LangGraph Python SDK

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Quick Install

uv add langgraph-sdk

🤔 What is this?

This library provides the Python SDK for interacting with the LangGraph API. Use it to connect to a running LangGraph API server, manage assistants and threads, and stream runs from Python applications.

You will need a running LangGraph API server. If you're running a server locally using langgraph-cli, the SDK will automatically point at http://localhost:8123; otherwise, specify the server URL when creating a client.

📖 Documentation

For full documentation, see the API reference. For conceptual guides and tutorials, see the LangGraph Docs.

Quick Start

from langgraph_sdk import get_client

# If you're using a remote server, initialize the client with `get_client(url=REMOTE_URL)`
client = get_client()

# List all assistants
assistants = await client.assistants.search()

# We auto-create an assistant for each graph you register in config.
agent = assistants[0]

# Start a new thread
thread = await client.threads.create()

# Start a streaming run
input = {"messages": [{"role": "human", "content": "what's the weather in la"}]}
async for chunk in client.runs.stream(
    thread["thread_id"], agent["assistant_id"], input=input
):
    print(chunk)

Known Limitations

WebSocket transport requires websockets>=14 and is only available on the async client (AsyncThreadStream). The sync client (SyncThreadStream) uses SSE exclusively.
thread.extensions[name] opens a new subscription each time the same name is accessed. Assign the projection to a variable and reuse it within a single session rather than re-indexing across multiple iterations.
Sync streaming drives the lifecycle watcher in a background thread. Long-lived sync sessions will hold that thread open until the context manager exits.
Reconnect attempts are limited to 5 by default for both the shared SSE fan-out and the lifecycle watcher. Persistent network partitions will surface as RuntimeError on in-flight projections.

Thread-Centric Streaming (v3)

client.threads.stream() returns a context manager that owns the SSE session for one thread. Typed projections — values snapshots, message streams, tool calls, custom events — all share the same underlying connection.

from langgraph_sdk import get_client
import asyncio

client = get_client()

async with client.threads.stream(
    thread_id="my-thread",
    assistant_id="agent",
) as thread:
    await thread.run.start(input={"messages": [{"role": "user", "content": "hi"}]})

    # Start all consumers concurrently so they share one SSE connection.
    async def get_messages():
        return [s async for s in thread.messages]

    async def get_tool_calls():
        return [c async for c in thread.tool_calls]

    messages, tool_calls = await asyncio.gather(get_messages(), get_tool_calls())

    for stream in messages:
        print(await stream.text)  # accumulated text

    final = await thread.output  # terminal state values

📕 Releases & Versioning

See our Releases and Versioning policies.

💁 Contributing

As an open-source project in a rapidly developing field, we are extremely open to contributions, whether it be in the form of a new feature, improved infrastructure, or better documentation.

For detailed information on how to contribute, see the Contributing Guide.

Release files for langgraph-sdk 0.4.5

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for langgraph-sdk 0.4.5
File	Size	Uploaded
langgraph_sdk-0.4.5.tar.gz	349.8 kB	Sep 21, 2026	Details

Built distribution (wheel)

Table of built distributions (wheels) for langgraph-sdk 0.4.5
File	Interpreter	ABI	Platform	Reset
langgraph_sdk-0.4.5-py3-none-any.whl 162.3 kB Sep 21, 2026	Python 3	none	any	Details

Total release size: 512.1 kB

Release files / langgraph_sdk-0.4.5.tar.gz

Download URL	langgraph_sdk-0.4.5.tar.gz
Size	349.8 kB
Tags	Source
SHA-256 checksum How to use checksums	`d49a98a2ee8e0c494b101a7caf8061c8b4b94d3ee5ada0ea2dbe50903a5487b1`
BLAKE2b-256 checksum How to use checksums	`e89c7ff305b366ce986052a27dc5946839bef2823b3567664cbad22e294dff5a`
Upload date	Sep 21, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	Yes
Uploaded via	`twine/7.0.0 CPython/3.13.14`

Release files / langgraph_sdk-0.4.5-py3-none-any.whl

Download URL	langgraph_sdk-0.4.5-py3-none-any.whl
Size	162.3 kB
Tags	Python 3
SHA-256 checksum How to use checksums	`e03ef033a20d21288af496e9b6c08ae3afcc1b58dc5abcd37575bfd1a93045de`
BLAKE2b-256 checksum How to use checksums	`49a971a6499f3481bc00bf4f42a17cb81caf19a02fce762db356626d7214e2c2`
Upload date	Sep 21, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	Yes
Uploaded via	`twine/7.0.0 CPython/3.13.14`