START and END

START and END are virtual markers, not business functions. START routes graph input to the first node. END marks a completed path.¹

Tiny example

from langgraph.graph import START, END

builder.add_edge(START, "load_order")
builder.add_edge("send_reply", END)

Marker	Read it as
START	“When input arrives…”
END	“…this path is finished.”

You can also add a conditional edge from START when different inputs need different entry nodes.

Failure note

Reaching END stops routing; it does not prove that an external side effect succeeded. Record and verify the outcome inside the node that owns the side effect.

Related

• Edges
• Conditional edges
• compile()

Footnotes

1. LangChain, Graph API overview. ↩