Best AI LLM Observability Tools in 2026
Updated
In short: Agenta is ranked #1 of 23 as of 4 October 2026, ahead of Confident AI and Helicone. The best-ranked option with a free plan is Confident AI. The lowest first paid tier on this page is Respan (formerly Keywords AI) at $16.58/mo.
For applications built with large language models, observability tools can help you inspect traces, track failures, assess outputs, and follow latency and token costs. Compare the ranked entries on LLM trace capture, failure tracking, latency metrics, output evaluations, and token cost tracking. Free-plan availability and retention, along with paid starting prices, add practical comparison points. Arize AX, Langfuse, and Opik appear at the start of the ranking, followed by W&B Weave and Agenta. Focus on which signals you need to monitor, whether you need to evaluate model outputs, and what cost and retention details matter to your work.
23 AI LLM observability tools ranked on what their makers publish — plans and prices, free tiers, platforms and the facts on their own pages.
Recognised 40% · Phone app 26% · Documented 20% · Free plan 14% of the score
- 1 Agenta No phone app RecognisedPhone appDocumentedFree plan 6.4$29/mo
- 2 Confident AI No phone app RecognisedPhone appDocumentedFree plan 6.4$200/mo
- 3 Helicone No phone app RecognisedPhone appDocumentedFree plan 6.4$79/mo Token cost tracking: Yes
- 4 Langfuse No phone app RecognisedPhone appDocumentedFree plan 6.4$29/mo Token cost tracking: Yes
- 5 Maxim AI No phone app RecognisedPhone appDocumentedFree plan 6.4$29/mo
- 6 Opik No phone app RecognisedPhone appDocumentedFree plan 6.4$19/mo Token cost tracking: Yes
- 7 Portkey No phone app RecognisedPhone appDocumentedFree plan 6.4$49/mo LLM trace capture: YesToken cost tracking: YesOutput evaluations: Yes
- 8 PromptLayer No phone app RecognisedPhone appDocumentedFree plan 6.4$49/mo
- 9 W&B Weave No phone app RecognisedPhone appDocumentedFree plan 6.4$60/mo Token cost tracking: Yes
- 10 Arize AX No phone app RecognisedPhone appDocumentedFree plan 6.3$50/mo Token cost tracking: Yes
- 11 Braintrust No phone app RecognisedPhone appDocumentedFree plan 6.3$249/mo
- 12 Galileo No phone app RecognisedPhone appDocumentedFree plan 6.3$100/mo
- 13 MLflow Tracing No phone app RecognisedPhone appDocumentedFree plan 6.3Free Token cost tracking: Yes
- 14 OpenLIT No phone app RecognisedPhone appDocumentedFree plan 6.3Free Token cost tracking: Yes
- 15 Respan (formerly Keywords AI) No phone app RecognisedPhone appDocumentedFree plan 6.3$16.58/mo Token cost tracking: Yes
- 16 Fiddler AI No phone app RecognisedPhone appDocumentedFree plan 5.3 Token cost tracking: Yes
- 17 LangSmith No phone app RecognisedPhone appDocumentedFree plan 5.3 Token cost tracking: Yes
- 18 HoneyHive No phone app RecognisedPhone appDocumentedFree plan 5.2 Token cost tracking: Yes
- 19 LangWatch No phone app RecognisedPhone appDocumentedFree plan 5.2 Token cost tracking: Yes
- 20 Arize Phoenix No phone app RecognisedPhone appDocumentedFree plan 5.1 Token cost tracking: Yes
- 21 OpenLLMetry No phone app RecognisedPhone appDocumentedFree plan 5.1 Token cost tracking: Yes
- 22 Lunary No phone app RecognisedPhone appDocumentedFree plan 4.9 Token cost tracking: Yes
- 23 TruLens No phone app RecognisedPhone appDocumentedFree plan 4.7
Is your app 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 Samsung Mobile US Press?
Agenta is ranked #1 of 23 with a score of 6.4. Confident AI is second and Helicone third.
How many of these have a free plan?
15 of the 23 on this page publish a free plan on their own pricing pages.
Which is the cheapest paid option?
On this page, Respan (formerly Keywords AI) has the lowest first paid tier we found: $16.58/mo.
How is this list ranked?
Ranked mobile-first: a phone app alongside the web or desktop product, a free tier and the depth of its documentation. Paid placements never change a rank.