LangGraphCompileError
langgraph.errors.LangGraphCompileError
Stack trace
langgraph.errors.LangGraphCompileError: Missing entry point in graph definition. Please define an entry point node to compile the graph.
File "app.py", line 42, in build_graph
graph.compile()
File "langgraph/core.py", line 128, in compile
raise LangGraphCompileError("Missing entry point in graph definition.") Why it happens
LangGraph requires an explicit entry point node to start execution of the graph. If the graph definition does not specify this entry point, the compiler cannot determine where to begin, causing this error. This often happens when the graph is incomplete or the entry point is misnamed or omitted.
Detection
Before compiling, validate that the graph definition includes a node marked as the entry point. Use graph validation utilities or check for the presence of an entry point attribute to catch this early.
Causes & fixes
No node in the graph is designated as the entry point.
Add an entry point node to the graph definition using the appropriate method or decorator to mark it as the starting node.
Entry point node is defined but misspelled or incorrectly referenced.
Verify the entry point node's name matches exactly in the graph definition and compilation call, correcting any typos.
Graph definition is incomplete or missing due to conditional logic or import errors.
Ensure the graph is fully defined and imported before compilation, and that no conditional code paths skip entry point creation.
Code: broken vs fixed
from langgraph import Graph
graph = Graph()
# Missing entry point node definition
graph.compile() # This line triggers LangGraphCompileError: Missing entry pointimport os
from langgraph import Graph, entry_point
os.environ['LANGGRAPH_API_KEY'] = os.environ.get('LANGGRAPH_API_KEY', '') # Use env var for keys
graph = Graph()
@entry_point
def start_node():
return "Start"
graph.add_node(start_node)
graph.compile() # Fixed: entry point defined and marked
print("Graph compiled successfully.")Workaround
Catch LangGraphCompileError during compile(), then programmatically add a default entry point node if missing before retrying compilation.
Prevention
Always define and clearly mark an entry point node in your graph definitions as part of your development workflow and include validation checks before compilation.