ModuleNotFoundError: No Module Named ‘langgraph’ (2026)

LangGraph is LangChain’s graph-based agent orchestration library, now the default way to build multi-agent AI systems in 2026. If you see ModuleNotFoundError: No module named ‘langgraph’, you need to install the package separately from langchain itself. Here is the full setup with checkpointer and LangSmith integration.

Step 1: Install langgraph

pip install langgraph

# With persistence (SQLite checkpointer):
pip install langgraph langgraph-checkpoint-sqlite

# With Postgres checkpointer:
pip install langgraph langgraph-checkpoint-postgres

# Full stack (most production deployments):
pip install langgraph langchain langchain-openai langgraph-checkpoint-sqlite

Step 2: Minimal agent example

from langgraph.graph import StateGraph, START, END
from typing import TypedDict

class State(TypedDict):
    messages: list

def chat_node(state):
    state['messages'].append("Hello from chat_node!")
    return state

workflow = StateGraph(State)
workflow.add_node("chat", chat_node)
workflow.add_edge(START, "chat")
workflow.add_edge("chat", END)

app = workflow.compile()
result = app.invoke({"messages": []})
print(result)

Step 3: Add checkpointer for state persistence

from langgraph.checkpoint.sqlite import SqliteSaver

memory = SqliteSaver.from_conn_string(":memory:")  # or "sqlite:///state.db"
app = workflow.compile(checkpointer=memory)

config = {"configurable": {"thread_id": "user-123"}}
app.invoke({"messages": []}, config=config)
# State persists across invocations under thread_id

Why this error happens

Cause	Fix
Installed only langchain, expecting langgraph included	pip install langgraph separately
Old version of langchain (pre 0.2)	pip install -U langchain langgraph
Checkpointer extras missing	pip install langgraph-checkpoint-sqlite
Wrong Python version (under 3.9)	Upgrade to Python 3.10+

Quick step-by-step summary (click to expand)

1. Activate the correct virtual environment. Ensure you are in the venv where you want LangGraph installed.
2. Install langgraph and dependencies. Run uv pip install langgraph. This pulls in langchain-core and other required packages.
3. Install checkpointer for stateful graphs. For persistence, also install uv pip install langgraph-checkpoint-sqlite or langgraph-checkpoint-postgres.
4. Verify with import test. Run python -c “from langgraph.graph import StateGraph” to confirm the module loads.