Prediction of Prediction (PoP): Inter-Layer Activation Fusion for Single-Pass Hallucination Detection in Large Language Models

arXiv:2608.27165 · cs.CL · Submitted 2026-08-27 · Read on arXiv

cs.CL

Submitted: 2026-08-27

Updated: 2026-08-27

Comments: 7 pages, 3 figures, 9 tables. Single-author preprint on white-box, single-pass hallucination detection using inter-layer activation divergence, cross-layer fusion, temporal drift, and calibrated risk scoring. Evaluated on TruthfulQA, HaluEval 2.0, and FaithDial with Llama-3, Qwen2.5, and Mistral backbones

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Hallucination — 41× in this paper · explained in 3 episodes
• Calibration — 14× in this paper · explained in 7 episodes
• Prediction of Prediction — 12× in this paper
• Hallucination Detection — 11× in this paper · explained in 2 episodes
• Benchmark — 9× in this paper · explained in 2 episodes
• Transformer — 7× in this paper · explained in 2 episodes
• Verification — 7× in this paper · explained in 2 episodes
• Ablation — 6× in this paper · explained in 1 episode
• Perplexity — 4× in this paper · explained in 3 episodes
• Large Language Models (LLMs) — 3× in this paper · explained in 6 episodes
• AUC — 2× in this paper · explained in 2 episodes
• Robustness — 2× in this paper · explained in 5 episodes
• Spectral Geometry — 2× in this paper · explained in 2 episodes
• Accuracy — 1× in this paper · explained in 1 episode
• Activation Patching — 1× in this paper · explained in 2 episodes
• Analyzer — 1× in this paper · explained in 1 episode
• Attention Entropy — 1× in this paper · explained in 2 episodes
• Consistency — 1× in this paper · explained in 3 episodes
• Distribution Shift — 1× in this paper · explained in 5 episodes
• Steering — 1× in this paper · explained in 2 episodes
• Verifier — 1× in this paper · explained in 2 episodes

Sources

• A Survey on Hallucination in Large Language Models: Principles, Taxonomy, Challenges, and Open Questions
• Semantic Entropy Probes: Robust and Cheap Hallucination Detection in LLMs
• Unsupervised Real-Time Hallucination Detection based on the Internal States of Large Language Models
• ICR Probe: Tracking Hidden State Dynamics for Reliable Hallucination Detection in LLMs
• A Single Direction of Truth: An Observer Model's Linear Residual Probe Exposes and Steers Contextual Hallucinations
• EigenTrack: Spectral Activation Feature Tracking for Hallucination and Out-of-Distribution Detection in LLMs and VLMs
• The Geometry of Truth: Layer-wise Semantic Dynamics for Hallucination Detection in Large Language Models
• Automatic Layer Selection for Hallucination Detection
• Attention Sinks as Internal Signals for Hallucination Detection in Large Language Models
• Hallucination Basins: A Dynamic Framework for Understanding and Controlling LLM Hallucinations
• CrossHallu: Do Hallucination Signals Generalize Across Languages and Domains in Large Language Model's Internals?
• HALT: Hallucination Assessment via Log-probs as Time series
• Low-Cost Black-Box Detection of LLM Hallucinations via Dynamical System Prediction

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