LangChain vs LangGraph 2026 — Technical Decision Guide

1. Introduction and Motivation

Choosing between LangChain and LangGraph is not a style preference. It is an architectural decision with real consequences on your system’s maintainability, debuggability, and operational stability.

The confusion around this choice stems from how the ecosystem evolved. LangGraph is built on top of LangChain. Both come from the same organization. But they were designed to solve fundamentally different classes of problems, and using the wrong one creates systems that are harder to build, harder to debug, and harder to maintain.

The core problem this document solves is this: engineers who are new to the ecosystem often pick LangChain for everything because it came first and has more tutorials. Engineers who hear about agents often reach for LangGraph because it sounds more advanced. Both approaches frequently lead to the wrong tool for the job.

This guide explains the architectural difference, gives you a decision framework grounded in technical reality, and prepares you to discuss this trade-off in interviews with the depth a senior engineer needs to demonstrate.

---

2. Real-World Problem Context

How the Ecosystem Evolved

Phase 1: LangChain (2022–2023)

LangChain emerged in late 2022 to solve a practical problem: building LLM applications required enormous boilerplate. Every team was writing the same code to manage prompts, chain API calls, handle conversation memory, and integrate with vector stores.

LangChain standardized these patterns into a composable abstraction layer. You could define a prompt template, connect it to an LLM, attach a memory component, and chain the result into another operation. The “chain” metaphor was accurate: operations connected sequentially, each passing its output to the next.

This model worked well for the dominant patterns of 2022 and 2023: document Q&A, chatbots with conversation history, simple tool-using agents. These are fundamentally linear workflows. Input arrives, processing happens in defined steps, output is returned.

Phase 2: Agents and the Limits of Chains (2023–2024)

As the field matured, use cases became more complex. Teams wanted agents that could reason across multiple steps, use external tools, and revise their approach based on intermediate results. They wanted systems where:

• An agent could loop back and retry a failed action
• Different branches of execution could happen conditionally
• Human approval could pause a workflow mid-execution
• Multiple specialized agents could coordinate on a shared task

Chains cannot support these patterns. A chain executes sequentially and terminates. There is no mechanism for cycles, persistent state across invocations, or conditional routing based on the result of one step affecting which step runs next.

LangGraph was released in early 2024 to address this gap. It replaced the chain metaphor with a graph metaphor: nodes represent operations, edges represent transitions, and the graph can have cycles. This is a fundamentally different execution model.

Phase 3: Production Consolidation (2024–Present)

The current state is that LangChain and LangGraph coexist in most production systems. LangChain handles straightforward components. LangGraph orchestrates complex workflows. The question is not which to learn—you need both—but which to use for each specific system design.

The Structural Problem with Using LangChain for Agent Workflows

When engineers try to implement agent behavior using LangChain’s built-in AgentExecutor, they encounter real limitations:

• No persistent state: Each chain execution is stateless. Restarting after a failure means losing all intermediate state.
• Limited branching: Conditional logic requires custom callbacks or wrapper code that fights the framework.
• Debugging opacity: When a multi-step agent loop fails, the error trace passes through multiple abstraction layers, making root cause identification difficult.
• No human-in-the-loop: Pausing mid-execution for human approval requires architectural workarounds.

LangGraph was specifically designed to eliminate these limitations.

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3. Core Concepts and Mental Model

The Fundamental Architectural Difference

The most important concept to internalize is this:

LangChain thinks in pipelines. LangGraph thinks in state machines.

A pipeline executes linearly: A → B → C → done. Each component receives the output of the previous component and passes its output to the next.

A state machine executes through transitions: based on the current state, a transition rule determines the next state. The same “node” can be visited multiple times. The execution ends when a terminal state is reached.

Execution Model Comparison

LangChain executes a pipeline once. LangGraph cycles until the agent decides it is done.

Pause

LangChain — PipelineOne pass · deterministic · stateless

Input

Prompt

LLM

Parser

Output

LangGraph — State MachineCycles until terminal condition · state persisted

AgentState

persisted

Thought

Action

Observe

Loop or END

Idle

State: The Core Concept in LangGraph

LangGraph introduces the concept of a State object that persists throughout a workflow execution. Every node in the graph reads from and writes to this state. This is what enables:

• Cycles: A node can read state, decide to loop back, and the state carries everything accumulated so far
• Resumability: State can be checkpointed to a database; if a process crashes, it restarts from the last checkpoint
• Human-in-the-loop: A human can review and modify state before the workflow continues

from typing import TypedDict, Annotated, List
from langgraph.graph.message import add_messages

# LangGraph: State is explicit and typed
class AgentState(TypedDict):
    messages: Annotated[list, add_messages]  # messages accumulate
    next_step: str                            # routing decision
    iteration_count: int                      # loop control
    approved_by_human: bool                   # human-in-the-loop flag

In LangChain, there is no equivalent concept. The closest analog is ConversationBufferMemory, but it only handles message history, not arbitrary workflow state.

📊 Visual Explanation

Execution Model Comparison

LangChain vs LangGraph — Execution Model

LangChain

Pipeline model — linear, stateless, executes once

• Composable Runnable chains via | operator (LCEL)
• Sequential execution: Prompt → LLM → Parser
• Rich ecosystem: 100+ tool integrations
• Fast iteration and prototyping
• No cycles — every execution is a straight line
• No persistent state between invocations
• Cannot pause, resume, or checkpoint mid-execution

VS

LangGraph

State machine model — cyclic, stateful, resumable

• Graph of nodes with typed persistent state (TypedDict)
• Cycles allowed — agents can loop until done
• Checkpointer: pause/resume from any node
• Human-in-the-loop: interrupt() at any node
• Higher conceptual complexity than LangChain
• Steeper learning curve for teams new to state machines
• Overkill for simple linear pipelines

Verdict: Use LangChain for deterministic, single-pass pipelines (RAG, extraction, summarization). Use LangGraph when the workflow requires cycles, persistent state, or human-in-the-loop.

Use LangChain when…

You know all the steps upfront. The workflow is linear. Prototyping a new GenAI feature.

Use LangGraph when…

The agent decides its next action at runtime. You need retry logic, state persistence, or human approval.

---

4. Step-by-Step Explanation

How LangChain Works Internally

LangChain’s core abstraction is the Runnable interface, which defines a standard protocol for components that process inputs and produce outputs. Chains are created by composing Runnable objects using the | operator (pipe operator) or explicit RunnableSequence constructors.

from langchain_core.prompts import ChatPromptTemplate
from langchain_core.output_parsers import StrOutputParser
from langchain_openai import ChatOpenAI

# Composing Runnables into a chain
prompt = ChatPromptTemplate.from_template(
    "Answer this question based on the context.\n"
    "Context: {context}\nQuestion: {question}"
)

llm = ChatOpenAI(model="gpt-4o-mini")
parser = StrOutputParser()

# The pipe operator creates a RunnableSequence
chain = prompt | llm | parser

# Execution: synchronous, one pass, left to right
result = chain.invoke({
    "context": "Python was created by Guido van Rossum.",
    "question": "Who created Python?"
})

What happens when you call .invoke():

1. The input dict is passed to prompt, which formats the template
2. The formatted prompt is passed to llm, which calls the API and returns a ChatMessage
3. The ChatMessage is passed to parser, which extracts the string content
4. The final string is returned

There is no state object. There is no loop. If step 2 fails, there is no built-in mechanism to retry from step 2 without re-running step 1. The chain is a function.

LangChain Retrieval (LCEL style):

from langchain_core.runnables import RunnablePassthrough

retriever = vector_store.as_retriever(search_kwargs={"k": 5})

# RAG chain: parallel retrieval + question passing
rag_chain = (
    {"context": retriever, "question": RunnablePassthrough()}
    | prompt
    | llm
    | parser
)

response = rag_chain.invoke("What is RAG?")

This is where LangChain excels: expressing a data transformation pipeline concisely, with the component graph determined at construction time.

How LangGraph Works Internally

LangGraph represents workflows as a directed graph. Nodes are Python functions. Edges define transitions between nodes. A special StateGraph class holds the schema for the shared state object.

from langgraph.graph import StateGraph, END
from langgraph.checkpoint.sqlite import SqliteSaver
from typing import TypedDict, Annotated, List
from langgraph.graph.message import add_messages

class AgentState(TypedDict):
    messages: Annotated[list, add_messages]
    next: str

def should_continue(state: AgentState) -> str:
    """Routing function: determines next node based on state."""
    last_message = state["messages"][-1]
    # If the last message has tool calls, go to tools; otherwise end
    if hasattr(last_message, "tool_calls") and last_message.tool_calls:
        return "tools"
    return END

def call_model(state: AgentState) -> AgentState:
    """Node: call the LLM."""
    response = llm_with_tools.invoke(state["messages"])
    return {"messages": [response]}

def call_tools(state: AgentState) -> AgentState:
    """Node: execute the requested tools."""
    last_message = state["messages"][-1]
    tool_messages = tool_executor.batch(last_message.tool_calls)
    return {"messages": tool_messages}

# Build the graph
graph = StateGraph(AgentState)
graph.add_node("agent", call_model)
graph.add_node("tools", call_tools)
graph.set_entry_point("agent")

# Conditional edge: routing function determines next step
graph.add_conditional_edges("agent", should_continue)
graph.add_edge("tools", "agent")  # After tools, always go back to agent

# Compile with checkpointing for state persistence
checkpointer = SqliteSaver.from_conn_string(":memory:")
compiled_graph = graph.compile(checkpointer=checkpointer)

# Execute with a thread_id for conversation continuity
result = compiled_graph.invoke(
    {"messages": [HumanMessage(content="What is the weather in NYC?")]},
    config={"configurable": {"thread_id": "user-123"}}
)

What happens during execution:

1. The graph starts at the entry point node (“agent”)
2. call_model reads from state["messages"], calls the LLM, and writes the response back to state["messages"]
3. The conditional edge calls should_continue, which inspects the latest message
4. If tool calls were made, execution moves to “tools”; otherwise it ends
5. call_tools executes all requested tools, writes results back to state
6. Control returns to “agent” and the cycle repeats
7. At each step, if a checkpointer is configured, the state is persisted to the database

Human-in-the-loop checkpoint:

from langgraph.graph import StateGraph, END

# Add an interrupt before the tools node
compiled_graph = graph.compile(
    checkpointer=checkpointer,
    interrupt_before=["tools"]  # Pause before executing tools
)

# First run: pauses before tools
initial_result = compiled_graph.invoke(
    {"messages": [HumanMessage(content="Delete all records in the database.")]},
    config={"configurable": {"thread_id": "admin-task-1"}}
)

# Human reviews the planned action
print("Agent plans to:", initial_result["messages"][-1].tool_calls)

# Human approves by resuming (passing None resumes from checkpoint)
final_result = compiled_graph.invoke(
    None,
    config={"configurable": {"thread_id": "admin-task-1"}}
)

This pattern is impossible to implement cleanly in LangChain without significant custom code.

---

5. Architecture and System View

When LangChain Is the Right Architecture

LangChain’s sequential execution model is the right choice when the problem can be expressed as a deterministic transformation pipeline:

Input Document
      │
      ▼
┌─────────────────┐
│  Text Splitter  │  (chunking)
└───────┬─────────┘
        │ chunks[]
        ▼
┌─────────────────┐
│  Embedding      │  (vectorization)
│  Generator      │
└───────┬─────────┘
        │ vectors[]
        ▼
┌─────────────────┐
│  Vector Store   │  (indexing)
│  Upsert         │
└─────────────────┘

User Query
      │
      ▼
┌─────────────────┐
│  Query Embed    │
└───────┬─────────┘
        │
        ▼
┌─────────────────┐
│  Retriever      │  (top-k similar chunks)
└───────┬─────────┘
        │ context docs
        ▼
┌─────────────────┐
│  Prompt Builder │
└───────┬─────────┘
        │
        ▼
┌─────────────────┐
│  LLM            │
└───────┬─────────┘
        │
        ▼
┌─────────────────┐
│  Output Parser  │
└─────────────────┘

Both flows execute in one pass. No cycles, no persistent state beyond conversation history.

When LangGraph Is the Right Architecture

LangGraph is correct when the problem requires a workflow that cannot be fully specified at design time because intermediate results determine subsequent steps:

                ┌─────────────────────┐
                │   Supervisor Agent   │
                │   (orchestrator)     │
                └──────────┬──────────┘
                           │ routes task
          ┌────────────────┼────────────────┐
          ▼                ▼                ▼
    ┌──────────┐    ┌──────────┐    ┌──────────┐
    │ Research │    │  Code    │    │  Review  │
    │  Agent   │    │  Agent   │    │  Agent   │
    └─────┬────┘    └─────┬────┘    └────┬─────┘
          │               │              │
          └───────────────┴──────────────┘
                          │ results merge
                    ┌─────▼─────┐
                    │  Shared   │
                    │  State    │
                    └─────┬─────┘
                          │
                    ┌─────▼─────┐
                    │ Supervisor│  (check: is task done?)
                    │  Review   │
                    └─────┬─────┘
                          │
              ┌───────────┴────────────┐
              ▼                        ▼
          (done)                  (retry agent)
           END              back to routing

📊 Visual Explanation

Framework Selection Cheat Sheet

When to Choose Each Framework

Choose LangChain

Simpler use cases, faster development

• RAG pipeline: retrieve → rerank → generate
• Document processing: extract structured data from PDFs
• Summarization or classification pipelines
• Prototyping a new idea quickly
• Team is new to LLM frameworks
• Workflow has no retries or state between runs

VS

Choose LangGraph

Complex agents, production workflows

• ReAct agent: decide → act → observe → loop
• Code generation with automated test-and-fix loop
• Research agent: plan → search → synthesize → verify
• Any workflow needing human approval mid-execution
• Multi-agent coordination with shared state
• Production systems needing crash recovery

Verdict: When the workflow is a known sequence of steps, LangChain wins (simplicity). When the workflow is a loop where the agent decides what to do next, LangGraph wins (control).

---

6. Practical Examples

Use Case 1: Document Q&A System (LangChain is correct)

A customer support team needs a system to answer questions from their documentation.

Why LangChain fits: The workflow is deterministic. Every query follows the same path: embed → retrieve → generate. There is no branching logic, no looping, no state that needs to survive a process crash.

from langchain_community.vectorstores import Chroma
from langchain_openai import ChatOpenAI, OpenAIEmbeddings
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.runnables import RunnablePassthrough
from langchain_core.output_parsers import StrOutputParser

embeddings = OpenAIEmbeddings(model="text-embedding-3-small")
vector_store = Chroma(embedding_function=embeddings)

retriever = vector_store.as_retriever(
    search_type="mmr",          # Maximal Marginal Relevance for diversity
    search_kwargs={"k": 5, "fetch_k": 20}
)

prompt = ChatPromptTemplate.from_template("""
Answer the question using only the context provided.
If the answer is not in the context, say "I don't have that information."
Do not make up information.

Context:
{context}

Question: {question}
""")

llm = ChatOpenAI(model="gpt-4o-mini", temperature=0)
parser = StrOutputParser()

def format_docs(docs) -> str:
    return "\n\n".join(
        f"Source: {doc.metadata.get('source', 'unknown')}\n{doc.page_content}"
        for doc in docs
    )

rag_chain = (
    {"context": retriever | format_docs, "question": RunnablePassthrough()}
    | prompt
    | llm
    | parser
)

# Usage
answer = rag_chain.invoke("What is the return policy?")

This is clean, testable, and comprehensible. No LangGraph needed.

Use Case 2: Research Agent (LangGraph is correct)

An agent needs to research a topic by searching the web, refining its searches based on what it finds, writing a report, and revising it until a quality threshold is met.

Why LangGraph fits: The workflow has cycles (search → evaluate → refine search → evaluate). The execution path cannot be determined at design time because it depends on what the searches return.

from langgraph.graph import StateGraph, END
from typing import TypedDict, Annotated, List
from langgraph.graph.message import add_messages

class ResearchState(TypedDict):
    query: str
    search_results: List[str]
    draft_report: str
    quality_score: float
    revision_count: int
    messages: Annotated[list, add_messages]

def search(state: ResearchState) -> ResearchState:
    """Execute web search and add results to state."""
    results = web_search_tool.run(state["query"])
    return {
        "search_results": state["search_results"] + [results]
    }

def draft_report(state: ResearchState) -> ResearchState:
    """Draft a report from accumulated search results."""
    context = "\n".join(state["search_results"])
    response = llm.invoke(f"Write a detailed report about: {state['query']}\n\nBased on: {context}")
    return {"draft_report": response.content}

def evaluate_quality(state: ResearchState) -> ResearchState:
    """Score the report quality."""
    score_response = evaluator_llm.invoke(
        f"Score this report quality 0.0-1.0 for accuracy and completeness. "
        f"Return only a number.\n\nReport: {state['draft_report']}"
    )
    score = float(score_response.content.strip())
    return {
        "quality_score": score,
        "revision_count": state.get("revision_count", 0) + 1
    }

def should_continue(state: ResearchState) -> str:
    """Routing: decide whether to refine or finish."""
    if state["quality_score"] >= 0.85:
        return END
    if state.get("revision_count", 0) >= 3:
        return END  # Safety limit
    return "search"  # Loop back for more research

graph = StateGraph(ResearchState)
graph.add_node("search", search)
graph.add_node("draft", draft_report)
graph.add_node("evaluate", evaluate_quality)

graph.set_entry_point("search")
graph.add_edge("search", "draft")
graph.add_edge("draft", "evaluate")
graph.add_conditional_edges("evaluate", should_continue)

research_agent = graph.compile(checkpointer=checkpointer)

result = research_agent.invoke({
    "query": "Latest advances in RAG systems",
    "search_results": [],
    "revision_count": 0
})

This cannot be expressed cleanly in LangChain. The cycle back from “evaluate” to “search” requires the graph model.

Use Case 3: The Hybrid Approach (Production Reality)

In production, most systems use LangChain components inside LangGraph nodes. LangGraph handles the orchestration, and LangChain handles the component-level logic.

from langgraph.graph import StateGraph, END
from langchain_core.prompts import ChatPromptTemplate
from langchain_openai import ChatOpenAI
from langchain_core.output_parsers import StrOutputParser

# LangChain components (used inside LangGraph nodes)
classify_prompt = ChatPromptTemplate.from_template(
    "Classify this query as 'simple' or 'complex': {query}"
)
classify_chain = classify_prompt | ChatOpenAI(model="gpt-4o-mini") | StrOutputParser()

rag_prompt = ChatPromptTemplate.from_template(
    "Answer using context: {context}\nQuery: {query}"
)
rag_chain = (
    {"context": retriever | format_docs, "query": RunnablePassthrough()}
    | rag_prompt | ChatOpenAI(model="gpt-4o-mini") | StrOutputParser()
)

deep_analysis_chain = (
    ChatPromptTemplate.from_template("Provide deep analysis of: {query}")
    | ChatOpenAI(model="gpt-4o") | StrOutputParser()
)

# LangGraph orchestrates which component to use
class QueryState(TypedDict):
    query: str
    classification: str
    response: str

def classify(state: QueryState) -> QueryState:
    result = classify_chain.invoke({"query": state["query"]})
    return {"classification": result.strip().lower()}

def handle_simple(state: QueryState) -> QueryState:
    result = rag_chain.invoke(state["query"])
    return {"response": result}

def handle_complex(state: QueryState) -> QueryState:
    result = deep_analysis_chain.invoke({"query": state["query"]})
    return {"response": result}

def route(state: QueryState) -> str:
    return "complex" if "complex" in state["classification"] else "simple"

graph = StateGraph(QueryState)
graph.add_node("classify", classify)
graph.add_node("simple", handle_simple)
graph.add_node("complex", handle_complex)
graph.set_entry_point("classify")
graph.add_conditional_edges("classify", route)
graph.add_edge("simple", END)
graph.add_edge("complex", END)

app = graph.compile()

---

7. Trade-offs, Limitations, and Failure Modes

LangChain Failure Modes

1. Abstraction Leakage

When a LangChain chain fails, the error message often originates deep inside framework code. You see an error from langchain_core.runnables rather than from your code. Debugging requires enabling verbose mode and often reading LangChain source code.

Mitigation: Wrap LangChain components in thin custom classes that log inputs and outputs. Use LangSmith for production trace visibility.

2. Version Instability

LangChain has historically introduced breaking changes between minor versions. A chain that worked on langchain 0.1.x may fail silently or require refactoring on langchain 0.2.x.

Mitigation: Pin exact versions in requirements.txt. Never use >= version specifiers for LangChain. Test on version upgrades before deploying.

3. Token Overhead from Abstractions

Some LangChain abstractions add tokens to your prompts without transparency. The exact prompt sent to the LLM can be different from what you intended. This has cost and quality implications.

Mitigation: Use chain.get_prompts() to inspect the actual prompts. Consider building prompts manually for cost-sensitive paths.

4. Premature Abstraction

The extensive integration ecosystem encourages using LangChain wrappers even when direct API calls would be simpler and more maintainable.

Mitigation: Ask whether the LangChain abstraction adds value over direct API calls. For simple use cases, direct implementation is often better.

LangGraph Failure Modes

1. State Explosion

As workflows grow complex, the state object grows. Every node adds more fields. State becomes an untyped dumping ground that is hard to reason about.

Mitigation: Keep state objects minimal. Use nested TypedDicts to organize related fields. Periodically audit state for fields that are no longer needed.

2. Graph Complexity

Large graphs with many conditional edges become hard to understand and modify. Tracing execution through a complex graph requires careful reading of routing functions.

Mitigation: Document routing logic. Break large graphs into subgraphs. Use LangSmith to visualize execution traces.

3. Checkpoint Storage Growth

The checkpointing system stores state for every thread. Without a retention policy, checkpoint storage grows indefinitely.

Mitigation: Configure checkpoint retention policies. Use SQLite for development, PostgreSQL with cleanup jobs for production.

4. Testing Complexity

Testing stateful workflows is fundamentally harder than testing functions. The full workflow must often be tested end-to-end because unit testing individual nodes misses interaction effects.

Mitigation: Write integration tests that run the full graph with mock tools. Test each node in isolation and the graph as a whole.

5. Overhead for Simple Workflows

LangGraph adds real overhead: state validation, graph traversal, checkpoint writes. For simple pipelines, this overhead is not justified.

Mitigation: Use LangChain for simple pipelines. Apply LangGraph only when the workflow complexity genuinely requires it.

Migration Between Frameworks

Migrating from LangChain to LangGraph:

The typical migration pattern is incremental:

1. Identify the parts of your system that require cycles, persistent state, or conditional branching
2. Extract those parts into LangGraph nodes
3. Keep the remaining components as LangChain Runnables
4. Use LangChain components inside LangGraph nodes (fully supported)
5. Migrate the orchestration layer to LangGraph without changing individual components

What requires refactoring:

• Replace AgentExecutor with StateGraph and explicit routing functions
• Replace implicit memory (ConversationBufferMemory) with explicit state fields
• Replace callback-based debugging with LangSmith tracing or explicit state logging

What does not require refactoring:

• ChatPromptTemplate, StrOutputParser, ChatOpenAI — all work identically inside LangGraph nodes
• Retrievers and vector store integrations — unchanged
• Document loaders and text splitters — unchanged

---

8. Interview Perspective

What Interviewers Assess

This topic appears in system design interviews for mid-level and senior GenAI engineering roles. The question is rarely direct (“compare LangChain and LangGraph”). More often it surfaces as:

• “How would you design an agent that needs to retry failed steps?”
• “Describe your approach to building a multi-agent system”
• “What framework would you use for an approval workflow, and why?”

What a weak answer looks like:

“I would use LangGraph because it’s better for agents. LangChain is for simpler stuff.”

This signals framework familiarity without architectural understanding. The interviewer learns that you’ve read the documentation but not thought through the decision.

What a strong answer looks like:

“The decision hinges on whether the workflow has cycles and whether state needs to persist across failures. For a purely sequential RAG pipeline, LangChain’s LCEL is the right abstraction — it’s composable, testable, and you can express the data flow clearly with the pipe operator. If the workflow requires a reasoning loop where the agent evaluates its output and decides whether to gather more information, or if the system needs to pause for human approval mid-execution, then LangGraph is the right tool because its state machine model directly maps to that behavior. In practice, we use both: LangChain components for the building blocks, LangGraph for the orchestration of complex workflows.”

Follow-up questions interviewers ask:

• “How does LangGraph’s state persistence work? What happens if a node fails?”
• “When would you NOT use LangGraph even for an agent use case?”
• “Walk me through debugging a LangGraph workflow in production.”

Strong answers to follow-ups:

For state persistence: “LangGraph uses checkpointers — implementations of the BaseCheckpointSaver interface. At each superstep, the current state is serialized and written to the checkpoint store, which can be SQLite, PostgreSQL, or Redis. If the process crashes mid-execution, the graph can resume from the last checkpoint by loading the state and re-entering at the most recently completed node. The thread_id config parameter uniquely identifies a conversation or workflow execution.”

For when not to use LangGraph: “When the overhead of state management, graph compilation, and checkpointing exceeds the benefit. For a simple chatbot with conversation history, ConversationBufferWindowMemory in LangChain is sufficient. Adding LangGraph complexity would make the system harder to understand and debug without adding capability.”

---

9. Production Perspective

How Companies Actually Use These Frameworks

Early-stage companies (1–10 engineers):

Typically start with LangChain for prototyping. If they need agent behavior, they often try AgentExecutor first, hit its limitations within weeks, and migrate the agent orchestration to LangGraph while keeping the component-level code in LangChain.

Mid-stage companies (10–50 engineers):

Commonly run LangChain for RAG-heavy features and LangGraph for anything involving autonomous agents or multi-step workflows. Teams often maintain a shared library of LangChain components that are used across both contexts.

Enterprise (50+ engineers with dedicated MLops):

Often find that LangChain abstractions, designed for rapid development, become a maintenance burden at scale. Common pattern: keep LangGraph for orchestration, replace specific LangChain components with direct API integrations for better performance and debuggability.

Production Architecture Patterns

Pattern 1: RAG with LangChain, Agentic Routing with LangGraph

User Query
    │
    ▼
┌─────────────────┐        LangGraph handles routing
│   Query Router  │◄────── and decides which pipeline
│  (LangGraph)    │        to execute
└───────┬─────────┘
        │
   ┌────┴────┐
   ▼         ▼
Simple    Complex
Query     Query
   │         │
   ▼         ▼
LangChain  LangChain
RAG Chain  Analysis Chain
           + RAG Chain
   │         │
   └────┬────┘
        ▼
    Response

Pattern 2: LangGraph for Orchestration, Direct APIs for Performance

High-traffic paths often bypass LangChain abstractions entirely:

# Production: LangGraph node using direct API, not LangChain
def generate_response(state: State) -> State:
    # Direct OpenAI API call - no LangChain abstraction
    response = openai_client.chat.completions.create(
        model="gpt-4o-mini",
        messages=state["messages"],
        temperature=0
    )
    return {"messages": [response.choices[0].message]}

This avoids LangChain version sensitivity and framework overhead in the critical path.

Observability in Production

Both frameworks benefit from LangSmith, but the implementation differs:

• LangChain: Tracing happens automatically via callback handlers when LANGCHAIN_TRACING_V2=true is set
• LangGraph: Tracing requires explicit configuration and captures state transitions at each node

For production monitoring, LangSmith traces are indispensable when debugging why an agent loop ran more iterations than expected, or why a routing function took an unexpected path.

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10. Summary and Key Takeaways

The Core Decision Rule

Use LangChain when:

• The workflow is a deterministic pipeline: A → B → C
• No cycles or conditional branching based on intermediate results
• State management means conversation history only
• Rapid prototyping is the priority

Use LangGraph when:

• The workflow has cycles (any form of retrying or looping)
• State must persist across process restarts or failures
• Human approval is required mid-execution
• Multiple specialized agents must coordinate with shared state
• Complex conditional routing based on LLM outputs is required

Decision Reference

Workflow Characteristic	LangChain	LangGraph
Single-pass pipeline	Preferred	Overkill
Conditional branching	Possible with LCEL	Natural
Cycles and retries	Not supported	Purpose-built
State persistence	Not supported	Built-in
Human-in-the-loop	Workaround required	First-class
Multi-agent coordination	Limited	Purpose-built
Debugging complexity	Low	Higher
Overhead	Low	Moderate
Time to first working prototype	Hours	Half-day

Practical Guidance by Career Stage

Beginners: Learn LangChain first. It is the prerequisite. Build 2–3 RAG applications using LCEL before touching LangGraph. Most entry-level positions require only LangChain proficiency.

Intermediate engineers: Add LangGraph to your toolkit. Rebuild one of your LangChain applications as a LangGraph workflow. The architectural difference will become clear once you experience both.

Senior engineers: Master both and develop the judgment to choose correctly. More importantly, develop the judgment to recognize when neither framework adds value and a direct implementation is better.

The Field Is Converging

LangChain and LangGraph are converging. As of 2025–2026, LangGraph’s patterns for stateful agents are influencing how the broader LangChain SDK is structured. The @chain decorator and streamlined LCEL syntax reflect lessons learned from LangGraph. Expect continued architectural evolution and increasing interoperability between the two frameworks.

The investment in learning both will compound: the architectural thinking required to use them correctly applies to any orchestration framework you encounter in the future.

Related

• AI Agents and Agentic Systems — How agents reason, use tools, and manage memory — the foundation that LangGraph implements
• Agentic Frameworks: LangGraph vs CrewAI vs AutoGen — Choosing between multi-agent orchestration frameworks for production systems
• Agentic Patterns — ReAct, reflection, tool use, and other patterns implemented in both frameworks
• Vector Database Comparison — Choosing the right retrieval backend for your LangChain RAG or LangGraph agent
• Cloud AI Platforms — Managed agent deployment on AWS Bedrock, Google Vertex AI, and Azure
• Essential GenAI Tools — The full production tool stack that LangChain and LangGraph slot into

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Last updated: February 2026. Framework recommendations and code examples reflect LangChain 0.3+ and LangGraph 0.2+ APIs.