7 LLM eval tools compared: promptfoo, DeepEval, Ragas, Langfuse, Phoenix, LangSmith, Braintrust
ComfortableAbroad357 · reddit · 2026-10-29
The author splits mainstream LLM eval tooling into libraries you run in code and platforms that store traces and experiments, noting many teams use one of each:
- promptfoo: prompt regression tests and red-teaming from YAML + CLI, results stored locally
- DeepEval: evals written as pytest-style tests, runs in CI
- Ragas: scoring retrieval quality and grounded answers
- Langfuse: open-source tracing plus LLM-as-judge scoring, self-hostable
- Arize Phoenix: OpenTelemetry-based traces and evals, runs locally
- LangSmith: natural fit for LangChain/LangGraph users, works standalone too
- Braintrust: managed platform built around datasets and experiment comparisons, commercial with a free tier
Key advice: before trusting any automated metric, start with a few dozen hand-labelled examples from real traffic.
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