AI agent observability tools in 2026: 13 compared by price
Last updated November 12, 2026. Every price comes from the tool's own site, as recorded in our open dataset. Each row shows the date we last verified it. This is a fact comparison, not a ranking by test score.
Short answer: most agent observability tools have a free tier. Flat paid plans start between $19 and $79 a month. Pick by what you need to see:
- The cheapest paid cloud plan: Opik Pro Cloud at $19 a month for 100k spans. Its open source version is free.
- Self-hosted tracing with an MIT core: Langfuse. Its Hobby cloud plan is free for 50k units a month.
- Per-seat pricing for a LangChain stack: LangSmith Plus at $39 per seat a month.
- Pay per trace with guardrails: Fiddler AI at $0.002 per trace on its Developer plan.
- A record of what coding agents do on a laptop: Agent Beacon or Agentmetry, both free and open source.
- Plain OpenTelemetry instrumentation with no platform: OpenLLMetry, free under Apache-2.0.
Price and ownership table
| Tool | Free option | First paid plan | License | Owner news | Verified |
|---|---|---|---|---|---|
| Opik | Open source; Free Cloud 25k spans/mo | Pro Cloud $19/mo | Apache-2.0 | None | Nov 9, 2026 |
| Langfuse | Hobby free, 50k units/mo; self-host | Core $29/mo | MIT (ee/ separate) | ClickHouse, Jan 2026 | Nov 9, 2026 |
| Laminar | Free $0 | Starter $30/mo | Apache-2.0 | None | Nov 9, 2026 |
| LangSmith | Developer $0/seat | Plus $39/seat/mo | Commercial | None | Nov 9, 2026 |
| AgentOps | Basic $0, 5,000 events | Pro from $40/mo | MIT | None | Nov 4, 2026 |
| Arize Phoenix | Phoenix self-host; AX Free $0 | AX Pro $50/mo | Elastic License 2.0 | Dynatrace, Oct 2026 | Oct 30, 2026 |
| W&B Weave | Free $0 | Pro from $60/mo | Apache-2.0 | CoreWeave, May 2025 | Nov 9, 2026 |
| Helicone | Free tier | Pro $79/mo | Apache-2.0 | Mintlify, Mar 2026 | Nov 9, 2026 |
| Fiddler AI | Free plan | Developer $0.002/trace | Commercial | CrowdStrike deal, not closed | Nov 5, 2026 |
| Galileo | Not stated | Not published | Commercial | Cisco, May 2026 | Nov 9, 2026 |
| OpenLLMetry | Free | None | Apache-2.0 | ServiceNow, Mar 2026 | Nov 9, 2026 |
| Agent Beacon | Free | Hosted options | MIT | None | Nov 9, 2026 |
| Agentmetry | Free sensor | Enterprise pilot by quote | Apache-2.0 | None | Nov 9, 2026 |
What a price unit means
Vendors meter in different units, so compare like for like. Opik counts spans. Langfuse counts units. AgentOps counts events. Fiddler counts traces. LangSmith charges per seat. A span is one step inside a trace, so a span limit fills faster than a trace limit.
What to check before you buy
Check four things. First, can you self-host it, and under which license? Second, does it accept OpenTelemetry data, so you can switch later? Third, who owns it now? Seven tools on this page have changed owners or signed a deal since May 2025. Fourth, does it only watch agents, or can it also block an action?
Watching or blocking
Most tools here only record and evaluate. Fiddler AI adds inline guardrails. Agentmetry can block at pre-execution hooks. If you need to stop risky actions, also compare MCP gateways and prompt injection guardrails.
Frequently asked questions
What is the cheapest AI agent observability tool?
Several are free. OpenLLMetry, Agent Beacon and Agentmetry are free and open source. The cheapest flat paid cloud plan here is Opik Pro Cloud at $19 a month.
Can I self-host agent tracing?
Yes. Langfuse, Opik and Arize Phoenix can run on your own servers. Check each license first, since Phoenix uses the Elastic License 2.0.
Which observability tools changed owners?
Langfuse joined ClickHouse, Arize Phoenix joined Dynatrace, Helicone joined Mintlify and Galileo joined Cisco. CrowdStrike signed a deal for Fiddler AI that has not closed.
Has Agent Security Index tested these?
Not yet. No lab results have been published. This page compares verified facts only.
Sources
Prices, licenses and owners come from each listing's sources in the open dataset. Key pages:
- Opik pricing: https://www.comet.com/site/pricing/
- Langfuse pricing: https://langfuse.com/pricing
- Helicone pricing: https://www.helicone.ai/pricing
- Fiddler AI pricing: https://www.fiddler.ai/pricing
- Langfuse and ClickHouse: https://clickhouse.com/blog/clickhouse-acquires-langfuse-open-source-llm-observability
- Arize and Dynatrace: https://www.dynatrace.com/news/press-release/dynatrace-completes-acquisition-of-arize/
- W&B and CoreWeave: https://www.coreweave.com/blog/coreweave-completes-acquisition-of-weights-biases
- Helicone and Mintlify: https://www.mintlify.com/blog/mintlify-acquires-helicone
- Traceloop and ServiceNow: https://www.traceloop.com/blog/traceloop-is-joining-servicenow
- Galileo and Cisco: https://www.splunk.com/en_us/about-splunk/acquisitions/galileo.html
- Fiddler and CrowdStrike: https://www.crowdstrike.com/en-us/press-releases/crowdstrike-to-acquire-fiddler-to-deliver-agent-observability/
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