Best AI LLM Observability Tools in 2026
Updated
In short: Agenta is ranked #1 of 23 as of 2 October 2026, ahead of Langfuse and Opik. The best-ranked option with a free plan is Langfuse. The lowest first paid tier on this page is Opik at $19/mo.
AI LLM observability tools help you inspect activity and results in applications built around language models. Compare LLM trace capture and failure tracking with latency metrics, output evaluations, and token cost tracking. Free-plan access and retention, along with paid-from pricing, add further dimensions when assessing fit. Arize AX and Langfuse lead the ranked entries, followed by Opik and W&B Weave; Agenta and Braintrust also appear near the start. Use these criteria to prioritize the signals you need for investigating behavior, reviewing outputs, and keeping costs visible.
23 AI LLM observability tools ranked on what their makers publish — plans and prices, free tiers, platforms and the facts on their own pages.
| # | Platform | Score | Why | From | Free plan | Paid from | LLM trace capture | |
|---|---|---|---|---|---|---|---|---|
| 1 | Agenta | 7.4 | RecognisedAPIDocumented | $29/mo | Yes | 29 /mo | — | View |
| 2 | Langfuse | 7.4 | RecognisedAPIDocumented | $29/mo | Yes | 29 /mo | — | View |
| 3 | Opik | 7.4 | RecognisedAPIDocumented | $19/mo | Yes | 19 /mo | — | View |
| 4 |  Portkey | 7.4 | RecognisedAPIDocumented | $49/mo | Yes | 49 /mo | Yes | View |
| 5 | W&B Weave | 7.4 | RecognisedAPIDocumented | $60/mo | Yes | 60 /mo | — | View |
| 6 |  Arize AX | 7.3 | RecognisedAPIDocumented | $50/mo | Yes | 50 /mo | — | View |
| 7 | Braintrust | 7.3 | RecognisedAPIDocumented | $249/mo | Yes | 249 /mo | — | View |
| 8 | Confident AI | 7.3 | RecognisedAPIDocumented | $200/mo | Yes | 200 /mo | — | View |
| 9 | Galileo | 7.3 | RecognisedAPIDocumented | $100/mo | Yes | 100 /mo | — | View |
| 10 | Helicone | 7.3 | RecognisedAPIDocumented | $79/mo | Yes | 79 /mo | — | View |
| 11 | Maxim AI | 7.3 | RecognisedAPIDocumented | $29/mo | Yes | — | — | View |
| 12 |  OpenLIT | 7.3 | RecognisedAPIDocumented | Free | Yes | — | — | View |
| 13 | PromptLayer | 7.3 | RecognisedAPIDocumented | $49/mo | Yes | 49 /mo | — | View |
| 14 |  MLflow Tracing | 7.2 | RecognisedAPIDocumented | Free | Yes | — | — | View |
| 15 | Fiddler AI | 5.5 | RecognisedAPIDocumented | — | Yes | — | — | View |
| 16 | LangSmith | 5.5 | RecognisedAPIDocumented | — | Yes | — | — | View |
| 17 | HoneyHive | 5.4 | RecognisedAPIDocumented | — | Yes | — | — | View |
| 18 | LangWatch | 5.4 | RecognisedAPIDocumented | — | Yes | — | — | View |
| 19 |  Respan (formerly Keywords AI) | 5.4 | RecognisedAPIDocumented | — | Yes | 199 /mo | — | View |
| 20 |  Arize Phoenix | 5.3 | RecognisedAPIDocumented | — | Yes | — | — | View |
| 21 |  OpenLLMetry | 5.3 | RecognisedAPIDocumented | — | Yes | — | — | View |
| 22 |  Lunary | 4.8 | RecognisedAPIDocumented | — | No | — | — | View |
| 23 |  TruLens | 4.6 | RecognisedAPIDocumented | — | — | — | — | View |
Is your platform on this list?
Numbered spots on this list can be sponsored. They are labelled, and the editorial order and scores never change for payment.
Questions about this list
Which AI LLM observability tool is ranked first on Inferse?
Agenta is ranked #1 of 23 with a score of 7.4. Langfuse is second and Opik third.
How many of these have a free plan?
13 of the 23 on this page publish a free plan on their own pricing pages.
Which is the cheapest paid option?
On this page, Opik has the lowest first paid tier we found: $19/mo.
How is this list ranked?
Ranked on what each maker publishes, open and connectable first: a public API, open-source code, the depth of its documentation and a free tier to try it on. Model lists are sorted by the figure in their title, exactly as each provider publishes it. Paid placements never change a rank.