DeepDrift: Zero-Training Hidden-State Monitoring for Robustness in Vision, Language, and Generative Models

We introduce DeepDrift, a unified internal monitoring framework for deep neural networks based on Semantic Velocity — the ℓ2‑norm of consecutive hidden‑state differences. Key results:• LLM hallucination detection: AUC 0.891, lead time 7.2 tokens• RL failure prediction: AUC 0.985 (DQN), AUC 1.000 (PPO+noise), lead time 168 steps• ViT semantic OOD (CIFAR‑100 → SVHN): AUROC 0.817 [0.788, 0.846]• Diffusion memorization: 3× earlier than validation loss divergence• External benchmark on CLIP, DINOv2, ConvNeXt confirms generalization The method requires zero gradient‑based training, operates as a plug‑in PyTorch monitor with