How do I set host to something that isn't localhost

[nmvega]

Hello Friends:

While looking at the LangChain University Langgraph course (specifically module-1/studio/), I'm running into trouble using langgraph dev [...] on a remote self-host server. I use a Fedora Linux headless server (instead of my laptop), to self-host my Agentic Gen AI ecosystem of services. As shown below, I'm trying to do the same with the langgraph(1) CLI.

The below demon starts fine, and I can even visit its main LangSmith WebUI with no problem. But within several seconds, I get the pictured error message. When I visit the API-URL (http://192.168.0.12:2024), indeed the browser says: "not found". Notice that the error is not "The site can't be reached", because it is reachable; but rather "not found" (and the rest of the page is blank).

Meanwhile, the API document site -- http://192.168.0.12:2024/docs -- does render correctly.

Any ideas? Perhaps the courseware is causing this error?

Thank you in advance!

(LG_pyvenv.d) nmvega@ollama$ langgraph dev --no-browser --host 192.168.0.12 --port 2024  
INFO:langgraph_api.cli:

        Welcome to

╦  ┌─┐┌┐┌┌─┐╔═╗┬─┐┌─┐┌─┐┬ ┬
║  ├─┤││││ ┬║ ╦├┬┘├─┤├─┘├─┤
╩═╝┴ ┴┘└┘└─┘╚═╝┴└─┴ ┴┴  ┴ ┴

- 🚀 API: http://192.168.0.12:2024 <---------------- PROBLEM
- 🎨 Studio UI: https://smith.langchain.com/studio/?baseUrl=http://192.168.0.12:2024
- 📚 API Docs: http://192.168.0.12:2024/docs

This in-memory server is designed for development and testing.
For production use, please use LangGraph Cloud.
[ ... snip ... ]

• More information:

(LG_pyvenv.d) nmvega@ollama$ uv pip list | grep lang
langchain                   0.3.24
langchain-community         0.3.23
langchain-core              0.3.56
langchain-openai            0.3.14
langchain-text-splitters    0.3.8
langgraph                   0.3.34
langgraph-api               0.1.20
langgraph-checkpoint        2.0.25
langgraph-checkpoint-sqlite 2.0.6
langgraph-cli               0.2.7
langgraph-prebuilt          0.1.8
langgraph-runtime-inmem     0.0.7
langgraph-sdk               0.1.63
langsmith                   0.3.38

(LG_pyvenv.d) nmvega@ollama$ python -V
Python 3.13.2

[hinthornw]

Hello! Why do you need to set an arbitrary IP address as the host?

You're running the server locally, so doing anything beyond localhost (127.0.0.1 or 0.0.0.0) wouldn't really be expected to work (since some studio code runs remotely)

[nmvega]

It's not an atribrary IP Address: That IP Address, is a server on my Local LAN, that host my RTX 4090 and RTX 5090 GPUs, my AI Stacks, my Podman/Docker Images (from ollama to Langfuse to Open WebUI, and so on). I use it as a headless "cloud server", which I access from my laptop or whatever else. All of the example services mentioned work perfectly.

Also, the below suggests that it would work (0.0.0.0 is for all interfaces on a device; 127.0.0.1 is for computers where access is via its console; and anything else should be accessible anywhere on the LAN where, if desired, one can limit access to just one interface - 192.168.0.12 in my case).

sage: langgraph dev [OPTIONS]

  🏃‍♀️‍➡️ Run LangGraph API server in development mode with hot reloading and
  debugging support

Options:
  --tunnel                     Expose the local server via a public tunnel (in
                               this case, Cloudflare) for remote frontend
                               access. This avoids issues with browsers or
                               networks blocking localhost connections.
  --allow-blocking             Don't raise errors for synchronous I/O blocking
                               operations in your code.
  --studio-url TEXT            URL of the LangGraph Studio instance to connect
                               to. Defaults to https://smith.langchain.com
  --wait-for-client            Wait for a debugger client to connect to the
                               debug port before starting the server
  --debug-port INTEGER         Enable remote debugging by listening on
                               specified port. Requires debugpy to be
                               installed
  --no-browser                 Skip automatically opening the browser when the
                               server starts
  --n-jobs-per-worker INTEGER  Maximum number of concurrent jobs each worker
                               process can handle. Default: 10
  --config PATH                Path to configuration file declaring
                               dependencies, graphs and environment variables
  --no-reload                  Disable automatic reloading when code changes
                               are detected
  --port INTEGER               Port number to bind the development server to.
                               Example: langgraph dev --port 8000
  --host TEXT                  Network interface to bind the development
                               server to. Default 127.0.0.1 is recommended for
                               security. Only use 0.0.0.0 in trusted networks
  --help                       Show this message and exit.

[nmvega]

@hinthornw

More helpful notes for others similarly wanting a remote networked / cloud-like experience.

On a laptop or PC (where one is required to be at the console):

• This succeeds.................: user$ langgraph dev --no-browser --host 127.0.0.1 --port 2024
• This fails (same error)...: user$ langgraph dev --no-browser --host 0.0.0.0 --port 2024

I didn't expect 0.0.0.0 to also fail on the laptop since it's referenced in the help page, but it does (error).

PS: FWIW, and not knowing exactly what its description meant, I also tried appending user$ langgraph dev --no-browser --host {0.0.0.0 | 192.168.0.12} --port 2024 --debug-port=2025, but no luck either way.

I suspect something is missing in the implementation. I'll use the laptop, but really wished this worked remotely.

Thank you! =:)

[hinthornw]

Got it thank you for the context! I was a bit hasty in my response, so appreciate your patience. We've tested it remotely but not in binding to a specific IP address. Underneath the hood, the in-memory dev server basically proxies through to uvicorn.run and passes the host parameter in there.

Re: "0.0.0.0." -> That one is bcs ther'es a difference between the host/port the server binds to locally and the host/port that is accessible from your browser.

If you bind your local server to http://0.0.0.0:2024, for instance, you could still access it via the url https://smith.langchain.com/studio/?baseUrl=http://127.0.0.1:2024 but you cannot access it from https://smith.langchain.com/studio/?baseUrl=http://127.0.0.1:2024

[nmvega]

Ah okay, that makes sense. Things get hairy whenever proxying anything. (Believe me, I know 😁).

Thank you for the clarifications. I'll just work off my laptop for the LangGraph university courseware. No big deal.

Thank you!

[hinthornw]

We do also have a --tunnel argument that may potentially work for your case