@langchain/langgraph-sdk

@langchain/langgraph-sdk

The JavaScript / TypeScript SDK for talking to a LangGraph API server. Use it to create and manage assistants, threads, runs, cron schedules, and the KV store — and, most importantly, to stream graph executions in real time.

Full documentation

Install

pnpm add @langchain/langgraph-sdk @langchain/core
# or: npm install @langchain/langgraph-sdk @langchain/core
# or: yarn add @langchain/langgraph-sdk @langchain/core

Quick start

import { Client } from "@langchain/langgraph-sdk";

const client = new Client({ apiUrl: "http://localhost:2024" });

// Open a thread-centric stream (the recommended way to stream).
const thread = client.threads.stream({ assistantId: "my-agent" });

await thread.run.start({
  input: { messages: [{ role: "user", content: "hello" }] },
});

for await (const message of thread.messages) {
  for await (const token of message.text) {
    process.stdout.write(token);
  }
}

console.log(await thread.output);
await thread.close();

With no apiUrl, the SDK points at http://localhost:2024 (the default langgraph dev URL).

What's in the SDK

Sub-client	Purpose	Docs
client.threads	Create threads, manage state, and stream runs.	Threads · Streaming
client.assistants	CRUD for assistants (schemas, graphs, versions).	Assistants
client.runs	Trigger / join / cancel runs without streaming.	Runs (legacy)
client.crons	Schedule recurring runs.	Crons
client.store	Namespaced KV + semantic store.	Store

Streaming

client.threads.stream(...) returns a ThreadStream with typed, lazy projections for every aspect of a run:

• thread.messages / thread.toolCalls — assembled chat output.
• thread.values / thread.output — graph state and final answer.
• thread.interrupts / thread.interrupted — human-in-the-loop.
• thread.subgraphs / thread.subagents — nested / deep-agent work.
• thread.extensions.<name> — typed custom server projections.
• thread.audio / thread.images / thread.video / thread.files — media.

Deprecated. The generator-based streaming APIs on client.runs.* (stream, joinStream) and client.threads.joinStream are preserved for backwards compatibility only. New code should use client.threads.stream(...). See Runs (legacy) for migration guidance.

Transports

Streaming defaults to Server-Sent Events (SSE) over HTTP. You can switch to WebSocket per-call or globally, or plug in a custom AgentServerAdapter:

const thread = client.threads.stream({
  assistantId: "my-agent",
  transport: "websocket",
});

See Transports for full details.

Framework adapters

If you're building a UI, use the framework-specific packages that wrap this SDK:

• @langchain/langgraph-sdk/react
• @langchain/langgraph-sdk/vue
• @langchain/langgraph-sdk/svelte
• @langchain/langgraph-sdk/angular

Use the SDK directly when you need low-level control, run it from a non-browser environment (Node.js server, edge workers, scripts), or integrate into a framework that does not yet have a first-party adapter.

Architecture

The client code is organized into sub-client modules under src/client/:

Path	Module
client/assistants/	AssistantsClient
client/threads/	ThreadsClient (includes the v2 stream(...) primitive)
client/runs/	RunsClient (legacy streaming + CRUD)
client/crons/	CronsClient
client/store/	StoreClient
client/stream/	ThreadStream, assemblers, transports
client/base.ts	BaseClient, shared config & helpers
client/index.ts	Main Client class & re-exports

Change log

See CHANGELOG.md.