Langfuse Via OpenInference With Response Model

Trace a YFinance stock-price agent with a Pydantic output_schema to Langfuse via the OpenInference Agno instrumentor and OTLP HTTP export.

Demonstrates Langfuse tracing for an Agno agent that returns structured output.

langfuse_via_openinference_response_model.py
"""
Langfuse Via OpenInference With Response Model
==============================================

Demonstrates Langfuse tracing for an Agno agent that returns structured output.
"""

import base64
import os
from enum import Enum

from agno.agent import Agent
from agno.models.openai import OpenAIChat
from agno.tools.yfinance import YFinanceTools
from openinference.instrumentation.agno import AgnoInstrumentor
from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import SimpleSpanProcessor
from pydantic import BaseModel, Field

# ---------------------------------------------------------------------------
# Setup
# ---------------------------------------------------------------------------
LANGFUSE_AUTH = base64.b64encode(
    f"{os.getenv('LANGFUSE_PUBLIC_KEY')}:{os.getenv('LANGFUSE_SECRET_KEY')}".encode()
).decode()
os.environ["OTEL_EXPORTER_OTLP_ENDPOINT"] = (
    "https://us.cloud.langfuse.com/api/public/otel"  # US data region
)
# os.environ["OTEL_EXPORTER_OTLP_ENDPOINT"] = "https://cloud.langfuse.com/api/public/otel"  # EU data region
# os.environ["OTEL_EXPORTER_OTLP_ENDPOINT"] = "http://localhost:3000/api/public/otel"  # Local deployment (>= v3.22.0)

os.environ["OTEL_EXPORTER_OTLP_HEADERS"] = f"Authorization=Basic {LANGFUSE_AUTH}"

tracer_provider = TracerProvider()
tracer_provider.add_span_processor(SimpleSpanProcessor(OTLPSpanExporter()))

# Start instrumenting agno
AgnoInstrumentor().instrument(tracer_provider=tracer_provider)


class MarketArea(Enum):
    USA = "USA"
    UK = "UK"
    EU = "EU"
    ASIA = "ASIA"


class StockPrice(BaseModel):
    price: str = Field(description="The price of the stock")
    symbol: str = Field(description="The symbol of the stock")
    date: str = Field(description="Current day")
    area: MarketArea


# ---------------------------------------------------------------------------
# Create Agent
# ---------------------------------------------------------------------------
agent = Agent(
    name="Stock Price Agent",
    model=OpenAIChat(id="gpt-5.2"),
    tools=[YFinanceTools()],
    instructions="You are a stock price agent. You check and return the current price of a stock.",
    output_schema=StockPrice,
)


# ---------------------------------------------------------------------------
# Run Example
# ---------------------------------------------------------------------------
if __name__ == "__main__":
    agent.print_response("What is the current price of Tesla?")

Langfuse export settings

Choose the endpoint for your project's region in the copied source. For current direct OTLP ingestion, replace its header assignment before creating the exporter:

os.environ["OTEL_EXPORTER_OTLP_HEADERS"] = (
    f"Authorization=Basic {LANGFUSE_AUTH},x-langfuse-ingestion-version=4"
)

Without the version header, traces can take up to ten minutes to appear in Langfuse's v4 data model. See Langfuse OpenTelemetry configuration.

Run the Example

Set up your virtual environment

uv venv --python 3.12
source .venv/bin/activate

Install dependencies

uv pip install -U agno openai openinference-instrumentation-agno opentelemetry-exporter-otlp opentelemetry-sdk yfinance

Export environment variables

export LANGFUSE_PUBLIC_KEY="your_langfuse_public_key_here"
export LANGFUSE_SECRET_KEY="your_langfuse_secret_key_here"
export OPENAI_API_KEY="your_openai_api_key_here"

Run the example

Save the code above as langfuse_via_openinference_response_model.py, then run:

python langfuse_via_openinference_response_model.py

Full source: cookbook/observability/langfuse_via_openinference_response_model.py