchestration layers.

When to Activate

Load this skill when:

• Deciding whether a task warrants multi-agent architecture vs single agent
• Choosing between Supervisor, Swarm, or Hierarchical patterns
• Building production LangGraph/LangChain multi-agent systems
• Designing Claude Code sub-agent dispatch strategies
• Diagnosing performance problems in an existing multi-agent system
• Briefing a team on multi-agent architecture trade-offs

Pattern Selection Quick Guide

Is the task too large for one context window?
    NO → Single agent. Multi-agent adds overhead, not capability.
    YES ↓

Do subtasks decompose cleanly into parallel work?
    NO → Sequential single agent with summarization between steps.
    YES ↓

Does the task need centralized control and human oversight?
    YES → Supervisor/Orchestrator pattern
    NO ↓

Does the task need flexible exploration with emergent structure?
    YES → Peer-to-Peer/Swarm pattern
    NO ↓

Does the task have clear hierarchical abstraction layers (strategy → planning → execution)?
    YES → Hierarchical pattern
    NO → Default to Supervisor

Reference Files

Core Concepts (Summary)

Why Multi-Agent?

Single agents face context ceilings. As tasks grow, context windows fill with accumulated history, retrieved documents, and tool outputs. Performance degrades via:

• Lost-in-middle effect: Information in context center gets ~10–40% lower recall
• Context poisoning: A hallucination that enters context gets reinforced on every turn
• Attention scarcity: All information competes for the same attention budget

Multi-agent architectures address this by partitioning work across multiple context windows.

The Three Patterns

Context Isolation Mechanisms

Consensus: The Sycophancy Problem

Simple majority voting among agents degrades to consensus on false premises — agents bias toward agreement. Mitigations:

• Weighted voting: Agents with higher confidence carry more weight
• Debate protocols: Agents critique each other's outputs (adversarial > collaborative for accuracy)
• Trigger-based intervention: Monitor for stall and sycophancy markers

Critical Production Finding: The Telephone Game Problem

Evidence: LangGraph benchmarks found supervisor architectures initially performed 50% worse than optimized versions.

Cause: Supervisors paraphrase sub-agent responses, losing fidelity at each hop.

Fix: Implement forward_message tool for direct pass-through when sub-agent output is complete:

def forward_message(message: str, to_user: bool = True):
    """
    Forward sub-agent response directly to user without supervisor synthesis.

    Use when:
    - Sub-agent response is final and complete
    - Supervisor synthesis would lose important details
    - Response format must be preserved exactly
    """
    if to_user:
        return {"type": "direct_response", "content": message}
    return {"type": "supervisor_input", "content": message}

With this pattern, swarm architectures can slightly outperform supervisor architectures for tasks where sub-agent output needs no synthesis.

Constraints

MUST DO

• Choose architecture pattern before dispatching agents
• Calculate token budget impact before committing to multi-agent (see references/token-economics.md)
• Define explicit handoff protocols with state passing
• Implement convergence constraints for swarm patterns (time-to-live, iteration limits)
• Validate agent outputs before passing to downstream agents

MUST NOT DO

• Use multi-agent for tasks a single agent can handle — overhead is ~15× tokens
• Use supervisor pattern without direct pass-through mechanism (telephone game problem)
• Run swarm patterns without convergence constraints (infinite loops)
• Assume model upgrade is always cheaper than parallelization (check token-economics.md)

Knowledge Reference

LangGraph, AutoGen, CrewAI, context isolation, context window management, token economics, supervisor pattern, swarm architecture, hierarchical agents, consensus mechanisms, sycophancy detection, agent handoffs, forward_message, BrowseComp evaluation, multi-agent coordination