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Chapter 10

LangGraph for Agentic Workflows

Learning Objective

Learn why graph-based orchestration is useful for multi-step, stateful GenAI systems.

What it means

LangGraph is designed for stateful, graph-based agent workflows. Instead of a single linear chain, a workflow is represented as nodes and edges. Each node can perform a task, update state, and decide where the workflow should go next.

Why it matters

Real enterprise workflows are rarely linear. They involve branching, retries, approvals, validation failures, and multiple specialized agents. LangGraph is useful when an AI system needs memory, decision routing, and controlled agent collaboration.

Healthcare Example

A healthcare document workflow may classify a document, extract information, validate required fields, retrieve policy evidence, generate a recommendation, and route low-confidence cases to human review.

Architecture Flow

StartClassifier NodeExtraction NodeValidation Nodeif missing data: Request Infoif valid: Policy RetrievalDecision NodeReview or Complete

Code: Graph-Style State Routing

def classifier(state):
    state["document_type"] = "clinical_note"
    return state

def validator(state):
    required = ["patient_id", "diagnosis"]
    state["missing"] = [f for f in required if not state.get(f)]
    return state

def route_after_validation(state):
    return "human_review" if state["missing"] else "policy_review"

state = {"patient_id": "P100", "diagnosis": None}
state = classifier(state)
state = validator(state)
print(route_after_validation(state), state)

Common Mistakes

  • Using agents without boundaries.
  • No state model.
  • No stop condition for loops.
  • No human review path.
  • No observability into agent decisions.

Interview Q&A

Q: Why LangGraph over LangChain?

A: LangChain is good for chains and components; LangGraph is better when workflows require state, branching, multiple agents, retries, and human review.

Q: Is ChatGPT LangChain or LangGraph?

A: No. ChatGPT is an LLM application. LangChain and LangGraph are developer frameworks used to build applications around LLMs.

Architect Takeaway

Use LangGraph when you need controlled agent orchestration, not just a prompt pipeline.