LangGraph

LangGraph compiles a graph. It does not authenticate the HTTP caller. Put require_auth on the route that invokes the graph, and pass the Authdog subject in as state. The graph reads that state. It does not read the Authorization header.

Sample: langgraph/python. Python 3.10+. Package langgraph==1.2.16.

The route is the hook

class State(TypedDict):
    subject: str
    reply: str

def build_graph():
    def respond(state: State) -> dict[str, str]:
        return {"reply": f"subject:{state['subject']}"}

    graph = StateGraph(State)
    graph.add_node("respond", respond)
    graph.add_edge(START, "respond")
    graph.add_edge("respond", END)
    return graph.compile()

authdog = Authdog(public_key=public_key)
compiled = build_graph()

@app.post("/invoke")
async def invoke(user=Depends(authdog.require_auth)):
    result = await compiled.ainvoke(
        {"subject": subject_of(user), "reply": ""}
    )
    return {"reply": result["reply"]}

Authdog comes from authdog.fastapi. require_auth is a FastAPI dependency, so a missing or rejected token never enters invoke. subject_of reads id, then sub, from the userinfo user.

Call graph.invoke or ainvoke only from a route that already depends on require_auth. A second route that invokes the compiled graph directly skips Authdog. This sample has one route.

The caller mints the bearer elsewhere. Use the exchange in Agent frameworks, or the client in the A2A sample. This process does not take AUTHDOG_CLIENT_SECRET.

What you should see

POST /invoke with no token returns 401. The body does not contain subject:.

The same call with Authorization: Bearer <token> that userinfo accepts returns:

{"reply": "subject:<id>"}

pytest checks both: 401 with no token, and subject:agent_1 when userinfo returns that id.

Configure

python -m venv .venv
source .venv/bin/activate
python -m pip install -r requirements-dev.txt
export PK_AUTHDOG=pk_...
uvicorn server:create_app --factory --port 8000

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