Spanlens

Spanlens, an MIT-licensed LLM observability platform, offers a drop-in replacement for OpenAI, Anthropic, and Gemini SDKs, providing full visibility into LLM requests without agents or infrastructure setup. It supports multiple providers and frameworks, is fully self-hostable, and offers a free self-hosted option with no usage cap, positioning itself as a LangSmith alternative with flat monthly pricing.

Get 20% off with code LAUNCH20 Last 30 days Last commit Repository age License Self-hosted Repository Spanlens is an MIT-licensed LLM observability platform that gives you full visibility into every request your app makes to OpenAI, Anthropic, or Gemini. It works as a drop-in replacement for the provider SDK, so you swap one import and start seeing data immediately. No agents to run, no infrastructure to wire up. It's built for teams shipping LLM-powered products who need to answer real questions fast: why did the bill spike, which agent step is slow, did the new prompt actually improve quality? Core capabilities: Spanlens supports OpenAI, Anthropic, Google Gemini, Mistral, Azure, Bedrock, and Vertex, plus framework integrations for LangChain, LlamaIndex, Vercel AI SDK, and LangGraph. It also ingests OpenTelemetry spans over OTLP/HTTP. For teams that can't send prompt data to a third party, it's fully self-hostable. Prompts and completions stay inside your own network. Data can be exported as JSON, CSV, or Parquet, or streamed to S3 or BigQuery. If you're evaluating LangSmith alternatives /alternatives/langsmith , Spanlens covers similar ground with a flat monthly pricing model rather than per-seat fees, and a free self-hosted option that has no usage cap. Last 30 days Last commit Repository age License Self-hosted Repository Every Sunday we deconstruct one proprietary app and pick the best open source alternatives worth switching to. Stars Last commit License Stars Last commit License Stars Last commit License Stars Last commit License Compare with Stars Stars Stars Stars Stars Stars Last commit License Compare with Last commit License Compare with Last commit License Compare with Last commit License Compare with Last commit License Compare with Last commit License Compare with