Best LLM Monitoring Tools for 2026

TL;DR: Best LLM monitoring tools for 2026 All-in-one solution: Braintrust — monitoring + evaluation + experimentation Open-source: Langfuse — self-hosted LLM observability platform Security and testing: Promptfoo — open-source red-teaming and eval CLI (now part of OpenAI) Logging: Datadog — unified infrastructure and LLM monitoring For production AI observability with built-in evaluations, token usage monitoring, and cost attribution for LLM apps, Braintrust delivers the most complete solution. Deploying a large language model to production is straightforward. Keeping it reliable, cost-effective, and high-quality over time is where teams struggle. Without LLM production monitoring, you have no idea how your AI is actually performing for customers. Latency spikes, quality regressions, and cost overruns happen quietly. By the time users complain, you've already burned through budget or damaged trust. LLM monitoring tools track every request through your LLM pipeline. They capture inputs,