How to stream state updates of your graph¶

LangGraph Cloud supports multiple streaming modes. The main ones are:

values: This streaming mode streams back values of the graph. This is the full state of the graph after each node is called.
updates: This streaming mode streams back updates to the graph. This is the update to the state of the graph after each node is called.
messages: This streaming mode streams back messages - both complete messages (at the end of a node) as well as tokens for any messages generated inside a node. This mode is primarily meant for powering chat applications.

This guide covers stream_mode="updates".

First let's set up our client and thread:

PythonJavascript

from langgraph_sdk import get_client

client = get_client(url="whatever-your-deployment-url-is")
# create thread
thread = await client.threads.create()
print(thread)

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

const client = new Client({ apiUrl:"whatever-your-deployment-url-is" });
// create thread
const thread = await client.threads.create();
console.log(thread)

Output:

{'thread_id': '979e3c89-a702-4882-87c2-7a59a250ce16',
 'created_at': '2024-06-21T15:22:07.453100+00:00',
 'updated_at': '2024-06-21T15:22:07.453100+00:00',
 'metadata': {}}

Now we can stream by updates, which outputs updates made to the state by each node after it has executed:

PythonJavascript

input = {
    "messages": [
        {
            "role": "human",
            "content": "what's the weather in la"
        }
    ]
}
async for chunk in client.runs.stream(
    thread["thread_id"],
    "agent",
    input=input,
    stream_mode="updates",
):
    print(f"Receiving new event of type: {chunk.event}...")
    print(chunk.data)
    print("\n\n")

const input = {
  "messages": [
    {
      "role": "human",
      "content": "What's the weather in la",
    }
  ]
}

const streamResponse = client.runs.stream(
  thread["thread_id"],
  "agent",
  {
    input,
    streamMode: "updates"
  }
);
for await (const chunk of streamResponse) {
  console.log(f"Receiving new event of type: {chunk.event}...")
  console.log(chunk.data)
  console.log("\n\n")
}

Output:

Receiving new event of type: metadata...
{'run_id': 'cfc96c16-ed9a-44bd-b5bb-c30e3c0725f0'}



Receiving new event of type: data...
{'agent': {'messages': [{'content': [{'id': 'toolu_0148tMmDK51iLQfG1yaNwRHM', 'input': {'query': 'weather in los angeles'}, 'name': 'tavily_search_results_json', 'type': 'tool_use'}], 'additional_kwargs': {}, 'response_metadata': {}, 'type': 'ai', 'name': None, 'id': 'run-1a9d32b0-7007-4a36-abde-8df812a0ed94', 'example': False, 'tool_calls': [{'name': 'tavily_search_results_json', 'args': {'query': 'weather in los angeles'}, 'id': 'toolu_0148tMmDK51iLQfG1yaNwRHM'}], 'invalid_tool_calls': []}]}}



Receiving new event of type: data...
{'action': {'messages': [{'content': '[{"url": "https://www.weatherapi.com/", "content": "{\'location\': {\'name\': \'Los Angeles\', \'region\': \'California\', \'country\': \'United States of America\', \'lat\': 34.05, \'lon\': -118.24, \'tz_id\': \'America/Los_Angeles\', \'localtime_epoch\': 1716062239, \'localtime\': \'2024-05-18 12:57\'}, \'current\': {\'last_updated_epoch\': 1716061500, \'last_updated\': \'2024-05-18 12:45\', \'temp_c\': 18.9, \'temp_f\': 66.0, \'is_day\': 1, \'condition\': {\'text\': \'Overcast\', \'icon\': \'//cdn.weatherapi.com/weather/64x64/day/122.png\', \'code\': 1009}, \'wind_mph\': 2.2, \'wind_kph\': 3.6, \'wind_degree\': 10, \'wind_dir\': \'N\', \'pressure_mb\': 1017.0, \'pressure_in\': 30.02, \'precip_mm\': 0.0, \'precip_in\': 0.0, \'humidity\': 65, \'cloud\': 100, \'feelslike_c\': 18.9, \'feelslike_f\': 66.0, \'vis_km\': 16.0, \'vis_miles\': 9.0, \'uv\': 6.0, \'gust_mph\': 7.5, \'gust_kph\': 12.0}}"}]', 'additional_kwargs': {}, 'response_metadata': {}, 'type': 'tool', 'name': 'tavily_search_results_json', 'id': 'a36e8cd1-0e96-4417-9c15-f10a945d2b42', 'tool_call_id': 'toolu_0148tMmDK51iLQfG1yaNwRHM'}]}}



Receiving new event of type: data...
{'agent': {'messages': [{'content': 'The weather in Los Angeles is currently overcast with a temperature of around 66°F (18.9°C). There are light winds from the north at around 2-3 mph. The humidity is 65% and visibility is good at 9 miles. Overall, mild spring weather conditions in LA.', 'additional_kwargs': {}, 'response_metadata': {}, 'type': 'ai', 'name': None, 'id': 'run-d5c1c2f0-b12d-41ce-990b-f36570e7483d', 'example': False, 'tool_calls': [], 'invalid_tool_calls': []}]}}



Receiving new event of type: end...
None

How to stream state updates of your graph¶

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