LangSmith
langchain.com · Observability
LangChain's platform for tracing, evaluating and monitoring LLM apps and agents, framework agnostic.
LangSmith is one of 10 observability tools on TrueIQ. See all observability tools or how we check facts.
Freemium
// guides
Guides that cover LangSmith
How to Use LangSmith with LangGraph (2026)
How to use LangSmith with LangGraph: set four environment variables, read node traces and threads, then score your graph and single nodes on a dataset.
Is LangSmith API Free? Keys, Limits and Costs
Is LangSmith API free? Yes: API keys and the REST API cost nothing, and the Developer plan covers 5,000 traces a month. See key types, limits and overage costs.
Is Langfuse Free for Commercial Use? (2026)
Is Langfuse free for commercial use? Yes: the MIT core can be self hosted in paid products at no cost. See what needs a license key and when the cloud bills.
Datadog LLM Observability vs Langfuse (2026)
Datadog LLM Observability vs Langfuse: how each bills (LLM spans vs units), retention, self hosting, evals and setup, with worked cost examples for 2026.
AI Agent Observability: What It Is and Top Tools
AI agent observability explained: trace tool loops, permissions and memory, the six PAI telemetry gaps, and which tools fit, from Langfuse to Datadog.
Best LLM Observability Tools in 2026, Compared
The best LLM observability tools in 2026 compared: Langfuse, LangSmith, Phoenix, Opik, Weave and more, with licenses, self hosting and who now owns what.
// related
LangSmith alternatives and related tools
Langfuselangfuse.comOpen source LLM engineering platform (MIT core) for tracing, prompt management, datasets and evals, free to self host. Owned by ClickHouse since January 2026.ObservabilityOpen source★ 36.6k
Laminarlaminar.shOpen source observability platform for AI agents with tracing, evaluations and browser session replays.ObservabilityOpen source★ 3.5k
Opikcomet.comComet's open source platform for logging, evaluating and monitoring LLM apps, RAG systems and agents.ObservabilityOpen source★ 23k
Arize Phoenixarize.comFree, self hostable tracing and evaluation tool built on OpenTelemetry, source available under the Elastic License 2.0. Arize became part of Dynatrace in October 2026.ObservabilityFree★ 12k
W&B Weavewandb.aiWeights & Biases toolkit for tracing, evaluating and iterating on LLM applications.ObservabilityFreemium★ 1.1k
Datadog Agent Observabilitydatadoghq.comDatadog's hosted tracing and evaluation product for LLM apps and agents (formerly LLM Observability), billed per LLM call and linked to Datadog APM and infrastructure data.ObservabilityFreemium