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JavaScript@langchain/langgraphindexConditionalEdgeRouter
Type●Since v0.3

ConditionalEdgeRouter

Type for conditional edge routing functions.

Use this to type functions passed to addConditionalEdges for full type safety on state, runtime context, and return values.

Supports two patterns:

  1. Single schema pattern - Single schema: ConditionalEdgeRouter<Schema, Context, Nodes>

  2. Type bag pattern - Separate schemas for state, context: ConditionalEdgeRouter<{ Schema; ContextSchema; Nodes }>

Copy
ConditionalEdgeRouter: IsConditionalEdgeRouterTypeBag<
  Schema
> extends true  (
  state: ExtractBagInput<Schema, unknown>,
  config: LangGraphRunnableConfig<ExtractBagContext<Schema, Record<string, unknown>>>) => ConditionalEdgeRouterReturnValue<ExtractBagNodes<Schema,
  string>, ExtractBagInput<Schema,
  unknown>> | Promise<ConditionalEdgeRouterReturnValue<ExtractBagNodes<Schema, string>,
  ExtractBagInput<Schema, unknown>>> : (state: ExtractStateType<Schema>, config: LangGraphRunnableConfig<Context>
) => ConditionalEdgeRouterReturnValue<Nodes, ExtractStateType<Schema>> | Promise<ConditionalEdgeRouterReturnValue<Nodes, ExtractStateType<Schema>>>

Used in Docs

  • Build a custom RAG agent with LangGraph
  • Build a custom SQL agent
  • Frontend
  • Graph API overview
  • Handoffs

Example 1

Copy
type MyContext = { userId: string };
const router: ConditionalEdgeRouter<typeof AgentState, MyContext, "agent" | "tool"> =
  (state, config) => {
    const userId = config.context?.userId;
    if (state.done) return END;
    return state.needsTool ? "tool" : "agent";
  };

graph.addConditionalEdges("router", router, ["agent", "tool"]);

Example 2

Copy
const router: ConditionalEdgeRouter<{
  Schema: typeof StateSchema;
  ContextSchema: typeof ContextSchema;
  Nodes: "agent" | "tool";
}> = (state, config) => {
  if (state.done) return END;
  return "agent";
};
View source on GitHub