Active Adaptation, Not Static Defense: Temporal Dynamics of Preventative Steering in Adversarial Fine-Tuning

TL;DR - This paper finds that preventative steering protects LLMs from malicious fine-tuning through active, early-stage adaptation rather than a persistent static weight offset. It proposes Progressive Intensity Scheduling (PIS), which improves safety robustness while reducing harmful trait expression across evaluated Qwen2.5 and Gemma-3 models.

• Defensive adaptation occurs early in fine-tuning, followed by a steady state in which the corrective signal decays.
• Attention output projections are identified as the dominant residual-stream write route for defensive parameter updates.
• Preserving or reinjecting the learned weight offset does not maintain protection, suggesting that static parameter changes are insufficient.
• PIS raises steering intensity after fixed-strength alignment starts degrading, outperforming static-strength steering in the reported evaluations.