Best AI Agent Observability Tools in 2026
Updated
In short: W&B Weave is ranked #1 of 32 as of 7 October 2026, ahead of PetalTrace and SigNoz. The best-ranked option with a free plan is PetalTrace. The lowest first paid tier on this page is Respan (formerly Keywords AI) at $16.58/mo.
When an AI agent runs, observability tools can help you inspect its prompts, tool calls, sessions, and associated costs. Compared on agent framework support, prompt and tool tracing, session replay, and trace retention, these entries also distinguish deployment options and free-plan availability. Paid-from pricing gives you another point to weigh alongside cost tracking. W&B Weave, PetalTrace, and SigNoz are among the names to compare for the visibility features you need. Consider what you want to review during and after an agent session, which frameworks matter to your work, and how long traces should remain accessible. The listed criteria make those trade-offs easier to examine.
32 AI agent observability tools ranked on what their makers publish — plans and prices, free tiers, platforms and the facts on their own pages.
32ranked
24free plans on this page
$16.58/molowest paid tier
7 Oct 2026last checked
Input list AI Agent Observability Tools 25 channels on this page · 84 of 200 spec lines stated by the makers
Ch Tool Free planPaid fromTrace retentionSession replayPrompt and tool tracingDeployment optionsAgent framework supportCost tracking Spec sheet Score
01 W&B Weave Free planYesPaid from$60/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 3/8spec lines stated 7.8
02 PetalTrace Free plannot statedPaid fromnot statedTrace retentionnot statedSession replayYesPrompt and tool tracingYesDeployment optionsself hostedAgent framework supportopen standardCost trackingYes 5/8spec lines stated 7.6
03 SigNoz Free planYesPaid from$49/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingnot stated 2/8spec lines stated 7.6
04 Opik Free planYesPaid from$19/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 3/8spec lines stated 7.5
05 OpenLIT Free planYesPaid fromnot statedTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsself hostedAgent framework supportnot statedCost trackingYes 3/8spec lines stated 7.4
06 Traccia Free planYesPaid from$99/moTrace retention30 daysSession replayYesPrompt and tool tracingYesDeployment optionshybridAgent framework supportsdkCost trackingYes 8/8spec lines stated 7.4
07 VoltOps Free planYesPaid from$50/moTrace retention90 daysSession replayYesPrompt and tool tracingYesDeployment optionsnot statedAgent framework supportopen standardCost trackingYes 7/8spec lines stated 7.3
08 Helicone Free planYesPaid from$79/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 3/8spec lines stated 7.2
09 Maxim AI Free planYesPaid fromnot statedTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingnot stated 1/8spec lines stated 7.2
10 Respan (formerly Keywords AI) Free planYesPaid from$199/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 3/8spec lines stated 7.2
11 LangWatch Free planYesPaid fromnot statedTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 2/8spec lines stated 7.1
12 Observe Free planNoPaid fromnot statedTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingnot stated 1/8spec lines stated 7.1
13 Agenta Free planYesPaid from$29/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingnot stated 2/8spec lines stated 7.0
14 Langfuse Free planYesPaid from$29/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 3/8spec lines stated 7.0
15 TraceRoot Free planYesPaid fromnot statedTrace retention30 daysSession replayYesPrompt and tool tracingYesDeployment optionsnot statedAgent framework supportsdkCost trackingYes 6/8spec lines stated 7.0
16 Arize AX Free planYesPaid from$50/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 3/8spec lines stated 6.9
17 Braintrust Free planYesPaid from$249/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingnot stated 2/8spec lines stated 6.9
18 Fiddler AI Free planYesPaid fromnot statedTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 2/8spec lines stated 6.9
19 Galileo Free planYesPaid from$100/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingnot stated 2/8spec lines stated 6.9
20 Laminar Free planYesPaid from$30/moTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 3/8spec lines stated 6.9
21 LangSmith Free planYesPaid fromnot statedTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 2/8spec lines stated 6.9
22 LogicGaze Free planYesPaid fromnot statedTrace retentionnot statedSession replayYesPrompt and tool tracingYesDeployment optionsnot statedAgent framework supportsdkCost trackingYes 5/8spec lines stated 6.9
23 MLflow Tracing Free planYesPaid fromnot statedTrace retentionnot statedSession replayYesPrompt and tool tracingYesDeployment optionshybridAgent framework supportopen standardCost trackingYes 6/8spec lines stated 6.9
24 Traceloop Free planYesPaid fromnot statedTrace retentionnot statedSession replayYesPrompt and tool tracingYesDeployment optionsnot statedAgent framework supportsdkCost trackingYes 5/8spec lines stated 6.9
25 Arize Phoenix Free planYesPaid fromnot statedTrace retentionnot statedSession replaynot statedPrompt and tool tracingnot statedDeployment optionsnot statedAgent framework supportnot statedCost trackingYes 2/8spec lines stated 6.8
Compare all 25 in a table
| # | Tool | Score | Free plan | From | Free plan | Paid from | Trace retention | Session replay |
|---|---|---|---|---|---|---|---|---|
| 1 | W&B Weave | 7.8 | Free plan | $60/mo | Yes | 60 /mo | — | — |
| 2 | PetalTrace | 7.6 | Free plan | Free | — | — | — | Yes |
| 3 | SigNoz | 7.6 | Free plan | $19/mo | Yes | 49 /mo | — | — |
| 4 | Opik | 7.5 | Free plan | $19/mo | Yes | 19 /mo | — | — |
| 5 | OpenLIT | 7.4 | Free plan | Free | Yes | — | — | — |
| 6 | Traccia | 7.4 | Free plan | $99/mo | Yes | 99 /mo | 30 days | Yes |
| 7 | VoltOps | 7.3 | Free plan | $50/mo | Yes | 50 /mo | 90 days | Yes |
| 8 | Helicone | 7.2 | Free plan | $79/mo | Yes | 79 /mo | — | — |
| 9 | Maxim AI | 7.2 | Free plan | $29/mo | Yes | — | — | — |
| 10 | Respan (formerly Keywords AI) | 7.2 | Free plan | $16.58/mo | Yes | 199 /mo | — | — |
| 11 | LangWatch | 7.1 | Free plan | €29/mo | Yes | — | — | — |
| 12 | Observe | 7.1 | No | — | No | — | — | — |
| 13 | Agenta | 7.0 | Free plan | $29/mo | Yes | 29 /mo | — | — |
| 14 | Langfuse | 7.0 | Free plan | $29/mo | Yes | 29 /mo | — | — |
| 15 | TraceRoot | 7.0 | Free plan | $30/mo | Yes | — | 30 days | Yes |
| 16 | Arize AX | 6.9 | Free plan | $50/mo | Yes | 50 /mo | — | — |
| 17 | Braintrust | 6.9 | Free plan | $249/mo | Yes | 249 /mo | — | — |
| 18 | Fiddler AI | 6.9 | Free plan | Free | Yes | — | — | — |
| 19 | Galileo | 6.9 | Free plan | $100/mo | Yes | 100 /mo | — | — |
| 20 | Laminar | 6.9 | Free plan | $30/mo | Yes | 30 /mo | — | — |
| 21 | LangSmith | 6.9 | Free plan | $39/mo | Yes | — | — | — |
| 22 | LogicGaze | 6.9 | Free plan | Free | Yes | — | — | Yes |
| 23 | MLflow Tracing | 6.9 | Free plan | Free | Yes | — | — | Yes |
| 24 | Traceloop | 6.9 | Free plan | Free | Yes | — | — | Yes |
| 25 | Arize Phoenix | 6.8 | Free plan | Free | Yes | — | — | — |
Is your tool on this list?
Numbered spots on this list can be sponsored, and a sponsored row is labelled as paid.
Questions about this list
Which AI agent observability tool is ranked first on Specifiction?
W&B Weave is ranked #1 of 32 with a score of 7.8. PetalTrace is second and SigNoz third.
How many of these have a free plan?
24 of the 25 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 on what each maker publishes, the fullest spec sheet first: how deeply the product is documented, the platforms it runs on, a free tier or trial to test it, and its standing.