Edges as Decisions

If Nodes are the "What", Edges are the "When".

Types of Edges

1. Normal Edge (Deterministic)

"After Node A finishes, always go to Node B." graph.add_edge("node_a", "node_b")

2. Conditional Edge (Probabilistic)

"After Node A finishes, check the state. If X, go to Node B. If Y, go to Node C."

graph.add_conditional_edges(
    "node_a",
    should_continue,
    {
        "continue": "node_b",
        "stop": "end"
    }
)

The Router Function

The logic for a conditional edge lives in a Router Function. This function must be purely logical. It reads the state and returns a string matching one of the destination keys.

graph TD
    A[Start] --> Router{Decision}
    Router -- "Path 1" --> B[Node B]
    Router -- "Path 2" --> C[Node C]