Multi Agent Coordination

Multi-Agent Coordination Instrumentation

Instrument multi-agent systems to trace coordination, handoffs, and hierarchies.

Core Principle

Multi-agent traces must answer:

1. Which agent started the workflow?
2. Which agents were involved?
3. How did work flow between agents?
4. Why did handoffs occur?
5. What was the hierarchy (parent-child)?

Trace Hierarchy

Session/Conversation (root span)
└── Supervisor Agent Run
    ├── Planning Phase (span)
    │   └── LLM Call (span)
    ├── Delegate to Agent A (span)
    │   └── Agent A Run (child trace)
    │       ├── LLM Call
    │       └── Tool Call
    ├── Delegate to Agent B (span)
    │   └── Agent B Run (child trace)
    │       └── LLM Call
    └── Synthesis Phase (span)
        └── LLM Call

Essential Span Attributes

Agent Identity

span.set_attribute("agent.name", "researcher")
span.set_attribute("agent.type", "worker")  # supervisor, worker, critic
span.set_attribute("agent.run_id", str(uuid4()))
span.set_attribute("agent.framework", "langgraph")

Parent-Child Linking

# Parent agent creates child context
child_context = create_child_context(current_span)
span.set_attribute("agent.parent_id", parent_run_id)
span.set_attribute("agent.parent_name", "supervisor")

# Pass context to child agent
child_agent.run(input, trace_context=child_context)

Handoff Tracking

# Log handoff decision
span.set_attribute("handoff.from_agent", "supervisor")
span.set_attribute("handoff.to_agent", "researcher")
span.set_attribute("handoff.reason", "needs_web_search")
span.set_attribute("handoff.task_summary", "Find pricing data")

Workflow State

span.set_attribute("workflow.step", "research")
span.set_attribute("workflow.total_steps", 4)
span.set_attribute("workflow.agents_involved", 3)
span.set_attribute("workflow.state", "in_progress")

Framework Patterns

LangGraph

from langgraph.graph import StateGraph
from langfuse.decorators import observe

@observe(name="agent.supervisor")
def supervisor_node(state):
    # Supervisor logic
    span = get_current_span()
    span.set_attribute("agent.name", "supervisor")
    span.set_attribute("agent.decision", state["next_agent"])
    return state

@observe(name="agent.worker")
def worker_node(state):
    span = get_current_span()
    span.set_attribute("agent.name", "worker")
    span.set_attribute("agent.parent_name", "supervisor")
    return state

graph = StateGraph()
graph.add_node("supervisor", supervisor_node)
graph.add_node("worker", worker_node)

CrewAI

from crewai import Agent, Crew, Task
from langfuse.decorators import observe

@observe(name="crew.run")
def run_crew(topic: str):
    span = get_current_span()
    span.set_attribute("crew.name", "research_crew")
    span.set_attribute("crew.agent_count", 3)

    researcher = Agent(name="researcher", ...)
    writer = Agent(name="writer", ...)
    editor = Agent(name="editor", ...)

    crew = Crew(agents=[researcher, writer, editor], ...)
    return crew.kickoff(inputs={"topic": topic})

AutoGen

from autogen import AssistantAgent, UserProxyAgent
from langfuse.decorators import observe

@observe(name="conversation.run")
def run_conversation(message: str):
    span = get_current_span()
    span.set_attribute("conversation.initiator", "user_proxy")
    span.set_attribute("conversation.participants", 2)

    assistant = AssistantAgent("assistant", ...)
    user_proxy = UserProxyAgent("user_proxy", ...)

    user_proxy.initiate_chat(assistant, message=message)

Coordination Patterns

Hub-and-Spoke (Supervisor)

span.set_attribute("coordination.pattern", "hub_and_spoke")
span.set_attribute("coordination.hub", "supervisor")
span.set_attribute("coordination.spokes", ["researcher", "writer", "critic"])

Pipeline (Sequential)

span.set_attribute("coordination.pattern", "pipeline")
span.set_attribute("coordination.sequence", ["intake", "research", "draft", "review"])
span.set_attribute("coordination.current_stage", 2)

Parallel (Fan-out/Fan-in)

span.set_attribute("coordination.pattern", "parallel")
span.set_attribute("coordination.parallel_agents", 4)
span.set_attribute("coordination.completed", 2)
span.set_attribute("coordination.pending", 2)

Hierarchical

span.set_attribute("coordination.pattern", "hierarchical")
span.set_attribute("coordination.depth", 3)
span.set_attribute("coordination.level", 2)

Context Propagation

Critical: Pass trace context to child agents:

# LangGraph - use config
def parent_node(state, config):
    # Context automatically propagated via config
    return child_graph.invoke(state, config)

# Manual propagation
from opentelemetry import trace
from opentelemetry.propagate import inject

def delegate_to_agent(agent, input):
    carrier = {}
    inject(carrier)  # Inject current context

    # Pass carrier to child agent
    return agent.run(input, trace_headers=carrier)

Anti-Patterns

See references/anti-patterns/multi-agent.md:

• Orphaned child spans (no parent link)
• Missing handoff context
• No agent identification
• Broken context propagation
• Logging full inter-agent messages

Related Skills

• instrumentation-planning - Overall planning
• session-conversation-tracking - Session context

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