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Define a LangGraph workflow using the entrypoint function.
The wrapped function must accept at most two parameters. The first parameter is the input to the function. The second (optional) parameter is a LangGraphRunnableConfig object. If you wish to pass multiple parameters to the function, you can pass them as an object.
To write data to the "custom" stream, use the getWriter function, or the LangGraphRunnableConfig.writer property.
The getPreviousState function can be used to access the previous state that was returned from the last invocation of the entrypoint on the same thread id.
If you wish to save state other than the return value, you can use the entrypoint.final function.
entrypoint<
InputT,
OutputT
>(
optionsOrName: string | EntrypointOptions,
func: EntrypointFunc<InputT, OutputT>
): Pregel<Record<string, PregelNode<InputT, EntrypointReturnT<OutputT>>>, __type, Record<string, unknown>, InputT, EntrypointReturnT<OutputT>, any, Awaited<EntrypointReturnT<OutputT>>>| Name | Type | Description |
|---|---|---|
optionsOrName* | string | EntrypointOptions | Either an EntrypointOptions object, or a string for the name of the entrypoint |
func* | EntrypointFunc<InputT, OutputT> | The function that executes this entrypoint |
import { task, entrypoint } from "@langchain/langgraph";
import { MemorySaver } from "@langchain/langgraph-checkpoint";
import { interrupt, Command } from "@langchain/langgraph";
const composeEssay = task("compose", async (topic: string) => {
await new Promise(r => setTimeout(r, 1000)); // Simulate slow operation
return `An essay about ${topic}`;
});
const reviewWorkflow = entrypoint({
name: "review",
checkpointer: new MemorySaver()
}, async (topic: string) => {
const essay = await composeEssay(topic);
const humanReview = await interrupt({
question: "Please provide a review",
essay
});
return {
essay,
review: humanReview
};
});
// Example configuration for the workflow
const config = {
configurable: {
thread_id: "some_thread"
}
};
// Topic for the essay
const topic = "cats";
// Stream the workflow to generate the essay and await human review
for await (const result of reviewWorkflow.stream(topic, config)) {
console.log(result);
}
// Example human review provided after the interrupt
const humanReview = "This essay is great.";
// Resume the workflow with the provided human review
for await (const result of reviewWorkflow.stream(new Command({ resume: humanReview }), config)) {
console.log(result);
}import { entrypoint, getPreviousState } from "@langchain/langgraph";
import { MemorySaver } from "@langchain/langgraph-checkpoint";
const accumulator = entrypoint({
name: "accumulator",
checkpointer: new MemorySaver()
}, async (input: string) => {
const previous = getPreviousState<number>();
return previous !== undefined ? `${previous } ${input}` : input;
});
const config = {
configurable: {
thread_id: "some_thread"
}
};
await accumulator.invoke("hello", config); // returns "hello"
await accumulator.invoke("world", config); // returns "hello world"import { entrypoint, getPreviousState } from "@langchain/langgraph";
import { MemorySaver } from "@langchain/langgraph-checkpoint";
const myWorkflow = entrypoint({
name: "accumulator",
checkpointer: new MemorySaver()
}, async (num: number) => {
const previous = getPreviousState<number>();
// This will return the previous value to the caller, saving
// 2 * num to the checkpoint, which will be used in the next invocation
// for the `previous` parameter.
return entrypoint.final({
value: previous ?? 0,
save: 2 * num
});
});
const config = {
configurable: {
thread_id: "some_thread"
}
};
await myWorkflow.invoke(3, config); // 0 (previous was undefined)
await myWorkflow.invoke(1, config); // 6 (previous was 3 * 2 from the previous invocation)