Best LLM Observability & Evaluation Tools (LLMOps) in 2026
Once an LLM app is live, you need to see what it's doing: trace calls, track cost and latency, catch regressions, and evaluate quality. These LLMOps tools give you that visibility.
The best Best LLM Observability & Evaluation Tools (LLMOps) for most people is Langfuse — Open-source LLM observability and evaluation. A strong alternative is Helicone.
| # | Tool | Best for | Pricing |
|---|---|---|---|
| 1 | Langfuse | Open-source LLM observability and evaluation | Free plan · from Free self-hosted / cloud tier; Core from $29/month |
| 2 | Helicone | Open-source LLM observability and AI gateway in one line of code. | Free plan · from $79/mo |
| 3 | Braintrust | Eval-first evaluation and observability platform for AI applications. | Free plan · from $249/mo |
| 4 | Portkey | Open-source AI gateway and control plane for production Gen AI. | Free plan · from $49/mo |
| 5 | Weights & Biases | The AI developer platform for experiment tracking and LLMOps. | Free plan · from ~$50/user/mo |
| 6 | Vellum | Build, evaluate, and deploy LLM apps and agents with confidence. | Free plan · from Free tier; paid is sales-led |
Shipping an LLM feature is the easy part; keeping it reliable is where observability tools earn their place. They log every prompt and response, measure cost and latency, and let you evaluate output quality over time.
Langfuse is the popular open-source choice for tracing and evals, with a generous cloud tier and self-hosting. Helicone makes logging and a proxy gateway trivial to add — though note its post-acquisition maintenance status before committing. Braintrust focuses on evaluation and the prompt-iteration loop for teams shipping fast. Portkey is an AI gateway with observability, routing, and governance (now fully open-source). Weights & Biases (Weave) brings mature, battle-tested experiment tracking and LLM observability under one roof. Vellum leans toward product teams building and testing prompt-based workflows.
Start with tracing and cost monitoring (Langfuse or Helicone), then add structured evaluation (Braintrust or Weave) as your app matures. A gateway like Portkey is worth it once you're juggling multiple providers and need central governance.
Open-source LLM observability and evaluation
Open-source LLM observability and AI gateway in one line of code.
Eval-first evaluation and observability platform for AI applications.
Open-source AI gateway and control plane for production Gen AI.
The AI developer platform for experiment tracking and LLMOps.
Build, evaluate, and deploy LLM apps and agents with confidence.
Frequently asked questions
What is the best Best LLM Observability & Evaluation Tools (LLMOps)?
Langfuse is our top pick — Open-source LLM observability and evaluation Langfuse is our top recommendation for teams that want LLM observability without vendor lock-in. Moving essentially the entire product to MIT was a rare, genuinely developer-friendly move: you can self-host the full feature set for free, with no seat or usage caps. The tracing, prompt management, and evaluation tooling are solid and framework-agnostic, so it fits whether or not you use LangChain. The ClickHouse acquisition looks like a stable, aligned home. If open source and self-hosting matter, start here.
What is the best free Best LLM Observability & Evaluation Tools (LLMOps)?
Langfuse offers a free plan. Open-source LLM observability and evaluation
What are the top Best LLM Observability & Evaluation Tools (LLMOps)?
Our current top picks are Langfuse, Helicone, Braintrust, Portkey, Weights & Biases. Each is hand-reviewed and ranked by real usefulness, with no pay-to-play.