Open-source LLM and agent observability and evaluation toolkit.
Phoenix, from Arize AI, is an open-source observability and evaluation library for LLM and agent applications, built on OpenTelemetry with tracing, evals, and experiment tracking that run locally or self-hosted. The commercial Arize AX platform adds hosted, enterprise-scale monitoring.
Phoenix is free and open-source (local-first, self-hosted). Arize AX hosted platform: Free tier, AX Pro $50/month, Enterprise custom.
pricing model, pricing details · as of 2026-11-03