For the complete documentation index, see llms.txt. Markdown versions of all docs pages are available by appending .md to any docs URL.

Integrate agentgateway with LangSmith for LLM debugging and monitoring

LangSmith is LangChain’s platform for debugging, testing, evaluating, and monitoring LLM applications.

Features

• Trace logging - Detailed request/response logging
• Debugging - Step-through debugging of LLM calls
• Evaluation - Automated testing and evaluation
• Monitoring - Production monitoring and alerting
• Datasets - Build and manage evaluation datasets

Setup

1. Sign up at smith.langchain.com
2. Create a project and get your API key

Configuration

LangSmith accepts OpenTelemetry traces directly. Configure agentgateway to export traces directly to LangSmith:

# yaml-language-server: $schema=https://agentgateway.dev/schema/config
frontendPolicies:
  tracing:
    host: api.smith.langchain.com:443
    protocol: http
    path: /otel/v1/traces
    randomSampling: true
    policies:
      backendTLS: {}
      requestHeaderModifier:
        set:
          x-api-key: "${LANGSMITH_API_KEY}"

gateways:
  default:
    port: 3000
routes:
- backends:
  - ai:
      name: openai
      provider:
        openAI:
          model: gpt-4o-mini
  policies:
    backendAuth:
      key: "$OPENAI_API_KEY"

Authentication

Set the API key that the tracing policy sends in the x-api-key header. The policy selects OTLP over HTTP, enables backend TLS, and uses the full trace ingestion path from the LangSmith OpenTelemetry guide.

export LANGSMITH_API_KEY="<your-langsmith-api-key>"

Docker Compose example

Agentgateway exports traces directly to LangSmith without needing an OTel Collector:

version: '3'
services:
  agentgateway:
    image: cr.agentgateway.dev/agentgateway:latest
    ports:
      - "3000:3000"
    volumes:
      - ./config.yaml:/config.yaml:ro
    command: ["-f", "/config.yaml"]
    environment:
      - LANGSMITH_API_KEY=${LANGSMITH_API_KEY}
      - OPENAI_API_KEY=${OPENAI_API_KEY}

Learn more

• LangSmith Documentation
• OpenTelemetry Integration