How to define input/output schema for your graph¶

By default, StateGraph takes in a single schema and all nodes are expected to communicate with that schema. However, it is also possible to define explicit input and output schemas for a graph. This is helpful if you want to draw a distinction between input and output keys.

In this notebook we'll walk through an example of this. At a high level, in order to do this you simply have to pass in separate Annotation.Root({}) objets as { input: Annotation.Root({}), output: Annotation.Root({}) } when defining the graph. Let's see an example below!

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import { Annotation, StateGraph } from "@langchain/langgraph";

const InputAnnotation = Annotation.Root({
  question: Annotation<string>,
});

const OutputAnnotation = Annotation.Root({
  answer: Annotation<string>,
});

const answerNode = (_state: typeof InputAnnotation.State) => {
  return { answer: "bye" };
};

const graph = new StateGraph({
  input: InputAnnotation,
  output: OutputAnnotation,
})
  .addNode("answerNode", answerNode)
  .addEdge("__start__", "answerNode")
  .compile();

await graph.invoke({
  question: "hi",
});
import { Annotation, StateGraph } from "@langchain/langgraph";

const InputAnnotation = Annotation.Root({
  question: Annotation,
});

const OutputAnnotation = Annotation.Root({
  answer: Annotation,
});

const answerNode = (_state: typeof InputAnnotation.State) => {
  return { answer: "bye" };
};

const graph = new StateGraph({
  input: InputAnnotation,
  output: OutputAnnotation,
})
  .addNode("answerNode", answerNode)
  .addEdge("__start__", "answerNode")
  .compile();

await graph.invoke({
  question: "hi",
});

{ answer: 'bye' }

Notice that the output of invoke only includes the output schema.