Arize Phoenix

Open-source LLM observability. Self-hostable, OpenTelemetry-native.

Tracing, evals, prompt management, and dataset tooling for LLM apps — self-host on your own infra or use Langfuse Cloud. The open-source default when you want full ownership of your observability stack.

LangChain's hosted observability + eval platform.

Tracing, dataset management, eval orchestration, and prompt playground from the LangChain team. Pairs naturally if LangChain or LangGraph already runs in your stack, but works standalone via SDKs.

Drop-in LLM proxy with logging, caching, and cost tracking.

One-line integration — change your OpenAI/Anthropic base URL and get a dashboard with every prompt, response, latency, and dollar tracked. Adds caching and rate-limit handling without code changes.

Open-source LLM evaluation, tracing, and monitoring.

Open-source platform from Comet for debugging and evaluating LLM and agent apps: full tracing of calls, tools, and agent steps, LLM-as-a-judge and heuristic evals, prompt management, and production dashboards. Self-host via Docker or Kubernetes, or use Comet's hosted cloud.