Best AI Observability Tools in 2026
Logfire connects agent observability, full-stack telemetry, evaluation, and improvement in one OpenTelemetry-native product. See how narrower AI tools and traditional observability stacks compare.
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Comparison overview
| Tool | Best for | Full-stack | OTel native | AI-first | Pricing |
|---|---|---|---|---|---|
| Logfire | Observe, evaluate, and improve AI systems end to end | Yes | Yes | Yes | Free: 10M records; Team $49 + $2/M over 10M |
| Braintrust | Evaluation-led AI development | No | Yes | Yes | Free: 10K scores; Pro $249 + data and score usage |
| Langfuse | LLM-focused observability | No | Yes | Yes | Free: 50K units; Core $29 + unit usage |
| LangSmith | LangChain ecosystem | No | No | Yes | Free: 5K base traces; Plus $39/seat + trace usage |
| Arize AX | ML model monitoring | No | No | Yes | Free: 25K spans; AX Pro $50 + spans and payload |
| Datadog | Enterprise APM | Yes | No | No | Free: 40K LLM spans; Pro $160 + spans and retention |
| Sentry | Established error and application monitoring workflows | Yes | No | No | Developer free; Team $26 + event usage |
| Grafana | Teams assembling a customizable observability stack | Yes | Yes | No | Free tier; Cloud Pro $19 platform fee + usage |
| SigNoz | Self-hosted observability | Yes | Yes | No | Teams Cloud $49 + usage; Community available self-managed |
| Honeycomb | OTel-native trace investigation | No | Yes | No | Free: 20M events; Pro $150 + $3/M events |
| Elastic Cloud Hosted | Observability with search and security | Yes | Yes | No | Standard $99 + deployment capacity |
See the exact pricing math and sources
Calculation scope
Entry plan and billing-meter summary for the overview table. These labels are not an equivalent-workload cost comparison; the detailed pages show calculations only where the products' units can be stated explicitly.
Basis: USD; public self-serve list prices. Prices checked .
Published inputs
- Logfire
- Free: 10M records; Team $49 + $2/M over 10M Pydantic Logfire source
- Braintrust
- Free: 10K scores; Pro $249 + data and score usage Braintrust source
- Langfuse
- Free: 50K units; Core $29 + unit usage Langfuse source
- LangSmith
- Free: 5K base traces; Plus $39/seat + trace usage LangSmith source
- Arize AX
- Free: 25K spans; AX Pro $50 + spans and payload Arize AX source
- Datadog
- Free: 40K LLM spans; Pro $160 + spans and retention Datadog source
- Sentry
- Developer free; Team $26 + event usage Sentry source
- Grafana Cloud
- Free tier; Cloud Pro $19 platform fee + usage Grafana Cloud source
- SigNoz
- Teams Cloud $49 + usage; Community available self-managed SigNoz source
Assumptions
- Purpose
- Meter comparison A short overview can compare how billing starts without pretending unlike traces, records, hosts, bytes, and scores are interchangeable.
Source ledger
- Pydantic Logfire — Pricing and plans for Pydantic Logfire https://pydantic.dev/pricing
“Covers 10 million logs, spans, and metrics every month.”
The official calculator shows 20 million records and no extra seats totaling $69/month on Team.
- Braintrust — Braintrust pricing https://www.braintrust.dev/pricing
“50k scores + $1.50/1k”
Braintrust's on-page calculator itemizes its platform, processed-data, score, and retention meters.
- Langfuse — Langfuse pricing and calculator https://langfuse.com/pricing?calculatorOpen=true
“100k units / month included, additional: $8/100k units.”
The official calculator shows a $37 Core total at 200,000 monthly units: $29 base plus $8 usage.
- LangSmith — LangSmith plans and pricing https://www.langchain.com/pricing
“Add unlimited seats $39 per seat/month”
The official calculator prices one LSU at $1 and each additional base trace at 0.005 LSU; at one million or more traces it invites customers to contact sales for volume pricing.
- Arize AX — Arize AI pricing https://arize.com/pricing
“$.0008 per additional span”
AX Pro lists 50,000 spans and 10 GB included, then $0.0008 per additional span and $3 per additional GB.
- Datadog — Datadog pricing: Agent Observability https://www.datadoghq.com/pricing/#products-ai--agent-observability
“Additional spans: $3.5 per 10K LLM spans.”
The pricing FAQ publishes annual, month-to-month, and on-demand rates plus separate 30-, 60-, and 90-day retention add-ons.
- Sentry — Sentry pricing and calculator https://sentry.io/pricing/
“Any usage above your quota is billed at pay-as-you-go rates.”
The default annual Team calculator shows $26/month with 50,000 errors, 5 GB logs, and 5 million spans included.
- Grafana Cloud — Grafana Cloud pricing https://grafana.com/pricing/?pg=pricing&plcmt=traces-details#calculator
“Platform fee of $19 per month includes:”
Grafana Cloud Pro includes 50 GB of traces, then separately meters processing, writing, and retention with graduated volume bands.
- SigNoz — SigNoz pricing and calculator https://signoz.io/pricing/
“Usage worth $49 (e.g. 163 GB logs/traces or 490 mn metric samples)”
SigNoz's own worked example prices 10,000 time series at a 30-second interval as 864 million samples and $86.40/month.
What this calculation does not include
- Enterprise contracts, taxes, discounts, and model-provider charges are excluded.
- Follow the head-to-head links for workload calculations and meter-specific assumptions.
See Logfire on your own telemetry
Start free with 10 million spans, logs, and metrics each month. No credit card required.
Why teams choose Logfire
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Browser-to-Agent Context
Move from browser RUM and session replay through backend services, databases, and infrastructure to the model and tool calls inside an agent run.
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Production Improvement
Run hosted evaluators, route low-scoring runs to human review, and turn the evidence into scheduled optimization proposals and model recommendations.
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AI-Assisted Operations
Ask the in-product Assistant about project or organization telemetry in plain language, then follow its answers into the underlying evidence.
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SQL and MCP
Use PostgreSQL-compatible SQL for ad hoc investigation and give coding agents the same access through MCP.
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Open Standards
OpenTelemetry-native instrumentation stays portable across vendors, frameworks, and languages.
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Predictable Economics
Start free with 10 million records. Paid plans begin at $49 a month and add records at $2 per million above the included allowance.
Head-to-head comparisons
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