Top Open Source LLM Observability & Evaluation Tools in 2026
A curated collection of the 13 best free and open-source LLM Observability & Evaluation tools in 2026. Compare features, GitHub stars, tech stacks, and self-hosted software.
OpenLLMetry
Open-source observability for LLMs with OpenTelemetry
Stars7,402Last commit27d agoLicenseApache-2.0Spanlens
Open source LLM observability & monitoring
Stars12Last commit16d agoLicenseMITLaminar
Open-source AI agent observability platform
Stars3,199Last commit12d agoLicenseApache-2.0
OpenLIT
Open source AI observability and harness platform
Stars2,719Last commit11d agoLicenseApache-2.0
mlop
Open source MLOps experiment tracking platform
Stars392Last commit6mo agoLicenseApache-2.0
Latitude
Open-source AI agent observability platform
Stars4,603Last commit10d agoLicenseMITLangWatch
AI agent testing and evaluation platform
Stars3,514Last commit10d agoLicenseApache-2.0
Langfuse
Open source AI agent observability platform
Stars33,799Last commit10d agoLicenseOpen SourceHelicone
Open-source LLM observability and monitoring platform
Stars6,106Last commit12d agoLicenseApache-2.0Grepture
Open-source AI gateway with tracing and PII protection
Stars7Last commit12d agoLicenseAGPL-3.0
Continue
Open-source coding agent for developers
Stars35,644Last commit1mo agoLicenseApache-2.0
Arize Phoenix
Open-source AI agent development platform
Stars11,212Last commit10d agoLicenseOpen Source
Agenta
Open-source workspace for building AI agents
Stars4,557Last commit11d agoLicenseOpen Source
