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 1Confident AI
DeepEval-powered LLM evaluation and observability
Raised
$2.2M
Stage
Seed
Observe
AI-native observability platform built on a data lake to replace Splunk and Datadog
Raised
$270M
Stage
S-C
Portkey
The control plane for production AI
Raised
$18M
Stage
Seed
Arize AI
The AI & Agent Engineering Platform for development, observability, and evaluation of LLM applications.
Raised
$132M
Stage
S-C
Traversal
The AI SRE agent that finds root causes in complex production systems
Raised
$48M
Stage
SEED AND SERIES A
Metaplane
Raised
$13.8M
Stage
S-A
Braintrust
The AI observability platform for building quality AI products at scale.
Raised
$80M
Stage
S-B
NeuBird
Hawkeye, an agentic AI SRE that autonomously diagnoses and resolves production issues
Raised
$63.8M
Stage
VENTURE
Phoebe
Raised
$17M
Stage
Seed
Ciroos
Multi-domain AI SRE teammate that automates and augments operations and incident response
Raised
$21M
Stage
Seed
TensorZero
Open-source stack for building industrial-grade LLM applications
Raised
$7.3M
Stage
Seed
Sifflet
AI-ready data observability platform to monitor pipelines, quality, and lineage end to end
Raised
$35.8M
Stage
VENTURE
Sazabi
The AI-native observability platform for fast-moving engineering…
Raised
$500K
Stage
Seed
Raindrop
Sentry for AI agents — monitoring that catches silent failures in production
Raised
$15M
Stage
Seed
HoneyHive
Observability and evaluation for production AI agents
Raised
$7.4M
Stage
Seed
Langfuse
Open source LLM engineering platform for debugging, analyzing, and iterating on LLM applications
Raised
$8M
Stage
Seed
OpenObserve
AI-native, open-source observability for logs, metrics, and traces
Raised
$10M
Stage
S-A
InsightFinder
AI-driven reliability and observability for IT systems and AI agents
Raised
$35M
Stage
S-B
Validio
Raised
$30M
Stage
S-A
Maxim AI
GenAI evaluation, simulation and observability platform for AI agents
Raised
$3M
Stage
Seed
PromptLayer
The prompt management workbench for LLM teams
Raised
$5M
Stage
Seed
Athina AI
Raised
$3.5M
Stage
Seed
Helicone
Helicone is an AI gateway and LLM observability platform that helps companies route, debug, and analyze their AI applications.
Galileo AI
The AI observability and eval engineering platform where offline evals become production guardrails.