LangSmith

LangSmith is a hosted platform from the LangChain team that provides observability, tracing and evaluation for LLM applications. It captures detailed traces of chains, tools and prompts, enabling teams to debug and measure model behavior, track performance regressions and manage evaluation data sets. LangSmith is a proprietary SaaS with limited support for non-LangChain workflows, making it most appealing to teams already invested in that ecosystem. Its integrated support for prompt evaluation and experimentation is notably more polished than open-source alternatives like Langfuse.