Arize Phoenix is one of the most popular open-source LLM observability platforms in 2026. If you are evaluating it alongside CortexOps, this article compares them directly on the things that matter for production agent workloads. Short version: Arize Phoenix is the right choice if you are doing notebook-based experimentation, RAG evaluation, or need embeddings analysis. It is well-established with 9,000+ GitHub stars and strong OTel support. CortexOps is the right choice if you ne...