spanlens/Spanlens

Overview

Open source LLM observability and monitoring tool. Acts as a drop-in proxy for OpenAI, Anthropic, and Gemini, logging requests, tracking costs, and tracing agents. Self-hosted via a single Docker command, licensed under MIT.

Best for

Best for
Developers who want lightweight, self-hosted LLM observability without vendor lock-in.

Use cases

• Monitor LLM API usage and costs
• Trace multi-step agent executions
• Log and inspect requests for debugging

How to use

Install

npx @spanlens/cli init

Tools exposed

• Self-hostable

Tested with

Claude Desktop, Cursor, Continue, ChatGPT

Notes

Open source LLM observability and monitoring tool. Acts as a drop-in proxy for OpenAI, Anthropic, and Gemini, logging requests, tracking costs, and tracing agents. Self-hosted via a single Docker command, licensed under MIT.

13 stars on GitHub. Last updated 2026-08-31. Licensed MIT.

Use cases

• Monitor LLM API usage and costs
• Trace multi-step agent executions
• Log and inspect requests for debugging

Pros

• Drop-in proxy requires no code changes
• Self-hosted with one Docker command
• MIT licensed, open source

Cons

• Low adoption (13 GitHub stars)
• Requires self-hosting and maintenance
• Adds a proxy layer, potential latency

Indexed from awesome-mcp-servers-punkpeye and enriched against its public facts.