API Reference: RouterNode

The RouterNode is the "choice" or if/else statement for your agent. It is a 100% deterministic node that uses pure Python logic to decide where the agent should go next.

This is the key to building complex, auditable, multi-agent systems and loops.

Key Features

• Deterministic: It's just a Python function. No AI, no "magic." It will do the same thing every time, given the same state.

• Multi-Path: It can route the agent down many different "assembly lines" (e.g., "BILLING" vs. "TECH_SUPPORT").

• Loop-Capable: By routing from a "Judge" node back to a "Tester" node, you can create powerful self-correcting loops.

Example Usage

First, define your simple, stateless "logic" function:

def judge_function(state: GraphState) -> str:
    """Reads the state and returns a string key."""
    if state.get("last_error"):
        return "failure_path" # This key must match the path_map
    else:
        return "success_path"

Then, wire it into your RouterNode:

# The RouterNode reads the string from judge_function
# and uses it to pick the next node.
judge_node = RouterNode(
    decision_function=judge_function,
    path_map={
        "success_path": success_node,
        "failure_path": corrector_node
    },
    default_node=critical_fail_node # Optional: for safety
)

What it Does

When execute(state) is called:

1. It runs route_key = self.decision_function(state).

2. It looks up that route_key in self.path_map.

3. If found, it returns the corresponding node (e.g., corrector_node).

4. If not found, it returns the default_node.

5. If no default, it returns None and stops the graph.

__init__ Parameters

Parameter	Type	Required	Description
decision_function	Callable	Yes	A Python function that takes a GraphState as input and returns a single str (the route key).
path_map	Dict	Yes	A dictionary that maps the string keys from your function to the BaseNode objects to run (e.g., {"success_path": ...})
default_node	BaseNode	No	(Optional) A fallback node to run if the decision_function returns a key that is not in the path_map.