TruLens

TruLens is an evaluation and tracing framework for Agent and LLM/RAG apps. It logs every step, turns quality into metrics, and lets teams compare experiments to keep improving retrieval and generation pipelines.

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TruLensLLM evaluation frameworkRAG Triad metricsAgent tracingLangChain observabilityhallucination detection tool

Features of TruLens

End-to-end execution traces that capture inputs, outputs, and every intermediate step

Automatic scoring via feedback functions to quantify answer and context quality

Built-in RAG Triad to measure context relevance, groundedness, and answer relevance

Native OpenTelemetry support—drop traces straight into your existing observability stack

Granular evaluation of retrieval, tool calls, and planning steps in Agent workflows

Experiment tracking and version diffing to pinpoint which change broke the chain

Zero-code instrumentation for LangChain, LlamaIndex, or custom Python code

Quickstart guides, concept docs, and full API reference to get productive fast

Use Cases of TruLens

Measure how well retrieved context matches the final answer in RAG Q&A systems

Track tool-call success rates and planning accuracy while building Agent workflows

A/B test prompts, retrieval parameters, or model versions with quantified results

Debug flaky answers by replaying traces to the exact failure node

Run automated quality gates when no human-labeled data is available

Share unified experiment dashboards across distributed LLM teams

Export traces to any OTel-compatible backend for enterprise-grade observability

FAQ about TruLens

QWhat is TruLens?

An open-source evaluation and tracing toolkit that turns Agent and LLM/RAG runs into measurable metrics.

QWhich problems does TruLens solve?

It records full execution graphs, scores answer quality, and compares versions so you can iterate with confidence.

QWhat is the RAG Triad?

Three core scores—context relevance, groundedness, and answer relevance—used to judge retrieval quality.

QCan I use TruLens with LangChain or LlamaIndex?

Yes, one-line instrumentation works out of the box with LangChain, LlamaIndex, or plain Python code.

QDoes TruLens support OpenTelemetry?

Yes, traces are emitted in standard OTel format so you can route them to any observability platform.

QHow do I get started?

Install the package, run the 5-minute Quickstart to trace a prompt, then open the built-in dashboard to inspect scores.

QWho should use TruLens?

Engineers, researchers, and teams shipping Agent or RAG apps who need continuous, data-driven quality checks.

QIs TruLens free?

The core library is open-source; check the official site for any enterprise or hosted plans.

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