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TruLens

Open-source evaluation and tracing for LLM and agent apps.

Categories
EvalObservability
Pricing
FREE
Source
Open source
Platforms
CLIAPI
Models
BYO key / model
Verified
Jun 13, 2026

TruLens is an open-source Python library for evaluating and tracing LLM, RAG, and agent applications. You wrap your app with feedback functions that score outputs on metrics like groundedness, context relevance, and answer relevance, then trace runs and compare versions on a metrics leaderboard. It integrates OpenTelemetry tracing and runs locally with a built-in dashboard.

Capabilities 2

What it actually does — grouped by capability family.

  • LLM evaluation (primary capability)
  • LLM observability (secondary capability)

Pros & cons

  • OpenTelemetry tracing, runs locally
  • RAG Triad feedback functions built in
  • Provider-agnostic LLM-as-judge metrics
  • Leaderboard to compare app versions
  • Python library, no hosted SaaS
  • Smaller community than LangSmith/Langfuse
  • Setup to wire feedback providers

Tags

Further reading

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