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class CommandOne or more commands to update the graph's state and send messages to nodes. Can be used to combine routing logic with state updates in lieu of conditional edges
Can be one of the following:
graph)Graph to send the command to. Supported values are:
Value to resume execution with. To be used together with interrupt.
Update to apply to the graph's state as a result of executing the node that is returning the command. Written to the state as if the node had simply returned this value instead of the Command object.
import { Annotation, Command } from "@langchain/langgraph";
// Define graph state
const StateAnnotation = Annotation.Root({
foo: Annotation<string>,
});
// Define the nodes
const nodeA = async (_state: typeof StateAnnotation.State) => {
console.log("Called A");
// this is a replacement for a real conditional edge function
const goto = Math.random() > .5 ? "nodeB" : "nodeC";
// note how Command allows you to BOTH update the graph state AND route to the next node
return new Command({
// this is the state update
update: {
foo: "a",
},
// this is a replacement for an edge
goto,
});
};
// Nodes B and C are unchanged
const nodeB = async (state: typeof StateAnnotation.State) => {
console.log("Called B");
return {
foo: state.foo + "|b",
};
}
const nodeC = async (state: typeof StateAnnotation.State) => {
console.log("Called C");
return {
foo: state.foo + "|c",
};
}
import { StateGraph } from "@langchain/langgraph";
// NOTE: there are no edges between nodes A, B and C!
const graph = new StateGraph(StateAnnotation)
.addNode("nodeA", nodeA, {
ends: ["nodeB", "nodeC"],
})
.addNode("nodeB", nodeB)
.addNode("nodeC", nodeC)
.addEdge("__start__", "nodeA")
.compile();
await graph.invoke({ foo: "" });
// Randomly oscillates between
// { foo: 'a|c' } and { foo: 'a|b' }