LangGraph OpenAI Serve
Serve LangGraph graphs through an OpenAI-compatible /v1 API so existing
OpenAI SDKs, Chainlit, Open WebUI, and similar clients can call them without a
project-specific protocol.
Install
Use uv for project dependency management:
uv add langgraph-openai-serve
The equivalent pip command is:
pip install langgraph-openai-serve
For deployments that use PostgreSQL for LangGraph checkpoints, Store data, or cross-worker interrupt coordination, install the optional integration:
uv add "langgraph-openai-serve[postgres]"
For built-in Langfuse tracing, install the tracing integration:
uv add "langgraph-openai-serve[tracing]"
Set LGOS_ENABLE_LANGFUSE=true together with LANGFUSE_PUBLIC_KEY and
LANGFUSE_SECRET_KEY. LGOS creates the callback lazily on the first graph run;
importing the package never initializes Langfuse.
The package contains the OpenAI-compatible server integration, not a built-in
LLM graph. Applications register their own graphs. The demo/ checkout keeps
each deployable application in an independent uv project with its own lockfile.
Its lgos-rag example indexes a small corpus packaged with the demo API, so the
entire directory can be copied and run without files from this repository.
Repository tasks require Bash and Just 1.58.0 or newer.
Run just for package recipes and just demo/ for independent demo workflows.
Use just --usage <recipe> to see a recipe's options and defaults.
Quick Demo
From this repository, prepare the demo environment and PostgreSQL:
cp demo/.env.example demo/.env
just demo/up lgos-db --wait
just demo/api --editable
Then call the demo with the OpenAI Python client:
from openai import OpenAI
client = OpenAI(base_url="http://localhost:3004/v1", api_key="DUMMY")
response = client.responses.create(
model="custom-input-output-context",
input="Show me custom schemas.",
store=False,
user="demo-user",
)
print(response.output_text)
Existing Chat Completions clients can call the same simple graph through the same base URL:
completion = client.chat.completions.create(
model="custom-input-output-context",
messages=[{"role": "user", "content": "Show me custom schemas."}],
user="demo-user",
)
print(completion.choices[0].message.content)
Use Responses for new clients and advanced workflow features. The Chat example is the compatibility path for existing Chat-only clients.
Use curl http://localhost:3004/v1/models only as a diagnostic to inspect the
registered demo graph names.
just demo/api --editable overlays this checkout without changing
the self-contained demo project or its lockfile. The demo publishes independent
API and Chainlit images and uses official images for third-party services such
as Open WebUI. See the demo Docker Compose guide.
The complete Compose demo lets one OPENAI_GATEWAY_TYPE=litellm|bifrost
setting place either gateway in front of both maintained UI clients. Chainlit
and Open WebUI use normal managed/native Responses and Files routes. Metadata
comes from LiteLLM's native /model/info after model sync,
or Bifrost's catalog-detail pass-through. Neither UI connects directly to LGOS. The
PostgreSQL-persistent Chainlit client uses a shared mock login by default, with
OIDC login available as an opt-in mode. See the
Chainlit demo.
Use In FastAPI
from fastapi import FastAPI
from langgraph_openai_serve import GraphConfig, GraphRegistry, LanggraphOpenaiServe
from your_graphs import my_graph
app = FastAPI()
graphs = GraphRegistry(
registry={
"my-graph": GraphConfig(
graph=my_graph,
description="Answer questions with my LangGraph workflow.",
streamable_node_names=["generate"],
)
}
)
LanggraphOpenaiServe(app=app, graphs=graphs).bind_openai_api()
The default base URL is {host}/v1. Registered graph names become OpenAI model
values.
LGOS accepts native Responses input_file parts with opaque file_id values,
but does not own file upload or storage. Deploy one Files API for the graph
services that share a file namespace, or use a gateway-native Files provider.
The standalone S3-backed demo Files API is a small
reference deployment. Chat Completions remains available for direct
compatibility clients; the maintained demo UIs use Responses exclusively. See
Choose Responses or Chat Completions
for a feature-by-feature comparison.
Docs
- Documentation home: docs/index.md
- Package getting started: docs/getting-started.md
- Architecture and state ownership: docs/explanation/architecture.md
- Self-contained demo stack: docs/demo/index.md
- Self-hosted service references: docs/demo/self-hosted.md
- Runnable demo API: docs/demo/api.md
- Demo graph catalog: docs/demo/graphs/
- OpenAI clients: docs/tutorials/openai-clients.md
- Custom graphs: docs/tutorials/custom-graphs.md
- LangGraph runtime settings: docs/how-to-guides/langgraph-runtime-settings.md
- OpenAI-compatible proxies: docs/how-to-guides/openai-proxies.md
- API and configuration: docs/reference.md
- Compatibility contract: docs/explanation/openai-compatibility.md
1 maintainer
Release files for langgraph_openai_serve 0.20.0
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