Researched and Edited by Rajat Gupta
Last updated: May 26, 2026 · How we review
LLM Observability & Evaluation Software overview
Spotsaas tracks 5 products in LLM Observability & Evaluation Software, ranked by SpotScore — a blend of feature coverage, verified review ratings, and value. Most buyers here are Engineers debugging why a RAG pipeline returns poor answers.
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Editor's Summary · LLM Observability & Evaluation Software
These tools answer two different questions and most teams need both. Tracing tells you what your application did — which prompts ran, what the retriever returned, where latency and cost went. Evaluation tells you whether the output was any good. LangSmith, Langfuse, Helicone and Traceloop lead on the first; Confident AI, Patronus, TruLens and Arize Phoenix lead on the second.
Self-hosting is the fastest way to shorten the list. Prompts and completions routinely contain customer data, and many teams cannot send them to a hosted service. Langfuse, Phoenix, Opik, Lunary, Athina and LangWatch all run in your own environment.
If you already run an observability stack, Traceloop's OpenLLMetry sends traces into Datadog, Grafana or Honeycomb rather than asking you to adopt another dashboard.
Portkey is the odd one out and worth knowing about: it sits in the request path as a gateway, so it adds routing, fallback and caching alongside observability, and captures traces without any application instrumentation.
For agents specifically, single-response evaluation misses the failure mode that matters — an agent can answer every individual turn well and still fail the conversation. Maxim and LangWatch test at the scenario level.
Quick picks for LLM Observability & Evaluation Software
- Best open-source all-rounder — Langfuse
- Best for RAG evaluation — Arize Phoenix
- Best gateway plus observability — Portkey
Who gets the most from LLM Observability & Evaluation Software
- 1Engineers debugging why a RAG pipeline returns poor answers
- 2Teams gating deployments on evaluation results in CI
- 3Platform owners tracking model cost and latency across providers
How to choose LLM Observability & Evaluation Software
Separate tracing from evaluation before shortlisting, because tools lead on one and follow on the other. If your prompts carry customer data, filter for self-hosting first and accept the shorter list. If you already run Datadog or Grafana, an OpenTelemetry-native tool avoids a second pane of glass. And if you are building agents rather than single-turn features, insist on scenario-level testing — per-response scoring will look healthy while the conversation fails.
Showing 1-5 out of 5
9.4
SpotScore
Langfuse
Open-source LLM observability platform for tracing, evaluation, and prompt management
Best for: SMB teams
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What is Langfuse?
Langfuse is an open-source LLM engineering platform for tracing, evaluation, prompt management, and metrics. It provides detailed traces of LLM application executions — capturing every LLM call, tool use, retrieval step, and agent action — and links traces to user sessions for production ...
Read more about LangfuseStarts from Freefree, also offers free forever plan
9.2
SpotScore
Helicone
Open-source LLM proxy with automatic logging, cost tracking, and caching in two minutes
Best for: SMB teams
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What is Helicone?
Helicone is an open-source LLM observability platform that works as a proxy — developers route their LLM API calls through Helicone's gateway with a single URL change, and it automatically logs every request, tracks cost and latency, enables prompt caching, and provides rate limiting. ...
Read more about HeliconeStarts from Freefree, also offers free forever plan
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9.0
SpotScore
LangSmith
LLM observability and evaluation platform for tracing, testing, and monitoring AI applications
Best for: SMB teams
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What is LangSmith?
LangSmith is the LLMOps observability and evaluation platform built by LangChain for teams developing production LLM applications. It provides tracing, debugging, and evaluation for any LLM application — not just LangChain ones. Developers use LangSmith to trace every LLM call and tool ...
Read more about LangSmithStarts from Freefree, also offers free forever plan
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What is Arize AI?
Arize AI is a revolutionary Machine Learning Observability Platform to quickly identify and address model and data issues. With a comprehensive analytics suite and no restrictions on model framework, platform, or environment, Arize ensures companies can monitor the performance of their products ...
Read more about Arize AIArize AI offers custom pricing plan
PromptLayer
Revolutionize your GPT requests with PromptLayer.
Best for: SMB teams · Mid-market · Enterprise
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What is PromptLayer?
Unveiling PromptLayer, the pioneering platform tailored for prompt engineers. This innovative tool is tailored to tackle the complexities that accompany managing GPT requests, marking a paradigm shift in how you analyze, troubleshoot, and delve into these requests. With PromptLayer, you wield ...
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