LangSmith
Free tierThe end-to-end platform for building, testing, and monitoring LLM-powered applications
Free tier available·Technical·Powered by LangChain (model-agnostic)·API available
Key strengths
Deep LangChain & LangGraph integration for zero-config tracingEnd-to-end LLM observability with detailed trace visualizationBuilt-in evaluation and dataset management for regression testingPrompt management with versioning and A/B testing supportProduction monitoring with feedback collection and alerting
Free tier + paid plans
San Francisco, USA
Founded 2023
Self-hostable
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- Distributed agent tracing — Automatically capture nested spans across multi-step LangGraph agents, tool invocations, and sub-chains with parent-child trace relationships.
- LLM-as-a-judge evaluation — Define evaluators that use an LLM (e.g., GPT-4o) to score outputs on criteria like correctness, helpfulness, and toxicity against a curated dataset.
- CI/CD quality gates — Integrate
evaluate()runs into GitHub Actions or other CI systems to block merges when evaluation scores drop below defined thresholds. - Custom feedback ingestion — Use the REST API or SDK to programmatically attach structured feedback (scores, corrections, labels) from end-user interactions back to production traces.
- Prompt hub & versioning — Pull versioned prompts from LangChain Hub directly in code (
hub.pull("my-org/my-prompt:abc123")) to decouple prompt iteration from code deploys. - Self-hosted observability — Deploy LangSmith on-premise via Helm/Kubernetes to keep all trace data within your own VPC, satisfying data-residency requirements.