A agentindex
Comparison

Arize Phoenix vs Pydantic Logfire

A like-for-like, spec-level comparison. Both entries are verified against their docs and repo.

Arize Phoenix

Open-source LLM tracing and eval.

  • + Open source with OTel foundations
  • + Good LLM-as-a-judge evals built in
  • − Elastic license restricts some hosted offerings
  • − Enterprise features in the paid Arize cloud

Pydantic Logfire

Observability from the Pydantic team.

  • + Best-in-class for Pydantic AI users
  • + Clean structured logging
  • − Proprietary platform
  • − Generalist, not LLM-only
Spec Arize Phoenix Pydantic Logfire
Category eval-observability eval-observability
License Elastic-2.0 Proprietary
Open source Yes No
Self-hostable Yes No
MCP support No No
Pricing free freemium
Starting price Self-host free Free tier
Models multi multi
Languages python, typescript python
GitHub stars 10.3k —
Last activity 2026-06-25 —