Applied PRO

Build a RAG Eval Harness That Catches Regressions

A repeatable test suite measuring faithfulness, answer relevance, and context precision across 50-200 Q&A pairs. Ship gates on it; your RAG quality stops being vibes-based and becomes observable.

●●●●● • ~4-6 hours • Claude 4 Opus, GPT-5

Prerequisites

  • A working RAG pipeline (any retriever + any generator)
  • 50-200 labeled Q&A pairs with expected answers and source docs
  • Python 3.10+, access to a strong judge model (Claude 4, GPT-5, or similar)

Why this playbook

Most teams ship RAG with no evals. Then when quality degrades after an embedding model change, a retrieval tuning, or a vendor model update, they find out from users. This harness takes a few hours to build and saves you forever.

The three metrics that matter

  1. Faithfulness: does the generated answer only make claims supported by retrieved context? Catches hallucination.
  2. Answer relevance: does the answer actually address the question? Catches dodging.
  3. Context precision: of the retrieved chunks, how many were actually used / useful? Catches retrieval bloat.

These are enough to ship. More-exotic metrics (context recall, groundedness) are marginal gains.

Pro playbook

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  • Full multi-step prompt chains you can paste into Claude, GPT, or Cursor
  • Failure-mode notes — what breaks in production and how to fix it
  • Adjacent variations for cheaper models and tighter latency budgets
  • New Pro playbooks as they ship — cancel anytime

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