How FaithLens Beats GPT-4: The 8B Parameter Model Stopping AI Lies

FaithLens in Plain English: How an 8-Billion-Parameter Model Outperforms GPT-4.1 on Hallucination Detection “ A practitioner’s walk-through of the open-source paper “FaithLens: Detecting and Explaining Faithfulness Hallucination” (arXiv:2512.20182). No hype, no jargon—just facts, code snippets, and reproducible numbers. Table of Contents Why “faithfulness hallucination” matters What FaithLens does in one sentence Architecture & training pipeline (SFT → RL) Data recipe: public sets only, no private APIs Benchmark results: 12 data sets, one table Install & inference in < 5 minutes Re-training on your own corpus Limitations you should know FAQ from real users Take-away checklist 1. Why “faithfulness hallucination” matters …