Weights & Biases sits at $245M Series C as the production-ML observability anchor, and CoreWeave's 2024 acquisition of W&B for ~$1.7B reset the upper bound for the category. Braintrust's $80M Series B targets the LLM-app eval layer specifically, where Arize AI, Galileo AI, Comet, and Langfuse compete on trace-level inspection and offline-to-online eval flow. Helicone overlaps on the gateway side. Cleanlab, Anomalo, and Credo AI extend the surface into data-quality monitoring and AI governance, the audit trail that EU AI Act compliance now formally demands. DataRobot and Dataiku represent the legacy enterprise-MLOps incumbents pivoting toward agent observability.
CATEGORY
Best Observability AI Tools
36 tools compared · 2026
Trace, eval, and govern LLM applications and agents from prompt iteration to production drift
36 ai observability startups tracked, with the largest concentration in US. Total tracked funding: $1.1B.
Tracked
36
Total Raised
$1.1B
Countries
7
Active Deals
1
1 
Confident AI San Francisco, US $2.2M 2 
Observe San Mateo, US $270M 3 
Portkey San Francisco, US $18M 4 
Arize AI — $132M 5 
Traversal New York, US $48M 6 
Metaplane — $13.8M 7 
Braintrust US $80M 8 
NeuBird Santa Clara, US $63.8M 9 
Phoebe — $17M 10 
Ciroos San Jose, US $21M 11 
TensorZero New York, US $7.3M 12 
Sifflet Paris, FR $35.8M
Funding by year — AI Observability
2021 → 2026Market overview
Key trends 2026
- Eval-first overtakes monitor-first. Braintrust and Galileo lead by treating offline evals as the core artifact, not afterthought dashboards.
- EU AI Act reshapes governance demand. Credo AI sees enterprise budget unlock for documented AI risk controls.
- W&B acquisition raises the ceiling. CoreWeave's ~$1.7B deal proves observability can clear unicorn-plus exits.
Benchmarks vs global
Largest exit
~$1.7B (W&B to CoreWeave)
vs Braintrust $80M Series B ↑
Median LLM-app trace cost
$0.001-0.005/trace
vs free OSS Langfuse ↓
Enterprise AI-governance budget growth
2-3x YoY (Credo AI cohort)
vs flat 2022 baseline ↑
Top countries
By startup countStage breakdown
Latest round typeTop investors backing AI Observability
See all →FAQ
Frequently asked
What's the difference between Arize, Braintrust, and Langfuse?
Arize AI sits closest to traditional ML monitoring with strong drift and embedding tooling. Braintrust prioritizes prompt-and-eval iteration loops for LLM app builders. Langfuse is open-source-first and self-hostable, often chosen by teams with strict data-residency requirements.
Which AI observability startup has raised the most?
Weights & Biases leads at $245M Series C and was acquired by CoreWeave in 2024 for ~$1.7B. Braintrust follows with an $80M Series B. Most other category players — Arize, Galileo, Helicone, Langfuse — sit at earlier stages.
Do I need observability if I'm just calling the OpenAI API?
For toy projects no. For anything in production yes — at minimum a logging gateway like Helicone catches latency spikes, cost runs, and bad outputs. Once you have evaluators, Braintrust or Langfuse let you regression-test prompt changes before deploying them.
Recent rounds in AI Observability
All rounds →| Date | Startup | Round | Amount |
|---|---|---|---|
| Apr 2026 | InsightFinder | Series B | $15M |
| Apr 2026 | NeuBird | Venture | $19.3M |
| Feb 2026 | Braintrust | Series B | $80M |
| Jan 2026 | Sazabi | Seed | $500K |
| Dec 2025 | Raindrop | Seed | $15M |
| Nov 2025 | AlertD | Pre-Seed | $3M |
| Aug 2025 | Confident AI | Seed | $2.2M |
| Aug 2025 | TensorZero | Seed | $7.3M |
All AI Observability startups
Page 2Comet
The AI Developer Platform for building, debugging, and deploying reliable AI agents.
Credo AI
One platform to discover, assess, and govern every AI agent, model, and application — continuously and in context.
Anomalo
The autonomous data system for the agentic enterprise, enabling self-driving data through AI-powered monitoring, investigation, and reporting.
Dataiku
The platform for AI success, powered by people, orchestration, and governance, built for enterprise scale.
LangWatch
Platform for LLM evaluations, agent testing and observability
Raised
$1.1M
Stage
Pre-S
Foundational
Code-aware data quality and lineage for AI-ready data
Raised
$8M
Stage
Seed
AlertD
Agentic AI for SRE and DevOps that surfaces AWS insights in plain language
Raised
$3M
Stage
Pre-S
ThoughtData
PRIVATEUnified AIOps observability with root-cause analysis and remediation
Cleanlab
Detect and remediate incorrect responses from any AI Agent, ensuring every output meets your standards for safety, compliance, and trust.
AVIAN
Always-on AI thermal monitoring to prevent industrial fires and equipment failures
Raised
$2.6M
Stage
Pre-S
Telmai
Open-architecture, AI-driven data observability
Raised
$5.5M
Stage
Seed
Weights & Biases
VerifiedThe AI developer platform
Raised
$245M
Stage
S-C