Conditional edges

A conditional edge calls a routing function after a node finishes. The function reads the updated state and returns the next node name, END, or a list of destinations.¹

Tiny example

from typing import Literal
from langgraph.graph import END

def route_refund(state: RefundState) -> Literal["approve", "review", END]:
    if state["policy_violation"]:
        return "review"
    if state["eligible"]:
        return "approve"
    return END

builder.add_conditional_edges("check_policy", route_refund)

Remember the order:

Node returns an update.
LangGraph applies the update.
Router reads the new state.
Router returns the destination.

Failure note

Every loop needs a tested stop condition. Otherwise the graph eventually reaches its recursion limit instead of completing normally.

LangChain, Graph API overview. ↩