Fiddler AI vs Langfuse (2026)
vs
Overview
Rating
10.0 / 10
Rating
10.0 / 10
Best For
Enterprises in regulated industries (financial services, healthcare, insurance, government) running AI agents and predictive ML models
Best For
Teams who want open-source LLM observability they can self-host and customize
Product Summary
Fiddler AI is an enterprise platform for observing, evaluating, and governing AI agents and ML models, with guardrails that run in your own environment.
Product Summary
Langfuse is an open-source LLM engineering platform for tracing, evals, and prompt management, self-hosted or on Langfuse Cloud with a free plan.
Starting Price
0
Starting Price
Free
Free Trial
No
Free Trial
No
Free Version
Yes
Free Version
Yes
Website
Website
Key features
Core capabilities each platform advertises.
- Agentic observability across multi-step agent workflows
- Continuous evaluations from testing through production
- Inline guardrails for PII, PHI, prompt injection, and jailbreaks
- AI governance, risk, and compliance reporting
- Tracing for LLM calls, tool runs, and agent steps
- Python and TypeScript SDKs plus OpenTelemetry
- LLM-as-a-judge and custom evaluations
- Datasets and experiments
- Prompt management and playground
Strengths and tradeoffs
What each tool does well, and the limitations to keep in mind.
Pros
- Covers AI agents and predictive ML models in one platform
- Evaluations and guardrails run in-environment, with no external LLM API call per check
- Free tier includes real-time guardrails
- Supports SaaS, VPC, on-premises, and AWS GovCloud deployment
Cons
- The free tier covers guardrails only; observability starts on the paid Developer plan
- VPC and on-premises deployment require the Enterprise plan
- Every plan on the pricing page starts with a demo request rather than self-serve signup
- No model routing or provider failover, so a gateway is a separate tool
Pros
- MIT-licensed core, self-hostable with Docker Compose or Kubernetes
- Tracing, evals, and prompt management in one tool
- Unlimited users on paid cloud plans
- Free Hobby plan with 50k units a month
- Native SDKs plus OpenTelemetry for other languages
Cons
- No LLM gateway, so routing, failover, and spend limits need a separate tool
- Hobby plan keeps 30 days of data and caps at 2 users
- Enterprise SSO and RBAC need the $300/month Teams add-on on Pro
- Self-hosting means running and scaling Langfuse's services yourself
Fiddler AI or Langfuse — which should you choose?
Choose Fiddler AI if you wantChoose if you want
- Governing AI agents in regulated industries
- Monitoring predictive ML models for drift and performance
- Redacting PII and PHI on agent requests and responses
Choose Langfuse if you wantChoose if you want
- Tracing and debugging LLM apps and agents
- Self-hosting LLM observability
- Versioning prompts across environments
- Scoring outputs with LLM judges and human review
Compare Fiddler AI and Langfuse on your own traffic
10KFree traces/mo
1,000+Models
5 minSetup
Respan lets you trace LLM and agent calls across any model or framework, A/B test prompts on production traffic, and route requests across 1,000+ models through one gateway.
Try Respan free